Inflammatory bowel diseases

Last Review Date: June 4, 2017

What are they?

Inflammatory bowel diseases (IBD) are chronic disorders characterised by swollen and damaged tissues in the lining of the intestinal tract, these conditions vary in severity from patient to patient and change over time. During a flare-up a patient may experience frequent bouts of watery and sometimes bloody diarrhoea, abdominal pain, weight loss, and fever. Between these flare-ups symptoms frequently diminish. Many patients may go through extended periods of remission before another flare-up occurs.

The cause of IBD is not known, but these diseases are thought to be due to an autoimmune process that has been triggered by a genetic predisposition, a viral illness or an environmental factor. IBD affects both sexes equally and is seen most frequently in Caucasians who live in industrialised countries.
The most common inflammatory bowel diseases are Crohn’s disease and ulcerative colitis.

Both diseases may affect anyone at any age, but the majority are first diagnosed in patients between 15 and 35 years of age (and a smaller number between the ages of 50 and 70). In addition to gastrointestinal symptoms, children affected by either disease may experience delayed development and growth retardation. Patients who are diagnosed with one of these conditions at a young age are also at an increased risk of developing colon cancer later in life.

Crohn’s disease can affect any part of the gastrointestinal tract from the mouth to the anus, but is most commonly found in the last part of the small intestine (the ileum) and the first part of the colon (large intestine or bowel). Bowel tissue may be affected in patches with normal tissue in between. Inflammation may penetrate deep into the tissues of the intestine and form ulcers or fistulae (tunnels through the intestinal wall into another part of the gut or another organ).

Other complications of Crohn’s disease may include bowel obstruction, anaemia from bleeding tissue, and infections. About 80% of patients with Crohn’s disease require surgery at some stage, either to remove damaged sections of the intestine or to treat an obstruction or fistula.

Ulcerative colitis primarily affects the surface lining of the colon. Although the symptoms may be similar to those seen with Crohn’s disease, the tissue inflammation is continuous and usually starts from the anus and moves up the colon. Ulcerative colitis tends to present more frequently with bloody diarrhoea. Its most serious complication is toxic megacolon, a relatively rare acute condition in which a section of the colon becomes paralysed. Faeces does not move through the section and it accumulates and dilates the colon. This can cause abdominal pain, fever, and weakness and can become life threatening if left untreated.

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The diagnosis of an inflammatory bowel disease is primarily made with non-laboratory tests, but laboratory testing is an important tool for ruling out other causes of diarrhoea, abdominal pain, and colitis. These causes can include viral or bacterial infections, parasites, medicines, abdominal or pelvic radiation, colon cancer, and a variety of other chronic conditions such as coeliac disease and cystic fibrosis.

Laboratory Tests
Tests that may be requested to exclude other causes of diarrhoea and inflammation include:

Tests that are not specific for IBD but may be done to detect and evaluate the inflammation and anaemia associated with IBD include:

There are several tests that are not widely used clinically but that may sometimes be requested to help differentiate between ulcerative colitis and Crohn’s disease. These tests are not sensitive or specific enough to diagnose either condition, but they may give the doctor additional information. They include:

  • pANCA (Perinuclear anti-neutrophil cytoplasmic antibody) which is found in 60% to70% of those with ulcerative colitis, but only about 5% to 20% of those with Crohn’s disease.
  • ASCA (Saccharomyces cerevisiae antibodies), IgG and IgA. ASCA IgG is found in 80% of Crohn’s patients and in about 20% of those with colitis. ASCA IgA is found in 35% of Crohn’s patients but in less than 1% of those with colitis.

Non-Laboratory Tests
These tests are used to help diagnose and monitor IBDs. They can be used to look for characteristic changes in the structure and tissues of the intestinal tract and to detect blockages. Care must be taken during an acute attack or flare-up of an IBD, however, as there is a slight chance of perforating the bowel during testing.

  • Barium meal and follow through: after swallowing barium contrast dye, abdominal X-rays picture the small intestine
  • Sigmoidoscopy: a slender tube is used to examine the last 2 feet of the colon
  • Colonoscopy: a slender tube is used to examine the entire colon; it includes a light and camera and can be used to take biopsies
  • Biopsy: tissue samples taken from the intestine are evaluated for inflammation and abnormal changes in cell structure. The only easily available biopsies are those that can be taken from the inner surface of the intestine and from superficial biopsies such as these it may not be possible to determine whether the cause is Crohn’s disease or ulcerative colitis.


Treatment of inflammatory bowel diseases is targeted at reducing inflammation, relieving symptoms such as pain and diarrhoea, controlling and healing damage where possible, identifying and addressing complications, and supplementing any nutritional shortages. Since the course of an IBD is usually one of flare-up followed by remission, the treatment will change over time.

Patients with ulcerative colitis or Crohn’s disease will need to be regularly monitored and should work with their doctors to become educated about their condition. While lifestyle changes, such as diet modification, rest and stress reduction, may help improve a patient’s quality of life and extend a remission, they cannot prevent an IBD flare-up. Acute symptoms are treated with a variety of medicines. These drugs are effective but some can only be given for short periods of time because of their side effects. Current therapies include the use of steroids, anti-inflammatory and immunosuppressive drugs, and antibiotics. One or more operations may also become necessary to remove damaged tissue, to treat fistulae and to relieve obstruction.

Related pages

On this site
Tests: C-Reactive Protein, Erythrocyte sedimentation rate (ESR), Full Blood Count, Calprotectin faeces
Conditions: Anaemia, diarrhoea

Elsewhere on the web
Healthdirect Australia: Inflammatory Bowel Diseases Inflammatory Bowel Disease
Centre for Digestive Diseases NSW: Crohn's Disease
Better Health Channel: Crohn's disease and ulcerative colitis