Transanal irrigation is effective for low anterior resection syndrome: a systematic review and meta-analysis of randomized controlled trials

Abstract

Background

The therapeutic value of transanal irrigation (TAI) for low anterior resection syndrome (LARS) has not been fully confirmed. This study aims to evaluate the efficiency of TAI in improving bowel function and quality of life (QoL) following sphincter-preserving resections (SPRs) for rectal cancer through a systematic review and meta-analysis of randomized controlled trials (RCTs).

Methods

The protocol was registered in PROSPERO (CRD42024598219). PubMed, Embase, Web of Science, Cochrane Library, CNKI, and WanFang databases were systematically searched for RCTs comparing TAI with conservative treatments for LARS published before December 2024. Outcomes included pooled risk ratios (RRs) for dichotomous variables and weighted mean differences (WMDs) for continuous variables, calculated using Review Manager 5.4.1 with 95% confidence intervals (CIs). P < 0.05 was considered statistically significant. The I² test was used to assess heterogeneity.

Results

Among 123 initially identified studies, six RCTs involving 317 patients were included. Meta-analysis demonstrated that the TAI group exhibited significantly lower LARS scores (WMD = −10.35, 95% CI [−15.92, −4.78], P < 0.01). The TAI group demonstrated significantly better outcomes across all five LARS subscales compared to controls, including flatus incontinence (WMD = −0.92; 95% CI [−1.30, −0.54]; P < 0.01), liquid stool incontinence (WMD = −0.83; 95% CI [−1.07, −0.59]), frequency (WMD = −1.33; 95% CI [−1.95, −0.72]; P < 0.01), stool clustering (WMD = –4.89; 95% CI [−5.90, −3.88]), and urgency (WMD = −5.35; 95% CI [−7.12, −3.58]). There was also a significant difference in Wexner score (WMD = −2.78, 95% CI [−4.13, −1.42], P < 0.01). However, no significant differences were observed in SF-36 mental (WMD = 7.27, 95% CI [−1.61,16.15], P = 0.11) or physical component scores (WMD = 6.97, 95% CI [−1.26,15.19], P = 0.10). Heterogeneity was substantial for LARS score analysis (I² = 86%) but resolved in subgroup analyses.

Conclusion

TAI significantly improves bowel function in patients with LARS, as evidenced by reduced LARS and Wexner scores. However, its impact on QoL remains inconclusive. Large-scale RCTs with extended follow-up periods are warranted to validate long-term clinical benefits.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10151-025-03201-8.

Introduction

With advances in both surgical and adjuvant therapies for rectal cancer, sphincter-preserving resection (SPR) with total mesorectal excision has become the preferred procedure in suitable patients without abdominoperineal resection (APR) and permanent colostomy. There has been increasing recognition of low anterior resection syndrome (LARS), which typically includes incontinence to flatus, incontinence to liquid stool, frequency of bowel movements, clustering of stools, and urgency [1]. The estimated prevalence of major LARS was 41%, and various LARSs led to a decrease in quality of life (QoL), often equating to the morbidity of a permanent colostomy [2]. It was reported that patients with major LARS have health-related QoLs as poor as for those following APR [3]. LARS significantly diminishes the advantages of SPR, leading many patients to prefer APR because of the severe impact of LARS.

Transanal irrigation (TAI) is a therapeutic procedure involving the controlled introduction of water into the rectum through the anus to facilitate bowel evacuation, primarily utilized in the management of patients with neurogenic or functional bowel dysfunction [4]. A specialized TAI device, Peristeen® Plus (Coloplast, Humlebaek, Denmark), comprises a rectal catheter equipped with an inflatable balloon, a manual control unit with a pump, leg straps, and a water reservoir bag. Unlike gravity-dependent systems, the constant-flow pump eliminates the need to elevate the bag [5]. It can provide efficient irrigation, performed independently by the patient.

