Anorectal physiologic evaluation of constipation.

Chronic constipation is a widespread problem which affects approximately 63 million people in North America alone. Although the majority of patients respond to changes in dietary fiber and water intake, as well as the judicious use of laxatives, a small portion will not and as a result, will be evaluated by gastroenterologists and colorectal surgeons. These patients most frequently have slow transit constipation, pelvic floor dysfunction, or some combination of the two. The physiologic evaluation of these patients comprises colonic transit studies, anorectal manometry, cinedefecography, electromyography, and pudendal nerve terminal motor latency testing. In this article, the authors describe the physiologic basis for these studies and review the techniques used in diagnosing these conditions.