Overview

Crohn's disease may be difficult to diagnosis or evaluate with only a standard yearly physical examination. Initially, the only evidence of the disease may be a low-grade fever, joint pain, or anemia along with abdominal pain, nausea, or diarrhea-although some people are diagnosed when they're in so much pain they're in the emergency room. A combination of blood tests, stool studies, radiologic imaging tests, and endoscopic procedures are often used to make a diagnosis of Crohn's disease, assess disease activity, and evaluate patients for complications.

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A CBC (complete blood count) is often taken to evaluate for anemia, signs of infection, or side effects to medications. The two most common types of anemia found in patients with Crohn's disease are due to iron deficiency and vitamin B₁₂ deficiency. Because of severe diarrhea or vomiting, electrolyte levels may be abnormal. An elevated C-reactive protein and a high red cell sedimentation rate are markers of systemic inflammation, infection, or other illnesses. Abnormal liver function tests may indicate liver or bile duct abnormalities or a side effect of medications. Because patients often present with diarrhea, stool studies are often checked to evaluate for treatable intestinal infections that may be contributing to symptoms.

Antibody testing may be useful in patients with "indeterminant colitis," in which the diagnosis of Crohn's disease or ulcerative colitis is uncertain. The two most common antibody tests are the ASCA (anti-Saccharomyces cerevisiae antibody) and pANCA (perinuclear anti-neutrophil cytoplasmic antibody) tests. Patients with Crohn's disease are often positive for ASCA but negative for pANCA. The opposite is often true for ulcerative colitis. While the tests are not perfectly reliable, results may help guide medical and surgical management of inflammatory bowel disease.

If a physician sees a patient suffering from frequent diarrhea or occasional abdominal cramps, and the person's laboratory values give cause for concern, generally the next step is to evaluate the patient's gastrointestinal tract. This section contains more on the two types of tests used:

• Imaging tests
• Endoscopic tests