BACKGROUND & AIMS:Disordered defecation is at-tributed to pelvic floor dyssynergia. However, clinical observations indicate a spectrum of anorectal dysfunc-tions. The extent to which these disorders are distinct or overlap is unclear; anorectal manometry might be used in diagnosis, but healthy persons also can have abnormal rectoanal pressure gradients during simu-lated evacuation. We aimed to characterize phenotypic variation in constipated patients through high-resolu-tion anorectal manometry.
METHODS:We evaluated anorectal pressures, measured with high-resolution anorectal manometry, and rectal balloon expulsion time in 62 healthy women and 295 women with chronic constipation. Phenotypes were characterized by princi-pal components analysis of high-resolution anorectal manometry.
RESULTS:Two healthy persons and 71 patients had prolonged (180 s) rectal balloon expul-sion time. A principal components logistic model dis-criminated healthy people from patients with pro-longed balloon expulsion time with 75% sensitivity and a specificity of 75%. Four phenotypes discriminated healthy people from patients with abnormal balloon expulsion times; 2 phenotypes discriminated healthy people from those with constipation but normal bal-loon expulsion time. Phenotypes were characterized based on high anal pressure at rest and during evacu-ation (high anal), low rectal pressure alone (low rectal) or low rectal pressure with impaired anal relaxation during evacuation (hybrid), and a short anal high-pressure zone. Symptoms were not useful for predicting which patients had prolonged balloon expulsion times.