What is the working of Magnetic Resonance (MR) enteroclysis?

MR Enteroclysis: Technique and Working Mechanism

MR enteroclysis is a specialized MRI-based examination that uses a nasoduodenal tube for controlled distention of the small bowel with infused contrast media to achieve optimal visualization of bowel pathology. 1

Technical Components and Procedure

• MR enteroclysis requires placement of a nasoduodenal tube to allow controlled and active distention of the small bowel 1
• Typically, 1.5-2 liters of biphasic enteral contrast (low signal on T1-weighted and high signal on T2-weighted images) is infused through the tube 1, 2
• Intravenous contrast (gadolinium) is typically administered during the examination to enhance visualization of bowel wall and extraluminal pathology 1
• The procedure includes specialized MRI sequences:
  • True fast imaging with steady-state precession (FISP) 2, 3
  • Half-Fourier acquisition single-shot turbo spin-echo (HASTE) 2, 3
  • T1-weighted three-dimensional fast low-angle shot sequences post-gadolinium 2
• MR fluoroscopy can be performed during the examination to monitor the filling process and evaluate motility disorders or low-grade stenosis 4, 3

Advantages and Performance

• MR enteroclysis provides excellent diagnostic performance for small bowel evaluation, at least equivalent to MR enterography 1
• It offers statistically better detection of superficial mucosal abnormalities compared to MR enterography, though shows no difference for stenoses and fistulas 1
• The technique accurately displays transmural abnormalities characteristic of Crohn's disease:
  • Bowel wall thickening 2, 3
  • Linear ulcers and cobblestoning 2
  • Mural hyperenhancement and stratification 1
• It can effectively detect the number and extent of involved small bowel segments and identify luminal narrowing or prestenotic intestinal dilatation 2, 3
• MR enteroclysis avoids radiation exposure, making it suitable for follow-up studies and monitoring disease activity 2, 5

Clinical Applications

• Primary applications include:
  • Evaluation of Crohn's disease (extent, activity, and complications) 1, 2
  • Detection of small bowel tumors 4, 3
  • Evaluation of small bowel obstruction 4, 3
  • Assessment of strictures, especially mild strictures without proximal dilation 1
• It is particularly valuable for:
  • Follow-up studies of known disease 2
  • Estimation of disease activity 2
  • Determination of extramucosal extent and spread of disease processes 2

Limitations and Considerations

• The invasive nature with nasoduodenal tube insertion and active contrast infusion makes it less favorable from a patient perspective 1
• Not typically suitable for acutely ill patients who may not tolerate the tube placement and contrast infusion 1
• Patients with significant acute flares or complications may poorly tolerate the procedure 1
• MR enteroclysis is not widely utilized compared to MR enterography, which has become more common in clinical practice 1, 6
• The technique requires specialized expertise and equipment 1

Comparison with MR Enterography

• The key difference is the method of bowel distention: active distention via nasoduodenal tube in enteroclysis versus oral ingestion in enterography 1
• Both techniques have similar capabilities for evaluating mucosal healing and assessing strictures for active disease versus fibrosis 1
• MR enterography is generally preferred due to being less invasive, though it may provide less optimal distention of the proximal small bowel 1, 5
• MR enteroclysis may be preferred when active distention is needed to confirm mild strictures without proximal dilation 1