Inflammatory bowel disease

Includes Crohn’s disease (CD) and ulcerative colitis (UC). UK incidence is ˜5.2/100,000/yr. CD is twice as common as UC. The cause is unknown, although there is a recognized genetic disposition.

Ulcerative colitis

• Involves colon only.

  • • Rectal (proctitis) is most common or may extend continuously up to involving the entire colon (pancolitis).

  • • Terminal ileum may be affected by ‘backwash ileitis’.

Crohn’s disease

  • • May affect any part of GI tract, but terminal ileum and proximal colon are commonest sites of involvement.

  • • Unlike UC, bowel involvement is non-continuous (‘skip’ lesions).

Prognosis

UC and CD are marked by relapse and remission. Patients can have very good quality of life with current therapy. Poor prognostic factors include extensive disease, frequent remissions, and young age at diagnosis.


Etiology

Though the etiology is unclear, Crohn’s disease is thought to result from a complex interaction of genetic, host immune, and environmental factors. Animal models have provided important insight into this relationship.

Genetics

The single greatest risk factor for the development of IBD is having a first-degree relative with the condition, with the estimated risk 30 to 100 times greater than in the general population.

Microbial Factors

A complex interaction of gut mucosal immune mechanisms with intestinal flora is thought to be critical in the development of Crohn’s disease.

However, no pathogen has reproducibly been identified as a potential cause of Crohn’s disease.