How Is Inflammatory Bowel Disease (IBD) Diagnosed?

If you suspect you or a family member is experiencing any symptoms of inflammatory bowel disease, be sure to see your doctor as soon as possible. A medical history of symptoms and a physical examination are usually adequate for strongly suspecting a diagnosis of Crohn's disease and ulcerative colitis, but further diagnostic testing is important in confirming the suspected diagnosis, determining the extent and severity of the disease, and screening for possible complications of the disease. These procedures include standard blood and stool tests, various imaging studies, endoscopies, and biopsy.

 

Not all tests or investigations are required in all patients. The tests chosen will depend on your specific symptoms, as well as the availability, potential risk, and discomfort of the specific investigation.

 

 

White blood cell or platelet count can be elevated in active IBD. Certain antibodies are found more frequently in the blood of patients with IBD. Antibodies are proteins produced by the immune system to defend against certain types of infection by binding to specific molecules found on the surface of viruses and bacteria. Some proteins, most commonly, C-reactive protein, are found in higher levels in the blood of people with inflammatory conditions.

 

In addition, the pattern of antibodies may help differentiate between ulcerative colitis and Crohn's disease. One of these antibodies, called perinuclear antineutrophil cytoplasmic antibody (pANCA), occurs more commonly in ulcerative colitis, whereas another antibody, anti-Saccharomyces cerevisiae antibody (ASCA), is fairly specific for Crohn's disease.

 

Blood tests may be particularly helpful in diagnosing children, where invasive diagnostic testing is more difficult to justify and carry out, particularly when the suspicion of actually finding disease is relatively low. These antibody tests can be used to help determine who should undergo further testing since it is very unlikely that a child with a negative pANCA and ASCA test will turn out to have IBD.

 

Other blood tests indicate evidence of possible complications or nutritional deficiencies that may have occurred as a result of IBD. These include anemia, liver disease, iron deficiency, vitamin B-12 deficiency, and calcium deficiency.

 

 

Stool samples may be sent for culture to rule out a bacterial infection as the cause for a patient's symptoms. While the yield from this is quite low, particularly when symptoms have been going on for many weeks or even months, it is important to rule out infections before embarking on many types of therapy for Crohn's disease and ulcerative colitis.

 

Stool may also be examined for parasites or the eggs of parasites. Occasionally, the laboratory will report that no parasites were seen, but that many white blood cells are present in the stool. The presence of white blood cells almost always indicates some type of inflammatory condition in the intestine. Stool can also be tested for certain proteins that are present in white blood cells that indicate the presence of active intestinal inflammation.

 

 

Imaging studies provide 'pictures' of the intestines and other internal organs without having to open up the abdomen by performing surgery. The use of imaging studies has been the mainstay of IBD diagnosis for many years. X-rays provide two-dimensional pictures of the intestine, while other types of imaging studies also provide information about surrounding structures within the abdomen, something which conventional x-ray studies cannot do. These include ultrasounds, computer assisted tomography (CT or CAT) scans, and magnetic resonance imaging (MRI). They provide multiple images of the abdomen in 'slices' that can be positioned crosswise or lengthwise through the abdomen. In this way, it is possible to provide a three-dimensional representation of the intestines, other abdominal organs, and even blood vessels.

 

 

Ultrasound examinations are very safe and widely available. A probe that transmits a high frequency sound wave is moved over the abdominal wall. That sound wave is reflected off structures within the abdomen and back to the probe, which has a sensor to detect the reflected sound waves or echoes. These echoes are then converted into an image. Patients must fast before an abdominal ultrasound study.

 

One particular type of ultrasound, a transanal ultrasound, is used to evaluate patients for possible anal abscesses and fistulas. This involves putting a special ultrasound probe into the anus in order to obtain images of the surrounding tissues. Although this may provide excellent detail, the procedure may be very difficult or impossible for patients with painful anal conditions associated with Crohn's disease.

 

 

Computer assisted tomography is a very safe and widely used imaging technique. This technology may supplant small bowel follow-through and small bowel enema procedures.

 

During a CT scan, the patient lies on a table, which is surrounded by a large donut-shaped structure that produces and detects x-rays. These x-rays are converted into very detailed images when processed in the machine's computer.

 

Patients undergoing CT scans of the abdomen are often given a contrast solution to drink 1 to 2 hours before the scan to provide better diagnostic images or an intravenous injection of another contrast material to show blood supply to the intestine and other tissues.

 

CT scans are generally not needed for routine follow-up of a patient's clinical disease activity. If an abscess is detected by CT scan, the images can be used by the radiologist to insert a needle or plastic tube through the skin and into the abscess in order to allow it to drain properly.

 

 

Magnetic resonance imaging is relatively new in IBD diagnosis. It uses a large magnet to create images based upon 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 barium x-rays and CT scans.

 

 

These various imaging methods provide very good information about the structure of the gastrointestinal tract and complications of IBD, such as fistulas or abscesses, but they do not always provide detailed information about the degree of inflammation present within the inner lining of the intestine. To show the amount of inflammatory cells (white blood cells) within the bowel wall, nuclear medicine labeled WBC imaging is used, most commonly when the physician wishes to evaluate the small intestine in a patient with Crohn's disease.

 

A blood sample is first taken from the patient and then the white blood cells are tagged with a molecular marker (radio-isotope) emitting radiation that can be detected by a special imaging machine. The tagged white blood cells are then reinjected into the patient's bloodstream, and images of the abdomen are taken using the special nuclear medicine imaging machine. The areas of inflammation attract many of the tagged white blood cells, and light up on the pictures that are taken by the machine. However, areas of the intestine that may be scarred from previous attacks of IBD, but are not presently inflamed, will not show up on the images.

 

 

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 to the desired direction to provide very detailed images of the inner lining of the gastrointestinal tract on a television 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 is a relatively straightforward procedure, but is done much less commonly in IBD than is colonoscopy. 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 in order 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 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.

 

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 complication, but some degree of abdominal pain and cramping is not unusual at times during the procedure. In most cases, the medication given before the procedures helps to minimize the discomfort.

 

 

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 good, but do not always provide the detailed images required by the physician to make management recommendations. Wireless capsule endoscopy (WCE) or PillCam is a very new technology 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. The patient wears a recording device, much like a Walkman, 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 doses 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.

 

 

Endoscopy also allows the operator to perform biopsies of the inner lining of the gastrointestinal tract. Small samples are taken with a tiny instrument with small jaws that can cut or pull off pieces of the inner lining. This part of the procedure is not painful; usually, the patient is not aware that it is happening. The biopsy process is very safe; complications, such as serious bleeding, are extremely uncommon.

 

In some instances, biopsies are done to screen for pre-cancerous changes. Some patients with IBD involving the large intestine for more than 8 to 10 years are at increased risk of colon cancer, and their physicians may recommend a surveillance program that involves regular colonoscopy with many biopsies taken throughout the colon.

 

 

Once the diagnosis of IBD has been confirmed using one or more of the available investigations, some of that information can be used to help the physician determine the severity and prognosis of a patient's particular IBD. However, even with the most complete diagnostic staging, the ultimate prognosis can be unpredictable, varying from person to person with the same disorder.