How IBD Is Diagnosed

It can sometimes be a frustrating experience when you are told that you may have inflammatory bowel disease (IBD) and that you need some tests in order to confirm the diagnosis. The diagnosis of IBD is based on a combination of exams: endoscopic (different types of scopes), radiologic (x-rays) and histologic (blood and tissue) tests. If you do have IBD, you may need additional tests from time to time to monitor the disease, or diagnose possible complications or the side effects of medications. These tests provide important information to your doctor, but often raise many questions and concerns for you as a patient. Questions such as: What information will the test provide to your doctor? What can you expect during the test? Will you feel any discomfort? How do you prepare for these different tests? How safe are they? These questions can make you feel even more anxious. The following is an overview of the tests that help diagnose and monitor IBD. It also attempts to answer the practical questions that you may have before you undergo testing.

Laboratory Tests

There are two major types of laboratory tests, which can be broken down into routine tests and antibody tests.

“Routine” Tests

Your doctor may request routine blood tests, such as a CBC (complete blood count), which help detect infection and anemia, as well as monitor for side effects of certain IBD medications. An electrolyte panel measures potassium and other minerals that can be depleted in IBD-associated diarrhea. (A low iron or vitamin B12 level can lead to anemia and may indicate decreased absorption from Crohn’s disease that affects the small intestine.) Liver function tests help screen for liver and bile duct abnormalities seen in some patients with IBD. Finally, stool studies are done to determine whether patients have treatable bacterial infections that can trigger a flare-up of IBD. It is important for your doctor to have all of this information before recommending other tests or changing your treatment.

Antibody Tests

Sometimes a definitive diagnosis of ulcerative colitis or Crohn’s disease cannot be made. This occurs in approximately 10-15% of patients. These unclear cases are called “indeterminate colitis.” For these patients, there are two new blood tests that may help. These tests look at antibodies that may form in the blood. The antibodies are named “perinuclear anti-neutrophil antibody” (pANCA) and “anti-Saccharomyces cervisiae antibody” (ASCA). Many patients with ulcerative colitis have the pANCA antibody in their blood, but not the ASCA antibody. For many Crohn’s patients, the opposite is true: the ASCA antibody is present, while the pANCA is not. Unfortunately, some patients have neither antibody in their blood, and some Crohn’s patients may have only the “ulcerative colitis” pANCA antibody in their blood! Nevertheless, sometimes these blood tests help your doctor determine which condition is more likely, which may help in making decisions regarding medications or surgery.

Endoscopy

If your symptoms suggest that you may have IBD, your doctor will probably recommend an endoscopic evaluation (or “scope”). The endoscopy will aid in determining whether you have ulcerative colitis or Crohn’s disease and how much of your bowel is affected. Colitis and Crohn’s have different complications and distinct medical and surgical treatments. Inflammation in Crohn’s disease often occurs in patches, or “skip areas” in the colon — that is, normal-looking colonic tissue appears in between areas of inflammation. Ulcerative colitis, on the other hand, has continuous inflammation that starts at the rectum and extends up throughout some or most of the colon.

Endoscopy has four main procedures, or different types of “scopes”, that are used to evaluate IBD. All use a thin, flexible tube with a lighted camera inside the tip, which allows your doctor to look directly at the lining of the gastrointestinal (GI) tract. The image is magnified and appears on a television screen used by your doctor to perform the exam. The part of the GI tract examined gives each procedure its name:

Sigmoidoscopy: examines the lining of the lower third of the large intestine (the sigmoid colon).

Colonoscopy: examines the lining of the entire large intestine (colon), and sometimes can peek into the very end of the small intestine (or ileum).

EGD (Esophagogastroduodenoscopy): examines the lining of the esophagus, stomach (gastro), and duodenum (first part of the small intestine).

ERCP (Endoscopic retrograde cholangiopancreatography):examines the bile ducts in the liver and the pancreatic duct.

What to Expect During Endoscopy

Your doctor depends on you to follow his or her instructions to properly prepare for the test. Stool and other debris can obscure the lining of the intestine, decrease the quality of the test, and unnecessarily prolong the procedure. For colonoscopy, proper preparation begins the day before the test. You should consume only a clear liquid diet and take the bowel preparation as prescribed by your physician. This purges the colon of stool and debris by causing diarrhea. Sigmoidoscopy often requires only taking enema preparations the night before and morning of the exam. Preparing for an EGD is quite simple. You should not eat or drink anything beginning at midnight before the test. This ensures that the stomach and intestine are given time to empty and the exam is not obscured. This also reduces the risk of regurgitating retained stomach contents into your lungs, which can cause severe pneumonia.

Sometimes preparing for these tests is not easy. It can be embarrassing, and often unpleasant, to take enemas, and downright distasteful to drink the “bowel prep” prescribed by your doctor. However, following these instructions ensures the best possible test outcome.

