Contrast Enhanced Ultrasound Evaluation of Nephron Sparing Treatment for Renal Cell Carcinoma

Purpose: To determine the accuracy of CEUS in identifying residual or recurrent tumor post nephron-sparing procedures. Materials and Methods: CEUS studies performed post nephron sparing procedure (RFA, cryoablation, MWA, partial nephrectomy) from January 2018 to May 2025 were retrospectively reviewed at 2 centers. Informed consent was waived. Patient charts were reviewed for follow-up procedures and patient status. CEUS studies were performed on a Philips Epic ultrasound with a C5-1 transducer using Lumason with a dose of 1.0 to 2.0cc. A 3-minute cine clip was saved. An examination was considered a true positive if there was contrast in the procedure site and either biopsy proven tumor or persistent enhancement for over 1 year. An examination was considered a true negative if there was no contrast enhancement in the procedure site. Results: There were 193 lesions in 188 patients. (mean age 68.0 years +/- 1.4 [SD] (range 33-90) ;115 men). There were 16 radiofrequency ablation, 38 cryoablations, 4 microwave ablations, and 135 partial nephrectomies. The average lesion size was 2.9cm (IQR 2.2,3.7; range 1.4cm-7.1cm). There were 17 (8.8%) true positive cases and 176 (91.2%) true negative cases. Time of follow-up ranged from 1-336 months (mean 35.1, IQR 12, 70). There were no false positive or false negative cases based on biopsy and long-term follow-up. There were 92 (47.7%) that also had CECT. There was 96.7% concordance of CEUS with CT. There were 3 CEUS cases positive with a negative CECT. Conclusions: CEUS is an accurate method in determining residual or recurrent tumor in patients having nephron sparing procedures.