In recent years, the use of TAI has been expanded to other conditions affecting defecation, such as LARS [6]. Through a review of the published literature, we found that most current studies on the role of TAI in LARS are single arm and observational. Due to the lack of control groups, the findings of these studies are not convincing [7, 8]. Although several randomized controlled trials (RCTs) suggest that TAI may be beneficial for LARS, the current evidence remains limited because of the small sample sizes [9, 10]. However, different studies may employ different functional scales to assess patients' bowel function, increasing the heterogeneity among studies. In addition, some studies suggested that TAI can be time-consuming, psychologically distressing, and ineffective for many patients [11–13].

Despite promising observational studies, the evidence supporting TAI’s efficacy remains limited by small sample sizes and methodological heterogeneity in existing RCTs. Furthermore, conflicting reports highlight challenges such as patient non-compliance and variable treatment protocols. This study aims to evaluate the efficiency of TAI for improving bowel function and QoL after SPRs by conducting a systematic review of the literature and meta-analysis of published RCTs. This study was performed according to the Cochrane Collaboration methodology and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [14, 15].

Methods

Protocol and registration

Following the PRISMA guidelines, this systematic review’s protocol was registered in PROSPERO (CRD42024598219) and is available at https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=598219 (Additional file 1). Ethical approval and patient consent were waived as the study relied solely on published data.

Search strategy and study selection

The search strategy, designed with a professional trial search coordinator, utilized MeSH terms and free-text keywords to query PubMed, Embase, Web of Science, Cochrane Library, CNKI, and WanFang databases for studies published before December 2024. Key search terms included "transanal irrigation" and "low anterior resection syndrome," with no language restrictions imposed. References from relevant articles were also examined to ensure comprehensive coverage.

Selection and exclusion criteria

Studies were selected based on the PICO (Patient problem, Intervention, Comparison, and Outcome) framework:

• 1. Population: Rectal cancer patients who underwent SPR.

• 2. Intervention: TAI.

• 3. Comparator: Alternative LARS management strategies, such as dietary modifications, laxatives, enemas, biofeedback, pelvic floor muscle training, and posterior tibial nerve stimulation.

• 4. Outcome: Primary outcomes included postoperative bowel function (e.g., LARS score, Wexner score, fecal incontinence score, St. Mark’s score), while secondary outcomes focused on quality of life (e.g., EORTC QLQ-C30, SF-36, VAS).

Excluded studies included case reports, conference abstracts, animal experiments, reviews, meta-analyses, case-control studies, and original studies with inaccessible data.

Data extraction and quality assessment

Two reviewers independently extracted study details, including author, publication year, country, multi-center status, duration, and patient numbers. Missing mean and SD values were estimated per Cochrane Handbook guidelines [16, 17]. Discrepancies were resolved via discussion or third-party consultation. RCT quality was assessed using the Cochrane risk of bias tool, covering randomization, allocation concealment, blinding, incomplete data, selective reporting, and other biases [18]. The Jadad scale was also used to assess variable methodological quality [19].

Statistical analysis

Continuous outcomes were analyzed as weighted mean differences (WMDs) in Review Manager 5.4.1. Missing means and SDs were estimated using the Hozo method [20]. Effect sizes with 95% CIs were pooled using fixed- or random-effects models [21]. Significance was set at P < 0.05 (two-tailed). Subgroup analyses and sensitivity analysis explored heterogeneity sources, and funnel plots were employed to assess publication bias.

Results

Included studies

The results of the literature search identified 123 studies, of which 42 citations remained after removing duplicates. After screening titles, abstracts, and full texts, six RCTs [10, 22–26] met the inclusion criteria for the meta-analysis (Fig. 1).

Fig. 1.

Flowchart of identification of trials eligible for inclusion in the meta-analysis

The six eligible trials included 317 participants, with 215 males and 102 females. The reported mean or median age ranged from 58 to 68 years old. All of the participants had undergone sphincter-preserving resections because of rectal cancer. The patient characteristics are summarized in Table S1. Three of the included studies [10, 22, 23] were performed in Western countries, and the other three [24–26] were published in Chinese. The interventions were TAI with the Peristeen irrigation system and a comparator including dietary modifications, loperamide medication, pelvic floor muscle training, posterior tibial nerve stimulation, and recto-anal inhibitory reflex. The basic characteristics of randomized controlled trials included in the systematic review are shown in Table 1.

