Preoperative Anorectal Manometry and Fecal Incontinence after Anal Surgery: Is Routine Assessment Justified?Abstract
Objective To evaluate whether preoperative anorectal manometric parameters are associated with postoperative fecal incontinence in continent patients undergoing anal surgery.
Materials and Methods The current prospective observational study included adult continent patients scheduled for elective anal surgery. All participants underwent preoperative high-resolution anorectal manometry following the London Protocol. Postoperative fecal continence was assessed using the Wexner score. Patients were classified according to postoperative continence status, and preoperative manometric parameters were compared between groups.
Results The study included 29 patients. Postoperative fecal incontinence was identified in 12 patients (41.4%), all classified as mild. Patients who developed fecal incontinence had significantly lower preoperative resting anal pressures compared with continent patients. However, all values remained within normal reference ranges. No significant differences were observed regarding age, sex, parity, prior anorectal surgery, or squeeze pressures.
Conclusions Although lower preoperative resting anal pressures were statistically associated with postoperative fecal incontinence, all values remained within normal reference ranges, limiting their clinical relevance. Routine preoperative anorectal manometry does not appear to provide meaningful predictive value for postoperative fecal incontinence in continent patients undergoing anal surgery.
Keywords
fecal incontinence; anorectal manometry; preoperative evaluation; anorectal surgery
Introduction
Fecal incontinence is a clinically-relevant condition due to its substantial impact on quality of life, social functioning, and psychological well-being.1 Its prevalence varies widely in the literature, and it may affect up to 22% of the general population.2 Despite its high prevalence, fecal incontinence remains underreported, largely due to stigma, embarrassment, and misconceptions regarding normal bowel function.3 Even mild symptoms can lead to embarrassment, activity restriction, social withdrawal, and reduced self-esteem, contributing to the fact that only about 1/3 of affected individuals seek medical assistance.4 Beyond its psychosocial burden, fecal incontinence is also associated with increased healthcare use, with affected individuals presenting up to 55% higher healthcare costs compared with those without the disorder.5
From a pathophysiological perspective, fecal incontinence is a multifactorial condition that rarely results from a single underlying mechanism. It reflects a complex interaction among anal sphincter integrity, pelvic floor function, rectal compliance, sensory perception, and central and peripheral neural control. It is estimated that approximately 80% of the patients present more than 1 contributing causal factor, which may act synergistically to impair continence.3 This complexity limits the ability to accurately diagnose underlying dysfunction and to predict postoperative functional outcomes, especially in patients who are continent at baseline.
Anal surgical procedures such as hemorrhoidectomy, fistulotomy, and fissurectomy are widely performed and generally considered safe, making postoperative functional outcomes particularly relevant in the colorectal practice. Although these procedures aim to treat benign anorectal conditions, they involve anatomical structures that play a critical role in continence, including the internal and external anal sphincters, the anoderm, and the supporting tissues.6 Even limited surgical trauma, tissue dissection, or postoperative inflammation may transiently or permanently alter anorectal function.7
Postoperative fecal incontinence, particularly in its mild form, has been reported with variable frequency, and it may occur even after technically-uncomplicated procedures.8 The reported rates may reach: up to 28% after hemorrhoidectomy, depending on the surgical technique, the extent of the hemorrhoidal prolapse, and surgeon experience; approximately 35% after fissurectomy when combined with sphincterotomy; and up to 64% following fistulectomy.9
Anorectal manometry is a well-established diagnostic tool in the evaluation of patients with fecal incontinence and other defecatory disorders. By providing objective measurements of anal sphincter pressures, rectal sensation, and anorectal reflex activity, manometry plays an important role in diagnostic clarification and therapeutic planning in symptomatic individuals. In patients with established fecal incontinence, manometric findings may help differentiate sphincter dysfunction from sensory or coordination disorders and guide conservative or surgical management strategies.10
The role of anorectal manometry in continent patients, particularly as a routine preoperative screening test before anal surgery, remains controversial.11 While some clinicians advocate for its use to identify patients with reduced functional reserve, others question its clinical usefulness in the absence of symptoms, especially given the lack of clear thresholds capable of predicting clinically-meaningful postoperative dysfunction.12
The current evidence regarding the predictive value of preoperative anorectal manometry is limited and heterogeneous. The studies available13,14 have primarily focused on patients undergoing fistula surgery and are often characterized by small sample sizes, retrospective designs, and diverse methodological approaches. As a result, reported associations between baseline manometric parameters and postoperative continence outcomes remain inconsistent, and no consensus has been established regarding the routine use of anorectal manometry in continent patients undergoing anal surgery. Consequently, clinical practice varies considerably among centers.
