IBD Academy: Diagnosing IBD

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Some of the first symptoms that people with inflammatory bowel disease tend to notice notice are persistent abdominal pain, nausea, bloating, weight loss, and blood in the stool. Before making a diagnosis of IBD, doctors have to rule out other potential causes for these symptoms, such as a GI bacterial or viral infection. Other conditions like IBS, a food allergy, celiac disease, diverticulitis, or cancer are also a possibility. The main tools used to differentiate and diagnose IBD are lab tests of blood and stool, imaging, and endoscopic procedures. Most people with IBD are diagnosed between the ages if 15 and 35.

Laboratory Tests

  • blood tests:
    • white blood cell (WBC) count: an increased number of WBCs in the blood often indicates a bacterial or viral infection. Having an infection may cause symptoms similar to those of IBD but point away from a diagnosis of IBD itself.
    • hemoglobin (Hgb) and hematocrit (Hct) levels: when these levels are low, it indicates anemia, a condition where there is an inadequate amount of iron in the blood. Anemia can occur from blood loss in the intestinal tract and may contribute to an IBD diagnosis.
    • platelet count: an increased number of platelets in the blood can indicate persistent bleeding somewhere in the body, like from the intestinal tract.
    • antinuclear antibody (ANA) test: ANAs are antibodies that attack the body's own tissue and can indicate an autoimmune disease when present.
    • C-reactive protein (CRP) test: increased levels of CRP in the blood indicate significant inflammation is present in the body.
  • stool sample tests:
    • fecal occult blood test: used to detect blood in the stool.
    • tests for common GI infections: helps to rule out IBD.
    • calprotectin test: an elevated level of this protein complex in the stool can indicate active IBD.


  • X-ray: used to look for serious complications that may be associated with IBD,  including an intestinal narrowing, a blockage, or a perforation.
  • fluoroscopy: barium, a substance that coats the walls of the GI tract, is administered orally (upper GI series) or rectally (lower GI series). Then, using a fluoroscope, which continually emits x-rays, details of the intestinal wall and the movement of barium through the GI tract can be observed.  
  • computerized tomography (CT) scan: creates cross-sectional images (a stack of x-rays) of the intestines and allows the location and extent of disease to be determined. It also helps to rule out other conditions and look for complications.
  • magnetic resonance imaging (MRI): creates detailed images of the bowel and surrounding organs using a magnetic field and radio waves instead of radiation. It is particularly helpful in identify fistulae, abnormal tunnels between the intestine and adjacent tissue.
  • magnetic resonance enterography (MRE): uses both IV and oral contrast, in addition to MRI technology, to produce detailed images of the small bowel. These scans can help to define the extent of small bowel Crohn's disease and reveal bleeding, inflammation, abscesses, tears, or blockages.


  • upper endoscopy: a flexible lighted tube is inserted in the mouth and lowered down through the esophagus and stomach into the duodenum, the first part of the small intestine. These areas can sometimes be affected by Crohn's disease.
  • capsule endoscopy: a capsule with a tiny camera in it, which can take up to 50,000 images, is swallowed and later passed in the stool. It is used to take pictures inside the small intestine to look for signs of Crohn's disease.
  • double-balloon endoscopy: a long scope with two balloons attached is advanced further into the small bowel than a traditional endoscope and can also be used to diagnose Crohn's disease.
  • colonoscopy: a scope is inserted into the rectum and is advanced up around the colon to visualize the large intestine. These images can lead to a definitive diagnosis of ulcerative colitis and can help to distinguish UC from Crohn's disease.
  • flexible sigmoidoscopy: a scope is used to examine just the rectum and the lowest part of the colon, the sigmoid. This procedure is sometimes done in the office to provide quicker initial answers than scheduling a full colonoscopy.
  • biopsies: during endoscopic procedures, tiny samples of intestinal tissue can be taken out and analyzed for indications of IBD. Certain microscopic characteristics of the mucosa can specifically indicate Crohn's or UC.

For some, the diagnostic process may take place over a matter of days under emergency circumstances. Others have symptoms for months or years before a definitive diagnosis is made. Additionally, even once the presence of inflammatory bowel disease is clear, it can still be difficult to differentiate between Crohn's and ulcerative colitis in certain people. Some may be diagnosed with UC only to have their diagnosis change to Crohn's disease later on. A smaller number IBD patients are are diagnosed with "indeterminate colitis" when the distinction cannot be made between Crohn's and UC despite extensive diagnostic testing.

That's it for diagnostics! Up next is IBD Academy: Treatment with 5-ASAs and Corticosteroids.

  1. Mayo Clinic: Inflammatory Bowel Disease: Diagnosis and Treatment: https://www.mayoclinic.org/diseases-conditions/inflammatory-bowel-disease/diagnosis-treatment/drc-20353320
  2. Crohn's and Colitis Foundation: Testing for Crohn's/UC: https://www.crohnsandcolitis.com/crohns/testing-for-crohnshttps://www.crohnsandcolitis.com/ulcerative-colitis/testing-for-uc
  3. Mayo Clinic: ANA test: https://www.mayoclinic.org/tests-procedures/ana-test/about/pac-20385204
  4. Mayo Clinic: C-reactive protein test: https://www.mayoclinic.org/tests-procedures/c-reactive-protein-test/about/pac-20385228
  5. Cleveland Clinic: GI X-ray examinations: https://my.clevelandclinic.org/health/diagnostics/7144-gi-x-ray-examinations
  6. Johns Hopkins Medicine Health Library: MR enterography: https://www.hopkinsmedicine.org/healthlibrary/test_procedures/gastroenterology/mr_enterography_135,61
  7. Geboes, K. Histopathology of Crohn's Disease and Ulcerative Colitis: http://www.med-info.nl/literatuur/Crohn_CU_IBS.pdf


Kristen Weiss Sanders is a proud ostomate and third generation girl with guts diagnosed with IBD in 2004. She is passionate about patient education and encourages those with chronic illness to be a knowledgable part of their healthcare team. Kristen credits the constant example and support of the strong women in her family for her determination to thrive with Crohn’s disease and use her IBD journey to empower others.