Your doctor may suggest one or more of the following special tests for constipation:
Plain x-ray of the abdomen (also known as a KUB)
This is a single or set of x-rays that can give your physician a rough idea if there is a lot of stool present. It may also indicate if the colon is dilated. This type of x-ray is also obtained prior to a barium enema which is described below.
Anorectal manometry or motility test
This test determines if the nerves and muscles responsible for passing a bowel movement are working together. It is performed by inserting a very small balloon at the end of a catheter into the rectum and blowing up the balloon. The response to inflating the balloon determines if the nerves and muscles are working together properly. Relaxation of the anal muscles, known as the anal sphincter, after inflation of the balloon should occur.
This is an x-ray test where barium or another type of contrast is inserted via a catheter into the rectum and x-rays of the abdomen are taken. The test may or may not require a special bowel preparation to clean out the bowel before the test. This test is used to diagnose a blockage in the intestine or an area that may be narrowed or abnormal. It is also used in the diagnosis of Hirschsprung’s disease.
This is a test where a small (pinch) biopsy is performed from the lining of the rectum to determine if normal nerve cells are present in its walls. The sample of tissue that is obtained is examined under the microscope looking for ganglion cells, which are special nerve cells. If they are absent then the diagnosis of Hirschsprung’s disease is made.
Transit study or marker study
This test is performed to determine if the reason for constipation is due to slow movement throughout the colon or just in the last part of the colon known as the rectum. Plastic markers, which can be seen on x-ray, are swallowed and then several x-rays are performed over the next 4-7 days to determine how long it takes them to pass through the GI tract. Patients with normal motility pass the majority (>80%) of the markers within 5 days. If the markers are not passed but are found to remain throughout the colon, this suggests slow transit of the entire colon. If the markers do not pass and are clustered in the rectum, this may indicate a problem in the rectum only.
This is an endoscopy of the lower GI tract. This test is usually not indicated for the evaluation of routine constipation in children. This test may be helpful if children have blood in their bowel movements not due to a fissure or straining or other concerns on history or physical exam to suggest inflammatory bowel disease and is also used for placing a colonic manometry catheter if necessary (see below).
This is a specialized test done in children who have continued problems with intractable constipation despite adequate medical therapy. It involves placing a catheter at the time of colonoscopy to determine whether there are normal contractions in all parts of the colon. The test requires a period of prolonged monitoring of the contractions of the colon after placement of the catheter. This test is used to establish the diagnosis of colonic pseudo-obstruction in children, a very rare condition.