Bile acids for liver‐transplanted patients

Abstract

Background

Liver transplantation has become a widely accepted form of treatment for numerous end‐stage liver diseases. Bile acids may decrease allograft rejection after liver transplantation by changing the expression of major histocompatibility complex class molecules in bile duct epithelium and central vein endothelium.

Objectives

To assess the beneficial and harmful effects of bile acids for liver‐transplanted patients.

Search methods

We performed searches of The Cochrane Hepato‐Biliary Group Controlled Trials Register, The Cochrane Central Register of Controlled Trials in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Expanded to September, 2009.

Selection criteria

Randomised clinical trials comparing any dose of bile acids or duration of treatment in liver‐transplanted patients versus placebo, no intervention, or another intervention. We included randomised clinical trials irrespective of blinding, language, and publication status.

Data collection and analysis

Two review authors extracted and checked data independently. We evaluated the risk of bias of the trials from the method of allocation sequence generation, allocation concealment, blinding, outcome data analysis, outcome data reporting, and other potential sources of bias. We used the intention‐to‐treat principle to perform meta‐analyses and presented the outcomes as relative risks (RR) or mean differences (MD), both with 95% confidence intervals (CI).

Main results

The updated search resulted in no new trials meeting the inclusion criteria of this review, thus leaving it to the seven already included randomised trials (six evaluating ursodeoxycholic acid versus placebo or no intervention, and one evaluating tauro‐ursodeoxycholic acid versus no intervention) enrolling a total of 335 participants. The administration of bile acids began one day or more after liver transplantation. All patients received the standard triple‐drug immunosuppressive regimen (steroids, azathioprine, and cyclosporine or tacrolimus) to suppress the allograft rejection response after liver transplantation. Bile acids compared with placebo or no intervention did not significantly change all‐cause mortality (RR 0.85, 95% CI 0.53 to 1.36), mortality related to allograft rejection (RR 0.30, 95% CI 0.01 to 7.12), retransplantation (RR 0.76, 95% CI 0.20 to 2.86), acute cellular rejection, or number of patients with steroid‐resistant rejection. Bile acids significantly reduced the number of patients who had chronic rejection in a fixed‐effect model but not in a random‐effects model meta‐analysis. Bile acids were safe and well tolerated by liver‐transplanted patients. However, this observation is based on data analysis from three trials with only 187 patients.

Authors' conclusions

We did not find evidence to support or refute bile acids for liver‐transplanted patients. Further randomised trials are necessary before bile acids can be recommended to liver‐transplanted patients.

Plain language summary

Bile acids for liver‐transplanted patients

Liver transplantation is a major surgical procedure that has been practiced for more than forty years and has nowadays become a generally accepted treatment option in patients with end‐stage liver disease. The most common cause for liver transplantation in adults is cirrhosis caused by various types of liver injuries such as infections (hepatitis B and C), alcohol, autoimmune liver diseases, early‐stage liver cancer, metabolic and hereditary disorders, but also diseases of unknown aetiology. All transplant recipients need lifetime immunosuppressive therapy to prevent transplant rejection.

Bile acids are being used for a variety of chronic liver diseases, mainly primary biliary cirrhosis and primary sclerosing cholangitis. However, their mechanisms of action and beneficial and harmful effects are poorly understood. This has led to the idea of the potential use of bile acids to prevent rejection in liver‐transplanted patients.

Results of the seven randomised clinical trials included in the review in which patients received standard immunosuppressive treatment (steroids, azathioprine, and cyclosporine or tacrolimus) with or without bile acids after liver transplantation, did not show any significant effects of bile acids on all‐cause mortality, mortality related to rejection, acute cellular rejection, steroid resistant rejection, or need for retransplantation. One analysis suggested that bile acids might beneficially influence number of patients with chronic rejection, but was contradicted by the analyses. The evidence that the use of ursodeoxycholic acid might have beneficial effects on chronic rejection and length of hospitalisation is weak as it is produced from trials with high risk of bias and insufficient number of included patients. That bile acids seemed well tolerated, with no reports of serious adverse events, is good knowledge, but much more research is needed before their use is acquitted. None of the randomised clinical trials assessed the effects of bile acids on quality of life or cost‐effectiveness.

Background

Liver transplantation has become a widely accepted treatment for numerous end‐stage liver diseases (Hussain 2002; Thalheimer 2002). Previous studies report an incidence of acute cellular rejection to range from 50% to 80% in adult recipients (Ascher 1988; Klintmalm 1989; Adams 1990; Wiesner 1992; FK506 1994). However, recent data suggest that the proportion of patients with rejection is currently down to 30% (Hirschfield 2009; Knechtle 2009). Despite advances in immunosuppressive treatment and care‐quality of liver‐transplanted patients, allograft rejection is still a major problem in the post‐transplantation period.

Acute cellular rejection usually occurs within the first 15 to 30 days after transplantation even if immunosuppression is achieved with tacrolimus or cyclosporine (FK506 1994; Haddad 2006; Corbani 2008). The cellular mechanisms of acute liver allograft rejection are not completely understood (Krams 1993). Initiation of allograft rejection is thought to involve the recognition of donor class II major histocompatibility complex alloantigens by recipient CD4+ T cells (Vierling 1992). Activated CD4+ T cells produce cytokines that induce lymphocyte proliferation and the maturation of CD8+ cytotoxic T cells, which are specific for donor class I major histocompatibility complex antigens (Calmus 1990). Both the bile duct epithelium and central vein endothelium are rich in class I and class II major histocompatibility complex antigens during rejection, whereas hepatocytes display a relative paucity of class I antigens and virtually no class II antigen (Vierling 1992). Therefore, the bile duct epithelium and central vein endothelium are the primary targets attacked by cytotoxic T cells during rejection. Impairment of the bile flow in the grafted liver may also cause rejection (Ericzon 1990). Mild cholestasis is a common finding after liver transplantation, and its association with clinically significant pathology is unlikely. Nevertheless, severe cholestasis should be treated as a potential cause of allograft rejection (Corbani 2008). In the study by Fusai 2006 the development of cholestasis was significantly related to prolonged warm ischaemia of the liver transplant. Cholestasis can induce hyper‐expression of major histocompatibility complex class I molecules by hepatocytes and, thereby, lymphocyte CD8+‐dependent cytotoxicity (Calmus 1992).

Bile acids include chenodeoxycholic acid, deoxycholic acid, lithocholic acid, and ursodeoxycholic acid (UDCA) (Fuchs 1999). In the course of cholestasis, intrahepatic accumulation of chenodeoxycholic acid and deoxycholic acid is thought to induce liver damage (Palmer 1972). In fact, the direct damage of membrane phospholipids and cholesterol components caused by the detergent‐like properties of hydrophobic bile acids results in hepatocyte necrosis (Sholmerich 1984; Perez 2009). It is also suggested that oxidative stress induced by hydrophobic bile acids plays an important role in liver damage during cholestasis. These effects can be prevented by the addition of UDCA, which modifies the bile acid pool resulting in an increase of the hydrophilic fraction and stabilisation of the cell membranes (Armstrong 1982; Perez 2009). Several studies on animal models showed evidence of potential immunomodulatory beneficial effects of UDCA and tauro‐ursodeoxycholic acid (TUDCA) by suppressing cytokine and immunoglobulin production and T‐cell mediated cytotoxicity (Yoshikawa 1998). In the study by Calmus 1990 it has been observed that UDCA down‐regulates the expression of abnormal major histocompatibility complex class I molecules in periportal hepatocytes in patients with primary biliary cirrhosis. Treatment with UDCA has been reported to have potential beneficial effects in various cholestatic liver conditions including primary biliary cirrhosis (Gong 2008), primary sclerosing cholangitis (Chen 2003a), and cystic fibrosis (Cheng 2002).

It has previously been suggested that UDCA, and perhaps tauro‐UDCA (TUDCA), may reduce the incidence of acute rejection and steroid‐resistant rejection in liver‐transplanted patients when administered with combination of immunosuppressive treatment. There are several potential mechanisms by which UDCA may inhibit allograft rejection in liver transplant recipients (Okolicsanyi 1986; Merion 1989; Calmus 1990; Terasaki 1991; Heuman 1993; Al‐Quaiz 1994; Friman 1994; Soderdahl 1998; Yoshikawa 1998; Assy 2007; Perez 2009). However, most of these studies included a relatively small number of patients, were not randomised, and often did not include histological information (Persson 1990; Friman 1992; Koneru 1993; Sharara 1995).

The previous version of this review by Chen 2003b stated that there was no convincing beneficial effects from the use of bile acids in liver‐transplanted patients; the risk of bias in the seven included trials was high. The review also found that there was a low occurrence of adverse events, and hence the use of bile acids could be considered safe. It should be noted, however, that this observation is based on reports from four trials with few patients. We have been unable to identify any other meta‐analyses or systematic reviews either. This review represents an update of the Chen 2003b Cochrane hepato‐Biliary Group review.

Objectives

To evaluate the beneficial and harmful effects of bile acids for liver‐transplanted patients by comparing bile acids versus placebo, no intervention, or another intervention in randomised clinical trials.

Methods

Criteria for considering studies for this review

Types of studies

We included randomised clinical trials irrespective of blinding, publication status, year of publication, or language. We assessed both included and excluded studies for the report of adverse events. We listed all studies reporting on adverse events in an additional table (Table 1). However, only data from the included trials were used in the statistical analysis.

