Utility Of Contrast-Enhanced Ultrasound In Differentiating Benign From Malignant Renal Masses: A Retrospective Observational Study

Background: Contrast-enhanced ultrasound (CEUS) is increasingly recognized for its ability to differentiate benign from malignant renal masses. This study aimed to evaluate the diagnostic performance of CEUS in characterizing renal lesions, using histopathology or radiologic follow-up as the reference standard. Methods: In this retrospective observational study, 40 patients with renal masses who underwent CEUS at a tertiary care centre between September 2021 and June 2024 were included. CEUS enhancement features—wash-in kinetics, wash-out pattern, enhancement homogeneity, and peripheral rim/necrosis—were recorded. Diagnostic accuracy metrics were calculated, and agreement with CT/MRI findings was assessed using Cohen’s kappa. Results: The mean age of the cohort was 52.8 ± 9.4 years, with 55.0% males. Of the 40 lesions, 23 (57.5%) were malignant and 17 (42.5%) benign. CEUS demonstrated a sensitivity of 91.3%, specificity of 76.5%, positive predictive value of 84.0%, negative predictive value of 86.7%, and an overall diagnostic accuracy of 85.0%. The area under the ROC curve (AUC) was 0.94, indicating excellent discrimination. CEUS showed concordant classification with CT/MRI in 76.7% of cases (κ = 0.53, moderate agreement). Subgroup analysis showed higher diagnostic accuracy in lesions >2 cm (sensitivity: 94.7%, specificity: 76.5%) compared to those ≤2 cm (sensitivity: 75.0%, specificity: 0.0%). Conclusion: CEUS is a reliable, non-invasive modality for renal mass characterization, with excellent diagnostic performance and moderate agreement with cross-sectional imaging. Its utility is especially pronounced in lesions >2 cm and in patients where CT/MRI is contraindicated. CEUS should be considered a viable diagnostic adjunct in renal mass evaluation.