Sigmoidoscopy is usually performed without sedation, because it is a very short procedure, making the added risks of sedation unnecessary. Colonoscopy, EGD, and ERCP are typically performed with sedation. You are monitored very closely with heart monitor leads placed on your chest, a blood pressure cuff on your arm, and an oxygen monitor placed on your finger. Once you are in the procedure room, you’ll receive a narcotic to prevent discomfort and a sedative is given to promote relaxation. Once you are comfortably sedated, the test will begin. If you do not feel comfortable, make sure to tell your doctor. Everyone responds to sedation differently, and your doctor may need to make adjustments. Don’t be afraid to speak up — your health care team can better assist you in making these procedures less unpleasant if they know you are uncomfortable. You usually will not remember the procedure. A typical EGD is completed in 10 to 15 minutes while a typical colonoscopy is completed in 20 to 30 minutes. Many things can affect the length of the test, including your own unique anatomy (for example, if you have had previous bowel surgery), improper preparation, and the need to take biopsies.

Although endoscopic tests are considered to be routine and safe, no procedure is completely risk-free. Risks of endoscopy can be divided into those related to sedation and those related to the procedure itself. Sedation can produce blood pressure or breathing problems in some patients. Unusual complications of endoscopy include perforation (a rupture or hole in the intestine), bleeding, and infection. The informed consent process for the procedure will allow your physician to review these risks and answer any questions you may have.

Types of Endoscopy

Sigmoidoscopy

Sigmoidoscopy looks at the lower one-third of the colon. This makes it is a useful test when your physician wants to confirm the presence of inflammation or a source of bleeding (such as hemorrhoids) within the reach of the scope. Sigmoidoscopy helps rule out infectious causes of inflammation, such as disease caused by bacteria, which may mimic IBD. It is also useful in evaluating symptoms that do not respond to your current treatment or that return despite treatment. In these cases, your doctor can use the scope to take biopsies from any abnormal areas. This will allow him or her to confirm the diagnosis as well, to exclude treatable infections that can trigger an IBD flare-up.

Colonoscopy

A full colonoscopy can assess the complete extent of colitis. This is important for determining the type of therapy offered. It is also useful for evaluating and taking biopsies of the distal small intestine (terminal ileum), which is important in the evaluation of Crohn’s disease. Chronic inflammation of the colon (colitis) increases the lifetime risk of colon cancer compared to the general population. Years of inflammation may lead to gene abnormalities in the cells within the lining the colon (called dysplasia). Dysplasia can only be seen under the microscope. When colonoscopy is performed to look for dysplasia, multiple biopsies are taken throughout the entire colon and rectum. The time to start performing colonoscopy for surveillance depends on how long the patient has had colitis, and how much of the colon is involved with the colitis. Surveillance refers to routine examinations of the colon to minimize the risk of cancer by checking for dysplasia and monitoring any changes.

EGD

EGD is a common procedure that is used to evaluate a wide variety of symptoms, such as abdominal pain, nausea, vomiting, and painful swallowing. Unlike ulcerative colitis, Crohn’s disease can affect the esophagus, stomach, and small bowel. Unfortunately, more than 20 feet of small bowel are beyond the reach of an EGD. Occasionally a longer EGD, called an enteroscope, may be used to look further in the small intestine to evaluate these symptoms. Even with an enteroscope, more than one-third of the small bowel cannot be reached. If small bowel Crohn’s is suspected, your doctor will recommend radiological tests, such as small bowel X-rays and other scans, to determine whether there is disease in the remainder of the small intestine.

Capsule “Minicamera” Endoscopy

Capsule endoscopy has received a lot of publicity recently. It is designed to show images of sections of the small intestine that are beyond the reach of an EGD. This test is being investigated to determine how useful it is in diagnosing obscure gastrointestinal bleeding. The preparation for the test consists of fasting after the evening meal. The morning of the test, you are fitted with a belt that contains a recorder. You then swallow the endoscopy capsule, which is the size of a large vitamin. While you go about your regular activities, the capsule travels down the small intestine and transmits approximately 50,000 images to the recorder. At the end of the day, you return to have the images downloaded. It takes approximately two hours for your doctor to review the images. The capsule is excreted in the stool normally and effortlessly. For patients with Crohn’s disease, patients must be examined carefully to determine that there are no strictures or bowel obstructions before the capsule can be used. Also, biopsies cannot be taken with the current capsule. Future studies will have to evaluate the utility and safety of capsule endoscopy in IBD.

