Crohn's disease. Endoscope view of ulceration (white areas) and inflammation in the colon (large intestine) due to Crohn's disease. This disease may affect any part of the digestive tract, but is most common in the colon or ileum (part of the small intestine). In the colon it causes inflammation (colitis), pain and bloody diarrhoea. Treatment is with anti-inflammatory drugs or surgery to remove the affected area of intestine. In severe cases, patients may require blood transfusions and intravenous feeding. Even after surgery the disease commonly recurs.