Predictors of biliary atresia outcome: Saudi National Study (2000 – 2018)

Abstract

Background:

Outcomes in biliary atresia (BA) have been well-documented in large national cohorts from Europe, North America, and East Asia. Understanding the challenges that preclude success of the Kasai portoenterostomy (KPE) is the key to improve the overall outcomes of BA and implementing intervention strategies. Here, we analyzed the data from the Saudi national BA study (204 BA cases diagnosed between 2000 and 2018) to identify the prognostic factors of BA outcomes.

Methods:

One hundred and forty-three cases underwent KPE. Several prognostic factors (center case load, congenital anomalies, serum gamma-glutamyl transferase, use of steroids, ascending cholangitis post-operatively, and degree of portal fibrosis at time of KPE) were investigated and correlated with the primary outcomes of interest: 1) success of KPE (clearance of jaundice and total serum bilirubin <20 mmol/l after KPE), 2) survival with native liver (SNL), and 3) overall survival.

Results:

Use of steroids after KPE was associated with clearance of jaundice, 68% vs. 36.8% in the BA cases that did not receive steroids (P = 0.013; odds ratio 2.5) and a significantly better SNL rate at 2 - and 10-year of 62.22% and 57.77% vs. 39.47% and 31.57%, respectively (P = 0.01). A better 10-year SNL was observed in centers with caseload <1/year (group 1) as compared to centers that performed ≥1/year (group 2) [45.34% vs. 26.66%, respectively; P = 0.047]. On comparison of the 2 groups, cases in group 1 had KPE at significantly earlier age (median 59.5 vs. 75 days, P = 0.006) and received steroids after KPE more frequently than group 2 (69% vs. 31%, P < 0.001). None of the remaining prognostic variables were identified as being significantly related to BA outcome.

Conclusion:

Steroids use post-KPE predicted clearance of jaundice and better short- and long-term SNL. There is a need to establish a national BA registry in Saudi Arabia aiming to standardize the pre- and post-operative clinical practices and facilitate clinical and basic research to evaluate factors that influence BA outcome.

INTRODUCTION

Early and accurate prediction of poor outcome after Kasai portoenterostomy (KPE) for biliary atresia (BA) helps clinicians in counseling the parents for the prognosis and early consideration of liver transplantation (LT). Outcomes in BA have been well-documented in large national cohorts from Europe,[1-6] North America,[7,8] and East Asia.[9-11] These studies identified several factors that determine the success or failure of KPE, including “modifiable” factors such as age at KPE, center case load and surgeon’s experience, and post-operative cholangitis, and “non-modifiable” factors: such as the presence of BA splenic malformation (BASM), anatomic type of BA, and prematurity.

While BA in Saudi Arabia is relatively rare, as reported recently in a national study[12] (occurring in 1 in 44,000 live births), it is a major indication of LT.[13,14] Although the overall survival of BA patients in Saudi Arabia (10-year survival rate of 72.5%)[12] has benefited from the successful results of LT (post-LT survival rate of 90%),[13,14] the success of KPE (45% clearance of jaundice) and the 2 - and 5-year SNL (35% and 27%, respectively)[12] were lower than reported by other national registries.[1-11] Extending the survival with native liver (SNL) and avoiding or postponing LT has a clear advantage in relieving the pressure on a limited pool of donor organs, and surviving more years free of immunosuppression-related morbidities, and allowing patients to complete vaccinations and acquire immunity to the common community infections. Hence, improving the results of the KPE in Saudi Arabia should be a healthcare priority. Understanding the challenges that preclude success of the KPE is the key to improve the overall outcomes of BA and planning and implementing intervention strategies. Here, we analyzed the data from the Saudi national BA study (2000 to 2018) to identify the prognostic factors of BA in Saudi Arabia.

METHODS

Study setting and design

This is a retrospective, multicenter, and nationwide study that included 10 tertiary care governmental hospitals (including 4 LT centers) in different regions across Saudi Arabia. Saudi Arabia consists of 13 provinces; the 10 hospitals are located in the 3 most populated provinces: Central (5 hospitals), Eastern (3 hospitals), and Western (2 hospitals) that receive referral of complicated cases from the remaining 10 provinces.