Table 1.

Basic characteristics of randomised controlled trials included in the systematic review

Study	Country	Study type	Duration	Irrigation system	Primary disease	Group	Number	Frequency of TAI	Volume of TAI	Temperature of TAI	Comparator of control group	Outcome	Jaded score
Rosen et al. 2020 [22]	Switzerland	RCT	NR	Peristeen	Rectal cancer	TAI	18	Every day	1000 ml	NR	Dietary modifications, biofeedback, and loperamide medication	LARS/Wexner/bowel movement	7
						Control	19
Enriquez et al. 2020 [23]	Spain	RCT	May 2017–Feb 2018	Peristeen	Rectal cancer	TAI	13	Every day initially	Individually	36–38℃	PTNS	LARS	4
						Control	14
Dai et al. 2022 [24]	China	RCT	Feb 2018– Feb 2020	Peristeen	Rectal cancer	TAI	42	Every day	500–1000 ml	37℃	Dietary modifications, loperamide medication, PFMT	LARS/Wexner/bowel movement/SF-36	6
						Control	44
Ma et al. 2022 [25]	China	RCT	May 2018–Feb 2019	Peristeen	Rectal cancer	TAI	38	Every day initially	750 ml	36–38℃	Dietary modifications, hip bath, RAIR training, medication	LARS/SF-36	6
						Control	36
Xi et al 2023 [26]	China	RCT	Jan 2021–Dec 2021	Peristeen	Rectal cancer	TAI	29	3–4 times per week	500 ml	NR	PFMT	LARS/Wexner/bowel movement	6
						Control	34
Meurette et al. 2023 [10]	Switzerland	RCT	NR	Peristeen	Rectal cancer	TAI	15	Every day	1000 ml	NR	Low-fiber diet, PFMT, medications	LARS/Wexner/bowel movement	5
						Control	15

Continuous variables are recorded as mean (SD) or median (range). RCT randomized controlled trial; TAI transanal irrigation; LARS low anterior resection syndrome; SF-36 36-Item Short Form Health Survey; NR not reported; PTNS posterior tibial nerve stimulation; PFMT pelvic floor muscle training; RAIR recto-anal inhibitory reflex

The risk of bias of eligible trials for each outcome is presented in Fig. 2. Most biases were due to incomplete outcome data and lack of blinding. Most of the included RCTs were of good quality, with a Jaded score ≥ 5.

Fig. 2.

Literature assessment of the quality of included RCTs

Bowel function

LARS

The LARS score was extracted from all six studies [10, 22–26]. The results showed that the LARS score in the TAI group was lower than that in the control group (WMD = −10.35; 95% CI [−15.95, −4.78]; P < 0.01). However, the heterogeneity was high (I² = 88%, P < 0.001) (Fig. 3a). After the subgroups were divided according to geographical location, we found that heterogeneity did not exist in the Western studies [10, 22, 23] (WMD = −10.34; 95% CI [−14.48, −6.20]; P < 0.01; I² = 0%, P = 0.73) (Fig S1a). We conducted an additional subgroup analysis stratified by follow-up duration, providing valuable insights. We categorized four studies [10, 22, 24, 26] into the short-term follow-up (1–3 months) group, and the other two studies [23, 25] were categorized into the medium-term follow-up (6 months) group. Heterogeneity was eliminated in the short-term follow-up subgroup. Sensitivity analysis was also carried out by excluding each study sequentially to find persistent heterogeneity (WMD = −6.30; 95% CI [−8.93, −3.66]; P < 0.01; I² = 28%, P = 0.24) (Fig S1b). After removing one Chinese study [25], the results showed that the TAI group still had lower LARS scores, and the findings did not show potential heterogeneity (WMD = −7.19; 95% CI [−10.08, −4.31]; P < 0.01; I² = 41%, P = 0.15). (Fig S1c).

