Anorectal manometry is a test that measures strength or weakness of the anal muscles as well as sensation and reflex activity in the rectum. The test is performed with the patient lying down comfortably and by placing a flexible, pencil-thick plastic probe into the rectum. It is generally well tolerated and takes about an hour. It is an essential test for a diagnosis of dyssynergic defecation.

A balloon expulsion test examines pelvic floor relaxation and opening of the anal canal. A stool-like device is placed in the rectum and, in private, the person expels it to learn how easy or difficult it is to pass a bowel movement. If unable to expel it in a timely manner, normally within one minute, dyssynergic defecation should be suspected. However, this test is most useful to rule out dyssynergia, but less useful to identify the condition.

Defecography uses a special x-ray machine to record moving images of a semi-solid paste (barium) as it passes through the rectum. This imitates passing a soft stool and provides useful information about anatomic and functional changes. However, many people are uncomfortable performing this test.

Manometry along with physical examination remains the preferred method of assessment. Multiple criteria must be met to diagnose dyssynergic defecation – in terms both of symptoms and of physical function. They include the Rome criteria for functional constipation plus evidence of dyssynergia.

Rome III Diagnostic Criteria* for Functional Constipation

  1. Must include 2 or more of the following:
    1. Straining during at least 25% of defecations
    2. Lumpy or hard stools in at least 25% of defecations
    3. Sensation of incomplete evacuation for at least 25% of defecations
    4. Sensation of anorectal obstruction/blockage for at least 25% of defecations
    5. Manual maneuvers to facilitate at least 25% of defecations (e.g., digital evacuation, support of the pelvic floor)
    6. Fewer than 3 defecations per week
  2. Loose stools are rarely present without the use of laxatives
  3. Insufficient criteria for irritable bowel syndrome

*Criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

Evidence of Dyssynergia*

  1. 1. Must demonstrate dyssynergic or obstructive pattern of defecation** with anorectal manometry, imaging, or electromyography recordings, and
  2. One or more of the following criteria during repeated attempts to defecate
    1. Inability to expel an artificial stool (50 ml water-filled balloon) within one minute
    2. Prolonged colonic transit time (retention of more than 5 markers) on a plain abdominal x-ray taken 120 hours after ingestion of one Sitzmark® capsule containing 24 markers
    3. Inability to evacuate or equal to or greater than 50% retention of barium during defecography

*Dyssynergia must be demonstrated during repeated attempts to defecate.

**Paradoxical increase in anal sphincter pressure (anal contraction); or less than 20% relaxation of the resting anal sphincter pressure; or inadequate propulsive forces.

Adapted from IFFGD Publication #237 by Satish S.C. Rao, MD, PhD, FRCP(LON), AGAF, Chief, Section of Gastroenterology/Hepatology and Director, Digestive Health Center, Medical College of Georgia, Georgia Regents University, Augusta, GA.

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