Real-time contrast-enhanced ultrasound in diagnosis of solid renal lesions

The purpose of this study was to investigate the efficacy of contrast-enhanced ultrasound (CEUS) in diagnosis of solid renal lesions (SRLs)--malignant or benign renal tumors. We retrospectively analyzed 91 cases with 100 SLRs with a mean diameter of 3.3±1.7 cm. CEUS was performed and their perfusion characteristics were analyzed by using contrast pulse sequences technique. CEUS findings were compared with histopathologic findings of biopsy. There were 85 malignant lesions (78 renal clear cell carcinoma, 5 renal papillary carcinoma, and 2 chromophobe cell carcinoma) and 15 benign lesions (13 angiomyolipoma and 2 renal oncocytoma). For malignancy, 74 lesions (87.1%) showed contrast agent fast perfusing and hyper-enhancement or iso-enhancement in cortical phase and 72 (84.7%) showed hypo-enhancement in later corticomedullary or late phase. For tumors with a diameter>4 cm, the heterogeneous enhancement feature was shown seemingly as "honeycomb" enhancement; for those≤4 cm, relatively homogeneous enhancement feature was observed. Meanwhile, 79 (92.9%) malignant lesions showed rim-like enhancement. For benignancy, 13 angiomyolipoma showed contrast agent slow wash-in and slow wash-out mode, while 2 renal oncocytoma showed similar enhancement characteristic to the malignant lesions. The specificity, accuracy, and positive predictive value of diagnosis for SRLs were 96.5%, 96%, and 82.4% for CEUS, and 72.9%, 71%, and 28.1% for conventional US, respectively (P<0.001). Meanwhile the sensitivity and negative predictive value for CEUS were 93.3% and 98.8%, respectively, compared with those of conventional US (60% and 91.2%, P>0.05). Real-time CEUS can provide valuable information for improving the diagnosis and differential diagnosis of SRLs.