To diagnose ulcerative colitis, your GP will first ask about your symptoms, general health and medical history. Then they will physically examine you, checking for signs such as paleness (caused by anaemia) and tenderness in the stomach (caused by inflammation).
The next step is to test your blood and a sample of your stool. Blood tests can show whether you have anaemia. There are also two specialised blood tests known as the erythrocyte sedimentation rate (ESR) test and the C reactive protein (CRP) test that look for changes in the blood that indicate disease and inflammation. Your stools will be checked for infection. X-rays may also be taken to help assess the extent of the condition.
Sigmoidoscopy
The diagnosis will then need to be confirmed by examining the level and extent of the inflammation of the bowel. This is initially done by using a sigmoidoscope, which is a flexible tube containing a camera that is inserted into your rectum.
The procedure is not painful, though you may be given a sedative to relax you. It usually takes around 15 minutes, after which you can go home.
The sigmoidoscope is only capable of looking at the rectum and lower part of the colon. If it is thought your ulcerative colitis has affected more of your colon, another examination will be required. This is known as a colonoscopy.
Colonoscopy
A colonoscopy uses a longer and more flexible tube called the colonscope, which allows your entire colon to be examined.
Before having the examination it will be necessary for your colon to be entirely empty. Therefore you will be required to take strong laxatives beforehand.
Again, the procedure is not painful though you may feel initial discomfort. You will be given sedatives to help you relax. The procedure takes around half an hour, after which you will be able to go home.
