2.1
Ulcerative colitis is a chronic condition in which inflammation develops in the large intestine. Its exact cause is unknown although hereditary, infectious and immunological factors have been proposed as possible causes. Symptoms vary according to the extent and severity of the disease and may include bloody diarrhoea, abdominal pain, weight loss, fatigue, anaemia and an urgent need to defaecate. Some patients may also have extra‑intestinal manifestations involving joints, eyes, skin and liver. Symptoms can flare up then disappear for months or even years, but approximately 50% of patients with ulcerative colitis will relapse at least once a year. Ulcerative colitis can cause complications such as primary sclerosing cholangitis (inflamed and damaged bile ducts), bowel cancer, osteoporosis and toxic megacolon (swelling of the colon caused by trapped gases, which can be life‑threatening).