Study population

The details of the study population, inclusion and exclusion criteria, and overall outcomes were published elsewhere.[12] In brief, 204 infants were diagnosed with BA between 2000 and 2018 (age at referral: Median 65 days, range 7 – 245 days; 106 females). One hundred forty-six (71.5%) underwent KPE at a median age of 70 days (range, 12-186 days). Successful KPE was achieved in 66 of the 146 cases (45%). Three of the 146 KPE procedures were performed outside Saudi Arabia and excluded from the analysis. Of the remaining 58 patients, seven patients (3.5%) presented late with advanced liver disease and died on the waiting list for LT while 51 underwent primary LT.

Of all the 204 patients with BA, SNL was 35%, 27%, and 25.5% at 2, 5, and 10 years, respectively. At the end of the study period, 148 of the 204 patients (72.5%) were alive [52 cases (25.5%) with native liver and 96 (47%) post-LT]. The average age of the study patients at last follow-up was 7.2 years ± 6 years.

Data collection

Data were collected using a standardized data collection form and entered into an electronic database. The following data were collected retrospectively: date of birth, gender, birth weight, gestational age, KPE case load per center, associated congenital anomalies, liver transaminases, total serum bilirubin, gamma-glutamyl transferase (GGT), use of steroids, occurrence of ascending cholangitis post-operatively, and degree of portal fibrosis at time of KPE. Not all requested data were available for every participant. For each variable, the number of subjects (“N”) from whom data were available is indicated.

Study outcomes

The primary outcomes of interest were: 1) success of KPE (defined as clearance of jaundice and total serum bilirubin <20 mmol/l any time after KPE), 2) SNL [ending at death, LT, or last follow-up], and 3) overall survival (ending at death or last follow-up with or without LT). All the patients had a minimum of 24 months’ follow-up.

Ethical considerations

The study was approved by the local institutional review board log number 16-001 at King Fahad Medical City, and the ethics committees in all hospitals.

Statistical analysis

All categorical variables are presented as numbers and percentages. Quantitative variables with normal distribution are expressed as mean and standard deviation (SD), quantitative variables with non-normal distribution are expressed as median and inter quartile range (IQR), and absolute number and percentage are used for categorical variables. Non-parametric tests were used when data was skewed. Kolmogrov-Smirnov test was used to check the assumption of normal distribution. Chi-square/Fisher’s exact test was applied to determine the association between categorical variables. Patients who underwent KPE were divided into 2 groups for analysis: Group 1, patients who had successful surgery and group 2 who had failed surgery. We used the chi-square test to assess the difference in clearance of jaundice among the 2 groups related to several prognostic factors such as center case load, presence or absence of other associated anomalies, GGT, use of steroids, occurrence of ascending cholangitis post-operatively, and degree of portal fibrosis at time of KPE. Survival curves for the native liver survival of the BA patients who underwent KPE and overall survival of the total 204 BA patients were calculated according to the Kaplan-Meier method and differences in survival rates were compared with a Cox proportional hazards model and log-rank test to determine the predictive value of each prognostic factor. All data were entered and analyzed through statistical package SPSS 25 (SPSS Inc., Chicago, IL, USA) and MEDCALC version 18.11.6 (Acacialaan 22 8400, Ostend, Belgium).

RESULTS

General features of the prognostic factors

1. Gestational age: Premature babies (gestational age <37 weeks) constituted 17% of the BA cases that underwent KPE. The remaining 83% were term babies.

2. Congenital anomalies: Out of the total study population (n = 204), 68 cases were associated with congenital anomalies (33%); 22 were BASM (10.8%), 9 of the 22 were isolated. The congenital anomalies associated with the remaining 46 cases included: heart disease (n = 32), renal (n = 12), situs inversus (n = 9), vascular (n = 8), gastrointestinal (n = 6), central nervous system (n = 4), and skeletal (n = 4). Among the 143 BA patients who underwent KPE, the data on congenital anomalies were available in 141 cases; 43 of the 141 had associated congenital anomalies (30.5%): 6 patients with isolated BASM (4.3%), 10 patients with BASM, and other congenital anomalies (7.1%), and 27 with congenital anomalies without BASM (19.1%).

