Fact-sheet: Crohn disease


Updated on 05/07/2023 at 8:16 AM

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Definition

Cryptogenic inflammatory bowel disease characterized by bowel involvement that may be discontinuous and affect any segment of the digestive tract. The terminal ileum and proximal colon are most often affected.

Genetic predisposition.
Prevalence: 2-3/100,000 among Caucasians.
Usually begins between 15 and 30 years of age.

Clinical features

Chronic diarrhea
Colicky abdominal pain
Fever
Weight loss, anorexia
Occult gastrointestinal bleeding and anemia
Perianal abscess and fistula
Malabsorption

Ultrasound

Target-like wall thickening (5 to 20mm) but without preferential involvement of the submucosal layer (DDx: Ulcerative colitis)
Hypoechoic thickening with loss of wall stratification due to transmural edema, inflammation, or fibrosis
Rigid, non-compressible bowel segment
Hyperemia on color Doppler
Swollen, inflammatory adjacent fat
Abscess
Fluid-filled distended loops
Hypoechoic fistulous tract

CT

In the acute stage:

  • Regular circumferential thickening of the terminal ileum with enhancement on the portal venous phase
  • Mesenteric hyperemia: "comb" sign, bristled and combed appearance of the vasa recta on the mesenteric side
  • Peritoneal effusion
  • Inflammatory lymphadenopathy
  • Abscess
  • possible mesenteric venous thrombosis

In the chronic stage:

  • Stenosis of the terminal ileum with delayed-phase enhancement (fibrosis)
  • Wall sclerolipomatosis
  • Fibrofatty proliferation of the mesentery (creeping fat sign)
  • Blind-ending or communicating fistulas