Background: Troublesome faecal incontinence following a lateral internal sphincterotomy (LIS) is often attributed to faulty surgical techniques: division of excessive amount of internal sphincter or inadvertent injury to the external sphincter. The aim of the present paper was to assess the anatomic and physiological factors that may contribute to faecal incontinence following a technically satisfactory lateral internal sphincterotomy by a group of colorectal specialists.
Methods: Fourteen patients (nine women, five men; median age: 38 years; range: 23-52 years) who developed troublesome postoperative faecal incontinence were evaluated by clinical assessment, endoanal ultrasonography and anorectal physiological studies (manometry, pudendal nerve terminal motor latency) by two independent observers. The Cleveland Clinic continence score (0-20; 0, perfect continence; 20, complete incontinence) was used to quantify the severity of faecal incontinence. Fourteen continent subjects after a LIS (nine female patients, five male patients; median age: 36 years; range: 20-44 years) were also evaluated as 'continent' controls (continence score </= 4).
Results: In the incontinent group, the median postoperative Cleveland Clinic continence score was 9 (range: 6-13) compared with a preoperative score of 1 (range: 0-3). On assessment by endoanal ultrasonography the site of the internal sphincterotomy was clearly identified. There were additional coexisting defects, on endoanal ultrasonography, of the external anal sphincter in seven female patients, of the internal sphincter in two female and two male patients; and a defect of both the external and internal sphincters in a male patient who had had a prior fistulotomy. The pudendal nerve terminal motor latency (PNTML) was prolonged in two female patients on the side contralateral to the lateral internal sphincterotomy. In two of five male patients there was no evidence of any occult sphincter injuries. In the continent controls a defect of the distal portion of the external sphincter was noted in one female patient. None of the patients had a prolonged PNTML. The maximum voluntary contraction was significantly lower in the female subjects than in the female continent controls (92 mmHg vs 140 mmHg; P < 0.05), while the resting anal canal pressures and length of the high pressure zone were similar between the study subjects and the continent controls.
Conclusion: Troublesome faecal incontinence after a satisfactorily performed lateral internal sphincterotomy is often associated with coexisting occult sphincter defects.