Flat colorectal neoplasms: Definition, importance, and visualization on CT colonography

OBJECTIVE. We discuss the definition of flat colorectal neoplasms, their clinical importance, CT colonography (CTC) findings, techniques for better visualization on CTC, and diagnostic pitfalls of such lesions. CONCLUSION. Flat lesions appear on CTC as plaque-shaped mucosal elevations with or without a central depression, thickened haustral folds, and nodular mucosal surfaces. The sensitivity and optimal techniques of CTC for the detection of flat lesions have not yet been established. Three-dimensional endoluminal fly-through may be helpful for lesion detection. Fecal tagging helps in the distinction of true flat lesions from feces. IV contrast enhancement and the review with intermediate soft-tissue window settings, although not routinely used for CTC, may also help lesion visualization.