3. Normal GGT level BA constituted 15% of BA cases that underwent KPE. The age-specific normal GGT reference range were as follows: <1 month old, GGT <200 IUL; 1-2 month old, GGT <150 IU/L; 2-3 month old, GGT <100 IU/L; >6 months, GGT <60 IU/L.[15,16]

4. Post-operative use of steroids: After KPE, steroid was used in only 45 patients of the 121 BA cases in whom these data were available (37%); they received intravenous methylprednisolone and/or oral prednisone in different protocols for variable duration and different regimens; median duration was 30 days (range 7 to 90 days) post-KPE.

5. Ascending cholangitis: After KPE, cholangitis either “suspected” (typically associated with rising liver transaminases and bilirubin and fever sufficient to require intravenous antibiotics) or “proven” (positive blood cultures) occurred in 50 of the 104 BA cases in whom these data were available (48%): 25 patients (50%) had a single episode, and remaining 50% had more than one episode. All the 143 cases that underwent KPE received IV antibiotics and 100 cases (68.5%) were prescribed prophylaxis antibiotics (mostly Bactrim) on discharge for variable duration (range between 3-12 months)

6. Kasai surgery case load: The 143 KPE procedures were performed in all the 10 participating centers: 3 centers with average caseloads of 1/year (total of 60 cases) and 7 centers with caseloads of <1/year (total of 83 cases). To maximize the chances of detecting a statistical difference in outcome relative to the caseload, the participating centers were divided into: a) group 1, centers that performed <1 KPE per year and b) group 2, centers that performed ≥1 KPE per year.

7. Degree of portal fibrosis at time of Kasai surgery: Among the 143 BA patients, the liver histology was available in 79 cases (55%). Portal fibrosis stage 3-4 (advanced fibrosis with septae formation) was reported in 57 cases and stage 1-2 (mild fibrosis without septae formation) in 22 cases.

Predictors of jaundice clearance after Kasai surgery

Use of steroids after KPE was associated with clearance of jaundice (68% vs. 36.8% in the BA cases that did not receive steroids, P = 0.013; odds ratio 2.571 [CI: 1.206 – 5.481]) [Table 1]. Ascending cholangitis developed in 18 of 45 patients in the steroid group (40%) as compared to 31% in the non-steroid group, but the difference did not reach statistical significance (P = 0.09). There was a trend (not statistically significant) suggesting that BA cases associated with anomalies had less favorable outcome compared to those without anomalies (32.5% success of KPE vs. 50%, P = 0.055). None of the remaining prognostic variables were identified as being significantly related to outcome [Table 1].

Table 1.

Prognostic factors of clearance of jaundice after Kasai surgery

Prognostic factor	Age at KPE Median (IQR)	P	Clearance of jaundice (%)	OR [95% C.I]	P
Gestational age
Term (n=95)	60 (75-26)	0.118	42/95 (44.21%)	1.735 [0.640-4.700]	0.275
Preterm (n=19)	70 (85-35)		11/19 (57.89%)
Congenital anomaly (n=141 patients)
No (n=98)	60 (75-27.5)	0.021	49/98 (50%)	0.482 [0.227-1.022]	0.055
Yes (n=43)	71 (86-31)		14/43 (32.55%)
Gamma-glutamyl transferase* (n=134 patients)
High (n=114)	65 (79-28)	0.018	49/114 (42.98%)	0.921 [0.354-2.396]	0.867
Normal/Low (n=20)	50 (76.5-34.5)		9/20 (45%)
Use of steroids (n=121 patients)
No (n=76)	60 (75-28)	0.989	28/76 (36.84%)	2.571 [1.206-5.481]	0.013
Yes (n=45)	60 (70-26)		27/45 (60%)
Post-Kasai cholangitis (n=104 patients)
No (n=54)	59.5 (62.5-13)	0.335	22/54 (40.74%)	1.851 [0.849-4.033]	0.120
Yes (n=50)	65 (84.75-36)		28/50 (56%)
Kasai surgery load
Caseload 1/year (n=60)	75 (86.5-26.5)	0.006	21/60 (35%)	0.525 [0.265-1.040]	0.097
Caseload<1/year (n=83)	59.5 (71.5-23.7)		42/83 (50.60%)
Histopathology of the liver biopsy (n=79 patients)
Stage 1-2 fibrosis (n=22)	56 (75.7-30)	0.503	10/22 (45.45%)	1.158 [0.431-3.108]	0.770
Stage 3-4 fibrosis (n=57)	60 (74-26)		28/57 (49.12%)

