Evaluating the influence of metabolic bariatric surgery on urinary and fecal incontinence outcomes: a one-year postoperative analysis

Abstract

Purpose

The most prevalent conditions affecting the pelvic floor include fecal incontinence (FI) and urinary incontinence (UI), both of which are particularly common among women with obesity. Although the effect of metabolic bariatric surgery (MBS) on FI remains a topic of ongoing discussion, the present study seeks to assess the impact of effective bariatric surgery on UI and FI in women with obesity.

Materials and methods

An observational prospective study was conducted at the Tours University Hospital, involving 212 women who underwent MBS. Participants completed pre-operative and post-operative questionnaires to evaluate UI and FI one-year after surgery. Additionally, urinary symptom profile (USP) and Wexner score (WS) were utilized for the assessment of UI and FI, respectively.

Results

Of the 212 patients, 148 achieved a weight loss of more than 20% of their weight one-year after surgery, and of these 40 (27.0%) completed all questionnaires. The median pre-surgical BMI was found to be 41.8 kg/m², which reduced to 29.1 kg/m² one-year post-surgery. A significant improvement was observed in stress urinary incontinence (SUI), which decreased from 32.5% pre-operatively to 22.5% post-operatively (p < 0.0001). FI showed slight exacerbation, with an increase in moderate FI (from 5.0% to 10.0%), frequency of liquid stool per week (from 2.5% to 5.0%), and gas-related symptoms (from 0 to 2.5%).

Conclusion

The findings of this study indicate that MBS significantly improves SUI in women with obesity, yet has minimal impact on FI one-year postoperatively. Further studies are required to more accurately assess the impact of metabolic bariatric surgery on postoperative FI.

Introduction

Fecal incontinence (FI) and urinary incontinence (UI) are common pelvic floor disorders affecting approximately 50% of women with a body mass index (BMI) greater than 35 kg/m² [1–3]. The literature reports that 16–63% of patients with obesity have FI and 60–70% of women with severe obesity have UI [4–6]. According to one study, the prevalence of FI was 20.7% (95% CI, 16.9%−24.5%), with loose FI reported by 20.3% and well-formed FI by 4.5%. Among women with loose FI, two-thirds also had UI, with a statistically significant association independent of age and BMI. However, well-formed FI did not show a significant association with UI after adjusting for age and BMI [2]. Identified risk factor for FI and UI includes obesity [3–8]. The underlying pathophysiology of the contribution of obesity to the development of FI is based on the increase in intra-abdominal pressure resulting in hypertonia of the anal sphincter, which reduces the number of muscle fibers available to meet additional demands such as loose stools or pregnancy [9, 10]. In relation to urinary incontinence, obesity is responsible for an increase in abdominal and bladder pressure and hypermobility of the urethra [11, 12].

Patients with obesity have significantly altered anorectal function, including longer anal canal lengths, higher resting pressures in the upper and lower anal canal, and greater maximum tolerated volumes. Due to significantly thicker internal and external sphincters, more liquid stools (Bristol 5/6/7) and a higher prevalence of irritable bowel syndrome (IBS), diarrhea-predominant symptoms are more common in patients with obesity [5]. The overall success rate for treating stress urinary incontinence with tension-free vaginal tape (TVT) was 81.2% for women of normal body weight, compared to 52.1% for patients who were severely obese (BMI >35) [13]. Metabolic bariatric surgery (MBS) is considered the most successful approach for achieving significant weight loss compared to other medical interventions [14]. This approach offers significant benefits, in particular a reduction in the prevalence of stress urinary incontinence (SUI) from 61% to 11% following a 50% reduction in excess body weight. Improvements in intravesical pressure and urethral mobility have also been observed [15–17]. MBS, including Roux-en-Y-shaped Gastric bypass (RYGB) and sleeve gastrectomy (SG), offer significant benefits for patients with severe obesity and obesity complications such as type 2 diabetes, hypertension and sleep apnea. Weight loss following metabolic and bariatric surgery (MBS) has been associated with an improvement in, or even a complete resolution of, urinary incontinence (UI) in up to 82% of patients. It has also been shown to significantly reduce faecal incontinence (FI), with a decrease from 19.4% to 8.6% at 12 months postoperatively [18–20]. However, recent studies have reported that MBS can lead to an increase in gastrointestinal symptoms, such as diarrhea, without a notable improvement in FI or UI [21, 22]. Some authors have suggested that MBS may reveal pre-existing weaknesses in the continence mechanisms. The present study aims to evaluate the impact of effective MBS - defined as substantial postoperative weight loss - on UI and FI in women. Given the high prevalence of pelvic floor disorders among obese individuals and conflicting evidence regarding FI outcomes, this study addresses an important knowledge gap concerning the continence-related effects of bariatric surgery.