Fig. 3.

Comparison of bowel function between TAI and control group. a Forest plots of LARS; b forest plots of Wexner scores; c forest plots of daytime bowel movements

We also performed a meta-analysis of five LARS scale subscale items reported in two studies [10, 25]. The TAI group demonstrated significantly better outcomes across all five LARS subscales compared to controls, including flatus incontinence (WMD = −0.92; 95% CI [−1.30, −0.54]; P < 0.01), liquid stool incontinence (WMD = −0.83; 95% CI [−1.07, −0.59]), frequency (WMD = −1.33; 95% CI [−1.95, −0.72]; P < 0.01), stool clustering (WMD = −4.89; 95% CI [−5.90, −3.88]), and urgency (WMD = −5.35; 95% CI [−7.12, −3.58]) (Fig. 4).

Fig. 4.

Comparison of five items on the LARS scale between the TAI and control group. a flatus incontinence; b liquid stool incontinence; c frequency; d stool clustering; e urgency

The Wexner score, reported in three studies [10, 22, 26], revealed that TAI provided significantly better outcomes than in the control group (WMD = −2.78; 95% CI [−4.13, −1.42]; P < 0.01). Heterogeneity was negligible (I² = 0%, P = 0.69), supporting the consistency of the findings (Fig. 3b). This indicates that TAI effectively alleviates fecal incontinence in LARS patients.

Bowel movement

A meta-analysis was conducted on bowel movement frequency data extracted from four independent studies [10, 22, 24, 25]. The pooled analysis revealed a statistically significant reduction in daytime bowel movements within the TAI group compared to controls (WMD = −1.33; 95% CI [−2.17, −0.48]; P = 0.002). The between-study heterogeneity was moderate, as indicated by an I² statistic of 57% (P = 0.07), suggesting acceptable but notable variability across the included studies. These findings are presented in Fig. 3c.

Quality of life (based on SF-36)

Three included studies [22, 24, 25] employed the SF-36 questionnaire as the evaluation tool. The SF-36 is a widely used tool for assessing health-related quality of life. It consists of two main components: mental and physical [27]. The SF-36 mental and physical components were extracted from the same three studies [22, 24, 25]. The mental component was not significantly affected by TAI compared to the control group (WMD = 7.27; 95% CI [−1.61, 16.15]; P = 0.11). Similarly, no significant differences in the physical component were observed between the groups (WMD = 6.97; 95% CI [−1.26, 15.19]; P = 0.10)(Fig. 5). Sensitivity analyses excluding each study sequentially demonstrated persistent heterogeneity (all I² > 50%), suggesting robust differences between studies rather than outlier effects.

Fig. 5.

Comparison of QoL between TAI and control group by forest plots of SF-36. a Mental component; b physical component

Publication bias

To evaluate potential publication bias, we performed a comprehensive assessment using funnel plot analysis across five key outcome measures spanning two critical domains: bowel function and quality of life. The funnel plots demonstrated a symmetrical distribution of study points, with no evidence of significant asymmetry. This graphical pattern indicates a low likelihood of publication bias or other systematic biases within the included studies. The consistent symmetry observed across all analyzed outcomes strengthens the reliability of our findings and suggests that the meta-analysis results are not substantially influenced by selective publication of studies with significant results (Fig. 6).

Fig. 6.

Funnel plots of publication bias. a LARS score; b Wexner score; c frequency of bowel movements; d SF-36 mental component; e SF-36 physical component

Discussion

The therapeutic application of TAI for postoperative bowel dysfunction management was first documented in 1989 [27], marking a significant milestone in rectal rehabilitation. Over the past decade, there has been a substantial increase in clinical research exploring TAI's efficacy in managing LARS [28–30], reflecting growing interest in this intervention. Current clinical guidelines, based on expert consensus, position TAI as a secondary therapeutic option for LARS patients, recommending its use only when conventional conservative measures prove ineffective, regardless of symptom severity [6]. This conservative approach in clinical protocols stems from the need for more robust evidence comparing TAI's effectiveness against standard conservative treatments. The field continues to evolve, with ongoing research aimed at establishing clearer indications and optimizing treatment protocols for postoperative bowel dysfunction management.

