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

Abstract

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.

Thermal Protection during Percutaneous Thermal Ablation of Renal Cell Carcinoma

“…The ice-ball diameters for these probes may vary according to the tissue and blood supply, but their freeze lengths are consistent at approximately 4.5 cm. Ice-ball diameters refer to the outer 0°C margin, but cytotoxic temperatures (<−20°C) are known to occur 3-5 mm behind visualized ice margins (13,15). For soft tissues (eg, liver and kidney), a conservative ice-ball diameter estimate for the 2.4-mm probe is 2.0 cm.…”

“…There are several options for protecting vital structures adjacent to tumors from thermal injury. Some vital structures can be actively cooled (11,12) or heated (13) by fluid infusions. In a laparoscopic approach, the vital structure can be mechanically separated from the tumor.…”

Cryosurgery for prostate cancer: New technology and indications

“…This study demonstrates the compromise between cancer control and urinary morbidity when a urethral warmer is used. The ideal urethral warmer is still being developed [35].…”

Cryoablation of Prostate- Improving Efficacy and Safety

“…To avoid this undesirable quality of life complication, the cells of the urethral lining are now routinely protected by active warming techniques through the insertion of a warming catheter that expands under fluid pressure to conform to the luminal channel. 58,[63][64][65] The catheter is designed as a counter current heat exchanger operating at 38 to 40°C to provide sufficient warming and protection of a 1-2mm thickness of the urethral wall. The reported incidence of urethral sloughing following cryoablative procedures with use of a warming catheter ranges between 0 to 15% compared to rates in excess of 25% without the catheter.…”