Anal incontinence and obstetric sphincter tears

Abstract

PURPOSE: To evaluate the prevalence of anal incontinence (AI) in primiparous women five years after their first delivery; to investigate if an 8-12 hour time delay of primary repair affects AI at 1-year follow-up; to study the association between endoanal ultrasonography and anorectal manometry in relation to AI in primiparous women; to evaluate whether an endoanal ultrasonographic derived sphincter length-index correlates to subjective AI.

METHODS: Primiparous women were prospectively followed with questionnaires before the pregnancy, at 5 and 9 months, and 5 years after the delivery. 242/349 women completed all questionnaires. Women with sphincter tear at their first delivery were compared to women without such injury. Risk factors for development of AI were analyzed. 165 women diagnosed with obstetrical sphincter tear at delivery were randomised to immediate or delayed (8-12 hour delay) repair. 78 were allocated to immediate operation and 87 to a delayed repair and followed for 12 months. A nested case-control study of 108/165 women from the randomized controlled trial was performed to compare findings at anorectal manometry and endoanal ultrasound 1 year after their repair. Cases were defined as having a greater score than 2 on the Pescatori incontinence scale, controls as having a score of 2 or less. 116 primiparous women who had experienced a 3rd or 4th degree obstetric tear were examined using three-dimensional endoanal ultrasonography and compared to a control group of nineteen nulliparous women to evaluate a sphincter length-index.

RESULTS: AI increased significantly during the 5-year follow-up. Among women with sphincter tears, 44% reported AI at nine months and 53% at five years (p=0.002). Risk factors for AI at five years were age (OR 2.2, 95% CI 1.0; 4.6), sphincter tear (OR 2.3, 1.1; 5.0) and subsequent childbirth (OR 2.4, 1.1; 5.6). In the randomized study of delayed vs. immediate sphincter repair there was no significant difference in AI between the groups. Of the manometric variables, volume of first sensation and volume of first urge proved to be associated with AI at univariate statistical analysis. A distal scar in the external anal sphincter, age, degree of tear, and duration of second stage of labor were independently associated with AI. Patients with a previous grade 3-4 obstetric injury had a shorter external anal sphincter (p<0.001) and a lower IAS-index (p=0.03) than the controls. Patients with fecal urgency and flatus incontinence had a lower IAS-index (p=0.03 and 0.01 respectively). The EAS-index score was significantly lower in patients with fecal urgency (p=0.02).

CONCLUSIONS: AI among primiparous women increase over time and is affected by further childbirth. There is no benefit or harm, with regards to anal continence at 1 year follow up, in delaying primary repair up to 12 hours after the delivery. Impaired rectal sensation at ano-rectal manometry and a distal scar at endoanal ultrasonography are associated with AI one year after primary sphincter repair in primiparous women. Measured by 3D endoanal ultrasound, the sphincter complex in nulliparous women is anatomically different when compared to women who have experienced primary repair after an obstetrical sphincter injury. An internal anal sphincter length index can be calculated based on ultrasonographic measurements and the IAS-index may correlate to the degree of AI.