From Our Archives
Medical Author: Jay W. Marks, M.D.
I often am asked by other physicians to assist with their patients who have difficult-to-diagnose gastrointestinal problems. Many of these patients are suspected of having irritable bowel syndrome (IBS). Since there is no specific test for IBS, the diagnosis of IBS is made by recognizing a grouping of characteristic symptoms and excluding diseases that can mimic IBS. The issue always arises as to what constitutes complete testing in order to exclude diseases other than IBS. Not all patients thought to have IBS require complete testing. The patients who do are those with moderate or severe symptoms that do not respond sufficiently to simple and safe treatments. When the generalist (family practice physician or internist) is unable to make a diagnosis and/or recommend other treatment, it is time for the patient to see a specialist, a gastroenterologist.
A detailed medical history that is taken by a knowledgeable, experienced, and interested physician is the single most important "test" for IBS. It may be necessary to ask patients to return for further history-taking after instructing them to make additional observations about their symptoms. The goal is to find consistent patterns of symptoms. By the time a thorough history has been obtained, the physician usually will have a good idea of whether IBS or another disease is present. For example, intermittent obstruction of the small bowel (a common problem) causes symptoms that are similar to IBS. However, there is a difference between the sequence and timing of symptoms in small bowel obstruction and IBS. If a disease other than IBS is suspected, specific testing for that disease should be performed.
After the history, a thorough physical examination, particularly of the abdomen, is important, although only occasionally does the physical examination reveal a cause for difficult-to-diagnose symptoms.
The next step in testing is the consideration of diseases or conditions other than IBS that may be the cause of the patient's symptoms. For example, there may be a tumor or inflammation ("itis") of the intestinal lining. Theoretically, these may occur anywhere along the gastrointestinal tract from the stomach to the colon. X-rays of the stomach, small intestine, and colon are helpful, but for the colon and uppermost gastrointestinal tract (esophagus, stomach, and duodenum) endoscopy is preferred. Endoscopy is a procedure in which a lighted tube and camera are inserted into the gastrointestinal tract so that the doctor can examine the structures inside the tract. Endoscopy can identify anatomical abnormalities that can be seen with the naked eye; however, endoscopy is especially helpful in diagnosing histologic abnormalities with the microscope because the tissue of the lining of the gastrointestinal tract can be biopsied during the endoscopic procedure. It is important to biopsy each part of the gastrointestinal tract many times since some diseases are "patchy," which means that they affect some parts of the lining but not others.
When endoscopy and biopsies do not reveal a cause for the symptoms, it is time to consider special x-ray studies of the small intestine. The small bowel, or small intestine, is a part of the gastrointestinal tract that cannot be examined easily by endoscopy . There are several types of small bowel x-rays. In the more common types, either thick or thin barium is swallowed and multiple x-ray films are then taken as the barium progresses through the small intestine. A third type of small intestinal x-ray is called an enteroclysis study. For enteroclysis, a tube is passed progressively through the mouth or nostril, the stomach, and into the first part of the small intestine. A thin barium solution is then injected through the tube, followed by a watery fluid. As in the other types of small intestinal x-rays, films are taken as the barium progresses through the small intestine. Each of the three types of x-rays has advantages and disadvantages as compared with the other types. Which type of x-ray is best for a patient needs to be decided by the gastroenterologist and radiologist jointly. One type is not appropriate for all patients. In fact, it may occasionally be appropriate to perform two types of studies in the same patient.
X-rays of the small intestine are an important part of the evaluation for a patient with possible IBS. Unfortunately, as radiology has moved into the age of ultrasound, computerized tomography (CT), and magnetic resonance imaging (MRI), fewer small intestinal x-rays are being done. As a result, few radiologists develop the experience and skills necessary to perform the different types of x-rays or to do them well. In even the largest of cities there are a limited number of radiologists who are recognized by knowledgeable physicians as being skilled in small intestinal x-rays. It is worth seeking out these radiologists. In an attempt to get around the lack of experience and skill with x-rays, CT studies--that do not require the same skills--have been developed using barium that do a reasonable job of examining the small intestine.
When the small bowel x-rays or CT studies do not reveal a cause for the symptoms, it is time to consider ultrasound, CT (if not already done), and MRI, as well as other blood tests, stool tests, and less common radiological procedures. Tests of intestinal motility, which detect and measure muscle contractions, also may be of value, although they are not widely available. The suitability of doing these studies must be made on an individual, patient-by-patient basis.
In conclusion, a thorough history, physical examination, endoscopy with biopsy, and x-rays (or CT) of the small intestine form the basis of a careful evaluation of patients who are suspected of having IBS, but are not responding to treatment. Other specialized studies will not often be necessary.