*Normal values of GGT were as follows: < 1 month old, GGT < 200 IUL; 12-month-old, GGT < 150 IU/L; 2-3 month old, GGT < 100 IU/L; > 6 months, GGT < 60 IU/L (15,16). Not all requested data were available for every participant. For each variable, the number of subjects (‘N’) from whom data were available is indicated

Prognostic factors of survival with native liver after Kasai operation

Two of the 7 prognostic variables had significant impact on the SNL. Use of steroids post-operatively had a significant positive effect on the SNL rate (2-year and 10-year SNL of 62.22% and 57.77% vs. 39.47% and 31.57%, respectively; P = 0.01) [Figure 1]. A better 10-year SNL after KPE was observed in centers with caseload <1/year (group 1) as compared to centers that performed ≥1/year (group 2) [10-year SNL of 45.34% vs. 26.66%, respectively; P = 0.047] [Figure 2]. When a sub-analysis and comparison of the two groups was performed, age at KPE was significantly earlier in group 1 (59.4 days [IQR 23.7 – 71.5] vs. 75 days [26.5 – 86.5]; P = 0.006) [Table 1], and use of steroids after KPE, prematurity, and grade 3-4 portal fibrosis occurred more significantly in group 1 than in group 2 [Table 2]. No differences were noted between the two groups with respect to frequency of congenital anomalies, GGT level, and frequency of ascending cholangitis. Within all the centers, several different surgeons performed the KPE.

Figure 1.

Kaplan-Meier Transplant-free survival analysis of biliary atresia cases stratified according to the use of steroids post-Kasai surgery

Figure 2.

Kaplan-Meier analysis of transplant-free survival of biliary atresia cases stratified according to the center caseload

Table 2.

Comparison of the centers that performed <1 Kasai surgery/year (Group 1) versus centers that performed ≥1 Kasai surgery/year

Prognostic factor	Group 1 (n=83)	Group 2 (n=60)	P
Gestational age (data available in 114 patients)
Preterm (n=18)	13/18 (72.22%)	5/18 (27.77%)	0.005
Congenital anomaly (n=141 patients)
Yes (n=43)	18/43 (41.86%)	25/43 (58.139%)	0.131
Gamma-glutamyl transferase (n=134 patients)
Normal/Low (n=20)	11/20 (55%)	9/20 (45%)	0.527
Use of steroids (n=121 patients)
Yes (n=45)	31/45 (68.88%)	14/45 (31.11%)	<0.001
Post-Kasai cholangitis (n=104 patients)
Yes (n=49)	28/49 (57.14%)	21/49 (42.85%)	0.157
Histopathology of the liver biopsy (n=79 of Kasai patients)
Stage 1-2 fibrosis=22	12/22 (54.54%)	10/22 (45.45%)	0.546
Stage 3-4 fibrosis (++ septae) =55	35/55 (63.63%)	20/55 (36.36%)	0.004

Not all requested data were available for every participant. For each variable, the number of subjects (“N”) from whom data were available is indicated

As regards to the association with congenital anomalies and the outcome, the Kaplan-Meier curves for this variable demonstrated that BA cases associated with anomalies had less favorable SNL, although the difference was not statistically significant (2-year and 10-year SNL of 37.20% and 27.90% vs. 52% and 41%, respectively; P = 0.066) [Figure 3]. No significant impact on SNL was noted with respect to gestational age, GGT, ascending cholangitis or degree of portal fibrosis [Figure 4(a-d)].

