resonance imaging is relatively new in IBD diagnosis. It uses a large magnet to create images based on the different water content and molecular makeup of different tissues. A patient undergoing an MRI scan lies on a table that slides into the machine. The patient lies very still during the procedure, which can last up to 20 or 30 minutes. Like a CT scan, the MRI provides cross-sectional images, but because the intestines are continuously contracting in the abdomen during the procedure, the images of the intestines may not be as clear as they are in CT scans, where the image is obtained in a fraction of a second. Some studies are done after patients are administered an injection of a contrast agent into the vein. Because it does not involve any exposure to radiation, MRI may become the investigation of choice once the technology has advanced to the point where it provides images that are comparable in quality to CT scans.
Assessing the Anus
MRI is particularly useful for assessing the anus and the surrounding tissue for complications, such as fistulas and abscesses, in Crohn’s disease.
MRI is particularly useful for assessing the anus and the surrounding tissue for complications, such as fistulas and abscesses, in Crohn’s disease. MRI is also useful in determining whether areas of the intestine are inflamed or whether the changes seen are due to scarring. This is a particularly helpful distinction because tissue that is inflamed may respond to therapy with medication, whereas areas of scarring will likely not improve with medical therapy.
Endoscopy
In endoscopy, a long, narrow tube with a light and a camera on its tip is passed into the gastrointestinal tract. The endoscope can be steered in the desired direction to provide very detailed images of the inner lining of the gastrointestinal tract on a video monitor. When the procedure examines the esophagus, stomach, and duodenum, it is called an upper gastrointestinal endoscopy or, more commonly, a gastroscopy. When the instrument is inserted through the anus into the rectum and colon, it is called a colonoscopy. When doing a colonoscopy, the physician can often also examine the ileum (last part of the small intestine). This is one of the areas most commonly involved in Crohn’s disease.
Gastroscopy
Gastroscopy is a relatively straightforward procedure, but is done much less commonly in IBD than is colonoscopy, with the possible exception of individuals first diagnosed in childhood. In that case, gastroscopy is frequently carried out at the time of diagnosis. Gastroscopy is usually carried out following an overnight fast so that the stomach is empty. The back of the throat is sprayed with a local anesthetic so that the gag reflex is reduced, and, in some cases, a mild sedative is given intravenously to relax the patient. The whole procedure usually takes no more than 10 to 15 minutes and is typically not painful. In young children, it may be necessary to administer heavier sedation or general anesthetic in order to carry out the procedure.
Colonoscopy
Colonoscopy requires preparation of the bowel with a special diet (usually clear liquids) and a special laxative for one or more days prior to the procedure. This is important because the presence of feces can interfere with visibility and make the procedure almost useless. In some cases, the physician may not order a special laxative for the patient. Usually this is when the IBD is very active, but even in these instances, a smaller or more gentle preparation is probably still advisable and safe.
Upper Gastrointestinal Endoscopy
Colonoscopy
The colonoscopy procedure itself is usually performed with a sedative and an analgesic (pain medication). It typically takes 15 to 45 minutes to complete. It is generally quite a safe procedure, with a very small risk of serious complications, but some degree of abdominal pain and cramping is not unusual at times during the procedure. In most cases, the medication given before the procedure helps to minimize the discomfort.
Extremely Useful
Colonoscopy is an extremely useful diagnostic test in IBD. It will always detect ulcerative colitis if it is present, and will detect Crohn’s disease in 80% to 90% of cases. In 10% to 20% of cases of Crohn’s disease, the procedure is not able to examine the areas of disease because of technical factors or because the disease is beyond the reach of the colonoscope.
Wireless Capsule Endoscopy
Standard gastroscopy and colonoscopy are not able to reach large segments of the small intestine that may be affected in Crohn’s disease. The imaging studies that can take pictures of those areas of the small intestine are improving, but do not always provide the detailed images required by the physician to make management recommendations. Wireless capsule endoscopy (WCE), or PillCam technology, was developed to provide the types of high-quality visual images of the inner lining of the small intestine that are provided by gastroscopy in the stomach and duodenum and by colonoscopy in the colon and ileum. In most cases, the procedure allows examination of the entire length of small intestine.
A capsule — about the size of a large vitamin pill or capsule — that contains a battery, light source, and a tiny lens and camera chip is swallowed by the patient and begins taking two pictures every second during an 8-hour period. It is propelled through the esophagus, stomach, and small bowel by the normal muscular movements of the gastrointestinal tract in the same way food is passed down along the gastrointestinal tract. The patient wears a recording device, much like a cellular telephone, and can go about daily activities. Once the procedure is over, images are downloaded from the recorder to a computer. The physician can then look for signs of Crohn’s disease.
Despite the fact that the WCE can provide excellent images of the entire small intestine, it is not commonly used in IBD diagnosis. In ulcerative colitis, the small intestine is not involved and does not require this type of detailed evaluation. In Crohn’s disease, care must be taken because the capsule could produce a blockage or bowel obstruction in any strictures of the intestine. Nevertheless, the capsule may be helpful in diagnosing subtle degrees of Crohn’s disease in the small intestine, where the other imaging techniques do not provide a full answer to the patient’s symptoms.
Enteroscopy
A number of innovations have been developed in the area of endoscopy to allow examination of areas of the small intestine that are beyond the reach of the standard gastroscope and colonoscope.
•Push enteroscopy uses a longer-than-normal gastroscope to get farther into the small intestine, but the success of this procedure is limited because of the floppiness and many twists and turns of the small intestine.
•Double balloon enteroscopy (DBE) generally allows more extensive examination of the small intestine through sequential inflation and deflation of two balloons near the tip of the instrument. This inflation and deflation helps to propel the tip of the instrument along the small intestine. The technique can be performed through the mouth, esophagus, and stomach into the first part of the small intestine, or it can be performed through the colon into the last part of the small intestine. It tends to be a longer procedure than standard endoscopy and typically requires general anesthetic or propofol for deep sedation. Using this technique, it is often possible to examine the entire length of small intestine that cannot be examined by gastroscopy or colonoscopy. Biopsies can be obtained of the inner lining of the small intestine, and the rate of progress through
