Anal sphincter asymmetry in anal incontinence after restorative proctectomy for rectal cancer

Abstract

PURPOSE: The morphology and physiology of the anorectum can be altered after restorative proctectomy, which may result in anal incontinence. Thus far, there have been few reports regarding the specific characteristics and management of anal incontinence after rectal cancer surgery. We attempted to determine the characteristics of anorectum in anal incontinence after restorative proctectomy. METHODS: We compared the clinical and physiologic factors between consecutive 138 patients with continence and 48 with iatrogenic anal incontinence at 1 year after rectal cancer resection. This study excluded patients at less than 1 year after operation or ileostomy takedown. RESULTS: The two groups were comparable with regard to age, sex ratio, radiotherapy, and complication rate. The percentages of asymmetry of the resting and squeeze sphincter were significantly higher in the anal incontinence group (37.2 +/- 9.3% vs 32.5 +/- 6.7%, P = 0.01; 32.4 +/- 7.8% vs 28.3 +/- 6.3%, P = 0.011). High-pressure zone length, mean resting vector volume, and rectal compliance were not less in the anal incontinence group than in the continence group. In multivariate analysis of manometric variables, the percentages of asymmetry of the resting and squeeze were independent factors associated with anal incontinence (P < 0.05). The mean thickness of the anal cushion and internal anal sphincter did not significantly differ between the anal incontinence and continence groups. CONCLUSION: Sphincter asymmetry is one of the hallmark characteristics of iatrogenic anal incontinence patients after proctectomy, which suggests that anal canal symmetry may be a beneficial factor with regard to anal continence.