Diagnosis of Crohn’s disease is most commonly confirmed using imaging studies like colonoscopy.
There are several other tests that are used to rule out other conditions that may mimic the symptoms of Crohn’s disease.
Investigations for diagnosis of Crohn’s disease include:-
Initial assessment
The initial assessment involves enquiry into change in diet patterns, a recent travel that may have resulted in traveller’s diarrhea (this may be confused with Crohn’s disease) or if the patient is taking any medication, including any over-the-counter (OTC) medicines.
Enquiry into the family history of Crohn’s disease is also important as many individuals with the condition may have someone in the family who could suffer from Crohn’s disease.
Physical examination
Physical examination includes checking the pulse, blood pressure and measurement of weight and height to determine evidence of malnutrition.
Temperature is taken to assess fever and abdomen is examined for abnormalities.
Blood tests and laboratory investigations
After initial assessment a series of blood tests are advised. These help to assess the level of inflammation in the body as well as presence of infection.
In patients with anemia there may be a low red blood cell count.
Stool sample is usually taken for laboratory testing. The stool sample can be checked for blood and mucus.
Sometimes parasitic or worm infections e.g. roundworm infestations may mimic Crohn’s disease. These can be checked when the stool sample is examined.
Colonoscopy
This is a procedure that is used to look at the inside walls of the intestines, particularly the colon.
The procedure involves inserting a long flexible tube, known as an endoscope, into the rectum via the anus.
The tube is inserted up to the colon and has a light and a camera on the end. The camera sends images of the inside walls of the colon to a computer that can be viewed by the physicians.
Sometimes surgical tools may also be fitted onto the tip of the endoscope and this could be used to take a number of small tissue samples from different sections of the gastrointestinal tract. This is known as biopsy.
This tissue samples are then mounted onto a glass side and are examined under the microscope after staining them with appropriate dyes.
Distinctive cellular changes that are significant of Crohn’s disease are noted under the microscope.
Small bowel enema
This is a test that is used to examine the inside of the small intestine especially at its junction with the colon (ileocecal junction) that cannot be seen using colonoscopy.
The test involves passage of a thin flexible tube via the nose and throat and threading it until it reaches the ileocecal junction.
Barium in form of a liquid is passed down the tube. The barium coats the lining of the small intestines so that they can be viewed on X rays.
The X rays show up areas that have been affected by inflammation caused by the disease.
Other imaging studies
Other imaging studies like computerised tomography (CT) scan and magnetic resonance imaging (MRI) scan are advised to rule out complications.
Sometimes wireless capsule endoscopy is also performed. In this type of test a small capsule is ingested that enters the intestines and takes pictures of them and transmits them to the computer.
Further Reading
High-quality early diet linked to lower IBD risk in children