This systematic review and meta-analysis provided compelling evidence that TAI demonstrates superior clinical efficacy than conservative management for patients experiencing major LARS following rectal cancer surgery. Our pooled analysis shows that TAI is associated with significant improvements across multiple validated outcome measures, including reduced LARS symptom scores, lower Wexner incontinence scores, and decreased bowel movement frequency. Notably, this represents the first comprehensive synthesis of RCT data establishing TAI's therapeutic advantage over conventional conservative approaches. The robust methodology and consistent outcomes across studies suggest TAI should be considered a viable therapeutic option for refractory LARS cases.

While the exact mechanisms of TAI require further elucidation, current evidence suggests it operates through multiple complementary pathways. The intervention appears to facilitate bowel regulation by establishing predictable evacuation patterns through controlled rectal irrigation. In constipated patients, TAI may alleviate fecal retention by clearing the rectosigmoid region while simultaneously stimulating colonic motility. For incontinence management, the procedure's efficacy likely stems from achieving complete rectal emptying, which reduces urgency and accidental leakage for 24–48 h post-treatment. These effects collectively point to TAI's dual action in both immediate mechanical clearance and longer-term functional modulation of bowel activity [8, 31].

While TAI demonstrates efficacy in managing major LARS, several clinical challenges must be acknowledged. Many issues remain unclear, such as the ideal irrigation frequency, volume of water, flow rate, timing, use of additional oral laxatives or additives in the irrigation fluid, and the catheter type. The TAI specifics should be tailored individually and its use decided on a case-by-case basis [32]. Additionally, clinical studies report concerning discontinuation rates approaching 33%, primarily due to perceived inconvenience or inadequate symptom relief [13, 33, 34]. Therefore, improving patient compliance is another critical issue that colorectal surgeons need to address.

Several limitations should be considered when interpreting our findings. First, the evidence primarily derives from single-center studies with limited sample sizes, potentially affecting result reliability. Second, most analyses included only two or three studies, restricting our ability to conduct thorough heterogeneity assessments. Third, the included RCTs demonstrated high methodological quality based on Jadad scale assessment. However, according to the Cochrane risk of bias tool, some studies had biases, mainly due to incomplete outcome data and lack of blinding. In studies with inadequate blinding, the treatment effect may be overestimated. Finally, the included studies predominantly featured short-term follow-up, although one RCT demonstrated sustained benefits at 12 months [35]; long-term data from several ongoing studies are awaited to enable a more robust analysis of long-term quality of life.

Conclusion

The current evidence suggests that postoperative bowel functions of TAI were better than those in the control group. However, evaluation of the SF-36 failed to find any statistically significant difference between the TAI group and control group. To validate the clinical value of TAI, large-scale RCTs with extended follow-up periods are necessary.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

Sen Hou and Shengnan Zhang wrote the main manuscript text. Yingjiang Ye and Changkun Zhong designed the research and revised the draft. Sen Hou, Shengnan Zhang and Xi Zheng were the main investigators and data recorders; Xinchun Wu and Haodong Zhu analyzed and interpreted the data. Kai Shen and Zhidong Gao prepared tables and figures; they also revised and corrected the manuscript. All authors approved the revised final version of the manuscript.

Funding

The present study was supported by the Beijing Science and Technology Planning Project (grant no. 2159000118).

Data availability

The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Conflict of interest

The authors declare no competing interests.

Ethical approval and Informed consent

This study is a systematic review of existing literature and does not involve direct participation of human or animal subjects. Therefore, ethical approval was not required, as confirmed by Peking university people's hospital’s ethics committee.