Outlet dysfunction constipation

Abstract

The diagnosis of outlet dysfunction constipation in patients with idiopathic constipation that responds poorly or not at all to conservative measures, such as fiber supplements, fluids, and stimulant laxatives, is based upon diagnostic testing. These tests include colonic transit of radio-opaque markers, anorectal manometry or electromyography, barium defecography, and expulsion of a water-filled balloon. The literature suggests that conditions such as pelvic floor dyssynergia exist but may be over-diagnosed as a laboratory artifact. In our laboratory, we screen patients with balloon expulsion studies, and then test for dyssynergia only if the result of the balloon expulsion test is abnormal. In my opinion, anal sphincter electromyogram and manometry are equivalent in establishing the diagnosis. Barium defecography is helpful in making a diagnosis of a rectocele, but I prefer to document that vaginal pressure on the rectocele significantly improves rectal evacuation. Manometry also helps to establish the presence of megarectum, hypotonia, and weak expulsion efforts. Conceptually, biofeedback training, which incorporates simulated defecation, is the most logical approach to pelvic floor dyssynergia. It incurs no risk and benefits 60% to 80% of patients. The drawbacks are the time-intensive nature of the therapy and the short-term costs, which are offset if there is sustained benefit. There is no evidence that biofeedback is helpful in children with constipation. Habit training has established benefits, but recurrences are frequent and long-term reinforcement is helpful to maintain success. Laxatives and enemas are adjunctive therapies in both habit training and biofeedback. Surgery is effective in those uncommon patients with physiologically significant rectoceles, but surgical division of the puborectalis muscle is risky and unproven. Likewise, botulinum toxin injection into the puborectalis is unproven, but the effects are rarely permanent should incontinence occur. Diagnostic measures and therapeutic success are enhanced when patients are seen in centers experienced with the evaluation of these disorders.