How to prepare for anorectal manometry

Anorectal manometry measures how strong the anal sphincter muscles are; as well as whether they relax during passage of stool. To prepare for anorectal manometry, do not eat or drink anything 2 hours before your procedure. Use Fleet® enema 2 hours before your appointment.

What is anorectal manometry?

Anorectal manometry measures pressures of the anal sphincter muscles, the sensation in the rectum, and the reflexes that are necessary for normal bowel movements. The test is done for patients with chronic constipation and fecal incontinence.

When stool enters the rectum, the muscles of the anal sphincter tighten up to prevent passage of stool when you don’t want it. If these muscles are weak or do not tighten up, leakage of stool (incontinence) may occur.

When a person bears down to poop, the muscles of the anal sphincter relax allowing passage of stool. If the muscles do not relax, stool does not come out leading to constipation.

Who should not do anorectal manometry

  • Patients with known obstruction of the anus or rectum.
  • Those that cannot follow instructions.
  • Patients with recent anus or rectum surgery.

What are the risks of anorectal manometry

Anorectal manometry is a safe out-patient procedure. Some people may experience sensation of wanting to poop during the procedure. Slight anal irritation and bleeding can occur. Perforation or tear in the rectum is rare. Equipment malfunction can occur.

How long does the anorectal manometry lasts

The test lasts about 30 minutes to 1 hour.

How do I prepare for anorectal manometry

7 days before your procedure

  • Call your doctor’s office if you’re unable to keep your appointment or you need to reschedule.
  • Buy Fleet® enemas from a pharmacy or drug store.


The day of your procedure 

  • Do not eat or drink anything 2 hours before your procedure.
  • You can take essential medications with small sips of water 2 hours before the test.
  •  If you have diabetes mellitus and take insulin, your insulin dose will be adjusted. Do not take short-acting insulin while you’re fasting.
  • Use one Fleet® enema 2 hours before your appointment. If you have no bowel movement after the Fleet® enema, use the second Fleet® enema.


What to expect during anorectal manometry

Your name and the procedure will be confirmed. You will change into a hospital gown and lie on your left side.  A small flexible tube (catheter) with a balloon at the end is inserted into the rectum. The tube is connected to a machine that measures the pressure. The small balloon is inflated in the rectum to assess reflexes that are necessary for normal bowel movements.

You will be asked to squeeze, relax, and push at various times. The anal sphincter muscle pressures are measured during each of these maneuvers. To squeeze, you tighten the sphincter muscles as if trying to prevent anything from coming out. To push or bear down, you strain down as if trying to have a bowel movement.

Two additional tests are also done.

Anal Sphincter EMG

An anal sphincter electromyography (EMG) is a test to evaluate the nerve supply to the anal muscle. It confirms the proper muscle contractions during squeezing and muscle relaxation during pushing.

In this test, a small electrode is placed in the anal canal. You will be asked to relax, squeeze and push at different times. The anal sphincter muscle electrical activity is displayed and recorded on a computer screen.

Balloon expulsion test

The balloon expulsion test evaluates your ability to evacuate stool.

In this test, a small balloon is inserted into your rectum and then inflated with water. You will be instructed to expel (defecate) the balloon from the rectum. How long it takes to expel the balloon is recorded. Prolonged balloon expulsion time suggests a problem with defecation.


What to expect after anorectal manometry

You do not need a driver to take you home because anesthesia is not used during the test. Resume regular activities after this. You can eat and take your medicines.

Your doctor will notify you of the results.


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