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Inflammatory Bowel Disease for the PA Exam

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Inflammatory Bowel Disease (IBD) for the Physician Assistant Licensure Exam
Overview
  • Inflammatory Bowel Disease (IBD) consists of Ulcerative Colitis (UC) and Crohn’s Disease (CD), both chronic inflammatory disorders of the gastrointestinal (GI) tract.
  • UC is limited to the colon, while CD can affect any part of the GI tract from the mouth to the anus.
Pathophysiology
  • Immune dysregulation: IBD results from an inappropriate immune response to intestinal microbiota in genetically predisposed individuals.
    • In UC, the inflammation is limited to the mucosa and submucosa.
    • In CD, inflammation is transmural, affecting the entire thickness of the bowel wall.
  • Genetic predisposition: Mutations in genes such as NOD2 are associated with Crohn’s disease.
  • Environmental triggers: Factors like smoking affect the two diseases differently—smoking worsens Crohn's disease but has a protective effect in UC.
  • Microbiome: Dysbiosis (imbalance in gut flora) contributes to the pathogenesis of both UC and CD.
Ulcerative Colitis (UC)
  • Location: Always starts in the rectum and extends proximally in a continuous pattern. It affects only the colon.
Ulcerative Colitis
  • Histology: Inflammation is confined to the mucosa and submucosa.
  • Clinical presentation:
    • Bloody diarrhea is the hallmark symptom, often accompanied by tenesmus (feeling of incomplete evacuation).
    • Abdominal pain localized to the left lower quadrant (LLQ).
  • Complications:
    • Toxic megacolon: Acute dilation of the colon with risk of perforation.
    • Colon cancer: Risk increases with the duration of disease, particularly after 8–10 years of extensive colitis.
Crohn’s Disease (CD)
  • Location: Can affect any part of the GI tract but most commonly involves the terminal ileum and colon. It is characterized by skip lesions (discontinuous areas of inflammation).
Crohn’s Disease
  • Histology: Inflammation is transmural, extending through the full thickness of the bowel wall.
  • Clinical presentation:
    • Non-bloody diarrhea and right lower quadrant (RLQ) pain are common.
    • Perianal disease: Fistulas, abscesses, and skin tags are frequent findings.
  • Complications:
    • Strictures: Narrowing of the bowel due to fibrosis and inflammation, leading to obstruction.
    • Fistulas: Abnormal connections between the bowel and other organs (e.g., skin, bladder).
    • Malabsorption: Particularly in patients with extensive small bowel disease, leading to deficiencies like vitamin B12 and fat-soluble vitamins.
Diagnosis
  • Endoscopy with biopsy: Gold standard for diagnosis.
    • UC: Continuous mucosal inflammation starting in the rectum.
    • CD: Skip lesions and deep, transmural ulcers.
  • Histopathology:
    • UC: Crypt abscesses and superficial inflammation.
    • CD: Non-caseating granulomas and transmural inflammation.
  • Lab tests: Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) indicate active inflammation.
  • Fecal calprotectin: A marker of intestinal inflammation that helps differentiate IBD from irritable bowel syndrome (IBS).
Treatment
  • Corticosteroids: Used to induce remission during acute flares but not for long-term maintenance due to side effects.
  • Aminosalicylates (5-ASA): First-line agents for mild to moderate UC.
  • Immunosuppressants: Azathioprine or methotrexate for long-term management and steroid-sparing effects.
  • Biologic agents: Anti-TNF agents (e.g., infliximab) are used for moderate to severe disease that is unresponsive to other treatments.
Key Points
  • Ulcerative Colitis affects the colon in a continuous pattern and presents with bloody diarrhea. Inflammation is limited to the mucosa and submucosa.
  • Crohn’s Disease can involve any part of the GI tract, characterized by skip lesions and transmural inflammation. It often presents with non-bloody diarrhea and perianal disease.
  • Complications include toxic megacolon and colon cancer in UC, while CD is prone to strictures, fistulas, and malabsorption.
  • Diagnosis relies on endoscopy with biopsy and histopathology.
  • Management involves corticosteroids for flares and immunosuppressants or biologics for long-term control.

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