How is Dyssynergic Defecation Diagnosed?
General Issues – The doctor will begin with a history as well as an examination of the abdomen and the area around the anus and rectum. He or she will want to rule out other conditions that can cause constipation, such as disease, injury, or inflammation.
Many conditions, like an anal fissure, hemorrhoid, stricture, spasm, or tenderness can be diagnosed by examination in the doctor’s office. If the doctor suspects dyssynergic defecation, he or she may suggest one or more tests before making a definitive diagnoses.
Conditions may also co-exist with dyssynergic defecation. Examples of common tests to identify other conditions include blood tests, sigmoidoscopy (examination of the inside of the sigmoid colon and rectum using a thin, flexible, lighted tube), and colonic transit time tests.
A colonic transit time test is a simple way to study how quickly stool matter moves through the colon. Capsules containing small markers are swallowed and x-rays taken over several days. Transit time is measured based on the progress of the markers, which eventually pass out of the body. Slow or delayed transit time leads to infrequent bowel movements, straining, and hard stools.
But dyssynergic defecation can make stool passage much more difficult regardless of whether stool transit in the colon is normal or delayed.
Digital Rectal Examination – The physical and digital examination of the anal and rectal area is not only important, but is often most helpful in making a diagnosis. The physical inspection will reveal visible abnormalities to the skin and tissue. In the digital exam, the doctor will carefully insert a lubricated, gloved finger into the anus. This again is helpful to reveal possible abnormalities, including lack of sensation in the rectum. During the digital exam, the patient is asked to bear down as if having a bowel movement. This exam provides clues to the doctor, as to whether or not a patient has dyssynergic defecation.
Digital rectal examination is a good screening tool for identifying dyssynergia. Despite this, not all doctors have sufficient knowledge of this useful clinical tool. This is an area of clinical medicine where improved training is needed.
If dyssynergic defecation is suspected after the physical examination, the doctor will likely order one or more tests to confirm the suspicion. These tests can measure different functions in the colon and rectum, and identify abnormal patterns.
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
- Must include 2 or more of the following:
- Straining during at least 25% of defecations
- Lumpy or hard stools in at least 25% of defecations
- Sensation of incomplete evacuation for at least 25% of defecations
- Sensation of anorectal obstruction/blockage for at least 25% of defecations
- Manual maneuvers to facilitate at least 25% of defecations (e.g., digital evacuation, support of the pelvic floor)
- Fewer than 3 defecations per week
- Loose stools are rarely present without the use of laxatives
- 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*
- Must demonstrate dyssynergic or obstructive pattern of defecation** with anorectal manometry, imaging, or electromyography recordings, and
- One or more of the following criteria during repeated attempts to defecate
- Inability to expel an artificial stool (50 ml water-filled balloon) within one minute
- 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
- 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.