1. Adverse events.

Study	Pts. in experimental group	Patients in control group	AE in experimental group	AE in control group	Author's conclusion
Barnes 1997	28	24	Diarrhoea (1 pt.)	Diarrhoea (1 pt.)	Adverse reactions attributable to study medication were rare.
Keiding 1997	54	48	Diarrhoea and difficulties in swallowing capsules (5 pts.)	Diarrhoea and difficulties in swallowing capsules (5 pts.)	No other presumed drug‐induced side effects were observed.
Angelico 1999	16	17	No AE	No AE	TUDCA administration was well tolerated in all patients and no drug‐related side effects were recorded.
Assy 2007	14	12	Mild diarrhoea (1 pt)	No AE	No dose reduction was required.

pt(s) = patient(s)

AE = adverse events

Types of participants

Patients who underwent liver transplantation.

Types of interventions

Any dose of a bile acid or duration of treatment versus placebo, no intervention, or another intervention. 
 We allowed co‐interventions if received equally by the intervention groups within a trial.

Types of outcome measures

The primary outcome measures were: 
 1. All‐cause mortality. 
 2. Death due to allograft rejection (acute cellular rejection or chronic rejection or liver retransplantation because of rejection). 
 Acute cellular rejection was diagnosed by the combination of abnormal liver biochemical variables (bilirubin, aspartate transaminase, alanine transaminase, alkaline phosphatases, and/or gammaglutamyl transpeptidase), clinical signs such as fever, and liver histological changes including mononuclear portal inflammation, bile duct damage, and subendothelial inflammation of portal or terminal hepatic veins (IWP 1995). Chronic rejection was characterised by liver histological changes including the progressive loss of interlobular bile ducts and arteriopathy characterised by foam cell infiltration of the arterial intima.

The secondary outcome measures were: 
 3. Number of patients who experienced rejection ‐ irrespective of the type: acute cellular rejection, chronic rejection, or both types of rejections. 
 4. Number of patients with acute cellular rejection. 
 5. Number of patients with chronic rejection. 
 6. Number of patients with steroid‐resistant rejection. 
 7. Biochemical responses: serum activities of alkaline phosphatases, gammaglutamyl transpeptidase, alanine aminotransferase, and aspartate aminotransferase and serum bilirubin concentration and/or number of patients with abnormal liver biochemical variables mentioned above. 
 8. Adverse events. Adverse events were defined as any untoward medical occurrence not necessarily having a causal relationship with the treatment but resulting in a dose reduction or discontinuation of treatment (ICH‐GCP 1997). 
 9. Quality of life. 
 10. Cost‐effectiveness.

Search methods for identification of studies

We performed searches of The Cochrane Hepato‐Biliary Group Controlled Trials Register (September 2009)(Gluud 2010) and The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Issue 3, 2009) by combining the terms 'liver' and 'transplantation' with the individual bile acid name (lithocholic acid, chenodeoxycholic acid, ursodeoxycholic acid, deoxycholic acid, dehydrocholic acid, and tauro‐ursodeoxycholic acid). We searched MEDLINE (January 1966 to September 2009), EMBASE (January 1980 to September 2009), and Science Citation Index Expanded (1945 to September 2009) by using the terms 'liver' and 'transplantation' in combination with the bile acids mentioned above (Royle 2003). The search strategies with the time span of the searches are given in Appendix 1. We contacted the Chinese Cochrane Centre regarding the search of The Chinese Biomedical Database and received a reply that they are unable to help us with this search. Therefore, the latter database could not be included in the search strategy of this update.

Further trials were identified by reading the reference lists of the identified studies. We wrote to the principal authors of the reports of the identified randomised clinical trials in September 2009 and enquired about additional trials, which they might know of. The first team of authors had also written to pharmaceutical companies involved in the production of bile acids to obtain information on published or unpublished randomised clinical trials in 2002, but no information had been received at that time.

Data collection and analysis

The update of this review was conducted according to the protocol, previously published in The Cochrane Library (Chen 2003b), and following the recommendations given by the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2008) and the Cochrane Hepato‐Biliary Group Module (Gluud 2010).

Trial identification 
 Identified trials were listed, and the two review authors evaluated whether the trials fulfilled the inclusion criteria. Excluded trials were listed with the reasons for exclusion.

Data extraction 
 GP and VG extracted the data independently, and disagreements were resolved by discussion or by CG. We extracted the following characteristics from each trial: primary author, number of patients randomised, patient inclusion and exclusion criteria, methodological quality, follow‐up (number and reasons for withdrawal), sample size calculation, intention‐to‐treat analysis, intervention regimens, mean age, proportion of males and females, aetiology of liver disease, origin of allograft, matching criteria between donor and recipient, time to follow‐up, number of outcomes, and number and type of adverse events in both the intervention and the control groups. Additional information was sought by correspondence with the principal investigator or co‐investigators of the trial in cases where the relevant data were not published.

Assessment of risk of bias 
 Risk of bias was defined as the confidence that the study design and reporting restricted bias in the intervention comparison (Schulz 1995; Moher 1998; Kjaergard 2001; Wood 2008). Due to the risk of overestimation of intervention effects in randomised trials with unclear or inadequate components, we assessed the risk of bias by separate domains.

Allocation sequence generation

• Adequate, if the allocation sequence was generated by a computer or random number table. Drawing of lots, tossing of a coin, shuffling of cards, or throwing dice was considered as adequate if a person who was not otherwise involved in the recruitment of participants performed the procedure.

• Unclear, if the trial was described as randomised, but the method used for the allocation sequence generation was not described.

• Inadequate, if a system involving dates, names, or admittance numbers were used for the allocation of patients. Such quasi‐randomised studies were excluded.

Allocation concealment

• Adequate, if the allocation of patients involved a central independent unit, on‐site locked computer, identically appearing numbered drug bottles or containers prepared by an independent pharmacist or investigator, or serially numbered, sealed, and opaque envelopes.

• Unclear, if the trial was described as randomised, but the method used to conceal the allocation was not described.

• Inadequate, if the allocation sequence was known to the investigators who assigned participants or if the study was quasi‐randomised. The latter studies were excluded.

Blinding

• Adequate, the trial was described as blinded, the parties that were blinded, and the method of blinding was described, so that knowledge of allocation was adequately prevented during the trial.

• Unclear, the trial was described as double blind, but the method of blinding was not described, so that knowledge of allocation was possible during the trial.

• Not performed, the trial was not blinded, so that the allocation was known during the trial.

Incomplete outcome data

• Adequate, if the numbers and reasons for dropouts and withdrawals in all intervention groups were described or if it was specified that there were no dropouts or withdrawals.

• Unclear, if the report gave the impression that there had been no dropouts or withdrawals, but this was not specifically stated.

• Inadequate, if the number or reasons for dropouts and withdrawals were not described.

Selective outcome reporting

• Adequate, if study protocol is available and all pre‐specified outcomes are reported in the manuscript or if the study protocol is not available, but it is clear that the report includes all expected outcomes.

• Unclear, if there are no sufficient information to permit judgement.

• Inadequate, if not all of the pre‐specified outcomes were reported and/or were reported incompletely or one or more reported outcomes were not pre‐specified.

Baseline imbalance

• Adequate, if there is no baseline imbalance in the main characteristics;

• Unclear, if there is no sufficient information to assess baseline characteristics;

• Inadequate, if there was a baseline imbalance due to chance or due to imbalanced exclusion after randomisation.

Early stopping

• Adequate, if sample size calculation was reported and the trial was not stopped, or the trial was stopped early by formal stopping rules at a point where the likelihood of observing an extreme intervention effect due to chance was low.

• Unclear, if sample size calculation was not reported and it is not clear whether the trial was stopped early or not.

• Inadequate, if the trial was stopped early due to informal stopping rules or the trial was stopped early by a formal stopping rule at a point where the likelihood of observing an extreme intervention effect due to chance was high.

Furthermore, we registered whether the randomised clinical trials had used an intention‐to‐treat analysis (Gluud 2001) and had calculated a sample size estimate.

Statistical methods 
 We performed the analyses in RevMan 5 (RevMan 2008). Analyses included all patients irrespective of compliance or follow‐up, according to the intention‐to‐treat principle, and using the last reported observed response ('carry forward') . Regarding death, both a worst‐best‐case scenario analysis considering all dropped‐out patients in the bile acid group as dead and the dropped‐out patients in the control group as alive, and a best‐worst‐case scenario analysis considering all dropped‐out patients in the bile acid group as alive and the dropped‐out patients in the control group as dead were performed. Both a random‐effects model (DerSimonian 1986) and a fixed‐effect model (DeMets 1987) were used. The results of the fixed‐effect model were reported if there were no differences between the results produced by the two models; otherwise, we reported the results produced by both models. We presented binary outcome measures as relative risks (RR) with 95% confidence intervals (CI) and continuous outcome measures as mean differences (MD) with 95% CI.

The risk of type I errors increases in single trials with interim analyses. To avoid type I errors, group sequential monitoring boundaries (Lan 1983) can be performed when deciding to terminate the trial earlier than planned. This requires analyses at different time intervals to record when the P‐value has become sufficiently small, that is, when the cumulative Z‐curve will cross the monitoring boundaries. Sequential monitoring boundaries, the so called 'trial sequential monitoring boundaries' can also be applied to meta‐analyses. In a trial sequential analysis (TSA), every trial that is added in a cumulative meta‐analysis is regarded as an interim meta‐analysis, and the information it adds on, helps on deciding if more trials need to be included.

The interpretation of the TSA is as follows; if the cumulative Z‐curve has crossed the boundary, a sufficient level of evidence is reached and no further trials may be needed. If the Z‐curve has not crossed the boundary, then the evidence is insufficient in order to reach a conclusion. To construct the trial sequential monitoring boundaries, information size is needed. It is calculated as the minimum number of participants needed in a well‐powered single trial (Pogue 1997; Pogue 1998; Brok 2008; Wetterslev 2008). We applied TSA since it prevents an increase of the risk of type I error due to sparse and multiple updating in a cumulative meta‐analysis and provides us with important information in order to estimate the level of evidence of the experimental intervention. Additionally, TSA provides us with important information regarding the need for additional trials and the required information size. We applied trial sequential monitoring boundaries according to an information size suggested by the trials with low risk of bias and a 50% relative risk reduction (RRR).

