MRIkolonografi

MRIkolonografi, or MR colonography, is a radiologic imaging method that uses magnetic resonance imaging to visualize the colon and rectum. It provides a noninvasive, radiation-free alternative to optical colonoscopy for assessing the colonic lumen and mucosa, with particular use when colonoscopy is incomplete, contraindicated, or when avoidance of ionizing radiation is desired. The examination aims to detect polyps, tumors, inflammatory changes, or other colonic pathology.

Technique and preparation typically involve bowel cleansing and fasting. The colon is distended to improve visualization by using oral contrast agents that gently distend the lumen (for example, osmotic or contrast solutions), sometimes complemented by rectal infusion of gel or water to aid distension. Imaging employs MRI sequences that maximize soft-tissue contrast, including T2-weighted sequences for lumen and stool differentiation, diffusion-weighted imaging, and often a thin-slice 3D T1-weighted or heavily T2-weighted acquisition after intraluminal contrast. Some protocols use intravenous gadolinium-based contrast, while non-contrast approaches rely on high-resolution 3D sequences and DWI. Post-processing yields virtual endoluminal views and menus of reconstructions (such as maximum-intensity projections) to facilitate interpretation.

Indications and limitations: MRIkolonografi is considered when there is a need to minimize radiation exposure, when colonoscopy is not feasible, or for focused assessment of inflammatory bowel disease or colorectal pathology in selected patients. It is not yet as widely adopted as CT colonography or diagnostic colonoscopy in routine screening. Limitations include longer exam times, the need for thorough bowel prep and patient cooperation, variable sensitivity for small or flat lesions, and limited ability to evaluate extracolonic structures.