Anorectal Manometry: Does It Improve the Pathophysiology Knowledge?

Anorectal manometry (ARM) is the most established investigative tool to detect functional diseases of anal sphincter and/or rectoanal coordination. It allows to evaluate the pressure of the anal canal and the distal rectum, providing motor and sensory information on functional phases of defecation and continence of the anorectal tract and of the pelvic floor muscles. Manometric examination allows to recognize multiple mechanisms underlying several frequent anorectal diseases such as fecal incontinence, chronic constipation, and chronic proctalgia. It is also useful in the preoperative and postoperative evaluations of patients with anorectal disease and provides multiple indications for rehabilitation programs through the biofeedback therapy. The integrity of anal sphincter function is assessed evaluating the resting sphincter pressure, the functional length of the anal canal, and squeeze sphincter pressure and the integrity of neural reflex pathway by measurement of anocutaneous reflex, cough reflex, and rectoanal inhibitory reflex (RAIR). Rectal sensitivity and rectal compliance are assessed using a balloon distention filled with air or water. ARM should be performed in conjunction with a balloon expulsion test (BET) that is used to evaluate the patient’s ability to evacuate a stool surrogate. Recently, an advanced high-resolution anorectal manometry (HRAM) has been introduced. It allows a more intuitive evaluation of the anorectal function without the need for pull-through of the catheter; however, the high costs of the technology still strongly limit its diffusion and therefore its use in clinical practice.