Anorectal Manometry

What is anorectal manometry?

Anorectal manometry is a test to evaluate your anal and rectal muscles. These muscles work together with your brain to control your bowel movements. If you’ve been having difficulties with bowel movements, it could be related to how these muscles function. Anorectal manometry is a way of measuring your muscle contractions to determine if they’re activating and coordinating correctly.

Why would you need an anorectal manometry test?

A healthcare provider might recommend an anorectal manometry test if you've been having trouble pooping when and where you want to. It’s one step in the process of evaluating symptoms like:

• Dyschezia (pain or strain with pooping).
• Obstructed defecation (feeling like your poop can’t come out).
• Chronic constipation (hard, infrequent poops).
• Fecal incontinence (trouble holding poop in).

A healthcare provider may also use the test to evaluate your muscle function after an injury or surgery, or to check whether a chronic disease has begun to affect your anorectal motility (motor function).

Anorectal manometry can help diagnose conditions that may explain your constipation, such as:

• Anismus (dyssynergic defecation).
• Hirschsprung disease.

It can also explain the origin of fecal incontinence — what’s going wrong and where. After diagnosis, the same technology used in the test can be used as a treatment to retrain the muscles involved.

How does anorectal manometry work?

A manometer is a pressure transducer. It measures the pressure in your muscle contractions to determine whether they’re too strong, too weak or not triggering at the right time. A healthcare provider places the transducer inside your anus and rectum. It sends data to a machine that reads it.

The transducer is a long, flexible tube (catheter) with pressure sensors on it. On the inside end, it’s attached to a deflated balloon. When a healthcare provider inflates the balloon inside your rectum, it activates the nerves that trigger the urge to poop. This should stimulate your natural muscle reflexes.

What is the prep for an anorectal manometry?

It’s best that your anus and rectum are empty for the test. Your healthcare provider will ask you to refrain from eating before the test and to use an enema to clear out your anus and rectum at home. They’ll give you specific instructions on when and how to do this, and advice on which products to use.

What happens during the anorectal manometry procedure?

1. When you arrive for the test, you’ll undress from the waist down or change into a hospital gown. You’ll lie on a table on your side with your knees up.
2. A healthcare provider may perform a brief digital rectal exam before inserting the catheter. That means inserting a gloved finger to check for anything abnormal in your anus or rectum.
3. They’ll lubricate the end of the catheter to help it go in smoothly, then gently advance it through your anus into your rectum.
4. They’ll take pressure readings at different depths inside your rectum to establish your baseline internal pressure. Then, they’ll inflate the balloon.
5. Your healthcare provider will take pressure readings with the balloon inflated to different sizes and in different positions inside your rectum. They’ll ask if you can feel these changes or if you feel the urge to poop.
6. They’ll ask you to squeeze, relax, push and cough at different intervals. They’ll record your voluntary and involuntary muscle responses.

How long does anorectal manometry take?

It takes an average of 30 minutes. It may range from 15 to 45 minutes.

How painful is anorectal manometry?

You might find it mildly uncomfortable, particularly if you’re sore inside your rectum or anus, but it shouldn’t be painful. The catheter and the balloon only produce as much pressure as a normal poop would. If you’re anxious about it, though, you can discuss sedation with your healthcare provider.

What is a balloon expulsion test?

Your healthcare provider may combine anorectal manometry with a balloon expulsion test at the end. This is an extra step to see if you can “poop” out a filled balloon, and how long it takes you. You’ll do this part in privacy, in a sitting position. Sensors on the balloon will record the pressure and time involved.

Are there risks or side effects to anorectal manometry?

There aren’t any significant risks or side effects unless you have an allergy to the latex balloon. Your healthcare provider can provide a latex-free option if you discuss this with them in advance. If your anus or rectum was inflamed or irritated, you might feel a little sore or have mild bleeding afterward.

What will the results of my anorectal manometry show?

The results will show whether the muscles and nerves involved in pooping are functioning correctly, and where the problem is if they aren’t. Normal results will show:

• Stool entering your rectum causes it to relax and stretch to accommodate it (rectal compliance).
• Stretch receptors (nerves) in the wall of your rectum trigger the urge to poop (rectal sensation).
• Your internal anal sphincter automatically relaxes in response (rectoanal inhibitory reflex).
• Your external anal sphincter contracts when your internal one relaxes to hold on to your poop until you’re ready (rectoanal contractile reflex). It tightens if you cough (cough reflex).
• Your external anal sphincter responds to your voluntary commands to squeeze, relax or push.
• Attempting to poop increases pressure in your rectum while causing your external anal sphincter to relax to allow poop to pass (coordinated anorectal pressure changes).

If any of these functions don’t work as they should, you might have an abnormal test result. Abnormal results might show:

• Poop in your rectum doesn’t trigger the urge to defecate. Your rectum doesn’t stretch enough, or the stretch receptors aren’t transmitting signals to your brain.
• You feel the urge to poop, but your automatic muscle reflexes aren’t responding.
• Your muscles respond incorrectly. For example, they tighten when they should relax or relax when they should tighten.
• Your muscles do the right thing but at the wrong time, or they aren’t coordinating together.
• Your muscle contractions are weak and ineffective.
• Your muscles are too tight, even when they try to relax.

Can anorectal manometry lead to effective diagnosis and treatment?

Yes. Once your healthcare provider is able to determine which muscles are malfunctioning and how, they can employ different techniques to help retrain the muscles. Typical therapies include:

• Biofeedback therapy.
• Physical therapy for pelvic floor dysfunction.

A note from Cleveland Clinic

Anorectal manometry is a brief and painless test that can give your healthcare provider crucial information about how your anorectal muscles are functioning. You might feel reluctant to use your pooping muscles in a medical exam, but if you’re having pooping difficulties, it’s worth it to find out why. Once you do, you can begin an appropriate therapy program to treat your condition.