Long-term function and morphology of the anal sphincters and the pelvic floor after primary repair of obstetric anal sphincter injury.

AIM: More than 50% of women experience deteriorating continence over time following primary repair of obstetric anal sphincter injuries. The objectives of this study were to assess the function and morphology of the anal sphincters and pelvic floor in women with long-term faecal incontinence after sphincter repair (primary end-point) and to evaluate their correlation with severity of incontinence (secondary end-point). METHOD: The participants in this prospective study were recruited from a cohort of all women who sustained third or fourth degree obstetric sphincter injury reconstruction (cases) from January 1976 to November 1991. The women who delivered immediately before and after each case, without sustaining obstetric damage, were included as controls. Cases and controls were stratified into three categories: (i) continent; (ii) minor incontinence; and (iii) severe incontinence. The function and morphology of the anal sphincters and pelvic floor were evaluated by MRI, three-dimensional endoanal ultrasonography and anorectal physiology tests. RESULTS: Fifty-nine women (29 cases/30 controls; mean age 51/53 years; mean follow-up 23.7/24.1 years, respectively) were assessed. Morphologically, cases had a significantly shorter anterior external anal sphincter length compared with controls when evaluated by three-dimensional endoanal ultrasonography (8.6 vs 10.2 mm; P = 0.03). Functionally, cases with severe incontinence had a significantly shorter anterior sphincter length compared with cases with minor incontinence (7.7 vs 10.4 mm; P = 0.04). No correlation could be found between anal pressures and severity of incontinence in the case group. CONCLUSIONS: Cases had a significantly shorter anterior external anal sphincter length. Functionally, anterior sphincter length correlated with increased severity of incontinence.