Changes in fatigability of the striated anal canal after childbirth

Optimizing techniques for measuring anal resting and squeeze pressures with high-resolution manometry

BACKGROUND

The optimal methods for measuring and analyzing anal resting and squeeze pressure with high-resolution manometry (HRM) are unclear.

METHODS

Anal resting and squeeze pressures were measured with HRM in 90 healthy women, 35 women with defecatory disorders (DD), and 85 with fecal incontinence (FI). Pressures were analyzed with Manoview™ software and a customized approach. Resting pressures measured for 20, 60, and 300 s were compared. During the squeeze period, (3 maneuvers, 20 s each), the squeeze increment, which was averaged over 5, 10, 15, and 20 s, and squeeze duration were evaluated.

RESULTS

Compared to healthy women, the anal resting pressure, squeeze pressure increment, and squeeze duration were lower in FI (p ≤ 0.04) but not in DD. The 20, 60, and 300 s resting pressures were strongly correlated (concordance correlation coefficients = 0.96-0.99) in healthy and DD women. The 5 s squeeze increment was the greatest; 10, 15, and 20 s values were progressively lower (p < 0.001). The squeeze pressure increment and duration differed (p < 0.01) among the three maneuvers in healthy and DD women but not in FI women. The upper 95th percentile limit for squeeze duration was 19.5 s in controls, 19.9 s in DD, and 19.3 s in FI. Adjusted for age, resting pressure, and squeeze duration, a greater squeeze increment was associated with a lower risk of FI versus health (OR, 0.96; 95% CI, 0.94-0.97).

CONCLUSIONS

These findings suggest that anal resting and squeeze pressures can be accurately measured over 20 s. In most patients, one squeeze maneuver is probably sufficient.

Anal sphincter fatigability in assessing anal incontinence: A systematic review

BACKGROUND

Diagnosing anal incontinence (AI) based on manometry results is challenging due to the variation of the normal values and overlap between patients with and without AI. This study aimed to perform a systematic review on the difference in sphincter fatigability between patients with and without AI.

METHODS

MEDLINE, EMBASE, SCOPUS, and Google Scholar were searched. Studies were included if they included adult patients and assessed anal sphincter fatigability between using manometry. The effect size was estimated as the standardized mean difference (SMD) with 95% confidence intervals. A random-effects model was used.

RESULTS

The database searches identified 125 unique articles, and five additional articles were identified from the reference list of articles. One hundred thirteen were excluded through title and abstract review. Nine articles were included in the final analysis. There was no statistically significant difference in the resting pressure between the two groups. Patients with AI had significantly lower squeeze pressure. There was no statistically significant difference between the groups in the fatigue rate. The FRI was significantly lower in patients with AI (SMD 1.636, p = 0.001). Approximately a third of the patients in one study were able to maintain a contraction for 20s without reducing pressure. There was significant heterogeneity in the studies. The data available were inadequate for more robust calculations.

CONCLUSIONS

Sphincter fatigability, measured by the Fatigability Rate Index, has good discriminating power for anal incontinence. A standardized protocol needs to be followed by future researchers. Graphical Abstract The analysis used six studies with 413 patients to compare Fatigue Rate Index between patients with AI and controls. All studies reported a lower FRI in patients with incontinence and the FRI was significantly lower in patients with AI (standardized mean difference [SMD] 1.636, p= 0.001). Conflicting results were reported on the correlation between FRI and AI symptom scores.

Fatigability of the external anal sphincter muscles using a novel strength training resistance exercise device

Exercises involving pelvic floor muscles including repetitive voluntary contractions of external anal sphincter (EAS) musculature have been used to improve fecal incontinence. Muscle fatigue is a prerequisite for successful strength training. However, muscle fatigue induced by these exercises has not been systematically studied. We aimed to assess the fatigability of EAS muscles during various exercise methods. Twelve nulliparous (21 ± 2.7 yr) women were studied. We evaluated fatigue during 40 repetitive 3-s contractions and 30-s long squeeze contractions both with and without an intra-anal compressible resistant load. The sequence of exercises was randomized. This load was provided by the continence muscles Resistance Exerciser Device. Anal canal pressures were recorded by high-resolution manometry. Exercise against a resistive load showed significant decrease in anal contractile integral (CI) and maximum squeeze pressure during repetitive short squeeze contractions compared with exercise without a load. Linear regression analysis showed a significant negative correlation between anal CI and successive contraction against load, suggesting "fatigue." Similar findings were observed for maximum squeeze pressure (slope with load = -4.2, P = 0.0003, vs. without load = -0.9, P = 0.3). Long squeeze contraction against a load was also more susceptible to fatigue than without a load (P < 0.0001). In conclusion, repetitive contractions against a compressible load induce fatigue and thus have the potential to strengthen the anal sphincter contractile function than contractions without a load. Fatigue rate in long squeeze contraction exercises with a load is significantly faster than that without a load, also indicating greater effectiveness in inducing muscle fatigue.NEW & NOTEWORTHY Fecal incontinence is a distressing disorder with a mainstay of treatment being pelvic floor muscle exercises. However, none of these exercises has proven occurrence of fatigability, which is an important prerequisite for successful muscle strengthening in rehabilitative exercises. In this study, we proved that we can fatigue the external anal sphincter muscles more efficiently by providing a resistive load during anal repetitive short squeeze contractions and long squeeze contraction exercise.

External Anal Sphincter Fatigability: An Electromyographic and Manometric Study in Patients With Anorectal Disorders

Background/Aims

External anal sphincter (EAS) plays an important role in fecal and gas voluntary continence. Like every muscle, it can be affected by repeated efforts due to fatigability (physiological response) and/or fatigue (pathological response). No standardized fatiguing protocol and measure method to assess EAS fatigability has existed. The aim is to test a simple, standardized protocol for fatiguing and measuring EAS fatigability and fatigue to understand better the part of EAS fatigability in the pathophysiology of fecal incontinence.

Methods

Patients with anorectal disorders evaluated with anorectal manometry were included. They had to perform 10 repetitions of maximum voluntary contraction (MVC) of 20 seconds. Measurement was made with an anorectal manometry catheter and a surface recording electromyography (EMG). The primary outcome was the difference in EMG root mean square between the first and the last MVC. Secondary outcomes were differences in other EMG and manometry parameters between the first and the last MVC. Difficulties and adverse effects were recorded.

Results

Nineteen patients underwent the fatiguing protocol. All patients completed the entire protocol and no complications were found. No difficulty was declared by the examiner. A significant decrease in root mean square was found between the first and last MVC (0.01020 ± 0.00834 mV vs 0.00661 ± 0.00587 mV; P = 0.002), in maximum anal pressure area under the curve of continuous recordings of anal pressure and mean and total EMG power (P < 0.05).

Conclusions

This protocol is simple and minimally invasive to measure EAS fatigue and fatigability. We highlighted a fatigue of EAS in many patients with anorectal disorders.