MR Enterography (MRE)

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Magnetic Resonance Enterography (MRE) is a specialized MRI technique designed to evaluate the small bowel using oral contrast agents to distend bowel loops.

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It provides high-contrast, radiation-free cross-sectional imaging that allows assessment of bowel wall morphology, vascularity, motility, and extraintestinal complications, particularly in Crohn’s disease and other small bowel pathologies.

Principle and Technique

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MRE relies on T1- and T2-weighted sequences with fat suppression and dynamic gadolinium enhancement to visualize bowel wall enhancement patterns corresponding to inflammation, fibrosis, or ischemia.

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Technique:

Patient Preparation:

Fasting for 4–6 hours.
Administration of oral biphasic contrast (e.g., mannitol, PEG solution) to distend the bowel.
Intravenous antiperistaltic agents (e.g., glucagon) to reduce motion artifacts.
IV gadolinium-based contrast for assessing enhancement.
Patient positioned supine or prone; prone position helps bowel separation.

T2-weighted sequences	Single-shot fast spin echo or HASTE:
Fat-suppressed T2/STIR	Detecting high-signal mural inflammation and fluid
Dynamic post-contrast T1-weighted gradient-echo	Mural enhancement and vascularity
Diffusion-weighted imaging (DWI)	Restricted diffusion indicating active inflammation
Cine motility sequences	Assess peristalsis and strictures

Typical Sequences:

Indications

Evaluation of Crohn’s disease (extent, activity, complications).
Unexplained small bowel obstruction.
Detection of tumors, bleeding, or ischemia.
Assessment of postoperative recurrence or treatment response in inflammatory bowel disease (IBD).