Crohn’s disease is an inflammatory bowel disease most commonly affecting the ileum and the colon, presenting with diarrhea, abdominal, abscesses, fistulas, and bowel obstruction. It is diagnosed with colonoscopy and imaging and is treated with 5-aminosalicylic acid, corticosteroids, immunosuppresants, and antibiotics. Surgery may be necessary but is not currative.

Pathophysiology

• Crypt inflammation and abscesses -> focal aphthoid ulcers -> deep longitudinal/ transverse ulcers
• Transmurral inflammation -> lymphedema and bowel wall/ mesentery thickening -> muscularis mucosae hypertrophy, fibrosis, stricture -> bowel obstruction
• “Cobblestoned appearance”

Contextual Factors

• Family history of Crohn’s disease
• Stunted childhood growth

Clinical Manifestation

General

• Fever
• Anorexia
• Weight loss

Abdominal

• Chronic diarrhea
• Abdominal pain
  • Ileitis can mimic acute appendicitis or bowel obstruction
• Perianal disease: abscesses and fistulas
  • Often NO gross rectal bleeding

Musculoskeletal

• Arthritis

Dermatologic

• Erythema nodosum

Skip Areas

• Diseased bowel “skips” with areas of healthy bowel in between

Complications

• Bowel obstruction
• Fistula
• Abscess
• Cancer in affected areas
• Chronic malabsorption leading to vitamin D and B12 deficiency
• Toxic colitis - requires aggressive surgical intervention

Diagnosis

Labs

• Screening for:
  • Anemia
  • Hypoalbuminemia
  • Electrolyte abnormalities
• Liver function tests
  • Elevated alkaline phosphatase and GGT suggest primary sclerosing cholangitis secondary to colonic involvement
• Acute phase inflammatory markers for trending disease progression: ESR, CRP
• Bone density (DEXA scan)
• Antibodies specific to Crohn’s (not commonly measured for diagnosis)
  • Anti-Saccharomyces cerevisiae antibodies
  • Anti-OmpC
  • Anti-CBir1

Imaging

• Acute presentation: abdominal CT
  • Can also use CT or MT enterography with ingested contrast: looking for strictures or fistulas
• Not acute presentation: Small bowel follow-through (x-ray series with ingested barium contrast)
• Less often:
  • Upper endoscopy: suspicion for gastroduodenal involvement
  • Colonoscopy: to differentiate between ulcerative colitis and Crohn’s
  • Barium enema: for primarily colonic presentation)
  • Video capsule endoscopy: questionable findings in other modalities

Classification

• Primarily inflammatory
• Primarily stenotic/ obstructing
• Primarily penetrating/ fistulising

Treatment

Acute Flare-Up

• High-dose corticosteroids

Lifestyle

• Smoking cessation
• Immunisations
• Regular cancer screenings

Reducing Inflammatory Response

• 5-aminosalicylic acid: blocks prostaglandin and leukotriene production, reducing inflammatory response
• Immunomodulating medications
  • Azathioprine
  • 6-mercaptopurine
  • Methotrexate
• Biologic agents: all the -mabs

Supportive

• Loperamide, except during severe Crohn’s colitis which may result in toxic colitis
• Antispasmodics

Fistulas

• Metronidazole and ciprofloxacin
• If not responding after 3-4 weeks: immunomodulator with or without biologic

Surgery

• Done for recurrent intestinal obstruction or intractable fistulas/ abscesses
• Not curative