What is Anal Manometry? And Why Is It Used?

Posted by Clark Love on Nov 15, 2021 10:17:51 AM

Anorectal manometry is a medical procedure designed to measure whether the muscles—particularly the sphincter muscles—in the anus and rectum are functioning optimally.

Sphincter muscles tested during an anorectal manometry procedure

The Purpose of an Anorectal Manometry Procedure

The main purpose of an anorectal manometry test is to assess bowel movement in those suspected to be suffering from fecal incontinence.

Fecal incontinence is an embarrassing condition characterized by leakage of feces from the rectum at unexpected times and in unexpected places. 

While prevalence rates of fecal incontinence are less than 10% in community settings, the rates shoot up to between 45%-47% in care home settings—and is usually cited as one of the major factors for the institutionalization of the elderly. 

Conditions For Which an Anorectal Manometry Test is Required

An anorectal manometry test is not just required for evaluating fecal incontinence. While fecal incontinence and constipation are the leading anorectal conditions, other anorectal conditions for which the test may be recommended include:

  • Megacolon or megarectum: This condition is characterized by sustained dilation of the large intestine or the rectum.
  • Functional anorectal pain: This condition is characterized by chronic pain in the area around the pelvis.
  • Hirschsprung’s disease: This is a pediatric condition marked by the absence of some nerves in the large intestine muscles. As a result, stool passes through the intestines at a very slow speed.


How an Anorectal Manometry Procedure is Performed

This is an overview of what takes place when a doctor wants to test for the functioning of the muscles in the rectum in an anorectal manometry test. Most often the test is performed by a knowledgeable nurse that is trained in performing anorectal manometry testing, but on occasion the doctor will perform the test.

The steps include:

  • Having necessary tools or equipment.
  • Patient preparation.
  • Actual procedure.

Anorectal Manometry Testing Tools and Equipment

First, the nurse will ensure that they have the necessary tools and equipment for the anorectal manometry procedure.

Usually, the anorectal manometry testing system has four components:

  • A device that senses pressure, usually a balloon.
  • An amplifier that may also work as a recorder: This device converts, displays, and stores pressure signals and readings.
  • A screen or a monitor to display the readings, and
  • Anorectal manometry software for data analysis.

With tools and equipment ready, it will be time to prepare the patient.

Patient Preparation for an Anorectal Manometry Test

There’s no major preparation required for an anorectal manometry test. The patient may even continue taking their medications. However, the patient should empty their bowel before the test.

The gastroenterologist may recommend one or two enemas about two hours before the procedure.

The physician takes the history of the patient, including a record of surgical and anorectal events. The nurse will also document the presenting symptoms, known allergies, and history of drug use.

After this, it’s safe to head to the procedure room exam room where the test will be performed.


The Actual Anorectal Manometry Procedure

This procedure should start with positioning the patient correctly. Traditionally, the nurse administering the test will require patients to be positioned in a left lateral position as follows. 

Left lateral position required for an anorectal manometry procedure

However, some studies have shown that an anorectal manometry procedure can be performed when the patient is seated or squatted without compromising the diagnosis results.

One advantage of these other surgical positions is that they are more consistent with the natural physiological condition of the bowel.

Additionally, it’s important to note that a seated position may produce more accurate rectal pressure results, particularly if your provider is using a solid-state sensor.

After proper positioning, the nurse will gently insert a lubricated balloon through the patient’s anus and into his rectum. The balloon is usually attached to a catheter, which should be soft and very flexible.

The nurse then proceeds to perform a series of tests as follows.

Anorectal Manometry Tests

The components of a full anorectal manometry test are reviewed below.

Testing for At-Rest Pressure 

After gently inserting the balloon, give the patient around 5 minutes to relax. This is for the sphincter muscles to get back to their original tonal conditions. 

After this, take at least 20 seconds to measure the at-rest pressure at various distances from the anal verge. The difference between the intra-rectal pressure and the highest recorded at-rest pressure is the resting pressure.

