Anorectal manometric characteristics differ in biofeedback for postoperative fecal incontinence

Biofeedback training has been suggested as an acceptable treatment for postoperative anal incontinence. To clarify the mechanism underlying its successful use, we conducted a study involving 12 patients with diagnoses of anal incontinence. Six of the patients had had fistulectomies and the remaining six were post-low anterior resection (LAR) patients. All underwent anorectal manometry (ARM) before and after biofeedback training. ARM parameters analyzed were the anal mean resting pressure, anal maximal voluntary contraction pressure, the threshold of rectal sensation and rectal compliance. The group of post-fistulectomy patients showed a significant increase in anal mean resting pressure (p=0.0457) and maximal voluntary contraction pressure (p=0.026) after 3 months of biofeedback training. The group of patients with low anterior resection had different patterns of change, showing a significant decrease in rectal compliance (p=0.0039) and a slight decrease in the threshold of rectal sensation (p=0.0547). Different patterns of change in ARM imply that different mechanisms were responsible for the effects of biofeedback training in each group. Biofeedback was able to functionally strengthen the efficacy of both the external sphincter and the tonically contracted internal sphincter. However, the increase in rectal sensation after biofeedback training provided post-LAR patients more time to go the toilet before they had an episode of incontinence. Adjustment in biofeedback training to achieve different goals for different types of patients should be emphasized.