Inflammatory Bowel Disease
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- Inflammatory bowel disease (IBD) includes two separate clinical entities: ulcerative colitis (UC) and Crohn disease (CD). UC and CD are both uncontrolled immune-mediated inflammatory responses.
- UC: relapsing and remitting course; inflammation is limited to the mucosal layer. UC always involves the colon (proctitis > left-sided colitis > pancolitis) ± extracolonic manifestations; hallmarks: bloody diarrhea and abdominal pain
- CD: Transmural inflammation involving any part of alimentary canal, commonly affects small bowel (80% of cases), almost always involves the terminal ileum; hallmarks: skip lesions (spared areas of inflammation), fibrosis/strictures, intra-abdominal abscesses, and fistulas
- Approximately 1.5 million North Americans are affected with IBD; increasing incidence over time, specifically in developed countries (1)
- CD—20.2 per 100,000 person-years in North America and 12.7 per 100,000 person-years in Europe
- UC—19.2 per 100,000 person-years in North America and 24.3 per 100,000 person-years in Europe (2)
Increasing, particularly in Europe:
- CD—322 per 100,000 persons in Europe and 319/100,000 persons in North America
- UC—505 per 100,000 in Europe and 249/100,000 in North America (2)
Etiology and Pathophysiology
- Pathogenesis not well understood but multifactorial: genetic susceptibility; gut flora dysbiosis; external environment/geography; lifestyle and diet; and immune response
- High levels of HLA II/activated macrophages secrete increased proinflammatory cytokines (IL-1, IL-6, IL-8, and TNF-α) in conjunction with decreased production of downregulatory cytokines (IL-2, IL-10, and TNF-β) (1).
There are 163 IBD-associated gene loci (110 for both UC and CD, 30 CD-specific, and 23 UC-specific).
- Cigarette smoking doubles risk of CD (1).
- Age—bimodal peaks for UC (larger peak 30 to 40 and smaller peak 60 to 70); CD diagnosis peaks at 20 to 30 (1).
- Alterations in gut biome or disruption in intestinal mucosa; diets high in sugar, omega-6 FA, unsaturated FAs, and meat may be risk factors (1).
- Family history/genetic risk factors—up to 15% of patients have first–degree relative with IBD
- More often in Ashkenazi Jews; less often in African American or Hispanic populations
No prevention of primary disease. Treatment focus is prevention of remission and comorbid conditions.
Commonly Associated Conditions
- Extraintestinal manifestations: erythema nodosum, pyoderma gangrenosum, psoriasis, episcleritis, uveitis, scleritis, ankylosing spondylitis, sacroiliitis, osteoporosis, nephrolithiasis, DVT, primary sclerosing cholangitis ± cirrhosis, cholangiocarcinoma, chronic bronchitis, bronchiectasis, malabsorption, nutrition/vitamin deficiency
- Metastatic CD, colorectal cancer (CRC)