Diagnostic Evaluation of UC
Making a diagnosis of inflammatory bowel disease is like putting together a puzzle. A patient’s symptoms, laboratory tests, endoscopic findings, and radiographic tests serve as the pieces physicians fit together to determine a diagnosis. A brief overview of the diagnostic approach to UC includes the following:
1) Patient History and Symptoms: The evaluation of UC always begins with thorough history taking and physical examination of the patient. The most common symptoms experienced by patients with UC are rectal bleeding, a sense of urgency to have a bowel movement, and the passage of mucus from the rectum. Among patients in whom the disease spreads along the length of the colon, diarrhea and abdominal pain may become predominant symptoms. As noted in previous blog entries, UC is a systemic disease and can also be associated manifestations outside the GI tract such as arthritis, skin rashes, and eye changes.
2) Laboratory Tests: If a patient’s symptoms are suspicious for UC, the next step in the diagnosis involves performing laboratory tests. Some of the most common tests are:
Complete blood count (CBC) This blood test examines the types of cells in the blood. In UC and infectious colitis, infection fighting cells known as white blood cells and clotting factors known as platelets may be elevated. By contrast, the red blood cell count which measures the cells in the blood that carry oxygen may be decreased from blood lost by the inflamed colon.
Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) You may hear your doctor talk about the ESR or CRP rate. These are chemicals in the blood that become elevated when inflammation or infection is present in the body. The level of inflammation typically correlates with the degree of inflammation. Therefore, the levels of these factors can be followed as markers of disease activity.
Stool Cultures Infectious colitis can present with the same symptoms as UC. Therefore, it is important that a patient’s stool is examined for bacteria and parasites. It is common for several stool samples to be collected, as infectious organisms can be missed if only one specimen is examined.
Serologic Markers In recent years, research has suggested that there are particular antibodies in the blood of some patients with IBD. The antibody known as pANCA (Peripheral anti-neutrophil cytoplasmic antibody) is present in up to 70% of patients with UC and 20% of patients with Crohn’s colitis. Because these antibodies are not present in everyone with IBD, a person with a negative serologic test may still have disease.
3) Endoscopic studies: The most important test for making a diagnosis of UC is a colonoscopy. If a patient’s history, symptoms, and laboratory tests suggest a diagnosis of UC, then the next step is to evaluate the lining of the intestine and take tissue samples to examine under the microscope. The colonoscopy is performed under sedation and involves insertion of a long, flexible tube with a camera into the anus through the length of the colon. The colonoscopy is useful not only for making the diagnosis, but also to define the extent and severity of disease. If there is a question of UC vs. Crohn’s disease, some physicians may perform a video capsule endoscopy, which involves the patient swallowing a small pill containing a camera to examine the small intestine.
4) Radiographic tests: Sometimes x-ray tests are needed to help make a diagnosis of IBD or to differentiate UC from Crohn’s disease. The most common tests performed are:
Small bowel follow-through This test involves drinking barium material and serial x-rays are performed to examine how the intestine looks as the material travels through the gut. In patients with UC, changes to the lining of the intestine are seen in the large intestine and not the small intestine. In 15-20% of UC patients who have colitis affecting the entire length of the colon, x-ray changes may be seen in the very last portion of the small intestine called the terminal ileum. In this case, further evaluation is done to differentiate these changes from Crohn’s disease.
CT enterography A CT enterography is a cat scan test that involves drinking a contrast material that lines the intestine. A cat scan is then performed to examine the bowel wall for thickening and other changes suggestive of Crohn’s disease or UC.
From this overview, you can see that there are several important pieces of information that need to fit together to make a diagnosis of UC. This process can be both challenging and frustrating at times for patients when the pieces of the puzzle don’t fit together easily. With patience and a methodical stepwise approach, however, a confident diagnosis can usually be reached.