Subgroup analyses 
 We planned to perform the following subgroup analyses on the main outcome measures (all‐cause mortality and number of patients with acute rejection): 
 1. Risk of bias of the trials: comparing the intervention effect for trials with low risk of bias components to the intervention effect in trials with unclear or high risk of bias components. 
 2. Dose and duration of treatment with bile acids: comparing the intervention effect in trials administrating bile acid at or above the median dose multiplied by duration to the intervention effect of trials administrating bile acid at less than the median dose multiplied by duration. 
 3. Time between transplantation and the start of bile acids: comparing the intervention effect of trials having less than three days between transplantation and starting bile acid intake to the intervention effect of trials with a duration of three days or more between transplantation and the start of bile acid intake (Neuberger 1999). 
 4. Co‐interventions: comparing the intervention effect of trials with co‐interventions to the intervention effect of trials without co‐interventions.

Funnel plot analysis 
 We planned to explore bias by funnel plot analysis (Egger 1997).

Results

Description of studies

The performed electronic searches resulted in a total of 378 references. We excluded 362 duplicates or irrelevant references by reading abstracts. We excluded eight of the 16 further assessed references because they were observational studies, case series, or randomised clinical trials with a different reason for exclusion. They are listed under 'Characteristic of excluded studies' with reasons for exclusion. Seven references already included in the previous version of this review and one new reference, referring to an already included trial (Barnes 1997), were included in this review. We were not able to identify more trials by reading the reference lists of the identified studies, contacting the principle authors of the identified trials, or approaching pharmaceutical companies for unpublished trials. 
 
 Seven publications included in the review (five full publications and two abstracts) were randomised clinical trials that reported the random allocation of liver‐transplanted patients into groups receiving bile acid, placebo, or no treatment. We listed these trials in the table of Characteristics of included studies. All seven trials were published in English. Three randomised clinical trials were from the United States (Koneru 1993; Barnes 1997; Fleckenstein 1998), two from Italy (Sama 1991; Angelico 1999), one from France (Pageaux 1995), and one from Denmark (Keiding 1997).

Patients 
 In the included trials, all patients received blood group‐compatible grafts. The median size of the seven trials was 40 patients (range 29 to 102 patients). In total, 335 patients were randomised.

Five trials were published as full publications (Pageaux 1995; Barnes 1997; Keiding 1997; Fleckenstein 1998; Angelico 1999) which allowed us to extract detailed information on 263 of the patients. The mean age of the patients ranged from 44 to 51 years. One trial (Keiding 1997) also enrolled children, ranging in age from 0 to 13 years (median 1.5 years). The male to female ratio in these five trials was 159:104. The diseases that led to liver transplantation were alcoholic cirrhosis in 51 patients (19.4%), cirrhosis caused by chronic hepatitis C in 40 patients (15.2%), primary biliary cirrhosis in 36 patients (13.7%), cryptogenic cirrhosis in 22 patients (8.4%), metabolic diseases in 19 patients (7.2%), primary sclerosing cholangitis in 17 patients (6.5%), non‐specified post‐hepatitis cirrhosis in 17 patients (6.5%), cirrhosis caused by chronic hepatitis B in 13 patients (4.9%), 9 with autoimmune hepatitis and cirrhosis (3.4%), six with liver cancer (2.3%), five with biliary atresia (1.9%), and 28 with other diseases (10.6%). Only one trial reported the severity of liver function according to the Child‐Pugh class (Barnes 1997).

Bile acids and collateral interventions 
 Six trials (Sama 1991; Koneru 1993; Pageaux 1995; Barnes 1997; Keiding 1997; Fleckenstein 1998) compared UDCA versus placebo or no intervention. One trial (Angelico 1999) compared TUDCA versus no intervention. Bile acid treatment began one day after transplantation in the Keiding 1997 trial, three days after transplantation in the Koneru 1993 trial, three or five days in the Fleckenstein 1998 and Pageaux 1995 trials, five days after transplantation in the Barnes 1997 and Angelico 1999 trials, and five or seven days after transplantation in the Sama 1991 trial.

Patients received UCDA (10 to 15 mg/kg body weight/day) for two months in the Pageaux 1995 trial, for three months in the Koneru 1993; Barnes 1997; Keiding 1997; and Fleckenstein 1998 trials, and for six months in the Sama 1991 trial. In the Barnes 1997 trial, patients were followed up for 18 months. Patients in the Fleckenstein 1998 trial and the Keiding 1997 trial were followed up for nine months. There was no post‐treatment follow‐up in three trials (Sama 1991; Koneru 1993; Pageaux 1995). Patients received TUDCA (500 mg/day) for one year, and no follow‐up was conducted in the Angelico 1999 trial.

In addition to the bile acids or control intervention, all patients in the seven trials received standard triple‐drug regimens (steroids, azathioprine, and cyclosporine or tacrolimus). The patients who had steroid‐resistant rejection received treatment with immunosuppressive antibodies (OKT3). 
 
 Outcome measures 
 The outcome measures reported by most trials were all‐cause mortality and acute cellular rejection. Three trials reported on death related to rejection (Barnes 1997; Keiding 1997; Angelico 1999), two trials reported the number of patients who received retransplantation due to rejection (Keiding 1997; Fleckenstein 1998), three trials reported the number of patients with chronic rejection (Barnes 1997; Keiding 1997; Fleckenstein 1998), and four trials reported the number of patients with steroid‐resistant rejection (Pageaux 1995; Barnes 1997; Keiding 1997; Fleckenstein 1998). Four trials had adverse events as outcome measures (Barnes 1997; Keiding 1997; Fleckenstein 1998; Angelico 1999). Serum bilirubin level was only reported by the Fleckenstein 1998 trial. No trials provided data on other liver biochemical parameters, quality of life, or cost‐effectiveness.

Risk of bias in included studies

Two trials reported adequate allocation sequence generation by using computer‐generated random tables (Barnes 1997; Angelico 1999). One trial (Keiding 1997) reported adequate allocation concealment by using sealed, serially numbered envelopes. Three trials (Barnes 1997; Keiding 1997; Fleckenstein 1998) reported adequate blinding by using placebo with an identical appearance and taste. Five trials (Pageaux 1995; Barnes 1997; Keiding 1997; Fleckenstein 1998; Angelico 1999) reported adequate description of incomplete outcome data by the number of withdrawals, the reasons for withdrawal, or no patients dropped out. The trial by Keiding 1997 is the only one free of selective reporting since all the pre‐specified outcomes were fairly reported. Two trials (Barnes 1997; Keiding 1997) performed sample‐size calculations. Only the trial by Keiding 1997 seemed to be free of baseline imbalance and it is the only trial achieving the calculated sample size and therefore probably the only that was not terminated early. Other trials did not perform sample size calculation or the authors did not report whether the calculated sample size was achieved. The lack of this information made it unclear for us to judge whether a trial was terminated early, that is before an adequate number of patients was included in the trial. Three trials (Barnes 1997; Keiding 1997; Fleckenstein 1998) stated that intention‐to‐treat analyses were used (Figure 1; Figure 2).

1.

Methodological quality graph: review authors' judgements about each methodological quality item presented as percentages across all included studies.

2.

Methodological quality summary: review authors' judgements about each methodological quality item for each included study.

Following the assessment of risk of bias domains, none of the seven trials were considered to have low risk of bias, that is, having all the nine domains for risk of bias assessed as adequate.

Effects of interventions

We were able to include seven randomised clinical trials in this review. Six trials with 306 liver‐transplanted patients compared ursodeoxycholic acid (UDCA) with placebo or no intervention, and one trial with 29 liver‐transplanted patients compared tauro‐UDCA (TUDCA) with no intervention.

All‐cause mortality 
 Five trials including 257 liver‐transplanted patients reported on all‐cause mortality at the end of treatment or at maximum follow‐up. Bile acids did not significantly reduce all‐cause mortality (RR 0.85, 95% CI 0.53 to 1.36); there were 26 deaths among 132 patients treated with bile acids (19.7%) versus 29 deaths among 125 patients in the control groups (23.2%) (Analysis 1.1). There was no statistically significant heterogeneity (I² = 14.1%).

1.1. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 1 All‐cause mortality at maximum follow‐up.

Four trials (Sama 1991; Barnes 1997; Keiding 1997; Fleckenstein 1998) showed that UDCA did not significantly reduce all‐cause mortality (RR 0.80, 95% CI 0.49 to 1.30); 23 deaths among 116 patients treated with UCDA (19.8%) versus 27 deaths among 108 patients in the control groups (25.0%). The Angelico 1999 trial demonstrated that TUDCA was not able to reduce all‐cause mortality (RR 1.59, 95% CI 0.30 to 8.33); there were 3 deaths among 16 patients (18.8%) versus 2 deaths among 17 patients (11.8%).

The Fleckenstein 1998 trial and the Sama 1991 trial did not report the causes of deaths. In the three other trials, the deaths were considered to be caused by infections (n = 11), hepatic failure (n = 7), abdominal bleeding (n = 3), renal failure (n = 2), multiple organ failure (n = 2), hepatitis B virus fibrosis (n = 2), acute rejection (n = 1), hepatic artery thrombosis (n = 1), encephalitis (n = 1), lymphoproliferative disorder (n = 1), cerebral haemorrhage (n = 1), or other reasons (n = 6).

Worst‐best case and best‐worst case scenario analyses 
 In the worst‐best case scenario analysis, bile acids did not significantly reduce all‐cause mortality when compared with placebo or no intervention (RR 1.30, 95% CI 0.86 to 1.96); 40 deaths among 132 patients on bile acids (30.3%) versus 29 deaths among 125 patients in the control groups (23.2%). However, all‐cause mortality was significantly reduced by bile acids in the best‐worst case scenario analysis (RR 0.58, 95% CI 0.38 to 0.90); 26 deaths among 132 patients (19.7%) versus 42 deaths among 125 patients in the control groups (33.6%) (Analysis 1.2).

