Allery Treatment News

In Vitro, Ex Vivo And In Vivo Isotherms For Renal Cryotherapy

April 05, 2017

UroToday - "Don't believe everything you read." The isotherms that are published for the currently most-used cryoprobes from Galil Medical and Endocare Inc. are derived from trials in an ex vivo gel system; in this very meticulous study, the company results obtained in a gel environment could be largely duplicated.

BUT there is no congruence between the gel isotherm and the isotherms obtained in an in vivo perfused porcine kidney. While the manufacturers' gel isotherm show a -20°C isotherm for either probe type out to 2 cm, in this study only the Endocare probe achieved this temperature in the laboratory gel study. Far more worrisome is the observation that in the in vivo porcine kidney, neither probe provided -20°C at 2 cm, indeed the temperatures at this distance were always above 0°C; at 1 cm. distance from the probe, the Endocare probe did develop a -20°C isotherm, while the coldest temperature produced by the Galil probe at 1 cm. was only -13.5°C.

ALSO, at 5 mm beyond the tip of either probe, the recorded in vivo temperatures were always above +15°C!

For those urologists using cryoablation to treat renal tumors under laparoscopic/ultrasound or percutaneous/CT guidance, there are two take home points from this extensive laboratory study: a.) The use of temperature monitoring probes is essential in order to guide needle placement to assure achieving temperatures below -20°C.

b.) The tip of the cryoprobe needs to be advanced through the tumor until it rests 5mm beyond the far wall of the tumor. Read and don't want your patients to be left out in the cold when it comes to complete renal tumor ablation. Real time monitoring of the temperatures at the periphery of the tumor are essential to successful cryoablation therapy.

Young JL, Kolla SB, Pick DL, Sountoulides P, Kaufmann OG, Ortiz-Vanderdys CG, Huynh VB, Kaplan AG, Andrade LA, Osann KE, Louie MK, McDougall EM, Clayman RV
J Urol. 2010 Feb;183(2):752-8
doi: 10.1016/j.juro.2009.09.072

UroToday Medical Editor Ralph V. Clayman, MD

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