Indeterminate focal liver lesions incidentally discovered at gray-scale US: role of contrast-enhanced sonography.

OBJECTIVES: to assess the role of contrast-enhanced ultrasound (CEUS) in the characterization of focal liver lesions (FLLs) incidentally discovered but indeterminate at gray-scale ultrasound (US). MATERIALS AND METHODS: one hundred forty-two consecutive patients with 174 FLLs (169 benign and 5 malignant) incidentally discovered but indeterminate at gray-scale US, underwent CEUS after the administration of SonoVue. Two readers independently reviewed CEUS scans and: (1) classified each lesion as malignant or benign on a 5-point scale of confidence by means of definite diagnostic criteria; (2) provided if possible a specific diagnosis; (3) were requested if further imaging was needed for lesion characterization. Sensitivity, specificity, and areas under the receiver-operating characteristic curve (Az) as well as interobserver agreement were calculated. RESULTS: at CEUS, both readers correctly differentiated benign from malignant lesions in 168 of 174 (96.5%) cases (P < 0.0001). A specific correct diagnosis was provided in 123 of 174 (70.7%) and 127 of 174 (72.9%) cases for reader 1 and 2, respectively (P < 0.0001). A further imaging study to characterize the lesion after CEUS was requested in 67 cases (38.5%) for reader 1 (P < 0.001) and 46 cases (26.4%) for reader 2 (P < 0.001). Receiver-operating characteristic analysis after CEUS revealed Az value of 1 for both readers and sensitivity and specificity values of 100% and 97.04% for reader 1 and 100% and 96.45 for reader 2 respectively (P < 0.0001). Inter-reader agreement at CEUS was good (weighted k = 0.779). CONCLUSION: CEUS improves the diagnostic performance of radiologists in the characterization of indeterminate FLLs incidentally discovered at US and reduces the need for further radiologic work-up.