From the Guidelines
Ileocolonoscopy with biopsy is the first-line investigation for suspected Crohn’s disease, as it allows for direct visualization of the terminal ileum and histological confirmation of the disease. This approach is supported by the British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults 1. The guidelines highlight the importance of ileocolonoscopy with biopsy in establishing the diagnosis of Crohn’s disease, particularly in cases where the disease is limited to the terminal ileum.
In cases where ileocolonoscopy is normal, but there is still a high suspicion of Crohn’s disease, CT enterography or MR enterography may be used to visualize the entire small bowel and detect wall thickening, strictures, and fistulas 1. These imaging modalities are particularly useful in detecting proximal small bowel disease, which may be beyond the reach of ileocolonoscopy. For example, a study found that out of a cohort of 150 Crohn’s disease patients, 36 had active small bowel disease diagnosed using CT enterography following a normal ileocolonoscopy 1.
Some key points to consider in the diagnosis of Crohn’s disease include:
- Ileoscopy and radiological imaging are complementary in the diagnosis of ileal Crohn’s disease 1
- Dedicated small bowel oral contrast agents can be used to improve the accuracy of imaging studies 1
- Capsule endoscopy may be useful in examining areas of the small intestine not accessible by traditional endoscopy, particularly in patients with suspected Crohn’s disease and negative ileocolonoscopy 1
- Genetic testing is sometimes used to identify specific genetic markers associated with Crohn’s disease, though this is not routine 1
Overall, the diagnosis of Crohn’s disease requires a combination of clinical evaluation, laboratory tests, imaging studies, and endoscopic procedures. Ileocolonoscopy with biopsy remains the gold standard for diagnosing Crohn’s disease, and should be used in conjunction with other diagnostic modalities to confirm the diagnosis and assess the extent of disease.
From the Research
Diagnostics for Crohn's Disease
- The diagnosis of Crohn's disease is typically made with endoscopic and/or radiologic findings 2.
- Initial laboratory evaluation identifies inflammation and screens for alternative diagnoses, with measurement of fecal calprotectin having value to rule out disease in adults and children 3.
- Blood tests such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) can be used to assess disease activity, with CRP levels corresponding closely with clinical and pathological indices of relapse, remission, and response to therapy in patients with Crohn's disease 4.
- However, ESR and CRP may not be useful in predicting clinical, endoscopic, or histologic disease activity in all cases, particularly in ulcerative colitis 5.
- Endoscopy and cross-sectional imaging are used to confirm the diagnosis and determine the extent of disease 3, 2.
Laboratory Tests
- Fecal calprotectin: a useful test to rule out Crohn's disease in adults and children 3.
- Erythrocyte sedimentation rate (ESR): may be elevated in Crohn's disease, but does not closely reflect disease activity in individual patients 4.
- C-reactive protein (CRP): corresponds closely with clinical and pathological indices of relapse, remission, and response to therapy in patients with Crohn's disease 4.