Endosonography of the anal sphincter after ileal pouch-anal anastomosis. Relation with anal manometry and fecal continence.

PURPOSE

The aim of the present study was to visualize supposed defects of the internal anal sphincter after ileal pouch-anal anastomosis (IPAA) by anal endosonography and to relate these findings with anal manometry and fecal continence.

METHODS

We investigated 23 patients, visualized the sphincter complex by anal endosonography, and quantified the anatomic changes of the sphincter. Anal resting and squeezing pressures as well as length of the anal canal were determined by anal manometry. Continence was objectively scored by an observer not involved in treatment of patients and subjectively by patients themselves.

RESULTS

At anal endosonography, the mean thickness of the internal anal sphincter was 1.16 mm (95 percent confidence interval, 0.98-1.33), which is significantly less than in normal volunteers. Tapering of the internal anal sphincter only occurred in six patients (of whom two had a gap in the internal sphincter). In 17 patients endosonography showed a thin internal anal sphincter without essential variation in thickness over the complete circumference. Approximately eight weeks after ileostomy closure following IPAA, maximum resting pressure (MRP) and length of the anal canal appeared to be significantly decreased compared with values before IPAA (P = 0.001 and 0.002, respectively). These differences were less striking (P = 0.05 and 0.04, respectively) when measured six or more months after ileostomy closure. The extent of reduction of the MRP and thickness of the internal anal sphincter were not correlated with grade of continence or with subjectively scored continence.

CONCLUSIONS

IPAA leads to a reduction of thickness of the internal anal sphincter and reduction of the MRP. Tapering or gaps in the internal anal sphincter are probably caused by direct trauma to this sphincter because of mucosectomy, whereas in cases of circular reduction of thickness of the internal anal sphincter without tapering or gaps, direct trauma is an unlikely explanation; this reduction is probably caused by denervation. IPAA compromises continence to a variable degree in 18 of 23 patients. No correlations were found between the extent of reduction of the MRP and the extent of reduction in internal anal sphincter thickness or between these two parameters and objectively or subjectively scored continence. Difficulties in obtaining reliable information on continence may be a causal factor. A striking discrepancy was noticed among objective, scored disturbances in continence, and overall satisfaction concerning level of continence by patients themselves.