A retrospective review of 1495 patients with obstetric anal sphincter injuries referred for assessment of function and endoanal ultrasonography

Aim Obstetric anal sphincter injuries are a significant risk factor for faecal incontinence. Correct identification and successful primary repair are important. The aim of this study was to review the outcome of all patients, with an obstetric anal sphincter injury, referred to our unit. Method This is a retrospective review of 1495 patients over a 12-year period. All had a third or fourth degree tear and were referred at 4-months postpartum. Results Endoanal ultrasonography demonstrated residual sphincter defect in 792 (53%) and normal sphincters, with no evidence of repair, in 661 (44%). The majority of injuries involved both the external and internal sphincters (n = 501). Significant reductions in resting pressure and voluntary squeeze pressures were seen when those with a sphincter defect were compared to those with intact sphincters. However, there was no significant difference in the mean (SD) Cleveland Clinic faecal incontinence scores (5.8 (5.8) and 4.3 (5.5), p = 0.8). Conclusion Third and fourth degree tears appear to be over diagnosed. Primary repair appears to be unsuccessful in the majority of cases. There appears to be poor correlation between objective and subjective assessment of sphincter function.