The most widely used test for anorectal function is anorectal manometry, and "Guidelines" recommend anorectal manometry in patients with fecal incontinence and chronic constipation. However, it is also useful for pre/post-surgical evaluation of anal sphincter tone, functional anorectal pain, pelvic floor dyssynergia, and diagnosis of Hirschsprung’s Disease. Anorectal manometry measures the pressures of the anal sphincter muscles, sensation in the rectum, and the neural reflexes that are needed for normal bowel movements. A general list of indications for anorectal manometry is below, and a more detailed and descriptive list is further below.
- chronic constipation
- fecal incontinence
- differential diagnosis of the anal pain
- patients assessment before and during biofeedback training
- risk assessment of the rectoanal function disorders after rectal/anal surgeries
Anorectal manometry provides many useful data regarding anorectal function. Anorectal manometry indicates the prognosis of treatment, particularly in the management of sphincter injuries and may be used in biofeedback treatment of anismus and solitary rectal ulcer syndrome. Appropriate interpretation and clinical correlation of these tests are of paramount importance.
Anorectal Manometry is typically used to aid in the treatment of the following disorders:
- Chronic Constipation - Anorectal manometry can identify the cause of constipation in patients with suspected non-mechanical obstructive defecation
- Fecal incontinence - In women, the pudendal nerve or anal sphincter may be injured during childbirth, which may contribute to weakening of continence mechanisms. In such cases, the diagnosis can be established by combining anorectal manometry and anal endosonography. In one series that evaluated this approach, the combination of these two tests correctly identified 90 percent of known anal sphincter injuries1
- Pelvic floor dyssynergia - Patients with pelvic floor dyssynergia or obstructive defecation do not straighten the anorectal angle during defecation as a result of failed relaxation of the puborectalis muscle and the external anal sphincter. The diagnosis is suggested during anorectal manometry by inappropriate contraction of the external anal sphincter while the patient is attempting to stimulate defecation. The balloon expulsion test may also be useful for diagnosing this disorder
- Reduced rectal sensation - Reduced rectal sensation during balloon distention can be associated with increased rectal compliance or megarectum, which is often seen in children and elderly persons with fecal impaction
- Hirschsprung’s disease - Children and young adults with severe constipation from birth should be assessed for Hirschsprung’s disease (congenital megacolon), a disorder associated with absence of intramural ganglion cells of the submucosal and myenteric plexuses as a result of arrest of neural crest cell migration during embryonic development.
- Anismus - In patients with anismus the obstruction to defaecation is because of failure of normal relaxation of puborectalis and the external sphincter during straining. This condition is recognized by physiological measurements which show increased activity in the external sphincter on straining.
For additional information regarding American Gastroenterological Association "medical position statement on anorectal testing techniques", you will find the full guidelines here.
[Primary Source: Anorectal Manometry: Current Techniques and Indications]