Materials and methods

A retrospective study of a prospective database was conducted between January 2014 and December 2018 at the University Hospital of Tours, including 212 consecutive female patients who underwent MBS, including SG or Roux-en-Y-shaped Gastric bypass (RYGB). Participants were included if they had a BMI ≥ 40 kg/m² or ≥ 35 kg/m² and at least one comorbidity expected to improve after surgery, such as sleep apnea-hypopnea obstructive syndrome (SAOS), hypertension (HTA), other severe respiratory diseases, type 2 diabetes, disabling osteoarticular diseases or non-alcoholic steatohepatitis. Sample size was calculated using a standard normal distribution value of 1.96 for a 95% confidence level and a 5% margin of error.

Data collection

All patients were asked to complete a series of validated questionnaires to assess their pelvic floor function. These included the Urinary Symptom Profile (USP) and the Wexner Score (WS). The questionnaires were completed twice during the preoperative period: once during the initial surgical consultation and again the day before surgery.

As part of routine follow-up, the same questionnaires were given again 12 months after surgery. Only patients who achieved a minimum weight loss of 20% one year after surgery were included in the final analysis. Those who did not meet this threshold were excluded in order to evaluate the effect of successful metabolic bariatric surgery.

The 12-month follow-up visit forms part of the institution’s standardised postoperative protocol for such patients.

Assessment tools/questionnaires

UI has been assessed using the Urinary Symptoms Profile (USP) score developed and validated by the Association Française d’Urologie in 2005 [23]. It assesses 3 aspects of UI: SUI, overactive bladder and dysuria. It consists of 13 items with a score of 0 to 3 points depending on the answer. The higher the score, the more severe the incontinence. SUI is scored from 0 to 9, overactive bladder from 0 to 21 and dysuria from 0 to 9.FI was assessed using the Wexner score (WS), which is based on 5 items: incontinence with solid faeces, incontinence with liquid faeces, incontinence with gas, need for protection and impact on quality of life. The score classifies incontinence as minimal (0–4), moderate (5–9), significant (10–16) and severe (17–20) [24]. These scores were chosen because of their international validation.

The demographic and clinical variables collected included age, body mass index (BMI), baseline weight prior to bariatric surgery and any associated comorbidities. Obstetric factors and pre- and postoperative characteristics were also documented. Data on weight loss and types of MBS, including SG and RYGB, were included. Urinary symptoms were assessed by analyzing the presence of SUI, bladder function and dysuria. In addition, FI was assessed, including the occurrence of solid stools, liquid stools and gas. Changes in quality of life were also assessed.

Primary endpoint

The main aim of the study was to assess the impact of MBS on UI and FI at one-year after surgery.

Ethical considerations

This study was approved by the local Comité de l’Informatique et de la Liberté (CIL) (n° 2021_087). Data collection was in accordance with French legislation on non-interventional prospective studies evaluating routine care, as described in article L1121-1–2 of the French Public Health Code. Confidentiality and anonymity were strictly maintained, and participants had the right to withdraw at any time without repercussions. No incentives or compensation were offered for participation. This study was conducted according to the ethical standards of our institution’s Committee on Human Experimentation and reported according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines [25].

