How is Crohn’s disease diagnosed?

It is likely that Crohn’s disease will be diagnosed after other diseases and causes of the symptoms and signs have been ruled out. There is no single test for Crohn’s disease to be diagnosed.

Typically, the doctor will utilise a combination of diagnostic procedures consisting of an endoscopy and a biopsy, as well as radiological testing in order to confirm that the diagnosis is Crohn's disease. The patient may have one or a combination of the below procedures and tests:

Blood tests

• Tests for infection or anaemia – Blood tests may be conducted to check if the patient has anaemia (this is a condition where there is an insufficient amount of red blood cells in the body which leads to an inadequate amount of oxygen being transported to the organs). Blood tests can also be done to check for any infections. Currently, doctors do not recommend genetic or antibody testing for Crohn's disease.
• Faecal occult blood test – For this test to be conducted, the patient will provide the doctor with a stool sample in order for the doctor to test the stool for any hidden blood.

Procedures

• Colonoscopy – This is a test that allows for the doctor to see inside of the patient’s colon. For this procedure, a thin, flexible lighted tube with a camera attached to the end of it is inserted into the anus and directed through the colon while the patient is under anaesthesia. During the colonoscopy, the doctor may also obtain samples of the colon tissue, this is known as a biopsy, for the lab to analyse, this can often aid in confirming the diagnosis. If there are granulomas present, which are clusters of inflamed cells, then this often confirms the diagnosis of Crohn’s disease.
• Flexible sigmoidoscopy – This is a procedure wherein the doctor will use a thin, flexible and lighted tube to examine the patient’s sigmoid colon, this is the last portion of the colon. Both this procedure and a colonoscopy are screening tests.
• Magnetic resonance imaging (MRI) – This type of test makes use of radio waves and a magnetic field in order for detailed images to be created of the tissues and organs. A pelvic MRI is extremely useful when a fistula near the anus needs to be evaluated. Or if a fistula near the small intestine requires examination, a specialised MRI known as an MR enterography will be done.
• Computerised tomography (CT) – Otherwise known as a CT scan, this test uses a specialised X-ray machine that provides the doctor with more detail when compared to the standard X-ray. This scan will provide the doctor with a view of the entire bowel and the surrounding tissues. Another kind of CT scan is known as CT enterography, this provides clearer, more detailed visual images of the patient’s small bowel. In the majority of medical centres, this test has now replaced the popular barium X-rays (barium X-rays use a metallic compound known as barium sulphate to detect any issues in the digestive tract through the use of liquid suspension ingested by the patient). CT enterography uses an intravenously injected contrast material as well as material in liquid form that is ingested to help in producing high resolution visual images of the bowels, it is a quick and painless procedure.
• Double-balloon endoscopy – This test makes use of a long scope to move further through the small bowel in order to get a closer look at possible abnormalities, this kind of endoscope is longer than the standard one. This test cannot however, confirm the diagnosis of Crohn’s disease, it is simply one of the least invasive procedures that can be done and aids in detecting any abnormalities that may require further examination and/or testing means of an endoscopy or biopsy.
• Capsule endoscopy – This test requires the patient to swallow a small capsule containing a camera. The camera will then take pictures which will be transmitted onto a monitor on a belt worn by the patient. These images are then downloaded and displayed on a different screen to be examined for any signs of Crohn’s disease. This camera will painlessly exit the body through the patient’s stool. Once a capsule endoscopy has been conducted, the doctor may recommend that the patient has a biopsy or endoscopy done to confirm the diagnosis.
• Small bowel imaging – This is a kind of test that will look at the area of the small intestine (bowel) that cannot be detected in a colonoscopy. The patient will ingest a barium liquid and the doctor will use an X-ray machine, MRI or a CT scan to obtain images of the small intestine as the liquid highlights any abnormalities of the bowel. This is known as a combination technique as it uses one or more tests to confirm the diagnosis.