Introduction

Chronic constipation is a common self reported gastrointestinal problem that affects between 2% and 34% of adults in various populations studied. Among the subtypes of constipation, obstructed defecation seems particularly common, occurring in about 7% of the adult population.1 In most people with this conditionan inappropriate (paradoxical) contraction or a failed relaxation of the puborectal muscle and of the external anal sphincter often occurs during attempts to defecate (fig 1). This paradoxical contraction of the pelvic floor muscles during straining at defecation is considered a form of maladaptive learning and is generally defined (without specifying the underlying pathophysiological mechanism) as outlet dysfunction constipation or, more precisely, pelvic floor dyssynergia.2

Cardinal symptoms of pelvic floor dyssynergia are straining at stools and feelings of incomplete evacuation, and the diagnostic criteria, recently updated in the Rome II report, include those for functional constipation (see box)3 plus at least two out of three investigations (radiology, manometry, and electromyography) showing inappropriate contraction or failure to relax the pelvic floor muscles during attempts to defecate.2