Figure 3.

Kaplan-Meier analysis of biliary atresia cases stratified according to association with congenital anomaly

Figure 4.

(a-d) Kaplan-Meier analysis of transplant-free survival of biliary atresia cases stratified according to a) gestational age, b) GGT, c) ascending cholangitis, and d) degree of portal fibrosis

Prognostic factors of overall survival

Patients with BA and congenital anomalies had a significantly worse 5 - and 10-year overall survival (5 - and 10-year overall survival of 77% vs. 65% and 63%, respectively; P = 0.022) [Figure 5a]. There was a trend (not statistically significant) suggesting that prematurity had less favorable outcome compared with term babies (5 - and 10-year overall survival of 57.5% vs. 76%, respectively; P = 0.06) [Figure 5b]. No significant impact on overall survival was demonstrated for GGT level [Figure 5c].

Figure 5.

(a-c) Kaplan-Meier overall survival analysis of biliary atresia cases stratified according to a) presence or absence of congenital anomaly, b) gestational age, and c) GGT level

DISCUSSION

This is the first national BA study outside North America, Europe, and Far East Asia to provide insight into the predictors of outcome of BA and highlights a number of important observations. First, steroids use post-KPE predicted clearance of jaundice and better short- and long-term SNL. Second, the results of our study provide further evidence that BA cases associated with anomalies had less favorable outcome compared with BA without anomalies, particularly for the overall survival. Third, in contrast to previous studies, the lower BA caseload centers (<1 KPE per year) had more favorable rate of SNL than the centers with higher caseload (≥1 KPE per year). On comparison of the two groups of centers, cases in the first group had KPE at significantly earlier age and received steroids more frequently than the second group.

Our study is a timely effort to identify the factors that are associated with worse or favorable prognosis of BA in Saudi Arabia. In addition to the late referral to pediatric gastroenterologist (median 65 days) and late time at KPE (median 70 days) that we observed in our recent report,[12] our data here identified the use of steroids as “another modifiable factor” being associated with favorable outcome. It is believed that relief of bile duct obstruction by KPE is only one step towards a successful outcome and that pathogenesis of BA involves a persistent inflammatory process mediated by autoimmunity[17-19] which, if untreated, could proceed to progressive fibrosis and cirrhosis, despite initial success of the surgery. This has prompted investigators to study several drugs that have been or are being investigated in clinical trials.[19] One of these drugs are steroids which had no benefit in two double-blind, placebo-controlled randomized trials from United Kingdom and United States.[20,21] However, small observational studies showed that clearance of jaundice may be improved in some patients.[22,23] In Japan, where corticosteroids after KPE are used in most hospitals, the SNL of 3160 BA patients was 60%.[10] In our cohort, the BA cases that received steroids post-KPE were 2.5 times more likely to achieve jaundice clearance and had a significantly higher 2-year and 10-year SNL than those who did not. This variation in the effect of steroids on BA outcomes in different populations might suggest that different pathogenic mechanisms are involved in the development of BA in different ethnicities. Prospective multicenter trials are needed to better understand the specific effects of steroids post-KPE on improving BA outcomes in Saudi Arabia.

There is general consensus that BA patients with congenital anomalies are more likely to have poor outcome than patients with isolated BA;[8,24-26] however, some studies showed conflicting results.[1,2,27] National registries from different countries reported 3% to 20% incidence of congenital anomalies in BA patients.[1,2,10,24-27] In contrast, we report a higher rate of congenital anomalies (33%) that impacted negatively on the BA outcomes. It is suggested that the BA associated with anomalies begins in the first trimester of pregnancy during the same period when many of these anomalies, particularly the laterality defects, develop.[19] Patients with laterality defects (such as situs inversus, polysplenia/asplenia, preduodenal portal vein, and interrupted vena cava) have demonstrated mutations in various genes including ZIC3, CFC1, LEFTYA, ACVR2B, and NODAL[28,29]; mutations in CFC1 and ZIC3 were found in BA patients with major laterality defects and might cause defects in bile duct development in-utero.[30,31] Other clues for a genetic etiology include PKD1L1 variants identified in syndromic forms of BA; PKD1L1 controls cilia development, consistent with the hypothesis that cilia defects impair both bile flow and left-right axis determination.[19,32] These gene mutations could confer genetic susceptibility or act as gene modifier to trigger onset of BA in response to environmental factors (e.g. viral infection, drugs, or toxins). The overall rate of consanguinity in our study cohort is high (55%) as compared to all national registries which might suggest a role of some yet undetermined genetic variants in the higher development of “congenital” or “embryonic” forms of BA in our population. Large-scale genetic screening studies in the Saudi populations are needed to identify gene mutations that could have a role in regulating bile duct development.

