Anorectal function after low anterior resection of the rectum

Impaired neorectal function or sphincter incompetence have been respectively implicated as causative factors of increased frequency of defaecation or incontinence after low anterior resection of the rectum (LARR) for rectal carcinoma, although individual mechanisms of anorectal function have not been fully studied. Functional and laboratory results were evaluated in 19 subjects, who had a LARR for rectal carcinoma before and after the procedure, and were compared to those of normal subjects. LARR worsened anorectal function, mostly by significantly increasing the daily number of defaecations (p < 0.001), while major incontinence was reported in three cases. Patients with rectal carcinoma have a decreased resting anal pressure on manometry, as compared to controls (p < 0.001). LARR further reduces anal resting pressure (p < 0.001) as well as all parameters that express internal sphincter activity, such as presence and amplitude of either slow (p < 0.05 and p < 0.01) or ultraslow waves. LARR also impaired external anal sphincter activity, as expressed by the reduction in anal squeeze pressure (p < 0.001). Anorectal sampling was found reduced in incidence and frequency in LARR patients as compared to controls (p < 0.01 and p < 0.001), and was impaired even further postoperatively (p < 0.001). Rectoanal inhibitory reflex was present in all but three patients postoperative, but significantly impaired as compared to controls. Rectal volumes to elicit transient or permanent desire to defecate, maximal tolerable rectal volume and rectal compliance were also significantly reduced after LARR (p < 0.001, p < 0.001, p < 0.01 and p < 0.001 respectively). Large bowel transit was significantly enhanced after LARR (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)