1.2. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 2 All‐cause mortality: worst‐best case and best‐worst case scenarios.

Subgroup analyses 
 We performed subgroup analyses regarding the time that bile acid intake was started. The Keiding 1997 trial started bile acid intake less than three days after liver transplantation and demonstrated no significant effect of UDCA on all‐cause mortality (RR 1.24, 95% CI 0.61 to 2.54); 14 deaths out of 54 patients (25.9%) versus 10 out of 48 control patients (20.8%). The same effect was noticed in the four other trials (Sama 1991; Barnes 1997; Fleckenstein 1998; Angelico 1999), which started bile acids three days or more after liver transplantation (RR 0.63, 95% CI 0.33 to 1.20); 12 deaths among 78 patients (15.4%) versus 9 deaths among 77 control patients (24.7%) (Analysis 1.3). There were no statistically significant differences between the two estimates. 
 
 We also performed subgroup analyses regarding the duration of bile acid treatment. Bile acids were administrated for less than six months in three trials (Barnes 1997; Keiding 1997; Fleckenstein 1998) and were not able to significantly decrease all‐cause mortality (RR 0.78, 95% CI 0.45 to 1.38); 18 deaths in a group of 96 treated patients (18.8%) versus 21 deaths among 88 control patients (23.9%). In the other two trials (Sama 1991; Angelico 1999) patients were treated with bile acids for six months or more. The treatment did not show statistically significant decrease in all‐cause mortality (RR 1.02, 95% CI 0.43 to 2.4); 8 deaths in a group of 36 treated patients (22.2%) versus 8 deaths in a group of 37 control patients (21.6%) (Analysis 1.4). There were no statistically significant differences between the two estimates.

1.3. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 3 Subgroup analyses: all‐cause mortality at maximum follow‐up according to time of start of bile acids.

1.4. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 4 Subgroup analyses: all cause mortality at maximum follow‐up according to treatment duration.

Mortality related to allograft rejection 
 We did not find statistically significant reduction in mortality related to allograft rejection at maximum follow‐up in the three trials reporting cause of death (Barnes 1997; Keiding 1997; Angelico 1999) (RR 0.30, 95% CI 0.01 to 7.12); 0/98 (0%) versus 1/89 (1.1%)) (Analysis 1.5). The only death due to acute rejection was found in the placebo group of the Keiding 1997 trial.

1.5. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 5 Number of deaths related to rejection at maximum follow‐up.

Number of liver retransplantations 
 Two trials (Fleckenstein 1998; Keiding 1997) including 132 liver‐transplanted patients reported the number of liver retransplantations. UDCA did not significantly reduce the risk of liver retransplantation at maximum follow‐up (RR 0.76, 95% CI 0.20 to 2.86); 3/68 (4.4%) versus 4/64 (6.3%)) (Analysis 1.6). In the Keiding 1997 trial, one patient in the UDCA group was retransplanted due to chronic rejection, and four patients in the placebo group were retransplanted either due to chronic rejection (three cases) or acute rejection (one case). In the Fleckenstein 1998 trial, two patients in the UDCA group were retransplanted due to acute rejection (one case) and chronic rejection (one case), respectively.

1.6. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 6 Number of retransplantations at maximum follow‐up.

Number of patients with acute cellular rejection 
 Seven trials reported the number of patients who had acute cellular rejection after liver transplantation. Bile acids did not significantly reduce the number of patients who experienced acute cellular rejection (RR 0.89, 95% CI 0.74 to 1.06); 93/174(53.5%) versus 99/165 (60.0%)). There was no significant heterogeneity (I² = 0%).

Six trials (Sama 1991; Koneru 1993; Pageaux 1995; Barnes 1997; Keiding 1997; Fleckenstein 1998) compared UDCA with placebo or no intervention and demonstrated that UDCA did not significantly reduce the number of patients with acute cellular rejection after liver transplantation (RR 0.89, 95% CI 0.74 to 1.08; 85/158 (53.8%) versus 89/148 (60.1%)). Neither did the Angelico 1999 trial demonstrate significant reduction of the number of patients with acute cellular rejection with TUDCA (RR 0.85, 95% CI 0.45 to 1.60); 8/16 (50.0%) versus 10/17 (58.8%) (Analysis 1.7).

1.7. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 7 Number of patients with acute cellular rejection at maximum follow‐up.

Subgroup analyses 
 Two trials (Koneru 1993; Keiding 1997) in which the patients started bile acids intake less than three days after liver transplantation did not demonstrate any significant reduction of the risk of acute cellular rejection by bile acids (RR 0.84, 95% CI 0.63 to 1.11); 38/70 (54.3%) versus 41/64 (64.1%). The other five trials (Sama 1991; Pageaux 1995; Barnes 1997; Fleckenstein 1998; Angelico 1999), in which the patients were started on bile acid intake three days or more after liver transplantation, did not find a significant reduction of the risk of acute cellular rejection by bile acids (RR 0.92, 95% CI 0.72 to 1.17); 55/104 (52.9%) versus 58/101 (57.4%) (Analysis 1.8). There was no significant difference between the two estimates.

1.8. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 8 Subgroup analysis: number of patients with acute cellular rejection according to time of start of bile acid.

Bile acids did not significantly reduce the risk of acute cellular rejection in the five trials (Koneru 1993; Pageaux 1995; Barnes 1997; Keiding 1997; Fleckenstein 1998) in which the patients received treatment with bile acids less than six months (RR 0.87, 95% CI 0.71 to 1.07); 72/138 (52.2%) versus 76/128 (59.4%). Neither did bile acids in the two other trials (Sama 1991; Angelico 1999) in which the patients received bile acids for more than six months (RR 0.94, 95% CI 0.65 to 1.36); 21/36 (58.3%) versus 23/37 (62.2%) (Analysis 1.9). There were no significant difference between the two estimates.

1.9. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 9 Subgroup analysis: number of patients with acute cellular rejection according to treatment duration.

Number of patients with chronic rejection 
 Three trials comparing UDCA versus placebo (Barnes 1997; Keiding 1997; Fleckenstein 1998) reported the number of patients with chronic rejection after liver transplantation. UDCA significantly reduced the number of patients with chronic rejection in the fixed‐effect model analysis (RR 0.28, 95% CI 0.08 to 0.95); 3/96 (3.1%) versus 10/88 (11.4%) (Analysis 1.10), but not in the random‐effects model analysis (RR 0.30, 95% CI 0.08 to 1.13); 3/96 (3.1%) versus 10/88 (11.4%). There was no statistically significant heterogeneity (I² 0%). We performed trial sequential analysis for the available data from three trials (Figure 3) with heterogeneity corrected required information size based on proportion of this outcome of 12% in the control group, a relative risk reduction of 50% in the intervention group, at a type I error of 5% and a type II error of 10%. We obtained a required information size of 957 patients. UDCA was not able to reach or break the trial sequential monitoring boundary, and only 183 out of 957 (19%) patients were randomised regarding this outcome.

1.10. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 10 Number of patients with chronic rejection at maximum follow‐up.

3.

Trial sequential analysis for the number of patients with chronic rejection at maximum follow‐up. We calculated the heterogeneity‐corrected required information size (HCRIS) based on a proportion of 12% of the patients in the placebo group with chronic rejection at maximum follow‐up; a 50% risk ratio reduction in the bile acid group; an alpha of 5%, a beta of 10%, and a heterogeneity of 0%. Only 184 patients have been randomised reporting this outcome, which is only 19% of the HCRIS of 957 patients. The cumulative Z‐score crosses the conventional boundaries for P ? 0.05, but not the monitoring boundaries.

Number of patients with steroid‐resistant rejection 
 Four trials (Pageaux 1995; Barnes 1997; Keiding 1997; Fleckenstein 1998) reported the number of patients with steroid‐resistant rejection. These trials demonstrated that UDCA did not significantly reduce the number of patients with steroid‐resistant rejection when compared with placebo (22/122 (18%) versus 26/112 (23.2%); (RR 0.77, 95% CI 0.47 to 1.27) (Analysis 1.11). There was no significant heterogeneity (I² 0%).

1.11. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 11 Number of patients with steroid‐resistant rejection at maximum follow‐up.

Liver biochemistry 
 The Fleckenstein 1998 trial reported serum bilirubin levels after a three‐month‐treatment period in 30 liver‐transplanted patients. There was no statistically significant difference in serum bilirubin levels between the UDCA group and the placebo group (MD 2.60 mg/dl, 95% CI ‐0.96 to 6.16 mg/dl) (Analysis 1.12).

1.12. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 12 Serum bilirubin (mg/dl) at the end of treatment.

No data were available for other liver biochemical variables.

Cost‐effectiveness 
 One trial (Barnes 1997) with 52 liver‐transplanted patients reported the days of hospitalisation after liver transplantation. UDCA significantly decreased the number of days of hospitalisation when compared with placebo (MD ‐8.50 days, 95% CI ‐16.67 to ‐0.33 days) (Analysis 1.13). We were not able to extract other medical cost from the trials.

1.13. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 13 Number of days of hospitalisation after liver transplantation.

Adverse events 
 Among all the included and excluded trials only four reported on adverse events; however, adverse events only occurred in two of the included trials (Barnes 1997; Keiding 1997). There were no significant differences regarding adverse events (RR 0.88, 95% CI 0.30 to 2.60); 6/112 (5.4%) versus 6/105 (5.7%) (Analysis 1.14). In the Barnes 1997 trial, diarrhoea was reported by two patients (one in the UDCA group and one in the placebo group). In the Keiding 1997 trial, five UDCA patients and five placebo patients stopped intake of the trial medicine because of diarrhoea or difficulties in swallowing the capsules. The remaining included trial by Angelico 1999 stated that no adverse events occurred during the study period. The excluded trial by Assy 2007 was the only one reporting on a case of mild diarrhoea in one patient in the intervention group. No other excluded studies reported on adverse events (see Table 1).

