Question: What is the difference between ulcerative colitis and Crohn's disease? Looking for Online Tutoring? A. Presence of bleeding: severe in Crohn's disease, mild in UC. B. Presence of diarrhea: severe in Crohn's disease, mild in UC. C. Affected area: descending colon in Crohn's disease, ascending colon in UC. D. Course of the disease: prolonged in Crohn's, remission and exacerbation in UC