Statistical analysis

Data analysis was performed using SPSS version 20. Quantitative data were expressed as mean (SD)/median (range). Qualitative data were expressed as frequencies and percentages. Differences in means between two groups were analyzed using independent samples t-test or Mann-Whitney U test based on data distribution. Chi-squared test was used for relative comparisons in qualitative data. A p-value < 0.05 was considered significant.

Results

Demographic characteristics

The 212 patients who underwent MBS, 148 (69.8%) achieved a percentage weight loss of more than 20% within one year, and 40 (27.0%) fully completed the four questionnaires assessing UI and FI. The median age was 43.5 years, and the BMI one day before the surgery was 41.8 kg/m². Comorbidities included hypertension (40.0%), dyslipidemia (35.0%), obstructive sleep apnea (35.0%), type 2 diabetes (22.5%), gonarthrosis (15.0%), and heart disease (5.0%). Approximately 57.5% of patients underwent SG and 42.5% underwent RYGB. At one year, the median BMI decreased to 29.1 kg/m² with a median weight loss of 18,6% (Table 1). A large majority of patients had pregnancy before MBS (67.5%).

Table 1.

Participant’s baseline characteristics

Pre-operative features	Frequency (%)
Age, years	43.5 (24–63)
Weight at start of support, kg	112.0 (84.2–138.0)
BMI at start of treatment, kg/m2	41.8 (36.0–55.7.0.7)
Preoperative weight, kg	107.5 (84.0–163.0.0.0)
Preoperative BMI, kg/m2	41.0 (33.3–55.7)
Comorbidities
Diabetes 2	9 (22.5%)
Dyslipidemia	14 (35.0%)
HTA	16 (40.0%)
SAOS	14 (35.0%)
Gonarthrosis	6 (15.0%)
Heart disease	2 (5.0%)
Obstetric, pre-surgical history
Pregnancy history	28 (70.0%)
History of Low-birth babies	24 (60.0%)
Number of pregnancies	2 (0–3)
Intervention
SG	23 (57.5%)
RYGB	17 (42.5%)
Post-operative features
Pregnancy history	5 (12.5%)
Vaginal delivery	5 (12.5%)
Number of pregnancies	0 (0–2)
Maximum child weight, kg	3.8 (3.0–4.5.0.5)
M12 weight loss
Post-op weight M12, kg	76.6 (61.2–102.2.2.2)
BMI M12, kg/m2	29.1 (23.2–39.5)

HTA, hypertension; SAOS, sleep apnea-hypopnea obstructive syndrome

M12 weight loss: weight loss at post operative 12 months

Urinary incontinence

MBS led to an improvement in SUI symptoms, with 32.5% of patients experiencing SUI preoperatively compared to 22.5% at one-year postoperatively (p < 0.0001). However, post-operative improvements in overactive bladder and dysuria symptoms were modest, with prevalence rates decreasing from 60% to 50% and 15% to 10%, respectively (Table 2). Among patients who underwent Roux-en-Y gastric bypass (RYGB), there was no significant change in stress urinary incontinence (SUI) symptoms (17.6% preoperatively vs. 11.8% postoperatively; p = 0.01) or dysuria symptoms (5.9% both pre- and postoperatively). However, a significant improvement was observed in overactive bladder symptoms (58.8% vs. 52.9%; p < 0.001). In patients who underwent sleeve gastrectomy (SG), significant improvements were observed in SUI symptoms (43.5% preoperatively vs. 30.4% postoperatively; p < 0.001), overactive bladder symptoms (60.9% vs. 47.8%; p = 0.005), and dysuria symptoms (21.7% vs. 13.0%; p < 0.001).

Table 2.

