Can the cut of an Magnetic Resonance (MR) enterography affect the detection of Crohn's disease?

Impact of MR Enterography Cut on Crohn's Disease Detection

The cut (protocol) of MR enterography significantly affects detection of Crohn's disease, with optimized protocols including specific sequences and techniques being essential for accurate diagnosis and disease characterization. 1

Key MR Enterography Protocol Elements for Optimal Crohn's Disease Detection

Essential Sequences

• T1-weighted fat-suppressed post-contrast images - Critical for detecting mural hyperenhancement, a key marker of active inflammation 1
• T2-weighted sequences - Important for detecting intramural edema and bowel wall thickening 1
• Diffusion-weighted imaging (DWI) - Correlates with moderate to severe endoscopic inflammation 1, 2
• Balanced steady-state free precession sequences - Helps distinguish normal underdistended bowel from true wall thickening 1, 2

Technical Considerations

• Bowel distension - Large volume biphasic oral contrast is essential for accurate assessment of wall thickness and enhancement patterns 1
• Enteric phase timing - 45-70 seconds after IV contrast injection is optimal for assessing mural hyperenhancement 1
• Hypoperistaltic medication - Administration of glucagon or hyoscine butylbromide reduces motion artifact and improves image quality 1, 2
• Proper slice thickness and orientation - Thin slices in multiple planes are necessary for accurate assessment of small bowel pathology 1

Impact of Protocol Variations on Diagnostic Accuracy

IV Contrast Considerations

• IV contrast improves MRE sensitivity for detecting penetrating Crohn's disease complications 1
• Similar performance for detection of active inflammation in terminal ileum and colon can be achieved without IV contrast 1
• DWI can provide comparable identification of inflammatory wall thickening without IV contrast, but with lower specificity 1

Non-Enterography vs. Enterography Technique

• MR enterography is superior to standard MRI abdomen/pelvis for detecting bowel inflammatory lesions 1
• Non-enterography MRI has significantly lower sensitivity (50%) and positive predictive value (28%) for detecting small bowel wall thickening compared to MRE 1
• Pediatric patients particularly benefit from enterography technique due to smaller bowel caliber and less mesenteric fat 1

Imaging Findings Affected by Protocol Choice

Mural Features

• Segmental mural hyperenhancement - Requires proper contrast timing and fat suppression techniques 1
• Wall thickening - Accurate assessment requires adequate bowel distension with oral contrast 1
• Stratification patterns - Tri-laminar pattern is more often identified on contrast-enhanced MR due to superior contrast resolution compared to CT 1

Perienteric Features

• Engorged vasa recta (comb sign) - Better visualized with proper IV contrast timing 1, 2
• Fibrofatty proliferation - Requires adequate fat suppression techniques 2
• Perienteric edema - Best seen on T2-weighted sequences with fat suppression 1, 2

Common Pitfalls Related to Protocol Inadequacies

• Inadequate bowel distension can lead to false-positive wall thickening assessment 1
• Poor fat suppression can obscure mural enhancement patterns 1
• Respiratory and bowel motion artifacts can degrade image quality despite glucagon use 1
• Underdistended bowel segments may be misinterpreted as strictures 1
• Lack of proper timing for contrast-enhanced sequences can miss active inflammation 1

Practical Recommendations

• For optimal detection of Crohn's disease, use a comprehensive MR enterography protocol with proper bowel distension, IV contrast, and multiplanar imaging 1, 2
• When IV contrast is contraindicated, DWI sequences become particularly important but recognize their lower specificity 1
• In acutely ill patients who cannot tolerate oral contrast, standard MRI abdomen/pelvis may be performed but with recognition of its limitations 1
• For pediatric patients, MR enterography is particularly important due to smaller bowel caliber and less mesenteric fat 1

The diagnostic accuracy of MR enterography for Crohn's disease is highly dependent on proper protocol implementation, with sensitivity ranging from 66-95% and specificity from 64-97% when optimal techniques are used 1, 2.