Overview

• Prevalence

  • Approximately 600,000 adults in the US are affected by ulcerative colitis.

  • Ethnicity

    • Higher in White populations than in Black, Hispanic, or Asian populations

    • Highest among individuals of Ashkenazi Jewish descent

• Peak incidence

  • 15–35 years of age

  • Another smaller peak may be observed in individuals > 55 years of age.

  • Similar for men and women

• Genetic predisposition (e.g., HLA-B27 association)

• Ethnicity (White populations, individuals of Ashkenazi Jewish descent)

• Family history of inflammatory bowel disease

• Episodes of previous intestinal infection

• Increased fat intake (especially saturated fat and animal fat)

• Oral contraceptive use

• NSAIDs may exacerbate ulcerative colitis.

• Appendectomy

• Smoking

The exact mechanism is unknown but studies suggest that ulcerative colitis is caused by abnormal interactions between host immune cells and commensal bacteria. [5][6]

• Dysregulation of intestinal epithelium: increased permeability for luminal bacteria → activation of macrophages and dendritic cells → antigen presentation to macrophages and naive CD4+ cells leads to:

  • Secretion of proinflammatory cytokines (IL-6, IL-12, TNF-α) and chemokines (CXCL1, CXCL3, and CXCL8) → recruitment of other immune cells (e.g., neutrophils) to the site

  • Differentiation of naive CD4+ cells to Th2 effector cells

  • Recruitment of natural killer cells

• Dysregulation of the immune system: upregulation of lymphatic cell activity (T cells, B cells, plasma cells) in bowel walls → enhanced immune reaction and cytotoxic effect on colonic epithelium → inflammation with local tissue damage (ulcerations, erosions, necrosis) in the submucosa and mucosa

  • Autoantibodies (pANCA) against cells of the intestinal epithelium

  • Th2 cell-mediated response

• Pattern of involvement

  • Ascending inflammation that begins in the rectum and spreads continuously proximally throughout the colon

  • Inflammation is limited to the mucosa and submucosa.

The rectum is always involved in ulcerative colitis.