Abstracts
2000 Digestive Disease Week

# 2240 Morphological Changes of the Anal Sphincter Musculature During and After Temporary Stool Deviation.
Marco A. Sailer, Martin Fein, Karl H. Fuchs, Dieter Bussen, Claudia Grun, Arnulf Thiede, Wuerzburg, Germany

PURPOSE: Temporary stool deviation, using either an ileo- or a colostomy, is a well known surgical principle to protect low colorectal or coloanal anastomoses. The purpose of this study was to evaluate any morphological changes with regard to the anal sphincter muscles during and after temporary ileostomy. METHODS: Some 44 (21 female:23 male; median age 67) patients with rectal carcinomas of the lower and middle third were studied prospectively. All patients underwent a low anterior resection with total mesorectal excision and primary low colorectal or coloanal anastomosis. Reconstruction was performed using either a coloanal pouch (n=23) or a straight end-toend anastomosis (n=21). A protective stoma was fashioned in all cases (ileostomy n=41, colostomy n=3). Stoma closure was carried out after a median of 85 (41-330) days. Using a standardized protocol anal sphincter strength (puborectalis, external anal (EAS) and internal anal sphincter (IAS)) was assessed by endoanal ultrasound preoperatively, at the time of stoma closure, and three-monthly thereafter for one year. Statistical analysis was carried out using the Wilcoxon test (P<0.05). RESULTS: The thickness of the puborectalis muscle decreased from a median preoperative value of 6.3 to 5.7 mm at the time of stoma closure (P=0.03). After three months 6.2 mm were measured. This value remained stable for the complete follow-up period. Similar results were recorded for the EAS which dropped from 6.7 to 6.1 mm (P=0.008) reaching the preoperative level again after three months. The IAS thickness remained stable throughout the study period, measuring between 2.1 and 2.4 mm. CONCLUSION: It is concluded that temporary stool deviation does lead to morphological changes of the anal sphincter. While the smooth muscles (IAS) remains unchanged, the striated counterpart (puborectalis and EAS) undergoes hypotrophic transformation. However, after passage reconstruction, i. e. stoma closure, a rapid regeneration of the voluntary muscles is observed.