Clinical and Physiologic Evaluation of Anorectal Function Following Low Anterior Resection

Lee, Sang Jeon; Park, Yoon Sang

Abstract

Twenty to twenty-five percent of patients are reported to experience problems with anorectal function after low anterior resection, complaining particularly urgency of defecation and minor fecal leakage, but the mechanisms underlying its cause and the recovery process are not well understood. We designed this study to elucidate the mechanism of anorectal functional problems and its recovery process after low anterior resection for rectal cancer by autonomic nerve preserving procedure. Standardized interviews and anorectal physiologic studies including balloon proctometry and manometry were performed in 32 patients preoperatively, and at 1 month, 3 months, 6 months and 1 year after the operation. Postoperatively stool frequency increased, the ability to defer defecation and discriminate stool characters were compromised, and anal incontinence scores increased, which recovered progressively by 6~12 months after the operation. Balloon proctometry showed that threshold volume, urgent volume and maximal tolerable volume decreased remarkably after the operation. The latter two parameters recovered considerably by 1 year after the operation. Rectal compliance also decreased significantly but it showed no evidence of recovery by 1 year after the operation. Anorectal manometry showed that maximum anal resting pressure decreased significantly after the operation which recovered significantly by 1 year after the operation. Maximum anal squeeze pressure showed no significant decrease after the operation. In most patients rectoanal inhibitory reflex was abolished after the operation, which recovered only in some cases by after 1 year. The group of short residual rectum(<4 cm, N=18) showed more impairment in continence and decrease in neorectal capacity and compliance than that of the long residual rectum(> or =4 cm, N=14). These results suggest impairment in fecal continence occurs due to decrease in rectal capacity, compliance, and anal canal pressure, and loss of rectoanal inhibitory reflex. Autonomic nerve preserving procedure could not prevent the decrease in resting anal pressure. Continence recovers clinically with increase in neorectal capacity, compliance and anal canal pressure but not with recovery of rectoanal inhibitory reflex. The length of the residual rectum seems to play an important role in the degree of impairment of continence and good continence can be expected when the residual rectum is more than 4 cm.