Comparative Diagnostic Performance of Color Doppler Flow Imaging, MicroFlow Imaging and Contrast-enhanced Ultrasound in Solid Renal Tumors

Rationale and Objectives: Accurate distinguish malignant from benign renal masses remains a challenge for radiologists. The purpose of this study was to evaluate the value of Color Doppler Flow Imaging (CDFI), MicroFlow Imaging (MFI) and Contrast-enhanced Ultrasound (CEUS) in diagnosing solid renal tumors. Materials and Methods: A total of 291 patients with 300 solid renal tumors pathologically confirmed were retrospectively analyzed between January 2020 and December 2022. Each patient underwent CDFI, MFI, and CEUS examinations before surgery. The diagnostic efficacy of CDFI, MFI and CEUS in assessing renal tumors was compared based on blood flow grade, vascular morphology and CEUS characteristics. Results: MFI identified 243 renal lesions (81%) with blood flow grade (2, 3) and vascular morphology (IV, V), significantly outperforming CDFI, which detected 147 cases (49%). MFI demonstrated statistically significant differences in detecting blood flow signals and predicting renal malignancy compared to CDFI (p < 0.001). In CEUS examination, significant differences were observed in wash-in, enhancement intensity, wash-out, and perilesional rim-like enhancement of the contrast agent between malignant and benign renal lesions (all p < 0.001). The areas under the receiver operating characteristic curves (AUCs) for MFI and CEUS were 0.838 and 0.788, respectively, both higher than that for CDFI (0.695). In diagnosing solid renal tumors, MFI and CEUS showed significant differences compared to CDFI (p < 0.05), although no significant difference was found between MFI and CEUS (p = 0.075). The diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CDFI, MFI and CEUS were as follows: 0.600 vs.0.893 vs.0.920; 0.554 vs. 0.920 vs.0.984; 0.837 vs. 0.755 vs.0.592; 0.946 vs. 0.951 vs.0.925; 0.268 vs. 0.649 vs.0.879. Conclusion: MFI demonstrates higher sensitivity in detecting microvascular signs of renal tumors compared to CDFI. Moreover, MFI exhibits comparable diagnostic performance to CEUS in distinguishing malignant from benign renal masses.