1.14. Analysis.

Comparison 1 Bile acids for liver‐transplanted patients, Outcome 14 Adverse events.

Quality of life 
 None of the included studies assessed quality of life as an outcome.

Other subgroup analyses 
 We planned to perform subgroup analyses regarding the risk of bias of trials, the dosage of bile acid, and any co‐intervention. However, none of the trials were considered to be of low risk of bias; they all used a similar dosage of bile acid; and patients in all trials received similar immunosuppressive treatment as co‐interventions (steroids, azathioprine, and cyclosporine or tacrolimus) after liver transplantation. Therefore, we were not able to perform the planned subgroup analyses.

Funnel plot asymmetry 
 We did not draw a funnel plot analysis due to the limited number of trials included in the present review.

Discussion

In the update of this review we included no new trials assessing the use of bile acids for liver‐transplanted patients. The analyses of the seven previously included trials showed that bile acids did not significantly affect mortality, acute cellular rejection, steroid‐resistant rejection, retransplantation, or serum bilirubin. Bile acids might significantly decrease the length of hospital stay and the number of patients with chronic rejection included in these trials, but more supportive evidence is needed. The number of patients with chronic rejection was not significantly influenced by bile acids when a random‐effects model was used and length of stay was assessed in one single trial. Furthermore, none of the trials were considered to be of low risk of bias, and few patients were enrolled. Therefore, our positive findings may be due to bias (Schulz 1995; Moher 1998; Kjaergard 2001; Wood 2008) or random errors (Wetterslev 2008; Brok 2009; Thorlund 2009). On the other hand, we are not able to exclude type II errors (that is, finding no significant differences when in fact they exist) due to the low number of participants. Therefore, this topic could be of potential interest in future large randomised trials with adequate control of bias.

All‐cause mortality at one year after liver transplantation is reported to be about 20% (Thuluvath 2003), which we also observed for the patients included in the present review. According to our subgroup analyses, neither UDCA nor TUDCA significantly decreased all‐cause mortality. We also performed a subgroup analysis regarding treatment duration, but we were not able to find any difference between short (less than six months) and long treatment duration (six months or more). Thus, bile acids do not seem to have statistically significant effects in reducing all‐cause mortality after liver transplantation. We performed both worst‐best‐case scenario and best‐worst‐case scenario analyses. In the worst‐best‐case scenario, bile acids did not differ significantly from placebo or no intervention regarding all‐cause mortality. However, bile acids significantly decreased all‐cause mortality in the best‐worst‐case scenario analysis. However, such an analysis is very extreme and may not be realistic. We have also found that UDCA may be able to decrease the risk of chronic rejection in liver‐transplanted patients, but trial sequential analysis could not confirm this result. Due to a limited number of patients (Ioannidis 2001), we are not able to exclude the possibility that it may be relevant to perform placebo‐controlled trials with low risk of bias on the use of bile acids for liver‐transplanted patients.

We looked into the causes of deaths that were reported by the trials, and only one trial reported one death related to rejection. At the same time, the number of retransplantations was 3 among 68 liver‐transplanted patients who received treatment with UDCA and 4 among 64 liver‐transplanted patients who received treatment with placebo. We noticed that all patients in the included trials received co‐interventions of standard triple‐drug regimens (steroids, azathioprine, and cyclosporine or tacrolimus), which were able to control the possible acute or chronic rejection and prevent deaths due to allograft rejection (FK506 1994).

The assumption that UDCA might reduce the incidence of acute graft rejection came from the findings that UDCA could regulate major histocompatibility complex antigen expression in bile ducts and liver endothelia, and inhibit lymphocyte activity (Calmus 1990; Terasaki 1991; Perez 2009). However, in the present review, bile acids did not significantly reduce the risk of acute cellular rejection in liver‐transplanted patients. Considering that acute cellular rejection is commonly found within a few days after liver transplantation (Vierling 1992), some might argue that the administration of bile acids was started too late to prevent acute cellular rejection. We performed subgroup analyses regarding the time bile acids were started, and no statistically significant difference was found. Furthermore, bile acids were not able to decrease the risk of steroid‐resistant rejection. Therefore, the lack of effects of bile acids does not seem to be due to a delayed start to bile acid administration after liver transplantation. However, it is a possibility that one should start bile acids intake before liver transplantation. A retrospective study found that rejection rates differed significantly between patients with primary biliary cirrhosis treated with or without UDCA before liver transplantation (Heathcote 1999). One could argue whether UDCA‐induced delay in transplantation has an adverse effect on post‐transplantation outcome. Since we did not find any prospective randomised clinical trials addressing this issue, further research might be needed. Furthermore, some studies may provide an explanation why UDCA was not able to prevent acute cellular rejection. These studies found that UDCA did not appear to change the expression of major histocompatibility complex class II antigens, but rather major histocompatibility complex class I antigens (Calmus 1990). The initial mechanism of acute rejection is thought to be recognition of MHC class II antigens by CD4+ T cells (Vierling 1992). Moreover, the inhibition of the production of interleukin‐2 by peripheral blood lymphocytes with UDCA (Heuman 1993) might be negated by the immunosuppressive treatment after liver transplantation (van den Berg 1998), so that UDCA is unable to demonstrate effects on graft rejection. In a recent study by Assy 2007 a significant reduction in the mean dose of immunosuppressive medications was achieved in stable liver graft recipients treated with UDCA, indicating a possible influence of UDCA on rejection mechanisms.

In accordance with previous systematic reviews (Chen 2003a; Chen 2007; Gong 2008), bile acids were not associated with the occurrence of serious adverse events or any major occurrence of adverse events.

In summary, our results do not support or refute the use of bile acids (UDCA and TUDCA) additional to standard immunosuppressive treatment in liver‐transplanted patients.

Authors' conclusions

Implications for practice.

There seems to be no evidence to support or refute the use of bile acids for liver‐transplanted patients receiving standard immunosuppressive treatment.

Implications for research.

We need more randomised placebo‐controlled clinical trials with enough statistical power and low risk of bias to explore the potential effects of bile acids on chronic rejection and mortality in liver‐transplanted patients. Such trials should also consider evaluation of quality of life and length of hospitalisation. Such trials may consider starting bile acid and placebo interventions before liver transplantation; we were not able to identify any randomised trials addressing this regimen. Such trials ought to be reported according to the CONSORT statement (www.consort‐statement.org). However, before embarking on such trials, the effects of bile acids in other patient groups should be scrutinised as they may have small or negative effects.

What's new

Date	Event	Description
18 September 2009	New citation required but conclusions have not changed	This review is an updated version of a review that was published for the first time in Issue 3, 2005 of The Cochrane Library by Chen 2003b.
18 September 2009	New search has been performed	No new studies fulfilled the inclusion criteria.