Given the absence of robust evidence supporting routine preoperative functional assessment in this context, the present study aimed to evaluate whether preoperative anorectal manometric parameters are associated with the development of postoperative fecal incontinence in continent patients undergoing anal surgery.
Materials and Methods
The current prospective observational study was conducted at the Department of Coloproctology of tertiary hospital in the city of Porto Alegre, Brazil. Patient recruitment and follow-up occurred between August 2024 and October 2025. The study was designed to evaluate the association between preoperative anorectal manometric parameters and postoperative fecal continence outcomes in patients undergoing elective anal surgery.
The study obtained approval from the institutional Ethics in Research Committee and was conducted in accordance with the required bioethical standards (protocol number 82110424.8.0000.5336).
Adult patients (aged ≥ 18 years) scheduled for elective anal surgery were eligible. The inclusion criteria were perfect continence, defined as a Wexner score of zero, and provision of written informed consent. Patients with inflammatory bowel disease associated with anorectal disease were excluded.
Demographic and clinical data were collected during the preoperative visit, including age, sex, body mass index, comorbidities, smoking status, alcohol consumption, prior anorectal surgery, and obstetric history in women. Continence status was confirmed using the Wexner score, and only patients with a score of zero were included.
All participants underwent preoperative high-resolution anorectal manometry without bowel preparation. Examinations were performed with the patient in the left lateral position using a high-resolution catheter system, following the London Protocol. The recorded parameters included resting anal pressure, squeeze pressure, rectal sensory thresholds, and the presence of the rectoanal inhibitory reflex. All data were recorded and analyzed using the proprietary software (SetupAno, Alacer Biomédica) of the Multiplex high-resolution anorectal manometry equipment (Alacer Biomédica).
The patients underwent the planned anal procedures, including hemorrhoidectomy, fistulotomy, or fissurectomy. All surgeries were performed by experienced colorectal surgeons of the same institution.
The patients were followed in the outpatient clinic at 15, 30, and 60 days postoperatively. At each visit, wound healing, complications, and functional outcomes were assessed. The Wexner score was reapplied after complete wound healing, and the patients were divided in two groups according to the postoperative continence status.
Data were recorded in an electronic database and analyzed using IBM SPSS Statistics for Windows (IBM Corp.) software, version 20.0. The categorical variables were described as absolute and relative frequencies and compared using the Fisher's exact test. The normality of the continuous variables was assessed using the Shapiro–Wilk test. Normally-distributed variables were expressed as mean ± standard deviation values. Preoperative manometric parameters were compared between patients with and without postoperative fecal incontinence using the Student's t-test for independent samples. Values of p < 0.05 were considered statistically significant.
Results
A total of 29 patients undergoing elective anal surgery were included in the analysis. The baseline demographic and clinical characteristics are summarized in Table 1. The cohort was predominantly female (65.5%; n = 19), with a mean age of 49.3 (range: 19–75) years. Patients were stratified into two groups according to postoperative functional outcome: those who remained continent (n = 17; 58.6%) and those who developed postoperative fecal incontinence (n = 17; 58.6%).
No statistically-significant differences were observed between the continent and incontinent groups regarding age, sex distribution, obstetric history, or history of previous anorectal surgery (all p > 0.05). Although patients who developed postoperative fecal incontinence tended to be slightly older, this difference did not reach statistical significance.
Among female patients, parity was additionally evaluated. The overall mean number of childbirths was of 1.89. Women who developed postoperative fecal incontinence had a higher mean parity compared with continent women (2.25 versus 1.63), although this difference did not reach statistical significance. Despite the lack of formal significance, this finding suggests a potential contribution of obstetric factors to sphincter physiology.
Only 2 patients (6.8%) had a history of anorectal surgery, both hemorrhoidectomies. One remained continent postoperatively, while the other developed mild fecal incontinence, precluding any definitive association between prior surgery and postoperative continence outcomes in this cohort.
Hemorrhoidectomy was the most frequently-performed procedure, accounting for 22 cases (75.8%), followed by fistulotomy in 5 patients (17.2%) and fissurectomy in 2 patients (6.8%). The distribution of surgical procedures was similar between continent and incontinent patients, with no significant association between the type of surgery and the occurrence of postoperative fecal incontinence.
Postoperative fecal incontinence was identified in 12 patients (41.4%). All cases were classified as mild according to the Wexner score (≤ 7), with no instances of moderate or severe incontinence observed. No patient reported complete loss of continence, nor was there a need for additional therapeutic interventions during the follow-up period.