ERCP

A small percentage of patients with IBD also may have a liver disease called “primary sclerosing cholangitis,” or PSC. A doctor may suspect PSC if repeatedly abnormal blood test results reflect the activity of enzymes in the liver. If this is the case, an ERCP may need to be performed. ERCP is a method that combines X-ray and endoscopy to look at your bile ducts and pancreatic ducts. As in an EGD, a tube is passed through your stomach and into your small bowel. The papilla, a small bump with a tiny opening in your duodenum, leads to your biliary and pancreatic ducts. A small catheter is introduced through the papilla into either your bile ducts or your pancreatic duct and contrast dye is injected. An X-ray then demonstrates the anatomy of your ducts as outlined by the contrast dye. This test allows your doctor to look for disease in the ducts such as gallstones or PSC. It also allows him or her to open up ducts that are blocked or remove gallstones.

EUS

Endoscopic ultrasound, or EUS, is a relatively new technique that uses an ultrasound probe attached to an endoscope to obtain deep images of the gut below the surface. In IBD, this is most often used to look at fistulas in the rectal area. Fistulas are abnormal channels or loops from the intestine to another part of the intestine or another organ of the body and are a complication of Crohn’s disease. EUS can determine the depth and extent of the fistula and biopsies can be taken if needed.

What are Radiology Tests?

Radiology tests can provide important information that endoscopy alone cannot provide. Many types of radiological tests used in IBD, including: 1) X-rays (with or without contrast); 2) CT scan (“CAT scan”); 3) Magnetic resonance imaging (MRI); 4) Leukocyte scintigraphy (“tagged white blood cell scan”); and 5) Ultrasounds.

Types of Radiology Tests

Plain X-rays

X-rays are the oldest way of imaging the inside of the body. Plain X-rays (without contrast) are a quick, inexpensive, and effective way of detecting blockage in the small or large intestine. Patients with Crohn’s disease, for example, can have inflammation of the small bowel that narrows the intestine and prevents the easy passage of stool and air. This is called a small bowel obstruction. The large bowel can also become blocked and dilated. People with ulcerative colitis can develop a widening of the large bowel called toxic megacolon. This is a serious complication. These conditions are easily visible on a plain X-ray.

X-rays With Contrast

Contrast X-rays are used together with endoscopy in monitoring and treating IBD. These X-rays track special liquid (“contrast”) as it passes through the intestine, highlighting specific conditions. Contrast X-rays of the small intestine are useful for looking at the lining of the small intestine that is beyond the reach of the endoscope. This is important, for example, in assessing the presence of small bowel disease if you are diagnosed with Crohn’s. Even if the small bowel is accessible by endoscopy, contrast X-rays can easily highlight certain findings that endoscopy may miss. Narrowing of the bowel (stricture) and an abnormal channel between the bowel and another organ (fistula) are two conditions more easily diagnosed with a contrast X-ray.

The contrast used for these tests is barium. It is a thick, chalky liquid that can be given by mouth or via the rectum. There are two types of contrast X-rays of the small intestine: small bowel follow through and enteroclysis. The large bowel X-ray is called a barium enema. The preparation for a small bowel X-ray is not uniform, but at a minimum you should not consume anything by mouth beginning at midnight before the test. The preparation for a barium enema is similar to that of a colonoscopy and requires a liquid diet the day before, a bowel preparation to purge the colon of stool and debris, and no food or drink beginning at midnight before the test. It is important to follow the instructions your doctor gives you for your specific procedure.

After arriving for the test and changing into a hospital gown, the technologist will take a plain X-ray, called a scout film. For a small-bowel follow through, you will drink several cups of barium and then have an X-ray taken every 15-30 minutes as the barium travels down the small intestine and enters the large intestine. This can take as little as one hour or as long as four to five hours. An enteroclysis is similar, except that the barium is placed directly into the small intestine through a tube in your nose or mouth. In a barium enema, barium and air are introduced into the large intestine via a tube placed in the rectum. X-rays are taken to ensure that the entire large intestine is coated and well visualized. A barium enema takes approximately 30 minutes to complete.

Barium is generally safe, however it should not be given if there is a chance that an acute (sudden, recent) bowel obstruction or perforation is present. Similarly, to reduce the chance of complications, a barium enema should not be performed if there is severe inflammation in the colon. Barium can cause constipation, so you should drink plenty of fluids after your test to maintain regularity. As the barium passes out of your body, you may notice that your stools are whitish-gray for a few days. This is nothing to worry about. Finally, remember to let the technologist know if there is any chance that you might be pregnant. It is important to avoid exposing your fetus to X-rays.

CAT Scan

A CAT scan, also known as a CT scan, takes simultaneous X-rays from several different angles to reconstruct a realistic image of the internal organs. You may be given contrast by mouth, by rectum, or through the veins to improve the quality of the test. During the test, you will lie on a special table that advances through the scanner so images are taken at each level of your abdomen. Newer CT scanners may have an open design to minimize the claustrophobia (that feeling of being “closed in”). A CT scan of the abdomen takes five to 20 minutes to complete, depending on the information required.