The normal resting pressure range, which is acceptable, is relatively wide. For instance, in women aged above 50 years, it can range from 33–91 mmHg.

Testing for Squeeze Sphincter Pressure

Here, you’ll ask your patient to squeeze their anus continuously for a maximum of 30 seconds. You should monitor the movements of the balloon and adjust its location as needed. Squeeze tests measure the health and tone of external anal sphincter muscles. 

Generally, you should expect lower pressure readings for women than for men. Squeeze pressure also tends to decrease with age.

While low pressure may not indicate sphincter muscle injury, it may indicate:

    • Injury of the puborectalis muscle
    • Injury of the external anal sphincter
    • History of sexual abuse

On the flip side, high pressure may indicate chronic pelvic pain.

Cough Reflex Test

Here, the nurse will ask the patient to cough. Alternatively, the nurse may ask their patient to inflate a balloon. This procedure tests for the soundness of the spinal reflexes.

An irregular cough reflex in addition to a low squeeze pressure may indicate some defect in the sacral reflexes. This could be because the sacral spine is injured or, for some other reason, dysfunctional.

Simulated Defecation

Also known as simulated evacuation, this procedure tries to mimic what happens during normal defecation. The nurse will then carefully monitor the pressure and behavior of the sphincter muscles. 

In normal situations, an increase in rectal pressure simultaneously corresponds to a relaxation of the external sphincter muscles. This physiological reaction is assessed using a measure known as Defecation Index (DI).

A normal defecation index is above 1.5

Rectal Sensation Test

This manometry procedure measures the first sensation to pass stool. 

Here, the nurse will gently pull down the balloon from the rectum down towards the anal exit.

They’ll then tell the patient to indicate when they first sense an urge to defecate. This is normally done before the start of the procedure.

The medical practitioner will use this test to assess the rectum’s sensitivity using a sensitivity measure known as the rectoanal inhibitory reflex.

A complementary way to perform this test is by incrementally increasing the volume of the balloon by the continuous addition of 10ml at intervals. This should be done until the volume reaches 60ml.

Rectal hypersensitivity is usually a correlate of fecal incontinence.

Rectal Compliance Tests

Rectal compliance tests are usually performed contemporaneously with rectal sensation tests. This is because the data and results in the latter are useful inputs for the former. Rectal compliance is then found by plotting the relationship between balloon volume and the steady-state intrarectal pressure.

Lower compliance values are an indication of higher resistance to distention.

Balloon Expulsion Test

The purpose of this procedure is to assess how fast a patient can expel a balloon from their rectum.

The inability of a patient to expel a balloon within 180 seconds could be indicative of dyssynergic defecation.

Anal Sphincter Electromyography (EMG)

Here, the electrical activity of the anal sphincter muscles is recorded using sophisticated computing technology. The nurse will then analyze these results for indications of muscular dysfunction or abnormality.

What’s important to remember is that anorectal manometry is not a single test performed in isolation but a series of procedures that are done and interpreted comprehensively. 

We Can Help You Provide Anorectal Manometry in Your Practice

A direct links  to the video above is here.

Do you want to provide anorectal manometry services within your gastroenterology practice? If so, you’ll need to work with a trusted and experienced partner. We can help you include this procedure, so you treat your patients wholesomely and don’t have to refer them to other hospitals. 

The demand for this test is likely to increase, seeing we have an increasingly aging population. Age is a major risk factor in anorectal conditions for which anorectal manometry is usually indicated.

At Brighter Health Network, we serve OB-GYN, urology, urogynecology, and gastroenterology practices all across the U.S., providing a range of in-office diagnostic services. These diagnostic services typically include staffing, equipment, supplies, and interpretation software.

Contact us today to learn more about our quality services and unlock your potential in anorectal manometry testing, training, and staffing.

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Topics: anorectal manometry procedure, anorectal manometry test

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