Crohn Disease
Chronic inflammatory bowel disease causing deep ulcers and scarring anywhere from mouth to anus.
Emergency Management: Toxic megacolon (rare in Crohn compared to UC) or free bowel perforation presenting with rigid abdomen and pneumoperitoneum requiring emergent laparotomy.
An idiopathic, chronic inflammatory bowel disease characterized by transmural, granulomatous inflammation that can affect any part of the gastrointestinal tract from the mouth to the perianal area.
Detailed Overview
Crohn disease typically involves the terminal ileum and right colon, sparing the rectum (unlike Ulcerative Colitis). The transmural nature of the inflammation leads to strictures, fistulas, and abscesses. It follows a relapsing and remitting course. Treatment focuses on inducing and maintaining remission using immunosuppressants and biologics to prevent permanent bowel damage.
Epidemiology & Demographics
Incidence is highest in North America and Europe. Bimodal age distribution: peak onset between 15-30 years, and a second smaller peak at 60-70 years. Slightly more common in females.
Etiological Mechanism
Complex interplay of genetic susceptibility (NOD2 mutations), environmental triggers, and an exaggerated mucosal immune response to normal gut flora.
Primary Causes
Idiopathic autoimmune response.
Defective gut barrier function allows luminal luminal bacteria to invade the lamina propria. Macrophages and dendritic cells mount a massive Th1/Th17 mediated immune response, releasing TNF-alpha and IFN-gamma. This results in transmural inflammation (all layers: mucosa, submucosa, muscularis, serosa). The deep ulcerations coalesce to form cobblestoning. Healing leads to collagen deposition and strictures (fibrosis). Transmural fissures can burrow through the gut wall, forming fistulas to adjacent organs or skin.
Diagnostic Criteria & Guidelines
Combination of clinical presentation, endoscopic findings of skip lesions/cobblestoning, and biopsy showing transmural inflammation with non-caseating granulomas.
For mild disease (terminal ileitis): Oral Budesonide 9 mg daily for induction. For moderate/severe: Systemic corticosteroids (Prednisone 40 mg PO) to induce remission, immediately transitioning to anti-TNF biologic therapy (Infliximab 5 mg/kg IV or Adalimumab 160 mg subQ loading dose) for maintenance.
Second-Line & Adjunctive Therapy
Immunomodulators like Azathioprine (2.0-2.5 mg/kg daily) or Methotrexate to maintain remission if biologics fail. Alternative biologics: Vedolizumab (anti-integrin) or Ustekinumab (anti-IL-12/23).
Surgical & Procedural Management
Unlike UC, surgery is NOT curative. Resection is reserved for complications (strictures, fistulas, abscesses, refractory bleeding). Ileocecectomy is the most common procedure. Strictureplasty preserves bowel length.
Patient Counseling & Advice
Emphasize that surgery does not cure Crohn disease, as it often recurs at the anastomosis site. Medication adherence is critical to prevent short bowel syndrome from multiple surgeries.
Follow-Up & Monitoring Schedule
Fecal calprotectin every 6 months to check for subclinical inflammation. Colonoscopy 1 year after starting biologics to confirm mucosal healing. Surveillance colonoscopy for cancer starts 8 years after disease onset.
Preventive Strategies
No primary prevention. Avoid NSAIDs, which can trigger severe disease flares.
Chronic, lifelong disease. >70% will require at least one surgery in their lifetime. Life expectancy is slightly reduced compared to the general population.