Diagnosis

Crohn disease

Etiology

Cause [4d0][mze]

• The exact cause remains unknown

• Possible explanation:

  • Inappropriate immune response to environmental antigens like drugs, toxins, infections, or intestinal microbes in a genetically susceptible host

  • An imbalance between proinflammatory and anti-inflammatory mediators

Pathophysiology [4d0]

1. T-cell activation, Interleukin-12 and TNF-alpha --> Chronic granulomatous inflammation from --> injury to the intestine --> fever/malaise, diarrhea, abdominal pain

2. Transmural inflammation --> thickening of the bowel wall and narrowing of the lumen

Complications [4d0][mze]

• Obstruction

• Deep ulceration

• Fistulization

• Abscess formation

• Adhesions

• Malabsorption

• Terminal ileitis --> malabsorption, vitamin B12 insufficiency --> anemia

• Colorectal carcinoma

• Extraintestinal manifestations:

  • Eyes: episcleritis, scleritis, uveitis

  • Mouth: stomatitis, aphthous ulcers

  • Liver: cholelithiasis, cholangitis, primary sclerosing cholangitis

  • Kidneys: nephrolithiasis, hydronephrosis, urinary tract infection

  • Joints: ankylosing spondylitis, peripheral arthritis (knees, ankles, wrists, elbows)

  • Skin: erythema nodosum and pyoderma gangrenosum

Epidemiology

Incidence per 100.000 [du9][4d0][hoh][kcs][zsn]

Prevalence per 100.000 [du9][4d0][hoh][kcs][zsn]

Approach

• Blood test: complete blood count, metabolic panel, vitamin B12, iron, electrolytes, creatinine, liver enzymes, antibodies (ANCA), CRP, erythrocyte sedimentary rate

• Stool test: culture, C. difficile toxin, calprotectin

• Urinalysis: bacteriuria and leukocyturia

• Blood gas

• Colonoscopy + biopsy: The golden standard

• CT abdomen

Treatment

Treatment based on the disease site, pattern, activity, and severity. Treatment goal is to achieve best possible clinical, laboratory, and histologic control with the least adverse effects from medication. [4d0][mze]

1. Mild disease:

   • 5-aminosalicylic acid (5-ASA)

2. Moderate disease:

   • Corticosteroid (not preferred for maintenance due to side effects)

   • Inhibitors of DNA synthesis (immunomodulators): azathioprine or methotrexate

3. Severe disease:

   • Biologic agents (anti-TNF) after tuberculosis and hepatitis B virus is excluded

   • 5-ASA, corticosteroid, and/or immunomodulators

4. Surgical resection if hemorrhage, stenosis, perforation, abscess, fistula, cancer, and toxic megacolon

5. Other: Antibiotics (anal fistula), loperamide (chronic diarrhea), bile acid binders (for bile acid diarrhea), low-fat diet (defective bile salt absorption -> steatorrhea)

Differential diagnoses

Abdominal abscess, Acute mesenteric ischemia, Adhesion, Amebiasis, Anal fissure, Anorectal abscess, Anorectal fistula, Appendicitis, Arthritis, Behcet's disease, Benign neoplasm of the small intestine, Carcinoid tumor, Celiac disease, Cholelithiasis, Coccidioidomycosis, Cytomegalovirus, Diverticulitis, Drug side effects, Erythema nodosum, Femoral hernia, Foreign body, Gastroenteritis, Giardiasis, Histoplasmosis, Incisional hernia, Infectious colitis, Inguinal hernia, Intussusception, Iridocyclitis, Irritable bowel syndrome, Ischemic colitis, Lymphoma, Meckels diverticulum, Ovarian torsion, Peritonitis, Peutz-Jeghers syndrome, Primary sclerosing cholangitis, Pseudomembranous colitis, Pyoderma gangrenosum, Ruptured ectopic pregnancy, Salmonellosis, Sarcoidosis, Shigellosis, Small bowel cancer, Tuberculosis, Ulcerative colitis, Umbillical hernia, Yersinia enterocolitica