Renal cell carcinoma: real-time contrast-enhanced ultrasound findings

To investigate the findings of renal cell carcinomas (RCCs) on contrast-enhanced ultrasound (CEUS). CEUS features of 84 RCCs confirmed by pathologic examination in 81 patients were retrospectively analyzed. A contrast-specific mode and a sulfur hexafluoride-filled microbubble contrast agent were used for CEUS. The enhancement pattern, extent, and dynamic change in the cortical, corticomedullary, and late phases were evaluated. On CEUS, the emergence of tumor enhancement was earlier in two nodules (2.4%), simultaneous in 71 (84.5%), and later in 11 (13.1%), in comparison with the adjacent renal cortex. Seventy-four RCC nodules (88.1%) showed hyper-enhancement (n = 2) or iso-enhancement (n = 72) during the cortical phase, and the remaining 10 (11.9%) showed hypo-enhancement. Twenty-three nodules (27.4%) showed homogeneous enhancement and 61 (72.6%) inhomogeneous enhancement. In the corticomedullary phase, the nodules showed hypo-enhancement in 68 (81.0%) and iso-enhancement in 16 (19.0%). In the late phase, all RCCs showed the same enhancement pattern as that shown in the corticomedullary phase. Seventy-two (85.7%) nodules showed a clear perilesional rim-like enhancement in late phase. Hyper- or iso-enhancement during the cortical phase, subsequent washout in late phase, inhomogeneous enhancement, and perilesional rim-like enhancement are clues for RCCs, which might be useful for characterization of RCCs.