Road to diagnosis

This can be a frustrating time as you undergo multiple tests, all the while experiencing symptoms before arriving at a diagnosis of IBD.

It is common to take from 6 to 18 months from first symptoms until a positive diagnosis is made, as not all symptoms are specific to IBD. Other conditions such as IBS have to be excluded before a diagnosis can be made. Also, in Crohn’s disease, and in some patients with ulcerative colitis, the symptoms may come and go (flare-ups followed by remission). This may lead some people to defer investigation of their symptoms, as they appear to get better during the remission phase.

Read more about how Crohn’s disease and ulcerative colitis are diagnosed from the peak patient body representing people with IBD, Crohn’s & Colitis Australia.

There are many tests and tools you may come across when you are being investigated for IBD. For a general overview of the types of imaging tests you may come across, you can visit The Gut Foundation Australia’s gastrointestinal diagnosis page.

Blood tests

As IBD involves inflammation, a blood test may be able to identify elevated levels of biomarkers which are used to measure inflammation such as the white cell count (WCC; number of white blood cells), erythrocyte sedimentation rate (ESR; the rate at which red blood cells fall in a tube) and C-reactive protein (CRP; levels rise in response to inflammation). Testing for Saccharomyces cerevisiae antibodies (ASCA) and anti-neutrophil cytoplasmic antibodies (ANCA) can be used to help differentiate between Crohn’s disease and ulcerative colitis.

Stool samples

A small sample of your stool may be examined to exclude certain infections (parasite, bacterial, viral) to help rule out other causes of your symptoms and look for the presence of blood. They may also test for a protein called calprotectin that is released when there is inflammation in the bowel.

Colonoscopy, sigmoidoscopy and endoscopy

Colonoscopy uses a camera inserted through the rectum to examine the colon. Sometimes they may also take a small sample for pathology (biopsy). What is involved, how do I prepare and what are the risks? Information from the specialist’s point of view at the Gastroenterological Society of Australia’s website.

Find out about sigmoidoscopy from the specialist’s point of view at the Gastroenterological Society of Australia’s website.

Gastroscopy uses a camera inserted through the mouth to examine the first part of the small bowel. Some select centres may use small bowel capsule gastroscopy, which involves swallowing a vitamin-sized camera pill that takes images as it moves naturally through the digestive system. The Gastroenterological Society of Australia’s website has further information from the specialist’s perspective on what to expect with gastroscopy (also known as upper endoscopy).

Read more about small bowel capsule endoscopy at the Australian Centre for Digestive Diseases. Please note this procedure may not be covered by Medicare and may incur additional costs. Check with your healthcare provider for more information.


An abdominal ultrasound scan may be used to find the extent and location of IBD. Ultrasound uses high-frequency sound waves to make an image of internal body structures. Better Health Channel explains the basics of ultrasounds.

X-rays and CT scans

Radiography is the imaging of body structures using X-rays. There are special types of X-rays for looking at the gastrointestinal tract. Computed tomography (CT) colonoscopy (also known as colonography) is a specialised X-ray scan of the colon or large intestine. For more general information on CT scans, visit Lab Tests Online Au.


As mentioned earlier, it is common to take from 6 to 18 months to reach a positive diagnosis of IBD. During this time you may first be diagnosed and treated for other conditions as it can be difficult to distinguish between conditions like IBS and IBD. If your symptoms are mild and you have no rectal bleeding or weight loss, IBS is a common first diagnosis. A thorough medical history and any abnormal blood tests may be a clue to guide away from IBS. Testing for levels of calprotectin in the stool can also be used to distinguish between IBS and IBD. In IBD, calprotectin is generally very high. In IBS, the level is lower compared to people with active IBD (but may still be higher than the general population).