Internal MedicineGastroenterologyCrohn’s Disease

Crohn’s Disease

Must-Not-Miss / Red Flags

  • Toxic megacolon: colonic dilation >6 cm with systemic toxicity – surgical emergency
  • Intestinal obstruction: from stricture formation
  • Fistula/abscess: perianal disease requiring drainage and antibiotics
Patient Explanation
“You have a condition where your digestive tract is inflamed. It’s a chronic illness, but with the right medications, you can achieve long periods of remission and live a normal life.”
Board Fact
“Skip lesions (segmental areas of inflammation separated by normal bowel) and non‑caseating granulomas on biopsy are hallmark features of Crohn’s disease.”
ICD-10
K50.90

Definition & Core Concept

Crohn’s disease is a chronic, relapsing inflammatory bowel disease (IBD) characterized by transmural inflammation that can affect any part of the gastrointestinal tract from mouth to anus, most commonly the terminal ileum and colon.

Epidemiology & Risk Factors

  • Prevalence: 200 per 100,000 in North America and Europe
  • Bimodal age of onset: 15‑30 years and 60‑80 years
  • Smoking increases the risk 2‑fold and worsens disease course
  • Genetic association with NOD2/CARD15 mutations

Pathophysiology (Rule of 3)

  1. Genetic susceptibility + environmental trigger → dysregulated immune response to gut microbiota
  2. Th1/Th17‑mediated inflammation → transmural infiltration by lymphocytes and macrophages
  3. Chronic inflammation → stricture, fistula, abscess formation

Clinical Presentation

  • Chronic diarrhea (may be non‑bloody), abdominal pain (often RLQ), weight loss, fatigue
  • Perianal disease: fistulas, abscesses, skin tags
  • Extra‑intestinal manifestations: arthritis, erythema nodosum, pyoderma gangrenosum, uveitis, PSC

Diagnostic Workup

Colonoscopy with biopsy: skip lesions, cobblestoning, non‑caseating granulomas. CT/MR enterography: evaluate small bowel involvement, strictures, fistulas. Fecal calprotectin: marker of intestinal inflammation. Labs: anemia, thrombocytosis, elevated CRP.

Management Protocol

  1. Induction: Corticosteroids (Prednisone 40 mg/day taper) or Biologics (anti‑TNF: Infliximab, Adalimumab)
  2. Maintenance: Immunomodulators (Azathioprine, Methotrexate) or anti‑TNF agents
  3. Perianal disease: Ciprofloxacin + Metronidazole; Infliximab for fistulizing disease
  4. Surgery: for strictures, abscesses, refractory disease (not curative – disease recurs)
  5. Smoking cessation: essential for reducing relapse risk

Complications & Prognosis

  • Strictures and bowel obstruction
  • Fistulas (entero‑enteric, entero‑vesical, entero‑cutaneous)
  • Increased risk of colorectal cancer (related to disease duration and extent)
  • Malabsorption and nutritional deficiencies (B12, Vitamin D, iron)

ICU Criteria

ICU admission if: toxic megacolon, severe sepsis from abscess, or post‑operative complications.

Clinical Vignette

A 25‑year‑old man presents with 6 months of intermittent RLQ pain, weight loss of 10 kg, and non‑bloody diarrhea. Colonoscopy reveals patchy inflammation from terminal ileum to transverse colon with skip lesions. Biopsy shows non‑caseating granulomas.

Pearls & Pitfalls

  • Smoking cessation is the single most effective non‑pharmacologic intervention – continuing smokers have higher relapse rates and more aggressive disease.
  • Always consider TB screening before starting anti‑TNF therapy (risk of reactivation).

Discharge & Follow-Up

Regular colonoscopy surveillance (every 1‑2 years) for dysplasia screening starting 8 years after diagnosis. Monitor thiopurine methyltransferase (TPMT) levels if on Azathioprine. Vitamin and mineral supplementation.

Literature & Guidelines

AGA 2024 Clinical Practice Guidelines on Crohn’s Disease. PMID: 38626701.

Personal Clinical Notes