What is Anorectal Manometry?

When does an anorectal manometry need to be performed?

This procedure is performed in the following situations:

• The study of constipation associated with an excessive effort to defecate or when there is a sensation of incomplete evacuation.
• To assess the function of the anal sphincter in cases of faecal incontinence.
• Prior to rehabilitation treatment of anorectal function using a biofeedback technique.
• In cases of anal pain (proctalgia).
• Before haemorrhoid surgery.

The technique has few contraindications, with the most important being:

• Serious medical or psychological conditions that prevent the necessary collaboration of the patient.
• Anal or rectal disease that prevents the insertion of the catheter (stricture or obstruction at the anorectal level).
• Infectious diarrhoea.

How should I prepare for Anorectal Manometry?

• A 250 cm3 enema is given the night before the test, or on the same day in the morning, to evacuate the rectum.
• Fasting beforehand is not necessary and the patient’s usual medication can be taken. 
• The use of ointments or topical anorectal treatments should be avoided for 6-12 hours before the study.
• Recent tests related to the condition under evaluation should be available (e.g. x-rays, ultrasound scans or electromyograms).

How is Anorectal Manometry performed?

The patient lies on his left side and a very fine probe or catheter is inserted about 10-12 cm through the anus into the rectum. The test begins 3-5 minutes later, after the probe has had time to settle.

The patient follows the instructions given by the health personnel during the test, such as closing the anus, coughing or trying to defecate to evaluate both the pressure at rest of the anus and rectum and that during simulated situations.

For patients with constipation, the study can be completed with a balloon expulsion test, which consists of inserting a probe with a balloon incorporated into its distal end, which is filled with enough warm water (often about 50 ml) to trigger the sensation of wanting to defecate. Afterwards, the time it takes for the balloon to be expelled is counted in the privacy of a bathroom.

No special controls are required after the test, and patients can continue with their usual activities.

How long does the test last?

It takes around 30-45 minutes.

What will I feel during Anorectal Manometry?

Normally, the test is not painful and is well tolerated; although there may be some temporary local discomfort as the probe is inserted.

What complications could there be?

Because the examination requires the insertion of a probe through the anal canal, it may lead to some slight bleeding or perforation. This is because the probe has a balloon at its distal end to distend the rectum with different volumes of air. This complication is more likely in patients with inflammatory bowel disease or those who have had an operation for rectal cancer, especially if they have also received radiotherapy. However, such events are highly infrequent.