[CT findings of the small polypoid lesions of the gallbladder (2cm or less PLG): differentiation between benign and malignant disease on unenhanced CT].

Recently, the detection of polypoid lesions of the gallbladder (PLG), by using ultrasonography has been increased. Nevertheless, it is difficult to distinguish between benign PLG and malignant PLG. The purpose of this paper is to evaluate the efficacy of CT examination for differential diagnosis between benign and malignant PLG. Twenty-nine patients with PLG diagnosed by preoperative CT were retrospectively reviewed. Out of these patients, 20 patients had benign PLG and nine patients had malignant PLG. As a result, all PLG were well enhanced by contrast media. On unenhanced CT, malignant PLG appeared to be high density except one case. On the other hand, benign PLG were isodense except one case. Relatively larger amount of epithelial component of the malignant PLG contributes to high density on unenhanced CT. In contrast, benign PLG had larger amount of connective tissue, showing about the same density as bile on unenhanced CT. In conclusion, unenhanced CT examination is effective to differentiate benign PLG from malignant PLG.