Anorectal testing

Anal manometry and a rectal balloon expulsion test, occasionally supplemented by defecography, are necessary for diagnosing functional defecatory disorders. Diagnostic testing is also useful for evaluating the pathophysiology and guiding management in fecal incontinence. Anal resting and squeeze pressures measured by manometry refl ect predominantly internal and external anal sphincter function, respectively. Disordered defecation is diagnosed by assessing rectal balloon expulsion and the rectoanal pressure gradient during simulated evacuation. Endoanal ultrasound and magnetic resonance imaging (MRI) visualize anal sphincter defects, scars, and atrophy. Both tests are comparable for the internal sphincter but only MRI identifi es external sphincter atrophy. Barium defecography can characterize rectal evacuation and pelvic fl oor function and thereby reveal evacuation disorders, excessive perineal descent, and rectoceles. Dynamic MRI provides similar information and also images the bladder and genital organs. Since the measurement of pudendal nerve latencies suffers from several limitations, anal sphincter electromyography is recommended when neurogenic sphincter weakness is suspected.