Management after obstetric anal sphincter injury: anorectal manometry and symptoms predict long-term fecal incontinence

INTRODUCTION: Obstetric anal sphincter injury (OASI) is associated with serious morbidity and reduced quality of life. The role of anorectal manometry (ARM) to guide treatment is unclear. We aimed to define the role of ARM and symptom assessment after OASI in predicting anal incontinence at long-term follow-up. METHODS: Prospective evaluation of 205 consecutive post-OASI women who underwent baseline ARM and symptom assessment in a tertiary setting was undertaken. Ninety-nine women were available for long-term follow-up (median 6.6 years). Associations between post-OASI ARM testing and short-term and long-term anal incontinence were examined in addition to clinical and obstetric factors. RESULTS: Fourth degree tears and lower anal resting and squeeze pressures were associated with short-term anal incontinence. Women with anal incontinence at baseline and women with lower anal resting pressure were more likely to suffer from long-term fecal incontinence (FI). A best-fit cutoff value of 59 mm Hg for baseline anal resting pressure predicted long-term FI, and none of the short-term asymptomatic women with an anal resting pressure of >59 mm Hg reported FI at long-term follow-up. DISCUSSION: Symptoms of anal incontinence and ARM in patients after OASI are both useful to predict subsequent long-term FI with a best-fit cutoff of 59 mm Hg for anal resting pressure. This provides rationale for routine ARM and accurate symptom assessment in all patients after OASI, to identify high-risk groups to follow and treat, and it may assist decision making regarding mode of subsequent obstetric deliveries.