MR colonography with barium-based fecal tagging: initial clinical experience

To assess a strategy for fecal tagging with barium sulfate as an inexpensive tagging agent in conjunction with magnetic resonance (MR) colonography in patients suspected of having colorectal lesions.

Twenty-four patients suspected of having colonic lesions because of rectal bleeding, positive fecal occult blood test results, or altered bowel habits underwent MR colonography and subsequent conventional colonoscopy. A 200-mL dose of a barium sulfate-containing contrast agent was ingested with each of four low-fiber meals, beginning 36 hours before the examination. For MR colonography, the colon was filled with tap water. Gadobenate dimeglumine was injected intravenously. Images were acquired 75 seconds after gadobenate dimeglumine administration by using only a T1-weighted three-dimensional gradient-echo sequence. Images were reviewed by two radiologists blinded to conventional colonoscopic data. By using colonoscopy as the reference standard, sensitivity and specificity of MR colonography were determined for detecting colorectal masses.

On the basis of MR colonography, 15 polyps of 5-20 mm and 10 carcinomas were detected and later confirmed with conventional colonoscopy. Conventional colonoscopy depicted three additional lesions less than 8 mm in diameter. Thus, sensitivity of MR colonography was 89.3% (25 of 28) for lesions and 91.7% (22 of 24) for patients.

Barium-tagged MR colonography obviates bowel cleansing and depicts all lesions exceeding 8 mm in diameter.