This systematic review summarizes and reports available evidence on the effect of bariatric surgery on FI. For women, we found a statistically significant reduction in FI pre- and post-surgery [0.46; CI 0.22 to 0.94]. There was also a statistically significant reduction in patients after Roux-n-Y gastric bypass or one anastomosis gastric bypass. While there was a trend towards less FI following bariatric surgery among patients, this did not reach statistical significance [OR 0.55; CI 0.28 to 1.06; p=0.075]. The difference in the frequency of FI pre- and post-bariatric surgery was also not statistically significant. We assessed the effect of faecal incontinence on quality of life, across areas of behaviour change, depression, impact on lifestyle and feeling of embarrassment. We found no statistically significant difference pre- and post-operatively in these areas.
Faecal incontinence has important clinical and psychosocial consequences. It may contribute to loss of independence and significant psychosocial stress. Compounding this, it is currently underreported and likely underappreciated as a symptom . For clinicians treating obesity with bariatric surgery, it is important to be able to communicate the effect bariatric surgery may have on their symptoms. This may be most important for women, for whom other risk factors for FI are often present such as obstetric history and perineal injury. This systematic review shows that women have a statistically significant reduction in FI prevalence post-bariatric surgery. Reduction of FI may therefore be an important consideration for obese women undergoing bariatric surgery
Our study found a statistically significant reduction of FI after Roux-en-Y gastric bypass and one anastomosis gastric bypass. This could be because Roux-en-Y represented the most common surgery in our studies, hence had the most power to reveal a significant result. Alternatively, Roux-en-Y gastric bypass may be particularly effective at reducing FI possibly through greater weight loss. We did not, however, find a statistically significant correlation between the reduction in BMI and reduction of FI, so there may be other hidden factors.
Though our conclusion regarding FI severity is limited by the heterogenous data, some insights can be gained from the included studies. The largest study that assessed quality of life after FI, Elias et al., looked at 208 men and women and found a statistically significant improvement in lifestyle, coping and behaviour and embarrassment after bariatric surgery . Though we did not demonstrate a significant result, the results trended towards improvement in FI severity after bariatric surgery. Larger, standardized studies are needed to further elucidate this potential correlation.
We were not able to assess the pathophysiological factors that may be driving the reduction in FI after bariatric surgery. The literature suggests that obesity may increase intra-abdominal pressure and deplete the anal sphincter’s ability to remain continent. This evidence is particularly present in women, and thus reduced intra-abdominal and thus anal sphincteric pressure may explain the findings of our systematic review. However, our study showed that there is an improvement in FI after bariatric surgery independent of weight loss. We postulate that there are hidden factors driving the benefit of bariatric surgery on FI in women and gastric bypass patients.
We did not find an improvement in FI for men, or for patients undergoing other operations other than Roux-en-Y or one anastomosis gastric bypass. There were a small number of men and surgical procedures outside of gastric bypass in our study, so the study was perhaps not powered to detect these changes. In these patients, there may also be factors that are counteracting the benefits seen in women and bypass patients. Stool consistency is also an important determinant of continence. Elias et al. found a significant change in stool towards a looser consistency (p=0.04) in men and women after bariatric surgery. Diet is another important factor . Dietary changes after bariatric surgery can work both to promote FI by loosening stool and improve FI through increasing stool bulk, so the relationship is difficult to investigate systematically. It could be that looser stool or diet changes affecting intestinal function counteract some of the benefits of bariatric surgery on FI, at least in some populations.
Systematic reviews hitherto have had varying results between bariatric surgery and improvement of FI. This is the first systematic review to assess both prevalence and frequency of FI in bariatric patients, in both men and women. A strength of our study is the assessment of severity of FI after bariatric surgery, which up to this point has not be assessed in a meta-analysis. Another strength of our systematic review included the broad search strategy, which identified papers that looked at pelvic floor disorders as well as those that looked at gastrointestinal disorders after bariatric surgery.
There are limitations to this systematic review and meta-analysis. Our study included patients with an age range of 30.7 to 54.8, and thus we cannot comment on faecal incontinence and the impact of bariatric surgery in older patients. As age is an important determinant in faecal incontinence, this is a key area for further exploration. The 13 studies were heterogeneous in the study design, population, surgery and outcome measurement tools. Importantly, there was a difference in how FI was defined; in one paper, Burgio et al. included gas loss as a form of incontinence . On subgroup analysis in this paper, the FI was significantly improved if the definition was limited to liquid/stool loss. Regarding the assessment of severity, there was wide range of the measurement tools used, from validated questionnaires to researcher-made questionnaires. The measurement tools are thus of varying quality, even the validated ones. One commonly used validated questionnaire, GIQLI, is not specifically designed to detect FI and so has limited questions dedicated to FI symptoms . Other questionnaires, such as FISI and the Wexner Scale, are designed for FI and so assessed the quality-of-life impact of FI with more rigor.
The papers included in meta-analysis were overall ‘poor’ quality in our assessment, and most papers lacked a control group or were not able to control for potential confounders. This impacts our ability to draw valid conclusions from these studies, as there may be confounding factors unaccounted for in our meta-analysis. There were limited studies evaluating FI in men, and so it remains unclear how FI and bariatric surgery impact male patients. Due to limited numbers and studies, we were unable to conduct a sub-group analysis for men. The papers were also not ethnically or geographically diverse, with most papers being based in Europe or in patients of largely European heritage. The studies had an age range of 30.7 to 54.8, and as FI is highly correlated with increasing age, our results would not be generalizable to older bariatric patients.
Further studies are required, particularly in older patients, male patients and multiple ethnic groups. As FI has large psychosocial, physical and financial impacts on patients, it may be an important pre- and post-operative symptom for some patients. By understanding how bariatric surgery will impact FI, surgeons and clinical teams can target treatments and manage expectations of their patients, thus providing better overall care.