MR Enterography

MR Enterography

Wall Thickness

  • Measure at site of most severe inflammation
  • Avoid measuring nondistended bowel (may overestimate)
  • Look for nodularity/mass-like thickening that may indicate malignancy
Severity Thickness
Mild 3-5 mm
Moderate 5-9 mm
Severe ≧ 10 mm
Wall thickness

Active Inflammation

Finding Description Pearls Example
Segmental mural hyperenhancement Different subtypes:
  • Asymmetric (most specific for Crohn’s)
  • Homogeneous, symmetric
  • Stratified
Avoid “mucosal hyperenhancement”; instead use “inner wall hyperenhancement” Segmental mural hyperenhancement
Mural edema
  • Hyperintense signal on T2FS
  • Corresponds to more severe inflammation
Should be assessed ONLY on T2FS; hyperintense T2 signal may be edema or mural fat, which is a sign of chronicity, unrelated to active inflammation Mural edema
Ulcerations
  • Small focal breaks in the inner wall
  • Corresponds to more severe inflammation
Should not use term “penetrating ulcer”, so as not to be confused with penetrating disease Ulcerations

Stricture

  • May show delayed post-contrast enhancement
  • May be superimposed on active inflammation and penetrating disease
Upstream dilatation Severity
None (but multiple series shows fixed narrowing) “Probable stricture present”
3-4 cm Mild
>4 cm Moderate to severe *consider “SBO”
Stricture

Penetrating Disease

Penetrating Disease

Finding Description Example
Simple fistula Single tract connecting 2 epithelial structures Simple fistula
Complex fistula Multiple extra-enteric tracts, often asterisk- or clover-leaf-shaped Complex fistula
Sinus tract Tract that does not communicate with a second epithelialized structure  
Inflammatory mass Ill-defined mass-like process (may contain mixed fat or soft tissue, but not water) *Should not use the term “phlegmon” Inflammatory mass
Abscess Fluid collection with rim enhancement  

*Note: Perianal disease is not considered penetrating disease

Ancillary Findings

Ancillary Findings

Ancillary findings Description Example
Restricted diffusion
  • Non-specific, but when seen with other features of active inflammation (i.e. hyperenhancement, wall thickening, edema), suggests more severe inflammation
  • Non-distended small bowel may appear falsely restricting
Restricted diffusion
Perienteric edema
  • Often associated with mesenteric border inflammation
  • CRP may be elevated
Perienteric edema
Engorged vasa recta
  • Non-specific for active inflammation
  • AKA “comb sign”
Engorged vasa recta
Fibrofatty proliferation
  • Often on mesenteric side
  • “creeping fat”
Fibrofatty proliferation
Pseudosacculation
  • Arise from anti-mesenteric border 2/2 asymmetric mural inflammation shortening the gut along mesenteric side
Pseudosacculation
Adenopathy
  • 1.5 cm short axis
  • >1.5 cm short axis
 

Extraintestinal Manifestations

Category Finding
MSK
  • Sacroiliitis
  • Avascular necrosis
GI
  • Primary sclerosing cholangitis
  • Pancreatitis
  • Cholelithiasis
GU Nephrolithiasis
Vascular Mesenteric venous thrombosis/occlusion

Further Reading

Bruining DH, Zimmermann EM, Loftus EV, Sandborn WJ, Sauer CG, Strong SA, Society of Abdominal Radiology Crohn’s Disease-Focused Panel. Consensus Recommendations for Evaluation, Interpretation, and Utilization of Computer Tomography and Magnetic Resonance Enterography in Patients with Small Bowel Crohn’s Disease. Radiology. 2018 Mar;286(3):776-799.