What You Need to Know About Diagnosing Pediatric Functional Constipation

A contrast enema is performed to assess if there are any abnormalities in the colon or distal small intestine. The test uses a special type of enema solution that can show up on an X-ray. X-rays are taken of the colon and lower intestine to check for Hirschsprung's disease as well as any other issues that may be causing constipation. 

The following day, a plain abdominal X-ray may be performed to check for problems with colonic motility. If much of the contrast from the day before remains on a plain X-ray, then it is assumed that the child has a hypomotile (slow moving) colon. If the colon is empty the day after the contrast enema, this is an ideal time to initiate laxative therapy. Colonic hypermotility (excessive activity or movement of the colon) is suspected if the patient has fecal incontinence with a tendency toward diarrhea, a normal looking colon and no contrast on the follow-up X-ray.

A Sitz marker study involves the patient swallowing a type of gelatin capsule that contains tiny rings (markers), that once ingested, can show up on an X-ray. It’s important for the child to swallow all the rings. These “markers” are analyzed over the course of several days to help physicians estimate how fast or slow food and stool travels through the intestines.

A child with normal motility will have passed most of the markers by day four, and all of them by day seven. In a patient with total colonic inertia and almost no colon motility, these markers accumulate in the right colon. In patients with slow but steady colonic motility, the markers will be located predominately in the rectosigmoid colon. Other patients with segmental colonic dysmotility may have markers retained in the affected segment of the colon.  

Sitz marker study demonstrating colonic dysmotility:

Like a Sitz marker, a colonic nuclear transit study uses nuclear scintigraphy (the use of very tiny amounts of radioactive molecules) to diagnose disease. In this study, a radioactive tracer is ingested, and its progression through the colon is followed. The scintigraphic technique uses minimal radiation, is more sensitive than the Sitz marker study and can take a few days to complete.

Children with chronic constipation with or without soiling who have failed other medical therapies are good candidates for colonic manometry. Colonic manometry tests measure and record the pressure waves that are produced when the large intestine contracts before and after eating. It is like an EKG for the heart, but the idea applied to the movement of the colon. 

Learn more about colonic manometry.

The SmartPill™ Motility System is one of the latest, non-invasive tests that provides information not just from the colon, but the entire gastrointestinal tract. For this test, the child ingests a capsule that measures pressure, pH, transit time and temperature as it passes through the gastrointestinal tract. 

Read more about the SmartPill™ Motility System.

Anorectal manometry is usually performed when there is difficulty with bowel movements or soiling. This study can also be helpful in children who have had operations for anorectal malformations like imperforate anus or Hirschsprung's disease.

Learn more about anorectal manometry.