Interobserver agreement and diagnostic sensitivity of Doppler and contrast-enhanced ultrasound in characterizing indeterminate renal lesions

To assess inter-reader agreement for color Doppler vascularity and contrast-enhanced ultrasound (CEUS) enhancement in indeterminate renal lesions and to compare their sensitivity for characterizing renal masses. In this retrospective study, patients who underwent CEUS evaluation of indeterminate renal lesions at two tertiary care centers between January 1, 2019, and March 15, 2025, were identified. Two board-certified, subspecialty-trained radiologists, blinded to final diagnoses, independently assessed color Doppler vascularity and enhancement using sulfur hexafluoride microbubble contrast. Inter-reader agreement was evaluated using Cohen’s kappa. Discordant interpretations were classified as negative. Feature frequencies were compared using McNemar’s test. Pathology results were available and documented as the reference standard for 20% of the lesions (n=9). Sensitivity and 95% confidence intervals were reported. 45 renal lesions (12 solid, 33 cystic) in 38 patients (mean age 66.7 years; 21 male) were identified. Mean maximum lesion diameter was 32 mm (range: 8-99 mm). There was strong inter-reader agreement for assessment of vascularity (Kappa 0.738) and presence of enhancement (Kappa 0.814). Lesions were more likely to enhance (n=34,76%) than show vascularity (n=13, 29%), p<0.001. Only 7 (21%) enhancing lesions showed vascularity. 9 biopsied lesions were neoplasms (8 renal cell carcinoma, 1 oncocytoma); all 9 demonstrated enhancement (100% sensitivity; 95% CI: 66-100%), but only 5 demonstrated vascularity (56% sensitivity; 95% CI: 21-86%). CEUS demonstrated near perfect interobserver agreement and superior sensitivity compared with color Doppler ultrasound for detecting enhancement in indeterminate renal lesions. Most enhancing lesions do not demonstrate Doppler vascularity.