A colonoscopy is the most common test used to diagnose Crohn’s disease.
Several other tests may be used to rule out other possible causes of your symptoms, such as ulcerative colitis (a condition that causes inflammation of the colon).
Initial assessment
During your initial assessment, it is likely that your GP will ask you about the pattern of your symptoms and check whether there may be any contributing causes, such as:
- diet
- recent travel - for example, you may have developed travellers' diarrhoea while travelling abroad
- whether you are taking any medication, including any over-the-counter (OTC) medicines
- whether you have a family history of Crohn’s disease
Your GP may also carry out a series of standard tests to assess your general state of health. For example, they may:
- check your pulse
- check your blood pressure
- measure your weight and height
- measure your temperature
- examine your abdomen
Blood tests
The next stage of the diagnosis is to refer you for a series of blood tests. These can be used to assess:
- the levels of inflammation in your body
- whether you have an infection
- whether you have anaemia (low levels of red blood cells), which could suggest you are malnourished
Stool sample
You may be asked to provide a stool sample for testing. The stool sample can be checked for blood and mucus. It can also be used to determine whether your symptoms are being caused by a parasitic infection, such as roundworm.
Colonoscopy
A colonoscopy is a test used to examine the inside of your colon. It involves inserting a long flexible tube, known as an endoscope, into your back passage (rectum) and up into your colon.
The endoscope has a light and a camera on the end. The camera can be used to send images to a television screen. These will show the level and extent of inflammation inside your colon.
The endoscope can also be fitted with surgical tools that can be used to take a number of small tissue samples from different sections of your digestive system. This is known as a biopsy. The procedure may feel uncomfortable but it is not painful.
These tissue samples will be examined under a microscope for the distinctive cell changes known to occur in cases of Crohn’s disease.
Small bowel enema (SBE)
A small bowel enema (SBE) is a test to examine the inside of the small intestine, usually at the point where it meets the colon. This area cannot be seen using a colonoscopy.
During an SBE, a local anaesthetic spray is used to numb the inside of your nose and throat. A tube is passed down your nose and into your throat, before being threaded into your small intestines. This can feel unpleasant at first, but most people find that they get used to the sensation after a few minutes.
A liquid called barium is passed down the tube. The barium coats the lining of your small intestines so that they show up clearly on X-rays. A series of X-ray images will then be taken. The images can often highlight the areas of narrowing and inflammation that are caused by Crohn’s disease.
After the test, you will be advised to drink plenty of fluid to help wash the barium out of your body. You may notice that your stools are whiter than usual for the first few days after having an SBE. This is perfectly normal and it is nothing to worry about.
Further testing
Further testing is usually only required if the results of the above tests are uncertain, or if it is thought that you may have developed complications, such as a blockage in your colon or an abscess (a pus-filled cavity).
Tests that you may have include a:
A wireless capsule endoscopy is a new type of test that involves swallowing a small capsule (about the size of a headache tablet). The capsule works its way down to your small intestines where it transmits images to a computer.
A few days after the test, the capsule passes out of your body in a stool. The capsule is disposable so you do not have to worry about retrieving it from your stools.
