Crohn's Disease
Crohn's disease is suspected in people who have been experiencing symptoms such as abdominal pain, diarrhoea and weight loss that have lasted for weeks or months. Because there is no single test that can establish the diagnosis of Crohn's disease with certainty, and because Crohn's disease often mimics other conditions, it may take time and several investigations to arrive at the correct diagnosis.
Ulcerative Colitis
Whenever a person has a history of bleeding from the rectum - either with or without diarrhoea and abdominal pain - one of the conditions suspected as a possible cause of the symptoms is ulcerative colitis. Investigations are then carried out to differentiate between other diseases known to cause rectal bleeding (e.g. Crohn's disease or colorectal cancer) and to arrive at what is called a 'definitive diagnosis'.
Diagnostic Process
The diagnosis of Crohn's disease or ulcerative colitis is sometimes delayed as the same symptoms can occur with other diseases. It is usually necessary to exclude diseases such as bowel infections or irritable bowel syndrome.
Blood tests are useful to look for anaemia (low blood count) and to measure the severity of inflammation. They can also detect vitamin or mineral deficiencies. A faeces (bowel motion) specimen may be required to exclude infection.
Most people require an examination of part of the bowel, either by direct inspection through a flexible tube inserted through the back passage (colonoscopy or sigmoidoscopy) or mouth (gastroscopy), or by x-rays, include CT scan and barium small bowel series (where dye swallowed and x-rays taken). There is no one test that can reliably diagnose all cases of IBD, and many people require a number of tests.