All patients with a gallbladder polypoid lesion visited our department, diagnosed by conventional transabdominal US, were enrolled in this study.

Of these patients, we excluded: (1) gallbladder polyp with a diameter less than 10 mm. (2) lesions highly suspected to be cancer due to visible metastasis. (3) allergy to contrast agents and cannot received CT or CEUS examination. (4) women in pregnancy or lactation.

All patients received transabdominal US, abdominal high resolution CT and contrast-enhanced ultrasonography (CEUS) before the cholecystectomy.

CT examinations were performed using a 64-slice CT scanner. Arterial phase scanning was triggered by bolus tracking technique after 100 to 120 mL nonionic contrast material was injected through the antecubital vein. With a delay of 60 and 140 s after the beginning of contrast medium injection, portal venous and equilibrium phase image scanning were followed.