Crohn's disease - Tests and diagnosis

An overview is below and if you'd like more detail on the individual tests, simply use the sub-pages you can now see in the menu on the left.

Crohn's disease can be difficult to diagnose and is often confused with other conditions. It is not usual to test for Crohn's disease unless you are experiencing specific symptoms or you are at a high risk, for example, if you have a close relative with the condition. If you are concerned about your symptoms, see Symptoms and signs.

It is important to get the correct diagnosisThe process of determining which condition a patient may have. so that you can get the right treatment. Because there is no single test for Crohn's disease, it is helpful to exclude any other conditions that may be causing your symptoms. These include ulcerative colitis, bowel infections and irritable bowel syndrome (IBS). There are some simple initial tests that your doctor may recommend to rule out other illnesses such as these before you are referred on for diagnostic testing.

Initial tests

  • Blood tests can give information on problems such as anaemiaA reduced level of haemoglobin, which carries oxygen in the blood. Anaemia causes tiredness, breathlessness and abnormally pale skin., inflammationThe body’s response to injury., infectionInvasion by organisms that may be harmful, for example bacteria or parasites. and bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. chemical and mineral deficiencies that may have been caused by diarrhoeaWhen bowel evacuation happens more often than usual, or where the faeces are abnormally liquid.. Blood tests can also be used to assess liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. function and to look for particular antibodiesSpecial proteins in the blood that are produced in response to a specific antigen and play a key role in immunity and allergy. that may indicate which type of inflammatory bowel diseaseA group of inflammatory conditions of the intestine. The two major forms are Crohn’s disease and ulcerative colitis. is present.
  • Stool tests may reveal bacterial infectionInvasion by organisms that may be harmful, for example bacteria or parasites. or inflammationThe body’s response to injury. in your gastrointestinal tractThe gut, which begins at the mouth and ends at the anus.. Your doctor or nurse will give you a container so that you can provide a sample in private.

My parents and I knew something was wrong and I had loads of tests done, including bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. tests and food allergy tests. Aimee

Further tests

  • After performing a thorough examination and initial tests, a more detailed series of tests may be recommended to help your doctor to make the diagnosisThe process of determining which condition a patient may have. of Crohn's disease, or to exclude other conditions. These may be carried out in a hospital and may include:
  • Endoscopy: either sigmoidoscopy or colonoscopyExamination of the colon and rectum with a colonoscope, an imaging instrument that is inserted through the anus., depending on which part of the gastrointestinal tractThe gut, which begins at the mouth and ends at the anus. is being examined. A biopsyThe removal of a small sample of cells or tissue so that it may be examined under a microscope. The term may also refer to the tissue sample itself. may be taken at the same time if necessary
  • Wireless capsule endoscopy, a test which is especially useful when looking for signs of Crohn's disease in the small intestineThe section of gut, or gastrointestinal tract, from the stomach to the anus. (see Aimee's real patient story for her personal experience of this procedure)
  • X-rays to look at parts of the gastrointestinal tractThe gut, which begins at the mouth and ends at the anus. that endoscopyExamination of the inside of the body using a tube equipped with a light source and either a small camera or an optical system. is not able to reach
  • White blood cell scan (also called scintigraphy) to determine the location and severity of inflammationThe body’s response to injury. in the gastrointestinal tractThe gut, which begins at the mouth and ends at the anus., as well as to identify complications such as abscesses, localised sites of infectionInvasion by organisms that may be harmful, for example bacteria or parasites.
  • Ultrasound scan
  • Computerised tomography (CTA scan that generates a series of cross-sectional X-ray images.) scanning which can reveal complications of Crohn's disease such as abscesses and fistulae, which are abnormal channels formed, for example, between sections of the bowel
  • Magnetic resonance imaging (MRIAn abbreviation for magnetic resonance imaging, a technique for imaging the body that uses electromagnetic waves and a strong magnetic field.).

Getting the results

There may be a wait for the results of your diagnostic tests. This is because the information often needs to be assessed by specialists. It is important to ask how long it will take to get the results of any tests that are done, and whether you need to telephone or make an appointment to get the results.