Background and objectives

Cryoablation represents an alternative for treating small renal cortical neoplasms (RCN). Previously, we demonstrated that applying BioGlue during cryoablation diminished bleeding and incidentally noted that the iceballs seemed larger than those in controls. We examined the effects of BioGlue as a thermal insulator of cryoablated tissue to determine its effect on iceball size.

Methods

Laparoscopic cryoablation (LCA) was performed in 6 female pigs (24 ablations) by using a single 1.47-mm cryoablation probe. One pole of each kidney was randomly treated with BioGlue prior to ablation, while the contralateral pole was the untreated control. The size of the iceball was measured using laparoscopic ultrasound. The tissue ablation zone was measured grossly after the specimens were harvested. We also documented the amount of bleeding on a subjective scale.

Results

There were no differences in the diameters of the iceballs between the BioGlue and control groups when measured with laparoscopic ultrasound (P=.85). Similarly, the ablation zones on gross measurement were not significantly different (P=.47). No difference occurred in the amount of subjective bleeding.

Conclusions

In a porcine model, the application of BioGlue prior to LCA does not appear to increase the size of the iceball generated. No change was observed in the amount of subjective bleeding as a result of using BioGlue.

Introduction

Cryoablation is an acceptable treatment option for small renal cortical neoplasms (RCN). Unlike extirpative interventions, intraoperative needle biopsy is the only pathologic data for ablated tumors. It is imperative that sampled tissue accurately captures pathology. We studied the optimal intraoperative needle core biopsy protocol for small RCN during laparoscopic renal cryoablation (LCA).

Methods

Patients with RCN<4cm underwent intraoperative biopsy during LCA. Four biopsy cores were taken per tumor, 2 before and 2 after LCA by using both a standard and modified technique. Standard technique: needle biopsy device was deployed after insertion into the renal tissue at a depth of 5mm. Modified technique: needle biopsy device was deployed 1mm outside of the renal tissue. Biopsies were examined and compared with reference standard pathology. Percentage agreement was calculated across biopsy types (standard vs. modified) and time points (pre- vs. postcryoablation). Logistic regression was used to identify factors impacting biopsy accuracy.

Results

Thirty patients with 33 RCNs underwent LCA. The mean patient age was 69.1±8.0yrs, and mean tumor size was 2.3±0.7cm. No significant bleeding resulted from biopsies. A definitive diagnosis was made in 31/33 RCNs (94.0%). Ten tumors (30.3%) were benign, 21 (63.7%) were malignant, and 2 (6.0%) were nondiagnostic. Biopsy length was significantly longer using the standard vs. modified technique with mean lengths of 9.3mm vs. 7.0mm, respectively (P=.02). Highest agreement was seen in preablation biopsies (90.3%). A significant association with agreement was seen for younger age (P=.05) and larger tumor size (P=.02).

Conclusions

Younger age and larger tumor size were associated with improved accuracy. Preoperative sampling resulted in superior accuracy and the standard technique resulted in significantly longer cores. Use of preablation standard biopsy technique may result in the most accurate pathologic diagnosis for patients undergoing cryoablation for small RCNs.