Crohn Disease

Published on 18/07/2015 by admin

Filed under Radiology

Last modified 18/07/2015

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 Faster to perform, less operator dependent, more sensitive and specific

image Allow assessment of extraintestinal disease
image Distend bowel with water ± neutral contrast agent (e.g., VoLumen)
image Bolus IV contrast medium at 3-4 mL/sec
• Noncicatrizing, acute phase

image Target or double halo sign
image Hyperenhancing inner ring (mucosa)
image Low-density middle ring (submucosal edema)
image Engorged vasa recta: Comb sign
image Proliferation of mesenteric fat and lymphadenopathy
• Chronic or cicatrizing phase

image Strictures, ± dilated small bowel (SB) upstream
image Abscesses, fistulas, sinus tracts
• Barium enema, enteroclysis can depict strictures & fistulas
• Colonoscopy is best to assess colonic involvement, guide biopsy of colon and terminal ileum
• Capsule endoscopy may complement imaging studies

image Not of proven value following negative CT or MR enterography
image Contraindicated in patients with enteric strictures

TOP DIFFERENTIAL DIAGNOSES

• Ulcerative colitis (“backwash” ileitis)
• Mesenteric enteritis and adenitis
• Infectious ileitis or colitis

PATHOLOGY

• Transmural inflammation, lymphoid aggregates, noncaseating granulomas

image Predisposes to strictures, fistulas, sinus tracts, abscesses

CLINICAL ISSUES

• Crohn disease is characterized by intermittent periods of exacerbation of symptoms followed by remissions
• Complications: Fistulas, sinus tracts, toxic megacolon, obstruction, perforation

DIAGNOSTIC CHECKLIST

• Segmental, discontinuous inflammation of SB ± colon with mucosal hyperenhancement, submucosal edema, engorged vasa recta
• Consider associated findings (cholangitis, arthritis)
image
(Left) This graphic in the sagittal plane illustrates typical features of Crohn disease including, segmental small bowel (SB) wall thickening, mucosal hyperemia image, transmural inflammation with deep ulcers image, mesenteric vessel engorgement, and fibrofatty proliferation image.

image
(Right) This 19-year-old man has an acute flare of his Crohn disease. CT shows mucosal hyperenhancement, wall thickening, and luminal narrowing of the terminal ileum (TI) image.
image
(Left) CT in the same patient shows the inflamed TI image, as well as local mesenteric fibrofatty proliferation and engorged vasa recta image.

image
(Right) A spot film from a SBFT in the same patient shows diseased TI and colon with longitudinal and transverse ulcerations of the ileal mucosa (cobblestone pattern) and luminal narrowing. At least 2 sinus tracts image are opacified. Traditional barium studies remain valuable for evaluation of strictures, fistulas, and sinus tracts.

TERMINOLOGY

Synonyms

• Terminal ileitis, regional enteritis, ileocolitis

Definitions

• Disease of unknown etiology characterized by transmural inflammation of GI tract

IMAGING

General Features

• Best diagnostic clue

image Segmental, discontinuous inflammation of small bowel (SB) ± colon with mucosal hyperenhancement, submucosal edema, engorged vasa recta

– Usually accompanied by clusters of prominent mesenteric nodes
• Location

image Anywhere along GI tract, from mouth to anus

– Most common: Terminal ileum (TI) and proximal colon
image Distribution

– 80% of patients have SB involvement
– 50% have ileocolitis
– 20% have disease limited to colon

image Only 10% have rectal involvement
• Morphology

image Transmural inflammation

– Predisposes to strictures, fistulas, sinus tracts, abscesses
image Skip lesions (segmental or discontinuous)

Fluoroscopic Findings

• Barium studies: Early changes

image “Target” or bull’s-eye appearance of aphthoid ulcerations: Punctate shallow central barium collections surrounded by halo of edema
image “Cobblestoning”: Combination of longitudinal and transverse ulcers
image Deep fissuring ulcers
image Mural thickening: Transmural inflammation, fibrosis
• Barium studies: Late changes

image Skip lesions: Segmental disease with normal intervening segments
image Sacculations seen on antimesenteric border
image Postinflammatory pseudopolyps, haustral loss, intramural abscess
image String sign: Luminal narrowing and ileal stricture
image Sinus tracts, fissures, fistulas are hallmarks of disease
image Anorectal lesions: Ulcers, fissures, abscesses, hemorrhoids, stenosis

CT Findings

• Noncicatrizing, acute phase

image Stratified wall thickening of discontinuous SB segments

– Target or double halo sign
– Hyperenhancing inner ring (mucosa)
– Low-density middle ring (submucosal edema)
– Soft tissue density outer ring (muscularis propria and serosa)
image Comb sign: Engorged vasa recta

– Supply actively inflamed SB segments
image Proliferation of mesenteric fat and lymphadenopathy

– Nodes rarely more than 1 cm in diameter
• Chronic or cicatrizing phase

image Luminal narrowing, ± dilated SB upstream
image Mural stratification lost: Indistinct mucosa, submucosa, muscularis propria

– Alternatively, submucosal fat may proliferate, preserve stratification
image Abscesses, fistulas, sinus tracts

– Fistulas connect 2 epithelialized surfaces (e.g., bowel-to-bowel, bladder, vagina, or skin)
– Sinus tracts are blind-ending (e.g., bowel to abscess)
image Mesenteric changes: Abscess, fibrofatty proliferation, mildly enlarged nodes
image Perianal disease: Fistulas and sinus tracts

MR Findings

• Breath-holding, fat suppression, and gadolinium enhancement show extent and severity of inflammation

image Mucosal hyperenhancement, submucosal edema, engorged vasa recta in acute inflammation
• Allows real-time imaging to assess peristalsis in segments of suspected disease
• Sensitive in detecting and characterizing fistulas, sinuses, abscesses in perianal Crohn disease
• Diffusion-weighted imaging can reveal active inflammation even without IV contrast administration

Ultrasonographic Findings

• Grayscale ultrasound

image Transrectal sonography

– Mural thickening, abscesses, fistulas
– Anal sphincter heterogeneity

Other Modality Findings

• Colonoscopy is best modality to assess colon

image Often allows inspection and biopsy of terminal ileum
• Capsule endoscopy is commonly used to complement imaging studies

image 

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