An increased rectal maximum tolerable volume and long anal canal are associated with poor short-term response to biofeedback therapy for patients with anismus with decreased bowel frequency and normal colonic transit time

PURPOSE: Biofeedback is an effective therapy for a majority of patients wit h anismus. However, a significant proportion of patients still failed to re spond to biofeedback, and little has been known about the factors that pred ict response to biofeedback. We evaluated the factors associated with poor response to biofeedback. METHODS: Biofeedback therapy was offered to 45 pat ients with anismus with decreased bowel frequency (less than three times pe r week) and normal colonic transit time. Any differences in demographics, s ymptoms, and parameters of anorectal physiologic tests were sought between responders (in whom bowel frequency increased up to three times or more per week after biofeedback) and nonresponders (in whom bowel frequency remaine d less than three times per week). RESULTS: Thirty-one patients (68.9 perce nt) responded to biofeedback and 14 patients (31.1 percent) did not. Anal c anal length was longer in nonresponders than in responders (4.53 +/- 0.5 vs . 4.08 +/- 0.56 cm; P = 0.02), and rectal maximum tolerable volume was larg er in nonresponders than in responders. (361 +/- 87 vs. 302 +/- 69 ml; P = 0.02). Anal canal length and rectal maximum tolerable volume showed signifi cant differences between responders and nonresponders on multivariate analy sis (P = 0.027 and P = 0.034, respectively). CONCLUSIONS: This study showed that a long anal canal and increased rectal maximum tolerable volume are a ssociated with poor short-term response to biofeedback for patients with an ismus with decreased bowel frequency and normal colonic transit time.