Dyssynergic defecation

Defecation normally involves the coordinated relaxation of the puborectalis and external anal sphincter muscles as pressure is building in the rectum (control panel, left). However, in patients with dyssynergic defecation (patient panel, right), ineffective defecation is associated with a failure to relax, or inappropriate contraction of, the puborectalis and external anal sphincter muscles as pressure increases in the rectum.