Abdominal CT scans are used primarily to evaluate IBD patients who have abdominal pain and fever. Although this test can confirm that inflammation is present in the small or large intestine, it is used more importantly to rule out complications of IBD. These complications include intra-abdominal abscesses, strictures, small bowel obstructions, fistulas, and bowel perforation. A CT scan is also useful in eliminating other diagnoses that can mimic IBD, such as appendicitis. Additionally, CT scan can be used to help your physician drain an abscess. A small needle and a catheter can be passed through the skin into the abscess to drain the pus, thus avoiding surgery.

Although the contrast used for a CT scan is safe, the intravenous form can produce an allergic reaction in some patients. If you know that you have a contrast allergy, let the technologist know right away. In addition, because the kidneys excrete the intravenous contrast, they may be impaired in patients who are at risk. These patients tend to be older, diabetic, dehydrated, or have kidney disease. If you are taking metformin (Glucophage®) for diabetes, you must tell your doctor. You may need to stop taking it to avoid a rare but serious interaction with the contrast.

MRI

Magnetic resonance imaging (MRI) is useful for viewing internal organs, muscles, soft tissue, and the brain. It does not use X-rays or radiation. It works by detecting the signal produced by atoms in response to a strong magnetic field. It converts this signal into a realistic image of the body. During the test, you lie on a special table inside the MRI scanner while the magnet generates the images. Some patients may experience claustrophobia while inside the scanner; newer machines may have an “open scanner” which is less confining. Let your physician know if you have a pacemaker or any metal implants, in order to avoid a serious complication when the magnet is turned on.

For many years, technical problems have limited the role of MRI as an imaging tool in IBD. CT scans have been cheaper, faster, and better at detecting inflammation of the intestines. MRI was limited to investigating perianal Crohn’s disease, where MRI images are superior. Technologic improvements, however, have allowed for higher quality images of the abdomen. At this point, MRI is not commonly used in IBD, although many potential uses are being investigated. MRI enteroclysis is a new technique that is being evaluated as an alternative to the conventional enteroclysis. Its potential advantages include the capability to detect disease outside the intestine. It also produces clear images that are free of interference from overlying bowel loops. CAT scan enteroclysis is also being used in some patients.

White Blood Cell Scan

Inflammation of the GI tract is characteristic of ulcerative colitis and Crohn’s disease. Leukocyte scintigraphy or “tagged white blood cell scan” detects white blood cell accumulation in inflamed tissue. This test requires no preparation. It involves drawing blood from the arm, labeling the white blood cells in the test tube with a harmless amount of a radioactive substance, and then reinjecting the blood into your bloodstream. The labeled white blood cells travel through the bloodstream and migrate into the inflamed tissue. A special camera detects where the white blood cells accumulate and therefore can assess where and how much inflammation is present.

Leukocyte scintigraphy has been used to detect the location of bowel inflammation and to evaluate treatment response in IBD. It is not useful in defining anatomic details or looking at inflammation in the rectum. It is a relatively safe test and entails less radiation exposure than contrast X-ray or CT scan.

Ultrasound

Ultrasound technology is used to study many organs in the abdomen, most typically the liver, gallbladder, or organs in the pelvis. It is not as useful for the bowel in general. Ultrasound is harmless and relies on the shadows cast by sound waves (too high for people to hear). Although ultrasounds don’t usually require preparation, other than typically not eating for a number of hours before the test, you should check with your doctor. These tests are often used in combination with other radiological tests.

How Will These Tests Help?

It is essential that your doctor be able to get an accurate diagnosis of your particular disease in order to prescribe the most effective treatment for you. Proper diagnosis of IBD depends on determining the disease type (colitis or Crohn’s), disease extent, and the complications associated with each illness. Endoscopy with biopsy is the cornerstone for diagnosing and evaluating disease activity in IBD.

Radiology tests are used together with endoscopy to help evaluate the small bowel and look at the entire abdomen for infections, strictures, obstructions, and fistulas. Newer technologies, such as capsule endoscopy, antibody tests, and MRI, seek to make the diagnosis of IBD less invasive, but they have not replaced traditional tests. Even after you are diagnosed as having IBD and your disease type has been confirmed, you may still periodically need to undergo many of these tests. They are necessary for providing information to your doctor on any complications you may have and for determining how your treatment plan is working. These tests are valuable tools that help your doctor take care of you. Understanding how they fit into your overall care allows you to be an active participant in decisions about your health.

This information was prepared by FERNANDO VELAYOS, M.D. and UMA MAHADEVAN, M.D. in the Division of Gastroenterology at University of California, San Francisco, CA. It was originally published in the Spring 2002 issue of Foundation Focus and has been modified and updated