Arterial Clamping Increases Central Renal Cryoablation Efficacy: An Animal Study

Abstract

Introduction: The minimally invasive treatment of small renal masses with cryoablation has become increasingly widespread during the past 15 years. Studies with long-term follow-up are beginning to emerge, showing good oncological control, however, tumors with a central and endophytic location seem to possess an increased risk of treatment failure. Such tumors are likely to be subjected to a high volume of blood giving thermal protection to the cancerous cells. Arterial clamping during freezing might reduce this effect but at the same time subject the kidney to ischemia. The aim of this study was to evaluate the effect of renal artery clamping during cryoablation in a porcine survival model. Methods: Ten Danish Landrace pigs (approximately 40 kg) underwent bilateral laparoscopic cryoablation with clamping of the right renal artery during freezing. The cryoablation consisted of a standard doublefreeze cycle of 10-minute freeze followed by 8 minutes of thaw. Arterial clamping subjected the right kidney to 2 cycles of ischemia (10 minutes) with perfusion in between. After surgery, the animals were housed for 14 days prior to computed tomography perfusions scans, radioisotope renography, and bilateral nephrectomy. Results: No perioperative or postoperative complications were experienced. Mean differential renal function was 44% (95% confidence interval: 42-46) in the clamped right kidney group and 56% (95% confidence interval: 54-58) in the nonclamped left kidney group, P < .05. The +5% technical inaccuracy is not accounted for in the results. Mean maximum temperature between freeze cycles was 5.13 C (95% confidence interval: À0.1 to 10.3) in the clamped right kidney group and 22.7 C (95% confidence interval: À16.6 to 28.8) in the nonclamped left kidney group, P < .05. Mean cryolesion volume, estimated on computed tomography perfusion, was 12.4 mL (95% confidence interval: 10.35-14.4) in the clamped right kidney group and 6.85 mL (95% confidence interval: 5.57-8.14) in the nonclamped left kidney group, P < .05. Pathological examination shows a higher degree of vital cells in the intermediate zone of the cryolesions in the nonclamped left kidneys when compared with the clamped right kidneys. Conclusion: Arterial clamping increases cryolesion size by approximately 80%, and pathologic examinations suggest a decreased risk of vital cells in the intermediate zone. The clamped kidneys showed no sign of injury from the limited ischemic insult. This study was limited by being a nontumor model.

Feasibility and Safety of Single-Probe Cryoablation with Liquid Nitrogen: An Initial Experience in 24 Various Tumor Lesions

“…The “heat-sink effect” is a well-established phenomenon in radiofrequency ablation, in which tumors adjacent to large vessels are sometimes insufficiently ablated because perfusion-mediated tissue cooling reduces coagulation necrosis by heat energy [ 21 ]. An opposite mechanism has been described for cold ablation techniques [ 22 ]. In our study, the largest ice ball was obtained in a fatty soft tissue with poor vascularization, whereas the smallest ablation zones were obtained in the treatment of hypervascular lesions (thyroid metastasis).…”

Image-guided study of swine anatomy as a tool for urologic surgery research and training

“…Landrace pigs weighting between 30 and 40 kg, the same breed used in this study, took part in research about ischemia, reperfusion and renal transplantation 26 , 27 . In another study, 3-month-old pigs (weighting about 40 kg) were used to evaluate the efficacy of arterial clamping during the treatment of renal tumors by cryoablation technique 28 . This breed represents a good option for anatomical studies of the urinary system because it is available at an affordable cost, besides being widely used in research in the urological and endourological fields.…”

Recent progress in cryoablation cancer therapy and nanoparticles mediated cryoablation

“…To mitigate the heat transfer, embolization of blood vessels to prevent blood flow may increase the efficacy of cryoablation while delivering ischemic cytotoxicity to tumor cells. In a Danish Landrace pig model, arterial clamping to artificially reduce renal blood flow increased cryolesion size by approximately 80%, while seeing no sign of injury in the kidney tissues due to limited blood flow model 16 .…”