MRcolon

MR colonography, commonly called MR colon or magnetic resonance colonography (MRC), is a noninvasive imaging modality that uses magnetic resonance imaging to visualize the colon. It complements traditional colonoscopy and CT-based methods by providing detailed images of the colonic lumen, wall, and surrounding structures without ionizing radiation. The examination typically requires bowel preparation and the use of an oral luminal contrast agent to distend and tag the colon, with optional rectal contrast. Distension may be aided by limited air or CO2 insufflation in some protocols. Imaging protocols generally combine rapid T2-weighted sequences to depict the luminal surface, diffusion-weighted imaging for tissue characterization, and, when indicated, gadolinium-enhanced T1-weighted sequences. A multi-channel surface coil or torso coil improves signal-to-noise.

MR colonography offers several advantages, including avoidance of radiation exposure and simultaneous assessment of extraluminal structures such as mesentery and lymph nodes. It can be useful when colonoscopy is incomplete, contraindicated, or when a noninvasive test is preferred, such as in patients who require serial follow-up or in certain inflammatory conditions. Limitations include variable sensitivity for small polyps, dependence on optimal bowel distension and patient cooperation, longer exam times, and limited availability. Additionally, while MRC provides diagnostic information, it does not permit endoscopic therapy; positive findings typically require conventional colonoscopy for biopsy or removal and definitive treatment. Safety considerations include MRI compatibility and, if contrast is used, potential risks related to gadolinium-based agents in patients with renal impairment. MR colonography remains an adjunct option in colorectal imaging, with adoption varying by center and clinical scenario.