Crohn's disease colon, gross specimen. Raised mucosal areas of swollen tissue and ulcerated fissures can be seen. This is a chronic inflammatory condition for which the exact cause is unknown. It is ultimately associated with fistulas (abnormal tunnels connecting two body cavities), obstructions and occasionally cancer. Diagnosis is difficult, and full clinical symptoms may take months or years to emerge. It causes pain and common symptoms include diarrhoea and weight loss. Treatment is usually of the symptoms, though severely damaged sections of the colon may require surgical removal.