Ulcerative colitis is a superficial inflammation of the large intestine, not caused by bacteria, which results in ulceration and bleeding. The patient typically experiences alternating periods with no or few symptoms, and periods with frequent stomach pains and diarrhoea that is mixed with pus, blood, and mucus.

The symptoms of ulcerative colitiscan vary considerably.

The disease is characterised by periods with diarrhoea, mixed with pus, blood, and mucus, which alternate with periods of few or no symptoms.

When the colitis is active, the patient often has mild stomach pains, and sometimes a fever.

The symptoms vary according to the extent of the disease. A quarter of patients only have the disease in the rectum, which means that the symptoms are fairly mild. In one third of patients, the disease also affects the lower part of the large intestine. In the remaining patients, ulcerative colitis affects all of the large intestine.