What exams, procedures, and tests help diagnose the cause of severe constipation?
Many tests can diagnose severe constipation, and most people only need a few basic tests. First the doctor or health care professional will take a medical history and physical examination to allow the doctor to define the type of constipation that's present; uncover any supplements or prescription products you are taking; or diseases or other health problems you have. This, in turn, directs the diagnosis and therapy. For example, if defecation is painful, the doctor knows to look for anal problems such as a narrowed anal sphincter or an anal fissure. If small stools are the problem, eating foods low in fiber may be the cause. If the patient is experiencing significant straining, then pelvic floor dysfunction is likely.
A careful dietary history-which may require keeping a food diary for a week or two-can reveal a diet that is low in fiber and may direct the physician to recommend a high-fiber diet. A food diary also allows the physician to evaluate how well an individual increases his dietary fiber during treatment.
Other tests are available for people who have severe constipation that doesn't respond easily to treatment.
A physical examination may identify diseases (for example, scleroderma) that can cause constipation. A rectal examination with the finger may uncover a tight anal sphincter that may be making defecation difficult or it may find that the muscles of the pelvic floor do not relax normally. If a material-filled colon can be felt through the abdominal wall, it suggests that it is severe. Stool in the rectum suggests a problem with the anal, rectal, or pelvic floor muscles.
Blood tests may be appropriate in evaluating your condition. More specifically, blood tests for thyroid hormone (to detect hypothyroidism) and for calcium (to uncover excess parathyroid hormone) may be helpful.
Large amounts of material in the colon usually can be visualized on simple X-ray films of the abdomen, and the more severe constipation, the more visualized on X-ray.
A barium enema (lower gastrointestinal [GI] series) is an X-ray study in which liquid barium is inserted through the anus to fill the rectum and colon. The barium outlines the colon on the X-rays and defines the normal or abnormal anatomy of the bowel and rectum. Tumors and narrowings (strictures) are among the abnormalities that can be detected with this test.
Colonic transit (marker) studies
Colonic transit studies are simple X-ray studies that determine how long it takes for food to travel through the intestines. For transit studies, individuals swallow capsules for one or more days. Inside the capsules are many small pieces of plastic that can be seen on X-rays. The gelatin capsules dissolve and release the plastic pieces into the small intestine. The pieces of plastic then travel (as would digesting food) through the small intestine and into the bowel. After 5 or 7 days, an X-ray of the abdomen is taken and the pieces of plastic in the different parts of the bowel are counted. From this count, it is possible to determine if and where there is a delay in the colon.
In people who are not constipated, all of the plastic pieces are eliminated in the feces and none remain in the colon. When pieces are spread throughout the colon, it suggests that the muscles or nerves throughout the colon are not working, which is typical of colonic inertia. When pieces accumulate in the rectum, it suggests pelvic floor dysfunction.
Defecography is a modification of the barium enema examination. For this procedure, a thick paste of barium is inserted into the rectum of a patient through the anus. X-rays then are taken while the patient defecates the barium. The barium clearly outlines the rectum and anus and demonstrates the changes taking place in the muscles of the pelvic floor during defecation. Thus, defecography examines the process of defecation and provides information about anatomical abnormalities of the rectum and pelvic floor muscles during defecation.
Anorectal motility studies
Anorectal motility studies, which complement defecography tests, provide an assessment of the function of the muscles and nerves of the anus and rectum. For anorectal motility studies, a flexible tube, approximately an eighth of an inch in diameter, is inserted through the anus and into the rectum. Sensors within the tube measure the pressures that are generated by the muscles of the anus and rectum. With the tube in place, the individual performs several simple maneuvers such as voluntarily tightening the anal muscles. Anorectal motility studies can help determine if the muscles of the anus and rectum are working normally. When the function of these muscles is impaired, the flow of material through the GI tracts is obstructed, thereby causing a condition similar to pelvic floor dysfunction.
Magnetic resonance imaging defecography
The newest test for evaluating defecation and its disorders is magnetic resonance imaging (MRI) defecography and is similar to barium defecography. However, MRI is used instead of X-rays to provide images of the rectum during defecation. MRI defecography appears to be an excellent way to study defecation, but the procedure is expensive and somewhat cumbersome. As a result, it is used in only a few institutions that have a particular interest in constipation and abnormalities of defecation.
Colonic motility studies
Colonic motility studies are similar to anorectal motility studies in many aspects. A very long, narrow (one-eighth inch in diameter), flexible tube is inserted through the anus and passed through part or the entire colon during a procedure called colonoscopy. Sensors within the tube measure the pressures that are generated by the contractions of the colonic muscles. These contractions are the result of coordinated activity of the colonic nerves and muscles. If the activity of the nerves or muscles is abnormal, the pattern of colonic pressures will be abnormal. Colonic motility studies are most useful in defining colonic inertia. These studies are considered research tools, but they can help make decisions regarding treatment in individuals with severe constipation.