Pelvic floor investigations for bowel dysfunction (part 2): anorectal physiology (manometry)

Anorectal physiology (or anorectal manometry) is used to guide diagnosis and treatment of defecatory disorder, including constipation and faecal incontinence. Systems in use include cheaper water-perfused manometers with disposable catheters and high-resolution solid-state manometers with multiple transducers. These measure the pressure exerted on the anal canal by the anal sphincter complex. Resting pressure measures the passive contraction of the internal anal sphincter, while squeeze pressure measures the voluntary contraction of the external anal sphincter. Balloon-tipped manometers can also test for the recto-anal inhibitory reflex (RAIR), which is key to controlled defecation. Balloon distension can also test for rectal sensation. Pudendal nerve involvement can be assessed with pudendal nerve terminal motor latency (PNTML) and anal-mucosal electro-sensitivity (AMES) tests. Anorectal physiology should form part of a combined clinical assessment, in conjunction with clinical history, endoanal ultrasound and defaecation proctography, to inform diagnosis and treatment of bowel dysfunction.