INCONTINENCE AFTER LATERAL INTERNAL SPHINCTEROTOMY - ANATOMIC AND FUNCTIONAL-EVALUATION

PURPOSE: This study was designed to evaluate the anatomic and function al consequences of lateral internal sphincterotomy in patients mho dev eloped anal incontinence and in matched controls. METHODS: The study i ncludes 13 patients with anal incontinence after lateral internal sphi ncterotomy and 13 controls who underwent the same operation and were c ontinent and satisfied with the results of the procedure. Patients und erwent clinical evaluation, anorectal manometry, pudendal nerve termin al motor latency testing, and endoanal ultrasonography. RESULTS: Sphin cterot omies were longer in incontinent patients (75 vs. 57 percent), but the resting pressure and length of the high-pressure zone were not different between groups. Surpris ingly, maximum voluntary contractio n was higher in incontinent patients than in continent controls (136 v s. 100 mmHg). Rectal sensation and pudendal nerve terminal motor laten cy mere similar in both groups. The defect in the internal sphincter w as wider in incontinent patients than in continent controls (17.3 vs. 14.4 mm), but these differences were not statistically significant. Th e thickness of the internal sphincter measured by endoanal ultrasound was identical in both groups, but the external sphincter was thinner i n incontinent patients both at the site of the sphincterotomy (6.8 vs. 8.1 mm) and in the posterior midline (7.1 vs. 8.6 mm). CONCLUSIONS: A nal incontinence after lateral internal sphincterotomy is directly rel ated to the length of the sphincterotomy. Whether secondary to preoper ative sphincter abnormality or the result of lateral internal sphincte rotomy, the external sphincter is thinner in incontinent patients than in continent controls.