Appendices

Appendix 1. Search strategies

Data Base	Date of Search	Search Strategy
The Cochrane Hepato‐Biliary Group Controlled Trials Register	September 2009	#1: 'liver transplantation' and 'chenodeoxycholic' #2: 'liver transplantation' and 'cholic' #3: 'liver transplantation' and 'deoxycholic' #4: 'liver transplantation' and 'glycochenodeoxycholic' #5: 'liver transplantation' and 'glycocholic' #6: 'liver transplantation' and 'glycodeoxycholic' #7: 'liver transplantation' and 'glycolithocholic' #8: 'liver transplantation' and 'hyodeoxycholic' #9: 'liver transplantation' and 'lithocholic' #10: 'liver transplantation' and 'taurochenodeoxycholic' #11: 'liver transplantation' and 'taurocholic' #12: 'liver transplantation' and 'taurodehydrocholic' #13: 'liver transplantation' and 'taurodeoxycholic' #14: 'liver transplantation' and 'tauroglycocholic' #15: 'liver transplantation' and 'taurolithocholic' #16: 'liver transplantation' and 'tauroselcholic' #17: 'liver transplantation' and 'tauroursocholic' #18: 'liver transplantation' and 'tauroursodeoxycholic' #19: 'liver transplantation' and 'ursocholic' #20: 'liver transplantation' and 'ursodeoxycholic'
The Cochrane Central Register of Controlled Trials in The Cochrane Library	Issue 3, 2009	#1: LIVER‐TRANSPLANTATION *:ME #2: LIVER AND TRANSPLANTATION #3: BILE ACID *:ME #4: CHENODEOXYCHOLIC or CHOLIC or DEOXYCHOLIC or GLYCOCHENODEOXYCHOLIC or GLYCOCHOLIC or GLYCODEOXYCHOLIC or GLYCOLITHOCHOLIC or HYODEOXYCHOLIC or LITHOCHOLIC or TAUROCHENODEOXYCHOLIC or TAUROCHOLIC or TAURODEHYDROCHOLIC or TAURODEOXYCHOLIC or TAUROGLYCOCHOLIC or TAUROLITHOCHOLIC or TAUROSELCHOLIC or TAUROURSOCHOLIC or TAUROURSODEOXYCHOLIC or URSOCHOLIC or URSODEOXYCHOLIC #5: #1 or #2 #6: #3 or #4 #7: #5 and #6
MEDLINE	September 2009	#1: LIVER‐TRANSPLANTATION *:ME #2: LIVER AND TRANSPLANTATION #3: BILE ACID *:ME #4: CHENODEOXYCHOLIC or CHOLIC or DEOXYCHOLIC or GLYCOCHENODEOXYCHOLIC or GLYCOCHOLIC or GLYCODEOXYCHOLIC or GLYCOLITHOCHOLIC or HYODEOXYCHOLIC or LITHOCHOLIC or TAUROCHENODEOXYCHOLIC or TAUROCHOLIC or TAURODEHYDROCHOLIC or TAURODEOXYCHOLIC or TAUROGLYCOCHOLIC or TAUROLITHOCHOLIC or TAUROSELCHOLIC or TAUROURSOCHOLIC or TAUROURSODEOXYCHOLIC or URSOCHOLIC or URSODEOXYCHOLIC #5: #1 or #2 #6: #3 or #4 #7: #5 and #6 #8: RANDOMIZED‐CONTROLLED‐TRIAL *:ME #9: RANDOM* #10: #8 or #9 #11: #7 and #10
EMBASE	September 2009	#1: LIVER‐TRANSPLANTATION *:ME #2: LIVER AND TRANSPLANTATION #3: BILE ACID *:ME #4: CHENODEOXYCHOLIC or CHOLIC or DEOXYCHOLIC or GLYCOCHENODEOXYCHOLIC or GLYCOCHOLIC or GLYCODEOXYCHOLIC or GLYCOLITHOCHOLIC or HYODEOXYCHOLIC or LITHOCHOLIC or TAUROCHENODEOXYCHOLIC or TAUROCHOLIC or TAURODEHYDROCHOLIC or TAURODEOXYCHOLIC or TAUROGLYCOCHOLIC or TAUROLITHOCHOLIC or TAUROSELCHOLIC or TAUROURSOCHOLIC or TAUROURSODEOXYCHOLIC or URSOCHOLIC or URSODEOXYCHOLIC #5: #1 or #2 #6: #3 or #4 #7: #5 and #6 #8: RANDOMIZED‐CONTROLLED‐TRIAL *:ME #9: RANDOM* #10: #8 or #9 #11: #7 and #10
Science Citation Index Expanded	September 2009	#1: LIVER‐TRANSPLANTATION *:ME #2: LIVER AND TRANSPLANTATION #3: BILE ACID *:ME #4: CHENODEOXYCHOLIC or CHOLIC or DEOXYCHOLIC or GLYCOCHENODEOXYCHOLIC or GLYCOCHOLIC or GLYCODEOXYCHOLIC or GLYCOLITHOCHOLIC or HYODEOXYCHOLIC or LITHOCHOLIC or TAUROCHENODEOXYCHOLIC or TAUROCHOLIC or TAURODEHYDROCHOLIC or TAURODEOXYCHOLIC or TAUROGLYCOCHOLIC or TAUROLITHOCHOLIC or TAUROSELCHOLIC or TAUROURSOCHOLIC or TAUROURSODEOXYCHOLIC or URSOCHOLIC or URSODEOXYCHOLIC #5: #1 or #2 #6: #3 or #4 #7: #5 and #6 #8: RANDOMIZED‐CONTROLLED‐TRIAL *:ME #9: RANDOM* #10: #8 or #9 #11: #7 and #10
The Chinese Biomedical Database	Searched from January 1980 to April 2002.	#1: LIVER‐TRANSPLANTATION *:ME #2: LIVER AND TRANSPLANTATION #3: BILE ACID *:ME #4: CHENODEOXYCHOLIC or CHOLIC or DEOXYCHOLIC or GLYCOCHENODEOXYCHOLIC or GLYCOCHOLIC or GLYCODEOXYCHOLIC or GLYCOLITHOCHOLIC or HYODEOXYCHOLIC or LITHOCHOLIC or TAUROCHENODEOXYCHOLIC or TAUROCHOLIC or TAURODEHYDROCHOLIC or TAURODEOXYCHOLIC or TAUROGLYCOCHOLIC or TAUROLITHOCHOLIC or TAUROSELCHOLIC or TAUROURSOCHOLIC or TAUROURSODEOXYCHOLIC or URSOCHOLIC or URSODEOXYCHOLIC #5: #1 or #2 #6: #3 or #4 #7: #5 and #6 #8: RANDOMIZED‐CONTROLLED‐TRIAL *:ME #9: RANDOM* #10: #8 or #9 #11: #7 and #10

Data and analyses

Comparison 1. Bile acids for liver‐transplanted patients.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 All‐cause mortality at maximum follow‐up	5	257	Risk Ratio (M‐H, Fixed, 95% CI)	0.85 [0.53, 1.36]
1.1 UDCA versus placebo or no treatment	4	224	Risk Ratio (M‐H, Fixed, 95% CI)	0.80 [0.49, 1.30]
1.2 TUDCA versus no treatment	1	33	Risk Ratio (M‐H, Fixed, 95% CI)	1.59 [0.30, 8.33]
2 All‐cause mortality: worst‐best case and best‐worst case scenarios	5		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
2.1 Worst‐best case scenario	5	257	Risk Ratio (M‐H, Fixed, 95% CI)	1.30 [0.86, 1.96]
2.2 Best‐worst case scenario	5	257	Risk Ratio (M‐H, Fixed, 95% CI)	0.58 [0.38, 0.90]
3 Subgroup analyses: all‐cause mortality at maximum follow‐up according to time of start of bile acids	5	257	Risk Ratio (M‐H, Fixed, 95% CI)	0.85 [0.53, 1.36]
3.1 Less than three days after transplantation	1	102	Risk Ratio (M‐H, Fixed, 95% CI)	1.24 [0.61, 2.54]
3.2 Three days or more after transplantation	4	155	Risk Ratio (M‐H, Fixed, 95% CI)	0.63 [0.33, 1.20]
4 Subgroup analyses: all cause mortality at maximum follow‐up according to treatment duration	5	257	Risk Ratio (M‐H, Fixed, 95% CI)	0.85 [0.53, 1.36]
4.1 Less than six months	3	184	Risk Ratio (M‐H, Fixed, 95% CI)	0.78 [0.45, 1.38]
4.2 Six months or more	2	73	Risk Ratio (M‐H, Fixed, 95% CI)	1.02 [0.43, 2.40]
5 Number of deaths related to rejection at maximum follow‐up	1	102	Risk Ratio (M‐H, Fixed, 95% CI)	0.30 [0.01, 7.12]
5.1 UDCA versus placebo	1	102	Risk Ratio (M‐H, Fixed, 95% CI)	0.30 [0.01, 7.12]
6 Number of retransplantations at maximum follow‐up	2	132	Risk Ratio (M‐H, Fixed, 95% CI)	0.76 [0.20, 2.86]
7 Number of patients with acute cellular rejection at maximum follow‐up	7	339	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.74, 1.06]
7.1 UDCA versus placebo or no treatment	6	306	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.74, 1.08]
7.2 TUDCA versus no treatment	1	33	Risk Ratio (M‐H, Fixed, 95% CI)	0.85 [0.45, 1.60]
8 Subgroup analysis: number of patients with acute cellular rejection according to time of start of bile acid	7	339	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.74, 1.06]
8.1 Less than three days after transplantation	2	134	Risk Ratio (M‐H, Fixed, 95% CI)	0.84 [0.63, 1.11]
8.2 Three days or more after liver transplantation	5	205	Risk Ratio (M‐H, Fixed, 95% CI)	0.92 [0.72, 1.17]
9 Subgroup analysis: number of patients with acute cellular rejection according to treatment duration	7	339	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.74, 1.06]
9.1 Less than six months	5	266	Risk Ratio (M‐H, Fixed, 95% CI)	0.87 [0.71, 1.07]
9.2 Six months or more	2	73	Risk Ratio (M‐H, Fixed, 95% CI)	0.94 [0.65, 1.36]
10 Number of patients with chronic rejection at maximum follow‐up	3	184	Risk Ratio (M‐H, Fixed, 95% CI)	0.28 [0.08, 0.95]
11 Number of patients with steroid‐resistant rejection at maximum follow‐up	4	234	Risk Ratio (M‐H, Fixed, 95% CI)	0.77 [0.47, 1.27]
12 Serum bilirubin (mg/dl) at the end of treatment	1	30	Mean Difference (IV, Fixed, 95% CI)	2.6 [‐0.96, 6.16]
13 Number of days of hospitalisation after liver transplantation	1	52	Mean Difference (IV, Fixed, 95% CI)	‐8.5 [‐16.67, ‐0.33]
14 Adverse events	3	187	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.30, 2.60]

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Angelico 1999.

Methods	Study design: open‐label, randomised, one‐year pilot study.
Participants	Country: Italy. Publication language: English. Inclusion criteria ‐ patients who underwent liver transplantation from April 1994 to December 1994. Exclusion criteria ‐ not mentioned. Participants Two patients in TUDCA group and two patients in control group were excluded from the basic information of participants by the study due to withdrawal. ‐ TUDCA group (n = 14) Mean age (years +/‐ SD): 46.7 +/‐ 8.4. Ratio of sex (male/female): 12/2. Origins of liver diseases: hepatitis C cirrhosis (9), hepatitis B cirrhosis (2), hepatitis B and C cirrhosis (1), cryptogenic cirrhosis (2), alcoholic cirrhosis (0), Wilson cirrhosis (0). ‐ Control group (n = 15) Mean age (years +/‐ SD): 47.4 +/‐ 7.4; Ratio of sex (male/female): 12/3. Origins of liver diseases: hepatitis C cirrhosis (7), hepatitis B cirrhosis (2), hepatitis B and C cirrhosis (2), cryptogenic cirrhosis (2), alcoholic cirrhosis (1), Wilson cirrhosis (1).
Interventions	TUDCA group: ‐ Dose: 500 mg/day in two divided doses. ‐ Route: orally. ‐ Duration: the treatment was started on day 5 after transplantation and continued for one year. Control group: ‐ no treatment. Co‐interventions: all patients received standard triple‐drug regimens (steroids, azathioprine, and cyclosporine or tacrolimus).
Outcomes	All cause mortality. Number of patients with rejection after liver transplantation.
Notes	Letter was sent to the authors in September 2009. A reply with additional information was received shortly after.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	Computer generated table.
Allocation concealment?	Unclear risk	No information provided.
Blinding?	High risk	Not performed.
Incomplete outcome data addressed? All outcomes	Low risk	Withdrawal: two patients from the TUDCA group and two patients from the placebo group. Three of them died due to transplant non‐function in the first postoperative week and one patient was regrafted due to thrombosis of hepatic artery.
Free of selective reporting?	Unclear risk	Post‐transplant cholestasis and liver biochemistry specified as outcomes. Difference reported as not significant, but no actual data given.
Sample size calculation	High risk	Not reported.
Intention‐to‐treat analysis	High risk	Not stated and not used.
Baseline imbalance	Unclear risk	Not enough information provided.
Early stopping of trial	Unclear risk	Not enough information provided.

