Efficacy of Antegrade Pyeloperfusion to Protect the Renal Pelvis in Kidney Microwave Ablation Using an In Vivo Swine Model

Abstract

The purpose of this study was to evaluate the efficacy of antegrade pyeloperfusion with cooled 5% of glucose solution to protect the renal collecting system during microwave ablation (MWA). Computed tomographically guided nephrostomy was performed in 1 kidney in each of 14 female pigs by placing a 6F nephrostomy catheter. Pyeloperfusion was performed through infusion of cooled 5% of glucose solution via the nephrostomy catheter (4°C; 10 mL/min). Microwave ablation (915 MHz) was performed at 45 W for 10 minutes in the irrigated and the non-irrigated kidneys creating a central lesion and a peripheral lesion in each kidney. Maximum ablation diameters were measured and ablation volumes were calculated after the animals were killed. The extent of thermal injury of the renal pyelon was assessed histopathologically in the slice of maximal thermal injury on a 10-point scale ranging from 0 (none) to 10 (complete). Pyeloperfusion did not impact the ablation volume or the degree of thermal injury to the collecting system for the central or peripheral MWA procedures: The mean (SD) volume of the MWA zones was equivalent for the irrigated versus non-irrigated kidneys for the peripheral (3.07 [2.39] mL vs 3.87 [3.08] mL) and central MWA procedures (2.26 [1.55] mL vs 2.40 [1.60] mL). The mean (SD) histologic scores of the thermal damage of the pyelon were similar for the irrigated versus non-irrigated kidneys in the peripheral MWA (1.0 [2.7] vs 0.2 [0.6]) and in the central MWA (1.6 [2.7] vs 3.4 [3.4]). In MWA, cooled antegrade pyeloperfusion is not useful to modulate the ablation volume in peripheral or central locations. Accordingly, pyeloperfusion may not be useful as a protective measure to avoid thermal damage in MWA of the kidney. Therefore, MWA of central renal tumors does not seem advisable.