Anorectal manometry

An anorectal manometry test diagnoses fecal incontinence, constipation and other difficulties related to bowel movements. By measuring the pressure of your rectal or anal muscles, your doctor will better understand your condition.

Anorectal manometry is performed as a simple outpatient test. Pressure sensors measure:

• The strength of the anal sphincter muscles
• Movements of the rectal and anal muscles
• Sensation in the rectum
• Nerve reflexes needed for bowel movements

Why would you need an anorectal manometry test?

Your doctor may recommend an anorectal manometry test if you have difficulty with bowel movements. The test may be recommended if you experience:

• Chronic constipation
• Fecal incontinence, or difficulty holding stool in
• Irritable bowel syndrome or inflammatory bowel disease
• Obstructed defecation, meaning something is blocking your stool
• Painful bowel movements
• A related injury or surgery

Anorectal manometry prep overview

If you need an anorectal manometry, you’ll begin preparing two days in advance. Stop taking narcotic medications and those that increase muscle contractions 48 hours before your appointment.

One day (or 24 hours) before your appointment, stop taking the following:

• Antidiarrheal medications
• Calcium channel blockers
• Antihistamines
• Anti-inflammatory creams and gels
• Bile sequestrants, such as cholesterol-lowering drugs

Anorectal manometry prep on the day of the test

Stop eating solid food six hours before your appointment. One hour before, stop drinking all liquids. If you regularly take medicine during this time, take it with just a few sips of water.

For best results from your anorectal manometry, you’ll need to clear your bowels using an enema. Your doctor may direct you to do this twice.

How the anorectal manometry test works

Before your anorectal manometry test, you’ll undress from the waist down or wear a hospital gown. During the procedure, you’ll lay on your left side with one or both knees bent and pointing forward, as though sitting.

Your doctor might start by performing a digital rectal exam to detect abnormalities. Then they’ll insert a narrow tube called a catheter into your rectum. A small balloon on the end of the tube helps measure your reflexes and sends the results through the tube to a computer for your doctor to evaluate.

What is a balloon expulsion test?

A balloon expulsion test is commonly paired with an anorectal manometry. While an anorectal manometry takes pressure readings to determine your rectal strength, a balloon expulsion test is a direct demonstration of your ability to effectively poop.

During a balloon expulsion test, a latex balloon attached to a catheter is inserted into your rectum. A syringe filled with warm water inflates the balloon. You then expel the balloon while sitting upright, just like during a bowel movement.

How long does anorectal manometry take?

The average anorectal manometry takes 30–45 minutes, give or take roughly 15 minutes.

Does anorectal manometry hurt? Is anesthesia used?

Though the procedure may involve some discomfort, you shouldn’t experience pain. In anorectal manometry, anesthesia is not necessary and you can drive home afterward.

Does anorectal manometry have side effects or risks?

Side effects are not common after an anorectal manometry. If your anus or rectum is inflamed, a little soreness or bleeding can be normal. If you’re concerned about the risk of pain during your test, talk to your doctor in advance.

Also talk with your doctor beforehand if you have a latex allergy to ensure a latex-free procedure.

Anorectal manometry results

Results from your anorectal manometry are taken through pressure sensors and sent to computer software. The sensors measure things such as:

• Coordinated anorectal pressure changes: Whether internal pressure causes the external anal sphincter to relax
• Rectal compliance: If the rectum relaxes and stretches appropriately
• Rectal sensation: If rectal nerves correctly trigger the sensation that you need to poop
• Rectoanal inhibitory reflex: Whether your internal anal sphincter relaxes at the right time
• Rectoanal contractile reflex: If your external anal sphincter contracts when your internal one relaxes

Anorectal manometry vs. colonoscopy

An anorectal manometry test is different from a colonoscopy. An anorectal manometry test measures the pressure, sensation and reflexes of the anal sphincter and rectum using a catheter and pressure sensors. Its results are specific only to the anus and rectum.

A colonoscopy uses a camera to travel through the anal canal and visually inspect the large intestine, or colon. This diagnostic tool allows for visual inspection of abnormalities in the colon, particularly polyps, cancer or inflammatory bowel disease.

Is anorectal manometry the same as anal sphincter myography?

While anorectal manometry and anal sphincter myography both test the anal sphincter, anorectal manometry detects pressure levels whereas anal sphincter myography measures the amount of nerves present in the anal sphincter.

What are common treatments following anorectal manometry testing?

Following the results of an anorectal manometry, your doctor will be able to determine the best treatment for you and your condition.

Common treatment options

• Biofeedback therapy: A mind-body therapy that helps discipline the anal sphincter and pelvic floor muscles, improving sensation and coordination for better control and reduced straining during bowel movements.
• Diet and lifestyle changes: Increasing dietary fiber and drinking plenty of fluids can help make bowel movements easier and relieve constipation and fecal incontinence.
• Medications: If muscles function properly, laxatives or stool softeners may be recommended to ease bowel movements.
• Pelvic floor physical therapy: Specialized exercises to strengthen or relax pelvic floor muscles, often used alongside biofeedback therapy.
• Surgical options: Considered for severe cases, such as sphincter repair for incontinence or other structural issues.