Barnes 1997.

Methods	Study design: randomised, placebo‐controlled, double‐blind trial.
Participants	Country: United States. Publication language: English. Inclusion criteria ‐ patients aged 18 years or older who underwent liver transplantation at the Cleveland Clinic Foundation from April 1992 through June of 1994. Exclusion criteria ‐ patients who were found to have cancer at surgically resected margins of the biliary tree. ‐ patents who underwent retransplantation. Participants ‐ UDCA group (n = 28) Mean age (years +/‐ SD): 50.5 +/‐ 11.6; Ratio of sex (male/female): 18/10. Child class: A 7, B 13, and C 8. Origins of liver diseases: Laennec's cirrhosis 4, PBC 3, cryptogenic cirrhosis 6, hepatitis C/cirrhosis 4, hepatitis B/cirrhosis 3, autoimmune hepatitis with cirrhosis 3, PSC 2, other 3. ‐ Placebo group (n = 24) Mean age (years +/‐ SD): 50.7 +/‐ 9.3. Ratio of sex (male/female): 15/9. Child class: A 6, B 14, and C 4. Origins of liver diseases: Laennec's cirrhosis 9, PBC 5, cryptogenic cirrhosis 1, hepatitis C/cirrhosis 1, hepatitis B/cirrhosis 1, autoimmune hepatitis with cirrhosis 1, PSC 2, other 4.
Interventions	UDCA group: ‐ Dose: 10‐15 mg/kg body weight/day in divided doses. ‐ Route: orally. ‐ Duration: immediately after intestinal transit recovery, usually between postoperative days three and five, and continue for three months. Placebo group: ‐ identical‐appearing capsules administered in the same quantity and manner. Co‐interventions: all patients received standard triple‐drug regimens (steroids, azathioprine, and cyclosporine or tacrolimus).
Outcomes	All cause mortality. Number of patients with acute cellular rejection. Number of patients with chronic rejection. Number of patients with steroid‐resistant rejection. Number of days of hospitalisation. Adverse events.
Notes	Letter was sent to the authors in September 2009. A reply with additional information was received shortly after.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	Computer generated table.
Allocation concealment?	Unclear risk	No information provided.
Blinding?	Low risk	Quote: "...randomised to receive either UDCA or an identical placebo capsule..."
Incomplete outcome data addressed? All outcomes	Low risk	Mean follow‐up time: 18 months. Ten patients withdrawn from study, 6 in UDCA group and 4 in placebo group. Reasons for withdrawal were reported. Four patients died in the placebo group.
Free of selective reporting?	Low risk	All expected outcomes reported.
Sample size calculation	Unclear risk	The trial reported the method of sample size calculation, but the actual number of patients needed was not reported.
Intention‐to‐treat analysis	Low risk	Stated and used.
Baseline imbalance	Unclear risk	Not enough information provided.
Early stopping of trial	Unclear risk	The number of patients needed to gain the actual power was not reported. Whether the trial was terminated early is not clear.

Fleckenstein 1998.

Methods	Study design: prospective, randomised, double‐blind trial.
Participants	Country: United States. Publication language: English. Inclusion criteria ‐ patients who underwent liver transplantation at the Johns Hopkins Hospital. Exclusion criteria ‐ patients who were under 18 years old, undergoing repeat transplantation, had primary graft nonfunction, or refused consent. Participants ‐ UDCA group (n = 14) Mean age (years +/‐ SD): 44.3 +/‐ 12.7; Ratio of sex (male/female): 6/8. Origins of liver diseases: hepatitis C 6, alcohol 2, autoimmune 1, PBC 2, PSC 1, autoimmune cholangiopathy 1, hepatitis B 1. ‐ Placebo group (n = 16) Mean age (years +/‐ SD): 49.6 +/‐ 10.9. Ratio of sex (male/female): 12/4. Origins of liver diseases: hepatitis C 3, alcohol 3, autoimmune 3, PBC 1, PSC 2, cryptogenic 2, hepatitis B 1, alpha1‐antitrypsin deficiency 1.
Interventions	UDCA group: ‐ Dose: 15 mg/kg body weight/day in divided doses. ‐ Route: orally. ‐ Duration: immediately after intestinal transit recovery, usually between postoperative days three and five, and continue for three months. Placebo group: ‐ Identical‐appearing capsules administered in the same quantity and manner. Co‐interventions: all patients received standard triple‐drug regimens (steroids, azathioprine, and cyclosporine or tacrolimus).
Outcomes	All cause mortality. Number with retransplantation. Number of patients with acute cellular rejection. Number of patients with chronic rejection. Serum bilirubin levels at the end of treatment.
Notes	Follow‐up time: nine months. Letter was sent to the authors in September 2009. No reply was received.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	No information provided.
Allocation concealment?	Unclear risk	No information provided.
Blinding?	Low risk	Method of blinding not described, but probably adequate.
Incomplete outcome data addressed? All outcomes	Low risk	Withdrawal: one patient from the UDCA group and two patients from the placebo group because of capsule size.
Free of selective reporting?	Unclear risk	Outcomes were not completely described.
Sample size calculation	High risk	Not reported.
Intention‐to‐treat analysis	Low risk	Quote: "Three patients withdrew after inclusion...They were included in the statistical analysis."
Baseline imbalance	Unclear risk	Not enough information provided.
Early stopping of trial	Unclear risk	Not enough information provided.

Keiding 1997.

Methods	Study design: prospective, randomised, placebo‐controlled multicenter study.
Participants	Country: Denmark, Finland, Norway, and Sweden. Publication language: English. Inclusion criteria ‐ patients who underwent liver transplantation in Denmark, Finland, Norway, and Sweden from September 1, 1992 to May 31, 1994. Exclusion criteria ‐ patients with malignant diseases. Participants The age of the children ranged from 0 to 13 years (median 1.5), and the age of adults ranged from 14 to 59 years old (median 44). Male/Female ratio was 9/6 for children and 43/44 for adults. ‐ UDCA group (n = 54) Origins of liver diseases: paracetamol intoxication 1, hepatitis B 1, autoimmune hepatitis 0, biliary atresia 2, metabolic diseases 7, neonatal hepatitis 2, PBC 13, post hepatitis cirrhosis 8, PSC 3, cryptogenic cirrhosis 7, alcoholic cirrhosis 2, other reasons 8. ‐ Placebo group (n = 48) Origins of liver diseases: paracetamol intoxication 1, hepatitis B 0, autoimmune hepatitis 1, biliary atresia 3, metabolic diseases 11, neonatal hepatitis 0, PBC 7, post hepatitis cirrhosis 5, PSC 7, cryptogenic cirrhosis 2, alcoholic cirrhosis 6, other reasons 5.
Interventions	UDCA group: ‐ Dose: 15 mg/kg body weight/day in two or three divided doses. ‐ Route: orally. ‐ Duration: immediately after intestinal transit recovery, usually between postoperative days three and five, and continue for three months. Placebo group: ‐ Identical‐appearing capsules administered in the same quantity and manner. Co‐interventions: all patients received standard triple‐drug regimens (steroids, azathioprine, and cyclosporine or tacrolimus).
Outcomes	All cause mortality. Number of deaths related to rejection. Number of patients with acute cellular rejection. Number of patients with chronic rejection. Number of patients with steroid‐resistant rejection. Adverse events.
Notes	Letter was sent to the authors in September 2009. No reply was received.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	Patients were randomised at a ratio of 1:1.
Allocation concealment?	Low risk	Quote: " The allocation was performed in blocks of 10 patients, using the sealed serial envelope method..."
Blinding?	Low risk	Quote: "The UDCA and the placebo capsules had identical appearance and taste..."
Incomplete outcome data addressed? All outcomes	Low risk	Follow‐up time: 12 months. Five UDCA patients and five placebo patients withdrew from study. Reasons were reported.
Free of selective reporting?	Unclear risk	Insufficient information.
Sample size calculation	Low risk	Performed and allowed for a difference in the incidence of at least one episode of acute rejection of 50% between the treatment and placebo groups with 90% statistical power and a significance level of P value less than 0.05. The calculated sample size was 80 patients.
Intention‐to‐treat analysis	Low risk	Stated and used.
Baseline imbalance	Low risk	The study seems to be free of baseline imbalance.
Early stopping of trial	Low risk	Study attained the pre‐specified sample size.

Koneru 1993.