Comparison of Pre- and Post-Operative urinary symptoms and severity

	N = 40 pre-operative	N = 40 post- operative	P = value
SUI
Presence of SUI	13 (32.5%)	9 (22.5%)	< 0.0001
USP SUI	3 (1–6)	3 (1–7)	0.4586
	2.6 ±1.5	3.2 ±2.3
Overactive bladder
Presence of overactive bladder	24 (60.0%)	20 (50.0%)	0.5005
USP overactive bladder	3 (1–14)	2 (1–14)	0.6597
	3.8 ±3.2	4.1 ±4.1
Dysuria
Presence of dysuria	6 (15.0%)	4 (10.0%)	0.7370
USP dysuria	2.5 (1–8)	2 (1–3)	0.3412
	3.3 ±2.5	2.0 ±0.82
Urinary incontinence among the RYGB
SUI
SUI symptoms	3 (17.6%)	2 (11.8%)	0.2010
Overactive bladder
Overactive bladder	10 (58.8%)	9 (52.9%)	< 0.001
Dysuria
Dysuria symptoms	1 (5.9%)	1 (5.9%)	1.0000
Urinary incontinence among the SG
SUI
SUI symptoms	10 (43.5%)	7 (30.4%)	< 0.001
Overactive bladder
Overactive bladder	14 (60.9%)	11 (47.8%)	0.005
Dysuria
Dysuria symptoms	5 (21.7%)	3 (13%)	< 0.001

SUI Stress Urinary Incontinence; USP, Urinary Symptom Profile; RYGB, Roux-en-Y-shaped Gastric by pass; SG, sleeve gastrectomy

Fecal incontinence

In our population, FI was present 40% of the patients (minimum symptoms 32,5%, moderate 5%, important 2,5%, severe 0). Post-operative outcomes showed minimal changes in FI, bowel habits or quality of life. Although slight improvements were observed in some areas, such as absence of FI (60.0% vs. 55.0%) and reduced need for pads (87.5% vs. 92.5%), these differences were not statistically significant. However, there were some moderate exacerbations of FI. The proportion of patients with moderate FI increased from 5.0% preoperatively to 10.0% postoperatively. In addition, the incidence of liquid stools at least once a week increased from 2.5% to 5.0%, and 2.5% of patients reported gas at least once a week, a symptom not present preoperatively. With regard to fecal incontinence (FI), patients in the RYGB group exhibited an increase in symptoms after surgery (58.8% vs. 47.0%), though this difference was not statistically significant (p = 0.076). In the SG group, no change in FI prevalence was observed (34.8% pre- and postoperatively). Furthermore, no significant difference in stool consistency (solid vs. liquid) was observed based on the type of bariatric procedure (Table 3).

Table 3.

Comparison of Pre- and Post-Operative FI and its impact on quality of life

	N = 40 pre-operative	N = 40 post- operative	p-value
FI
• Absent	24 (60.0%)	22 (55.0%)	0.8213
• Minimum	13 (32.5%)	13 (32.5%)	0.6706
• Moderate	2 (5.0%)	4 (10.0%)
• Important	1 (2.5%)	1 (2.5%)
• Severe	0 (0.0%)	0 (0.0%)
Solid saddles
• Never	22 (55.0%)	25 (62.5%)	0.5534
• < 1 time/week	11 (27.5%)	9 (22.5%)
• ≥ 1 time/week	7 (17.5%)	6 (15%)
Liquid stools
• never	31 (77.5%)	31 (77,5%)	0.58292
• < 1 time/week	8 (20.0%)	7 (17.5%)
• ≥ 1 time/week	1 (2.5%)	2 (5.0%)
Gas
• Never	37 (92.5%)	37 (92.5%)	0.7299
• < 1 time/week	3 (7.5%)	2 (5.0%)
• ≥ 1 time/week	0 (0.0%)	1 (2.5%)
Alteration of quality of life
• None	32 (80%)	34 (85%)	0.3932
• Slightly/a little	5 (12.5%)	5 (12.5%)
• Much/considerably	3 (7.5%)	1 (2.5%)

FI, fecal incontinence

Discussion

The study evaluated the effects of MBS on UI and FI using two standardized assessment tools: the USP and the WS.

