What information does Magnetic Resonance Enterography (MRE) provide in Inflammatory Bowel Disease (IBD)?

Role of Magnetic Resonance Enterography (MRE) in Inflammatory Bowel Disease

Magnetic Resonance Enterography (MRE) provides comprehensive assessment of bowel inflammation, disease extent, strictures, penetrating complications, and extraintestinal manifestations in inflammatory bowel disease, serving as a crucial complement to endoscopy with high diagnostic accuracy. 1

Key Information Provided by MRE in IBD

Assessment of Active Inflammation

• Mural features of inflammation:

  • Bowel wall thickening
  • Mural hyperenhancement (best visualized during enteric phase, 45-70 seconds after contrast injection)
  • Intramural edema
  • Ulcerations
  • Restricted diffusion on diffusion-weighted imaging 1

• Perienteric features of inflammation:

  • Engorged vasa recta (comb sign)
  • Fibrofatty proliferation
  • Perienteric edema
  • Lymphadenopathy 1

Disease Extent and Distribution

• Evaluates entire small bowel, including segments inaccessible by endoscopy
• Particularly valuable for assessing terminal ileum when luminal narrowing prevents endoscopic evaluation 1
• Helps differentiate Crohn's disease from ulcerative colitis based on distribution pattern 1
• Identifies multifocal disease involvement and skip lesions

Penetrating Disease Complications

• Detects:
  • Sinus tracts
  • Fistulae (enteroenteric, enterocutaneous, perianal)
  • Abscesses
  • Inflammatory masses
  • Free perforation 1

Stricturing Disease

• Characterizes strictures as:
  • Inflammatory (with active inflammation)
  • Fibrotic (without active inflammation)
  • Mixed 1
• Provides information on:
  • Location and length of strictures
  • Degree of obstruction
  • Presence of upstream dilation 1

Extraintestinal Manifestations

• Identifies associated conditions:
  • Mesenteric venous thrombosis
  • Sacroiliitis
  • Primary sclerosing cholangitis
  • Avascular necrosis
  • Cholelithiasis
  • Nephrolithiasis 1, 2

Diagnostic Performance of MRE

• High sensitivity (66-95%) and specificity (64-97%) for detecting active bowel inflammation in pediatric patients compared to endoscopy and histology 1
• Superior to small bowel follow-through (SBFT) with sensitivity of 83% vs 76% and specificity of 95% vs 67% 1
• Excellent correlation between MRE findings and pathology/histology for determining:
  • Bowel wall thickness
  • Length of diseased bowel
  • Severity of inflammation 3

Treatment Decision Support

MRE findings directly influence treatment decisions:

• Identification of penetrating complications like fistulae may indicate need for biologic therapy
• Detection of abscesses may necessitate antibiotics and/or drainage procedures
• Assessment of stricture type (inflammatory vs fibrotic) helps determine medical vs surgical management 1
• Monitoring response to therapy through serial examinations

Technical Considerations

• Standard protocol includes:

  • Large volume biphasic oral contrast for bowel distension
  • IV contrast (enteric phase most useful for inflammation)
  • Single-shot T2-weighted sequences
  • Balanced steady-state free precession sequences
  • Diffusion-weighted imaging 1
  • Fat-suppressed T1-weighted post-contrast images 3

• Hypoperistaltic medication (glucagon or hyoscine butylbromide) may improve image quality 1

Pitfalls and Limitations

• Requires patient cooperation for oral contrast ingestion
• Some patients may not tolerate large volume oral contrast, particularly during acute symptoms
• Non-enterography MRI (without oral contrast) has lower sensitivity for small bowel wall thickening (50% vs 100% for MRE) 1
• IV contrast improves detection of penetrating complications but may not be necessary for assessing active inflammation in terminal ileum and colon 1
• Diffusion-weighted imaging may provide comparable information to contrast-enhanced sequences for inflammatory changes 1

Structured Reporting Recommendations

For optimal clinical utility, MRE reports should include:

• Disease location (stomach, duodenum, jejunum, ileum, terminal ileum, colon, rectum, anus)
• Number of diseased segments
• Type of disease (inflammation, stricture, penetrating)
• Detailed description of imaging findings of inflammation
• Comparison with prior studies to assess disease progression or response to therapy 1

MRE has become an essential tool in IBD management, providing comprehensive assessment of disease activity and complications that directly impact treatment decisions and patient outcomes.