Comparison of the histologic accuracy of needle biopsy before and after renal cryoablation: laboratory and initial clinical experience.

OBJECTIVES

To minimize the risk of needle biopsy, including tumor seeding and hemorrhage, we examined the feasibility of needle biopsy after renal cryoablation.

METHODS

Four cryolesions were created bilaterally on normal porcine renal tissue with an 8-minute double-freeze cycle using a single 17-gauge cryoprobe. Biopsies were obtained with a 16G biopsy needle before and after cryoablation under direct vision. Each biopsy specimen was evaluated for the number of glomeruli and arterioles. We used a two-sample t-test to analyze the data. Subsequently, 10 patients with small renal masses underwent laparoscopic cryoablation using a standard double freeze-thaw cycle. We used an 18G biopsy needle to sample the renal mass with a single core taken before and after cryoablation. A blinded pathologist evaluated the specimens for the histologic accuracy of the two sampling techniques. We used chi-square statistic to determine an association between the diagnostic quality of the core specimens.

RESULTS

Two hundred biopsies were obtained from porcine renal tissue. The average number of glomeruli for the pre- and postcryoablation sample was 9.6, and 7.8, respectively (P = 0.04). The average number of arterioles for the pre- and postcryoablation group was 2.3 and 1.9, respectively (P = 0.04). During clinical application, seven of 10 precryoablation and seven of 10 postcryoablation biopsies were diagnostic (P = 0.639). Histopathology was established in all 10 cases. There was no significant bleeding from any needle biopsy.

CONCLUSIONS

The porcine model established the feasibility of histologic diagnosis after cryoablation. Our preliminary clinical experience demonstrates that postcryoablation biopsy has similar diagnostic yields to precryoablation biopsy.