Tuberculosis deserves special mention.
The cecum is usually fibrotic and narrowed, and a few patients have typical calcified abdominal nodes. Culture and histological studies should be done on colonoscopic biopsy specimens and material from fistulae to rule out tuberculosis and actinomycosis. When a positive tuberculin skin test and other clinical features make tuberculosis a possibility, the physician may want to start the patient on antituberculous drugs, especially if corticosteroid or immunomodulator drugs are being considered as treatment for presumed Crohn's disease. In a small minority of cases, laparotomy is required to distinguish Crohn's disease from tuberculosis or, most importantly, lymphoma before therapy can be started.