Inflammatory Bowel Disease

Basics

Idiopathic, chronic inflammatory diseases of intestines, which can involve extraintestinal sites as well
Differentiation between ulcerative colitis (UC) and Crohn disease is not always clear; intermediate forms of inflammatory bowel disease (IBD) exist
May present as initial onset of disease or exacerbation of existing disease
Maintain high index of suspicion owing to frequent, subtle presentation of Crohn disease
Pediatric considerations:
- Can occur in first few years of life
- Extraintestinal manifestations may predominate
Differences between Crohn and UC:
- Rectum almost always involved in UC with continuous inflammation proximally
- Small intestine is not involved in UC
- Crohn can occur anywhere from mouth to anus, often with normal GI tract segments between affected areas
- Crohn involves transmural inflammation, whereas UC is confined to submucosa
Similarities between Crohn and UC:
- Higher rate of colon cancer with disease >10 yr
- Bimodal age distribution, with early peak between teens and early 30s and second peak about age 60 yr
Crohn disease clinical pattern:
- Ileocecal: ∼40%
- Small bowel: ∼30%
- Colon: ∼25%
- Other: ∼5%
UC clinical pattern on presentation:
- Pancolitis: 30%
  - Most severe clinical course
Proctitis or proctosigmoiditis: 30%
- Relatively mild clinical course
Left-sided colitis (up to splenic flexure): 40%
- Moderate clinical course

Unknown
Crohn disease and UC are separate entities with common genetic predisposition
A positive family history is very common
Multifactorial origin involving interplay among the following factors:
- Genetic
- Environmental
- Immune
Pathogenesis:
- Gut wall becomes unable to downregulate its immune responses, ultimately resulting in chronic inflammation
There is no definitive evidence for the etiologic role of infectious agents
Psychogenic factors may play a role in some symptomatic exacerbations

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