About Crohn's Disease

Crohn's Disease is a chronic and relapsing inflammatory disorder that can affect any part of the gastrointestinal tract, from the mouth to the anus, as well as other organs of the body.

Crohn's disease is a type of inflammatory bowel disease. Ulcerative colitis is also part of this category and shares some similar clinical features as Crohn's disease. However, ulcerative colitis only affects the large intestine.

Crohn's disease involves all three layers of the bowel wall (inner lining, muscular layer and outer lining). To contrast, ulcerative colitis only involves the mucosa (inner lining).

The patterns of intestinal involvement in Crohn's disease are divided into large bowel alone (colonic) (25%), small and large bowel (ileocolic) (40%), and small bowel alone (30%). The duodenum is rarely involved (only 2%).

The main pathological features of Crohn's disease are ulcers (shallow and deep), connection of the bowel lumen with surrounding structures (fistulae) and scar tissue leading to narrowing of the bowel lumen (strictures causing lumen obstruction).

The extra-intestinal structures involved in Crohn's disease can be local or systemic. Local involvement can occur when fistulae are present, such as between the bowel and the vagina or the bladder.

Systemic extra-intestinal manifestations include:

  • Skin
  • Mucous membranes: shallow ulcers of the mouth and vagina
  • Eyes: inflammation of the iris (iritis)
  • Joints: painful and inflamed large joints (arthralgia and arthritis)
  • Liver/gallbladder: chronic active liver inflammation (hepatitis) and scar tissue damage with liver dysfunction (cirrhosis), gallstones.


Who gets Crohn's Disease?

Crohn's disease is an important cause of morbidity in Australia and affects approximately 50 people per 100 000 of the population. The incidence is set to increase even further in future years.

The disease is most common in adolescents and young adults with up to 60% of patients being diagnosed before 25 years of age. However, Crohn's disease can occur at any age. Females are affected slightly more than males.


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