How to diagnose Crohn’s disease?
The diagnosis of Crohn’s disease is made by taking a complete patient and family medical history (anamnesis), clinical examination and tests. After taking the anamnesis and physical examination and Crohn’s disease is suspected, the doctor will carry out some additional medical tests. These tests may include the following.
Endoscopy is the most important diagnostic tool, using an endoscope, a thin, flexible tube with a light source and a small camera in its tip transmitting the image onto a screen. The gastroenterologist inserts an endoscope into your GI tract. When examining the colon, the endoscope is introduced through the anus - colonoscopy. When examining the upper part of the GI tract, the endoscope is introduced through the mouth – gastroscopy and enteroscopy.
During endoscopy, the doctor takes a sample of tissue from the affected areas (biopsy). The sample then undergoes a detailed microscopic analysis. Pathohistological opinion is very important as it confirms the disease, distinguishes between different forms of IBD, shows the degree of disease activity and potential dysplasia in a long-lasting disease.
- Blood tests (white blood cell count (leukocytes), platelets, haemoglobin and markers of acute inflammation such as CRP, ESR) do not confirm Crohn’s disease. They are important for determining disease activity, assessment of treatment efficacy and as a predictor of the exacerbation of the disease.
- Stool tests (calprotectin, used to detect acute inflammation in the intestines). Detection of calprotectin in a stool helps differentiate between IBD and irritable bowel disease and to assess the activity of bowel inflammation, the success of the treatment. Calprotectin can be used as a predictor of exacerbation of the disease.
Radiological scans are important complementary diagnostic tests that enable imaging of the affected part of the GI tract and/or complications of the disease.
Native abdominal X-ray (RTG) imaging: used in affected patients to exclude toxic megacolon, perforation of the GI tract and intestinal obstruction (ileus).
CT enterography (CTE): imaging test that gives similar data as MRE, however it exposes the patient to a radiation burden.
Magnetic resonance imaging (MRI): newer diagnostic procedure that does not involve radiation; the method is based on the resonance of hydrogen ions in a strong magnetic field. The body or investigated organ is in a static magnetic field, radio wave energy converts signals into realistic images of the body.
- MRI of the pelvis: important investigation used when complications of Crohn’s disease, such as perianal fistulas with abscesses, are suspected.
- Magnetic resonance enterography (MRE): very important diagnostic imaging of small intestines in patients with Crohn’s disease. Apart from detecting changes in lumen diameter, it also shows changes in the intestinal wall and the surrounding tissue (lymph nodes, fistulas). MRE shows active inflammation, luminal narrowing and distention before the narrowing (important for making a decision on the treatment type).
Ultrasound (US): ultrasound technology is used to evaluate organs in the pelvic and abdominal area, without exposing the patient to radiation.
- Contrast-enhanced transabdominal ultrasound: an increasingly important examination in diagnosing and monitoring IBD. This imaging test allows a clinician to examine the bowel wall thickness and perfusion patterns indicating inflammatory changes, especially in the terminal ileum area. It also detects enlarged lymph nodes, abscesses, strictures and even fistulas.
- Endoscopic ultrasound (EUS): shows perianal fistulas and complications. EUS differentiates simple from complex fistulas and their relation to the anal sphincter. This examination has a very high sensitivity for identification of perianal abscesses. EUS is radiation-free, safe and has a similar sensitivity and specificity for perianal abscesses and fistulas as MRI. As the perianal area is affected, the examination may be painful. In such cases, MRI of the pelvis is preferred.
Capsule endoscopy: a radiation-free diagnostic tool for examining of the small bowel. In this procedure, doctor uses a tiny wireless camera to take pictures of digestive tract. The camera is inside the capsule which patient swallows. It is more sensible than other imaging techniques (jejunoileography, MR enterography, CT enterography) in identifying areas of inflammation in the small intestine of patients without strictures or bowel obstructions. It is intended for patients with suspected small bowel Crohn’s disease that could not have been confirmed with previous endoscopic and imaging tests.