36 - Comparative Safety of Percutaneous Cryoablation for Renal Tumors near the Renal Pelvis with versus Without Prophylactic Ureteral Stent Placement

Purpose: To compare the safety of percutaneous cryoablation for treatment of renal tumors near the renal pelvis with and without prophylactic ureteral stent placement for renal protection.

Materials and Methods: A retrospective review of CT-guided percutaneous cryoablations performed from 2014-2024 at a single institution identified 21 patients who had prophylactic placement of ureteral stents by urology before cryoablation (stented group). Propensity score matching was used to identify an equal-sized cohort of patients who did not undergo ureteral stent placement before cryoablation (unstented group). Patients were matched on age, tumor size and tumor location. Outcomes included immediate and delayed (within 30-days post procedure) complications and change in renal function as measured by estimated glomerular filtration rate (eGFR) within one-year post-procedure.

Results: No significant difference was noted in baseline patient characteristics between the stented and unstented groups. 16/21 (76%) of patients in the stented group and 19/21 (90%) of patients in the unstented group were male (p=0.21). Median tumor size was 3.2 cm (IQR: 2.6-3.9) in the stented group and 2.6 cm (2.3-3.3) in the unstented group (p=0.21). All patients had tumors within 5 mm from the renal sinus fat. Post-procedure complication rates were similar between the two groups (10/21 [48%] vs 8/21 [38%], respectively, p=0.34). Majority of the complications were immediate minor perilesional hemorrhages, which did not require intervention (8/21 [36%] in stented vs 5/21 [23%] in unstented, p=0.51). There were no cases of major hemorrhage, ureteral obstruction, or hydronephrosis in either group within 30 days post-procedure. One patient within the stented group had a delayed presentation of pyelonephritis requiring hospitalization 2 days after a difficult removal of the ureteral stent. No significant difference was seen in percent change in eGFR by 1-year post-procedure between the two groups (-5.8% in stented vs -7.7% in unstented, p=0.76).

Conclusion: Prophylactic ureteral stenting prior to cryoablation of renal tumors near the renal pelvis may not provide additional renal protective benefit and carries added risks associated with a secondary procedure. Larger studies may be needed to validate these findings.