Our results indicate that weight loss of more than 20% one year after MBS significantly reduces SUI (p < 0.0001). These findings are in line with the existing literature, which reports a significant reduction in both the prevalence (from 66.7% to 41.0%) and severity (50%) of SUI post-MBS [18, 19]. Zhang et al.‘s meta-analysis of 10 studies further supports these findings, demonstrating that MBS significantly reduces the incidence of UI. Patients were found to be 4.04 times more likely to experience an improvement in UI one year after surgery (P < 0.00001), along with a significant improvement in quality of life [26]. While our study focused on patients who lost 20% of their weight after surgery, there is evidence that even modest weight loss can have a positive effect on UI. Subak et al. reported that moderately patients with obesity experienced improvements in UI symptoms with a 5–10% weight loss achieved through non-surgical interventions [8]. Similarly, a weight loss (BMI 45 to 28) resulted in a significant decrease in UI prevalence (p = 0.02) and total mean distress scores (p = 0.015). Quality of life scores improved significantly for urinary (p = 0.0005) and pelvic organ prolapse (p = 0.015) [20]. With a 30.9% weight loss (BMI 43.6 to 30.7), the prevalence of urinary incontinence (50.9% to 19%), urgency incontinence (36.8% to 7.9%) and dysuria (19.8% to 3.4%) decreased significantly and quality of life related to urinary symptoms improved (p < 0.0001) [27].

Although our analysis focused on two specific MBS, the literature suggests that the effect on UI is independent of the type of surgical procedure. Procedures such as laparoscopic gastric banding, RYGB and SG have all shown significant improvements in urinary symptoms, including frequency (p = 0.0032), incomplete emptying (p = 0.0298), nocturia (p < 0.0001) [28], and stress incontinence (p = 0.0164) [29–31]. MBS improved UI by reducing abdominal pressure and improving bladder function, but FI showed minimal changes. MBS improves UI by addressing obesity-related factors such as increased abdominal fat and pressure, which increase intravesical pressure and cause urethral hypermobility and detrusor instability. Weight loss after surgery reduces these pressures, increases bladder capacity and improves pelvic floor function, thereby relieving symptoms of SUI and urge urinary incontinence (UUI) [31].

Our results showed that postoperatively, FI showed minimal improvement, with the absence of FI increasing from 55.0% to 60.0% (p = 0. 8213). However, moderate FI, gas and liquid stools increased slightly. The literature has shown consistent results. Scozzari reported a comparison of 32 patients with obesity and 71 women without obesity with no significant changes in anorectal sphincter function including resting pressure, voluntary contraction pressure and anorectal inhibitory reflex. No significant change was observed in the total PFDI-20 score (24.2 vs. 26.6; p not significant, exact value not provided by the authors). However, a significant improvement was noted in the PFIQ-7 score (4.8 vs. 0.0; p = 0.044). There were also improvements in AI (28.1% to 40.6%) and fecal incontinence (18.8% to 37.5%) [32]. Pelletier et al. evaluated the effect of sleeve gastrectomy (SG) on AI and found no significant changes in anorectal function after surgery, but the prevalence of AI increased slightly (12.8% to 24.4%), but no patients developed de novo incontinence and the median Vaizey score remained unchanged (p = 0.1). Despite a decrease in anal pressure measurements post-operatively (resting pressure: 29 to 22 mmHg, p = 0.0015; squeeze pressure: 29–74 to 30–60 mmHg, p = 0.0008), proctological lesions were rare, occurring in only 2.4% of patients during follow-up [33].

The rate of FI is higher in people with obesity, as reported in the literature, but the relationship between the severity of obesity and the occurrence of FI has not been clearly established [20]. Whitehead et al. found that FI increases with age, from 2.6% in 20–29-year-olds to 15.3% in those aged 70 and over, and is associated with chronic diarrhea, UI and multiple chronic conditions. Other risk factors include obesity, frequent bowel movements, inability to exercise, and loose or watery stools [34].

