Renal cryotherapy in a sheep model; a feasibility study

PURPOSE

This study was designed to evaluate the safety and efficacy of renal cryotherapy as a possible treatment of renal malignancy with preservation of renal parenchyma.

MATERIALS AND METHODS

Ten Merino sheep were anaesthetised and the right kidney was exposed through a retro-peritoneal approach. A 5 mm. cryotherapy probe (LCS 3000 Cryotec UK) was inserted into the lower pole of the kidney and freezing was undertaken to form an iceball 5 cm. in diameter.

RESULTS

There was no mortality and no complications were observed. A transient rise in creatinine was observed post-operatively. The sheep were euthenased at 4 weeks and at necropsy macroscopic examination revealed a contracted, fibrotic wedge shaped lesion of 3 cm in diameter. Histological examination of the "cryolesion" revealed a central area of coagulative necrosis and a 5 mm rim of partial necrosis with preservation of renal tubules.

CONCLUSION

We conclude that renal cryotherapy is safe and can achieve effective renal necrosis in the sheep model.

In vitro and in vivo assessment of urethral warming catheters for the transperineal cryoablation of prostatic carcinoma

OBJECTIVE

To evaluate the two most common urethral warming catheters currently available for their effectiveness in preventing urethral injury in an animal model and thus during transperineal cryosurgery for the treatment of prostate cancer.

PATIENTS, MATERIALS AND METHODS

The warming efficiency of the variable-diameter thin latex-balloon catheter (Cook, Australia) and the fixed-diameter PVC catheter (Candela, USA) were evaluated in a water-bath. A sheep model was then used for subsequent experiments to further evaluate the better catheter. The technique used for the insertion of the Cook catheter in a series of 33 patients treated with prostate cryosurgery is also described.

RESULTS

In vitro, the Cook catheter was more effective (P < 0.01) than the Candela catheter in preventing localized cooling. In vivo, results in five animals showed that the urethral epithelium was viable in all sections that had been protected by the catheter and focally denuded or necrotic in those sections not protected, with each animal used as its own control (P < 0.01 Fisher's exact test). The 33 patients treated while using the Cook catheter had no subsequent complications.

CONCLUSION

The urethral warming catheter currently in use for prostatic cryosurgery in Australia is more effective in vitro than its competitor and is effective in preventing urethral injury in vivo.