Another important determinant of BA outcome is the KPE caseload and experience of the center with better clearance of jaundice, and SNL in centers performing higher numbers of this surgical procedure (>5 KPE/year in United Kingdom or >2 KPE/year in France).[1,2,4] However, studies from Canada and Netherland did not show this positive effect.[33,34] We too failed to demonstrate this positive effect probably because of the low caseload (no centers managed 2 cases annually) and the fact that several surgeons performed the KPE procedures in each center. In contrast to most of the studies, we observed a significantly better 10-year SNL after KPE in centers with lower caseload <1/year (group 1) as compared to centers that performed ≥1/year (group 2) [10-year SNL of 45.34% vs. 26.66%; P = 0.047] and better clearance of jaundice (50% vs. 35%, P = 0.09), although it did not reach a statistical significance. It is possible that the earlier age at KPE and the more significant use of steroids post-KPE (68.9%) in Group 1 centers contributed to the outcome difference.

Based on the 1:44,000 incidence (2.25 in 100,000 live births) and average annual 417,804 live births in Saudi Arabia,[12] we estimate an average 10 new cases each year, as compared to 40 to 45 new cases in the United Kingdom.[1,2] This entails that 2 or 3 centers should be assigned to do KPE in Saudi Arabia which is logistically very challenging in a geographically large country in which different health sectors (i.e. university hospitals, military hospitals, Ministry of Health hospitals) work independently. The healthcare system in Saudi Arabia is designed in a way that tertiary care is highly centralized to 3 main provinces, where the 10 participating centers reside, that receive referrals of complex cases from the remaining 10 provinces. Hence, to assess whether or not further centralization of the BA care to 2 or 3 of the 10 participating centers (and one surgeon does the KPE in every center) would improve BA outcome, large prospective studies are needed.

Development of ascending cholangitis post-KPE is another prognostic factor of BA outcome,[11,35-38] however some studies, including our study, showed conflicting results.[3,8,39] Indeed, our results seem to suggest a higher frequency of cholangitis in the group of BA cases that had clearance of jaundice than the group who did not clear their jaundice (56% vs. 71%, respectively) and better 5- and 10-year SNL of the BA cases that developed ascending cholangitis when compared to BA cases that did not develop ascending cholangitis (46% vs. 34%). Similar observation was reported by another study[8] which is possibly related to the fact that BA cases with better bile drainage post-KPE may be at greater risk for ascending infection. Ascending cholangitis leads to impairment of bile flow and, if repeated episodes occur, can cause progressive fibrosis and poor outcome. Therefore, early diagnosis and effective treatment of every episode is very critical to improve BA outcome.

The effects of other determinants of worse BA outcome cited previously in the literature such as prematurity and advanced portal fibrosis at time of KPE have not been consistent.[40-44] We did not observe significant differences in outcome related to gestational age and degree of fibrosis, probably due to the small number of premature babies and cases with stage 1-2 fibrosis in our study cohort (i.e. type 2 error).

A clear limitation of distinguishing the impact of factors contributing to BA outcomes was the relatively smaller number of BA patients included in this study, as compared to other international multicenter studies. Inherent to the retrospective design, we could not retrieve specific information on the effects of steroids use on delay in immunization and growth.

In conclusion, there is a need to establish a national BA registry in Saudi Arabia aiming to standardize the pre- and post-operative clinical practices, collect large amount of data prospectively, and facilitate clinical and basic research to evaluate factors that influence BA outcome.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.