Defecation disorders: an important subgroup of functional constipation, its pathophysiology, evaluation and treatment with biofeedback.

Functional defecation disorders are common and affect approximately 50% of patients with chronic constipation. The etiology of functional defecation disorders is not well known, but several pathophysiologic mechanisms have been described, including failure of rectoanal coordination, paradoxical anal contraction or insufficient relaxation of anal sphincter during defecation and impairment of rectal sensation as well as secondary slowing of colonic transit. Symptoms alone are inadequate to distinguish patients with defecation disorders from those with other types of constipation. Detailed clinical evaluation and anorectal physiologic tests are required for definitive diagnosis. There is also a pathophysiological association between functional defecation disorders and other anorectal conditions such as solitary rectal ulcer syndrome. Among the various treatment modalities, biofeedback therapy has emerged as an effective and specific treatment method for functional defecation disorders. The main goals of biofeedback therapy are to relax the pelvic floor and anal sphincter muscles during defecation and to improve rectoanal coordination and sensory perception. Today, it is possible to diagnose most functional disorders of defecation and either effectively treat or ameliorate symptoms in a majority of these patients.