Obstetric anal sphincter injury - Prospective evaluation of incidence

PURPOSE: An obstetrically damaged anal sphincter is the principal cause of the development of fecal incontinence in otherwise healthy females. Reports suggest that such damage complicates as many as 35 percent of primiparous vaginal deliveries, with 13 percent of first-time mothers becoming 13 sympt omatic. In maternity units delivering 3,000 patients annually, it would fol low that 390 symptomatic patients would develop new symptoms each year. Thi s incidence of dysfunction does not reflect current clinical practice. We h ave investigated this discrepancy to establish the actual incidence of anal sphincter trauma associated with childbirth. METHODS: During a six-week pe riod, 159 females (105 primiparous and 54 para-I) were prospectively assess ed postnatally using a standardized symptom questionnaire, endoanal ultraso und, and anal manometry. This group constituted 84 percent of all eligible deliveries occurring in the unit during the study period. RESULTS: One pati ent developed fecal urgency after this delivery; there were no reports of f ecal incontinence. Anal sphincter injuries were identified ultrasonically i n 6.8 percent of primiparous patients, 12.2 percent of para-I patients havi ng vaginal deliveries, and 83 percent of patients having forceps deliveries overall. Manometric data provided confirmatory evidence, with significantl y reduced maximum squeeze pressures in patients with a disrupted anal sphin cter (P < 0.0005), CONCLUSIONS: A symptom questionnaire is inadequate to id entify anal sphincter injuries. The incidence of sphincter injury in relati on to vaginal delivery has been overestimated in previous published work. T his study demonstrates that the true incidence is 8.7 percent overall and t hat symptoms of sphincter dysfunction are uncommon-this is in keeping with current clinical practice.