MR colonography without bowel cleansing or water enema: a pilot study.

OBJECTIVES: The value of screening for colorectal cancer has been well demonstrated, and national programmes are being implemented. At present the primary imaging modality is colonoscopy, which has an associated morbidity and mortality. CT colonography (CTC) has been proposed as an alternative, but this is associated with radiation exposure and generally requires bowel preparation. The aim of this pilot study was to assess the feasibility of MR colonography (MRC) without bowel preparation or water enema for the detection of colorectal neoplasia.
METHODS: Patients scheduled for colonoscopy were invited to participate in the study; informed consent was obtained. MRC (with oral barium faecal tagging and colonic air distension) was performed 1-2 weeks before the colonoscopy. Axial T(2) weighted single-shot fast spin-echo (prone and supine) and axial T(1) weighted fast spoiled gradient-recalled (pre- and post-iv gadolinium) supine MRI sequences were performed. The examinations were reported by two gastrointestinal radiologists by consensus. Colonoscopy following standard bowel preparation was performed by a single endoscopist blinded to the MRC results. Significant lesions were defined as polyps or masses >10 mm in diameter.
RESULTS: 29 patients were studied. Colonoscopy revealed 25 mass lesions in 13 patients. MRC correctly identified four of the nine lesions >10 mm in diameter (sensitivity 44%; specificity 100%). Although specificity remained high for smaller lesions, sensitivity was poor.
CONCLUSION: This pilot study has demonstrated the feasibility of performing MRC without bowel preparation or water enema. This would seem to be a promising modality for colorectal cancer screening. Larger studies are required to determine the accuracy of this modality for the detection of colorectal neoplasia.