Methods	Study design: randomised controlled trial.
Participants	Country: United States. Publication language: English. Inclusion criteria ‐ patients who underwent liver transplantation. Exclusion criteria ‐ not mentioned. Participants ‐ UDCA group (n = 16) Mean age (years +/‐ SD): no information. Ratio of sex (male/female): no information. Origins of liver diseases: no information. ‐ Control group (n = 16) Mean age (years +/‐ SD): no information; Ratio of sex (male/female): no information. Origins of liver diseases: no information.
Interventions	UDCA group: ‐ Dose: 900 mg/day. ‐ Route: orally. ‐ Duration: immediately after intestinal transit recovery, usually between postoperative days three and five, and continue for three months. Control group: ‐ no treatment. Co‐interventions: all patients received standard triple‐drug regimens (steroids, azathioprine, and cyclosporine).
Outcomes	Number of patients with retransplantation due to rejection. Number of patients with rejection episodes.
Notes	Abstract. Letter was sent to the authors in September 2009. No reply was received.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	No information provided.
Allocation concealment?	Unclear risk	No information provided.
Blinding?	High risk	Not performed.
Incomplete outcome data addressed? All outcomes	Unclear risk	The study gives the impression that there were no withdrawals, but this was not explicitly stated.
Free of selective reporting?	Unclear risk	Insufficient information provided.
Sample size calculation	High risk	Not performed.
Intention‐to‐treat analysis	Unclear risk	No information provided.
Baseline imbalance	Unclear risk	Not enough information provided.
Early stopping of trial	Unclear risk	Not enough information provided.

Pageaux 1995.

Methods	Study design: double‐blind randomised study.
Participants	Country: France. Publication language: English. Inclusion criteria ‐ patients who underwent liver transplantation. Exclusion criteria ‐ not mentioned. Participants ‐ UDCA group (n=26) Mean age (years +/‐ SD): 47 +/‐ 10; Ratio of sex (male/female): 17/9. Origins of liver diseases: alcoholic cirrhosis 14, post‐hepatic B cirrhosis 2, post‐hepatitis C cirrhosis 4, PBC 2, liver cancer 2, fulminant hepatitis 1, miscellaneous 1. ‐ Placebo group (n = 24) Mean age (years +/‐ SD): 51+/‐ 9. Ratio of sex (male/female): 15/9. Origins of liver diseases: alcoholic cirrhosis 10, post‐hepatic B cirrhosis 0, post‐hepatic C cirrhosis 6, PBC 3, liver cancer 4, fulminant hepatitis 0, miscellaneous 1.
Interventions	UDCA group: ‐ Dose: 600 mg/day in three divided doses. ‐ Route: orally. ‐ Duration: immediately after intestinal transit recovery, usually between postoperative days three and five, and continue for two months. Placebo group: ‐ identical‐appearing capsules administered in the same quantity and manner. Co‐interventions: all patients received standard triple‐drug regimens (steroids, azathioprine, and cyclosporine or tacrolimus).
Outcomes	Number of patients with acute cellular rejection. Number of patients with steroid‐resistant rejection.
Notes	Letter was sent to the authors in September 2009. No reply was received.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	No information provided.
Allocation concealment?	Unclear risk	No information provided.
Blinding?	Unclear risk	Method of blinding not described.
Incomplete outcome data addressed? All outcomes	Low risk	Five patients died from non‐immunological causes before the end of the first month, and were excluded from the study. Reasons were reported.
Free of selective reporting?	Unclear risk	Not enough information provided.
Sample size calculation	High risk	Not performed.
Intention‐to‐treat analysis	High risk	Not stated and not used.
Baseline imbalance	Unclear risk	Not enough information provided.
Early stopping of trial	Unclear risk	Not enough information provided.

Sama 1991.

Methods	Study design: randomised controlled trial.
Participants	Country: Italy. Publication language: English. Inclusion criteria ‐ patients who underwent liver transplantation. Exclusion criteria ‐ not mentioned. Participants ‐ UDCA group (n = 20) Mean age (years +/‐ SD): no information. Ratio of sex (male/female): no information. Origins of liver diseases: no information. ‐ Control group (n = 20) Mean age (years +/‐ SD): no information; Ratio of sex (male/female): no information. Origins of liver diseases: no information.
Interventions	UDCA group: ‐ Dose: 600 mg/day in two divided doses. ‐ Route: orally. ‐ Duration: immediately after intestinal transit recovery, usually between postoperative day five and day seven, and continue for six months. Control group: ‐ no treatment. Co‐interventions: all patients received standard immunosuppressive treatment (steroids and cyclosporine).
Outcomes	All cause mortality. Number of patients with acute cellular rejection.
Notes	Abstract. Letter was sent to the authors in September 2009. No reply was received.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	A randomisation list was performed before patients were admitted to the trial (information from principal author).
Allocation concealment?	Unclear risk	No information provided.
Blinding?	Unclear risk	The principle author provided information that the study was made according to a single‐blind randomised protocol. The primary outcome was the occurrence of biopsy proven rejection episodes. The pathologists were blind, but the patients were not.
Incomplete outcome data addressed? All outcomes	Unclear risk	Five patients from the UDCA group and six patients from the placebo group were excluded. Reasons for exclusion were not fully stated.
Free of selective reporting?	High risk	Data about survival of patients were not adequately reported.
Sample size calculation	High risk	Not performed.
Intention‐to‐treat analysis	High risk	Not stated and not used.
Baseline imbalance	Unclear risk	Basic characteristics of patients not reported.
Early stopping of trial	Unclear risk	Not enough information provided.

UDCA = ursodeoxycholic acid. 
 TUDCA = tauroursodeoxycholic acid. 
 PBC = primary biliary cirrhosis. 
 PSC = primary sclerosing cholangitis. 
 OKT3 = anti‐CD3 monoclonal antibody.

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Assy 2007	A randomised controlled trial that included only recipients of liver transplantation with stable graft function and no episodes of rejection for at least 2 years, that were then offered total immunosuppression withdrawal. Fourteen patients received UDCA (15 mg/kg body weight/day) and 12 received placebo. Rejection occurred in 43% and 75% of patients, respectively (no significant difference). None developed chronic rejection. After follow‐up two patients were free of immunosuppression, 80% were steroid free, and 50% were able to reduce their dose of cyclosporine.
Clavien 1996	Case series. Fifty consecutive liver‐transplanted patients were treated with a standard cyclosporine immunosuppressive regimen. Twenty three of the 43 survivors developed an episode of rejection, and UDCA (10 mg/kg weight/day) was initiated. Only one patient had a second episode of rejection.
Friman 1992	Observational study. Thirty‐three liver‐transplanted patients received 10 mg UDCA/kg body weight/day for median of 10 months (range four to 21 months). Eight historical liver‐transplanted patients served as control group. The rejection incidence was significantly lower in the patients who received the treatment with UDCA. Biochemistry one month after transplantation demonstrated significantly lower average values of aminotransferases and alkaline phosphatases in patients treated with UDCA than in the control group.
Heathcote 1999	Observational study. From 1987 to 1996, 37 UDCA treated and 53 placebo treated patients with primary biliary cirrhosis were referred for transplantation. Posttransplantation survival rates at one month were 93.9% in the UDCA group and 88.4% in the placebo group, and one year survival rates were 90.3% and 78.4%, respectively (no significant differences). However, rejection (type not defined ‐ a secondary outcome measure) occurred significantly less often in the UDCA group (42.9%) than in placebo group (68.8%).
Henriksson 1991	Observational study. All patients in this study were given sequential quadruple immunosuppression with antilymphocyte globulin, azathioprine, steroids, and cyclosporine. All patients with primary graft function (n = 11) were treated with 10 mg UDCA/kg body weight/day, starting during the first postoperative week. Patients who received liver transplantation in the first 6 months of 1989 (n = 8) served as controls. In the control group, one patient died after 9 months with chronic graft dysfunction, and six patients had rejection episodes during the first postoperative month. All patients in the UDCA group were alive without rejection episodes.
Persson 1990	Observational study. All 11 adult patients transplanted between August, 1989 and January 1990 with primary graft function, were treated with 10 mg UDCA /kg body weight/day. Eight patients transplanted during the first half of 1989 served as control. UDCA was started during the first postoperative week and the treatment was continued for six months. All patients in the UDCA treated group survived with satisfactory graft function. In the control group six patients had at least one rejection episode needing treatment during the first postoperative month.
Rafael 1995	Observational study. Seventeen patients who underwent liver transplantation between February 1990 and April 1993 and developed biliary complications after transplantation were retrospectively analysed regarding treatment with UDCA. UDCA was given in a dose of 500 to 1000 mg/day. Ten patients were treated for at least one year while seven patients were treated for 14 to 250 days. UDCA significantly improved gammaglutamyl transpeptidase in liver graft recipients with biliary complications. There was also a trend towards improvement in serum bilirubin and alanine transaminase values.
Sama 1998	Observational study. Thirty‐four patients who underwent liver transplantation between January 1995 and June 1996 were included in the study. Seventeen were treated with UDCA 10 mg/kg body weight/day during 6 months, while 17 served as controls on the basis of having undergone liver transplantation closest to UDCA patients. A significant decrease in serum bilirubin levels was observed in UDCA patients. There was a significantly higher incidence of recurrent hepatitis in the control group.

UDCA: ursodeoxycholic acid.

Differences between protocol and review

We assessed the risk of bias in the included studies for another four domains that were added to the review protocol (incomplete outcome data, selective outcome reporting, baseline imbalance, and early stopping of trial). In general, the text of the risk of bias domains were updated following Higgins 2008. Trials were considered at low risk of bias when judged as adequate in all domains.

Quasi‐randomised studies, observational and case‐control studies were included for the report of adverse events.

We performed trial sequential analysis for outcomes demonstrating a statistically significant result.

Contributions of authors

GP and VG independently performed searches of relevant databases, GP validated the search, selected trials for inclusion, contacted the authors of the trials, performed data extraction and data analysis, and drafted the systematic review. VG revised the review update. CG and DS revised the review update, solved discrepancies of data extraction, validated data analyses, and provided consultation.

Sources of support

Internal sources

• Copenhagen Trial Unit, Denmark.

External sources

• Danish Medical Research Council's Grant on Getting Research into Practice (GRIP), Denmark.

Declarations of interest

None known.

New search for studies and content updated (no change to conclusions)