Anal incontinence after obstetric sphincter tears: outcome of anatomic primary repairs

Obstetric sphincter tears lead to anal incontinence in 40 to 60 percent of affected women. Primary repair is usually performed without identifying the internal anal sphincter. Since 1999 digestive surgeons have participated in the primary repair of such tears at our hospital. The intention was to perform separate repair of the internal and external anal sphincter in cases of combined tears to achieve a lower incontinence rate than is usually reported after conventional primary repair. The aim of the present study was to evaluate our results after anatomic primary repair.

A follow-up study was undertaken after all primary repairs performed in 1999 and 2000. It included anal ultrasonography manometry and an assessment of incontinence (Wexner score).

A total of 74 women sustained obstetric sphincter tears during the study period, and 71 (96 percent) were assessed after a median of 27 months (range, 14-39 months). Nine women declined investigation with ultrasonography/manometry. Incontinence was present in 22 women (31 percent), of whom 17 had gas incontinence only. The symptoms were mild (Wexner score 1-2) in 11 women (50 percent). None of 17 women with normal ultrasonography results were incontinent versus 20 of 45 with pathologic ultrasonographic results (P = 0.001). The mean sphincter length, squeeze pressure, and resting pressure were significantly higher in women with Wexner scores of 0-2 vs. women with a score of more than 2. Sphincter length was inversely correlated with the degree of incontinence (P < 0.001).

The incontinence rate after anatomic primary repair is low compared with the last decade's reported results after conventional primary repair. A short anal sphincter after repair is associated with a poorer outcome.