What is inflammatory bowel disease (IBD)?

This is a collective term for the two main conditions:

• Ulcerative colitis and Crohn’s disease are inflammatory diseases of the gastrointestinal tract.

  • This is different from irritable bowel (IBS) where no inflammation is present.
  • These conditions have no known cause. They are not caused by an infection, any particular type of diet or stress.
  • The diagnosis is made by the combination of tests - not by one particular test.
  • Ulcerative colitis and Crohn’s disease have many features in common BUT are probably best considered as separate diseases.
  • There has been an increasing incidence of Crohn’s disease in recent years. The incidence of ulcerative colitis has remained about the same in western countries.
• In NZ 1:600 people have Crohn’s disease.
  • It is more common western countries (Northern Europe, North America and Australia and New Zealand).
  • It is now becoming more common throughout the world.
• About 1: 600 have ulcerative colitis. This also may be becoming more common in westerm countries
• Inflammatory bowel disease was uncommon in South Asia and China and Kapan but is becoming more common.   The rates are low in Maori and Pacific peoples but again starting to be diagnosed more frequently
• Smoking.
  • Increases the risk of Crohn’s disease.
  • Decreases the risk of getting ulcerative colitis.
• There is clearly a major influence of genetics.
  • First-degree relatives have a 30-fold increased risk of developing Crohn’s disease. This means an 8% lifetime risk for first-degree relatives.
  • There is a genetic influence in ulcerative colitis but this is less prominent.