When analyzed by type of procedure, the prevalences of fecal incontinence are illustrated in Fig. 1. Although a higher absolute number of incontinence cases was observed following hemorrhoidectomy, this finding reflects the proportional predominance of this procedure in the sample and does not indicate an increased risk without further adjusted analysis.
Preoperative anorectal manometry demonstrated significantly lower resting anal pressures in patients who developed postoperative fecal incontinence compared with continent patients. In contrast, the voluntary squeeze pressures did not differ significantly between groups. The manometric values are detailed in Table 2.
Discussion
The present study evaluated the association between preoperative anorectal manometric parameters and the development of postoperative fecal incontinence following elective anal surgery. Although a relatively-high proportion of patients developed postoperative fecal incontinence, all cases were classified as mild, with no progression to moderate or severe forms and no requirement for additional therapeutic interventions. These findings are consistent with the wide range reported in the literature. In a comprehensive review, Ommer et al.9 (2008) documented fecal incontinence rates ranging from 2 to 20% after conventional hemorrhoidectomy and varying between 18 and 64% after fistulotomy, depending on fistula depth, the extent of sphincter muscle involvement, and the surgical technique employed. Although methodological heterogeneity across studies limits direct comparisons, these findings reinforce that the rates observed in the present cohort are consistent with those reported in similar patient populations.
A statistically-significant difference in preoperative resting anal pressure was observed between patients who developed postoperative fecal incontinence and those who remained continent. However, the absolute pressure values remained within normal physiological ranges, typically between 40 and 70 mmHg.15 This finding suggests that the differences in resting pressure do not necessarily translate into clinically-meaningful impairment, thereby limiting the usefulness of resting pressure as an isolated predictive marker.
Therefore, the role of preoperative anorectal manometry as a predictive tool for postoperative fecal incontinence remains controversial. The studies available on this issue are scarce and largely limited to patients undergoing fistula-related procedures. In a landmark study, Pescatori et al.13 (1989) demonstrated that reduced baseline anal pressures could identify patients with lower functional reserve, enabling more conservative surgical strategies.
In a subsequent study, Pescatori, et al.14 (2004) evaluated men undergoing fistulectomy and found no significant differences in preoperative anal pressures between continent and incontinent patients. The authors concluded that manometry does not provide a clear predictive threshold for postoperative outcomes, which were more strongly associated with surgical factors such as the extent of sphincter division, residual anal deformity, and the need for reintervention.
The present study expands the existing literature by including patients undergoing hemorrhoidectomy and fissurectomy, thereby reflecting the routine clinical practice and broadening the applicability of these observations beyond fistula-related procedures.
No significant association was found between the type of surgical procedure and the occurrence of postoperative fecal incontinence. While hemorrhoidectomy accounted for most cases of postoperative incontinence, this finding reflects its predominance in the sample rather than suggesting a higher intrinsic risk.
Demographic variables such as age and sex were not significantly associated with postoperative continence outcomes. Among women, a higher mean parity was observed in the incontinent group, although this difference did not reach statistical significance. This finding is consistent with those of the existing literature, which suggests that parity alone is a weak marker for the development of fecal incontinence, whereas severe obstetric trauma represents the truly relevant predictor.16
Moreover, the clinical usefulness of anorectal manometry fundamentally relies on its ability to discriminate between normal and abnormal function. However, this applicability is limited by several factors, including the lack of technical standardization across centers, differences in equipment and measurement systems, variations in patient preparation, positioning, and instructions, as well as the substantial overlap between normal and abnormal reference values. This heterogeneity compromises diagnostic consistency and partially explains why up to 60% of the patients with clinical symptoms of fecal incontinence may present manometric values within the normal range.15
The low concordance regarding symptoms and manometric parameters further highlights the limitations of anorectal manometry when used as an isolated diagnostic tool, indicating its low sensitivity to detect subtle functional abnormalities that may underlie mild forms of anorectal dysfunction in the clinical practice.
The current study has limitations that should be acknowledged. The small sample size and single-center design limit statistical power and preclude a multivariate analysis. Additionally, the relatively short follow-up period may not capture late-onset continence changes. Future studies with larger, multicenter cohorts and longer follow-up are warranted to better define the role of preoperative physiological testing in anal surgery.
Conclusion
Although preoperative resting anal pressures differed statistically between patients who did and did not develop postoperative fecal incontinence, the values remained within normal ranges, and routine preoperative anorectal manometry is, therefore, not supported as a screening tool in continent patients undergoing elective anal surgery.
Data Availability
Data will be available upon request to the corresponding author.
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Editor-in-Chief:
Henrique Fillmann.