The increase in FI was mainly attributed to an increase in gas incontinence, which may be related to the increased incidence of bloating after surgery [19, 27]. Bloating after MBS is caused by diet factors such as consumption of carbonated drinks, gas-producing foods, and dehydration. Adjustments to the digestive system post-surgery also contribute to temporary bloating and discomfort [35], such as sphincter dysfunction and rectal compliance issues, which are less influenced by weight loss or pressure reduction [27]. In addition, surgical procedures can alter bowel transit, with restrictive procedures leading to constipation due to reduced water intake and malabsorptive procedures leading to diarrhea. These changes may affect post-operative FI.

In addition, the results of this study highlight the need for critical adjustments in the management of post-MBS. Effective management requires a comprehensive and collaborative approach with regular monitoring of nutritional status, alongside personalized physical activity, including pelvic floor exercises to strengthen muscle function [36].Early ambulation promotes recovery and reduces complications that can exacerbate UI and FI, while transition to a soft solid diet minimizes gastrointestinal distress [37]. Medication regimens should be adjusted to account for altered drug absorption, especially for medications that affect bladder or bowel control. Addressing co-morbidities such as diabetes and providing psychological support for stress management also help to improve UI and FI outcomes [38].

Limitations include a relatively short follow-up period of one year, which may not fully capture long-term functional outcomes, and a low response rate to questionnaires, which may introduce bias. Future studies should focus on longer follow-up periods to assess the long-term effects of MBS, include control groups for comparison, and explore the relationship between the extent of weight loss and improvements in UI. Larger, multicenter studies with improved response rates would also help to validate and generalize these findings. This study carries an inherent selection bias as we only included patients who had achieved successful weight loss following MBS (defined as a total weight loss of at least 20%) to evaluate the impact of effective surgery on pelvic floor symptoms. Additionally, we did not perform subgroup analyses based on obstetric history, since the majority of patients had experienced pregnancy prior to surgery and the sample size was insufficient to enable meaningful comparisons to be made between patients with and without prior pregnancies.

The primary objective of this study was to assess the efficacy of MBS in improving or resolving urinary and fecal incontinence in a population with clinically significant weight loss.

Conclusion

The effect of effectice MBS on UI and FI in women with obesity showed a significant improvement in SUI one year after surgery. However, improvements in symptoms of overactive bladder and dysuria were modest. In contrast, FI showed minimal improvement, with no significant reduction in the need for pads or the incidence of incontinence. Some modest exacerbations of FI were observed, including increases in moderate FI and liquid stool frequency. The study highlights the complex relationship between obesity, pelvic floor dysfunction and the outcomes of SUI. Despite improvements in urinary symptoms, FI and bowel-related quality of life showed limited change, highlighting the need for further research to explore effective treatments for FI in this population.

Author contributions

O. Iskander and N. Michot contributed to the conceptualization, software development, data visualization, formal analysis, funding acquisition, data curation, and provision of resources. L. Courtot prepared the original draft of the manuscript. G. Prouteau was responsible for data collection. C. Bourbao-Tournois, A. Artus, J. Thiery, E. Salamé, and A. Bouayed contributed to validation of the data and results. C.R.D. Demtröder, A. Deffain, and U. Giger-Pabst were involved in critical revision of the manuscript. M. Ouaissi supervised the project and was responsible for project administration, formal analysis, and funding acquisition.

Data availability

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

Declarations

Ethical considerations

This study was approved by the local Comité de l’Informatique et de la Liberté (CIL) (n° 2021_087). Data collection was in accordance with French legislation on non-interventional prospective studies evaluating routine care, as described in article L1121-1-2 of the French Public Health Code. Confidentiality and anonymity were strictly maintained, and participants had the right to withdraw at any time without repercussions. No incentives or compensation were offered for participation. This study was conducted according to the ethical standards of our institution’s Committee on Human Experimentation and reported according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.

Competing interests

The authors declare no competing interests.