Cm For Kidney Research Articles

Liquid Nitrogen-Based Cryoablation in In Vivo Porcine Tissue: A Pilot Study.

Introduction:Liquid nitrogen-based cryoablation induces freezing evenly throughout the probe tip surface, resulting in larger ablation volumes and faster treatment times. The purpose of this preliminary investigation is to determine the efficacy of the liquid nitrogen-based Visica2 Cryoablation System (Sanarus Technologies, Pleasanton, CA) in in vivo porcine kidney, liver, and fibro-fatty tissue. Methods:Ablations were performed under ultrasound guidance in 4 Yorkshire pigs. The target lesion cross-section width (W) and depth (D) were 1 cm for liver (n=8), kidney (n=4), and head-neck (n=5) and 2 cm for kidney (n=4). Expected axial length (L) of the resulting lesion is approximately 4 cm. After three-day survival, the ablated tissue was harvested and histologically analysed. The mean width and depth were compared with the target diameter using a one-sample t-test. Results:All animals survived the procedure. For the 1 cm target, mean dimensions (L x W x D) were 3.8±1.5 x 1.7±0.3 x 1.7±0.7 for liver, 3.0±0.5 x 2.0±0.4 x 1.7±0.6 for kidney, and 3.3±0.8 x 1.8±0.4 x 1.8±0.4 for head-neck. Mean width and depth were significantly greater than desired dimension. For the 2 cm target, mean dimensions were 3.2±0.5 x 3.1±0.8 x 1.9±0.7. Mean width and depth were not significantly different to desired target. Conclusion:Our preliminary results show that the Visica2 liquid nitrogen-based cryoablation system can efficiently and reproducibly create ablation volumes in liver, kidney, and fibro-fatty tissue within 4 minutes and 12 minutes for 1cm and 2cm targeted diameters, respectively. Further investigation is necessary to determine the optimal freeze-thaw-freeze protocol for larger ablation volumes.

3:20 PM Abstract No. 344 In vivo determination of cryoablation size after an abbreviated single 15-minute freeze protocol in swine hepatic and renal tissue in comparison to the conventional 10-8-10 minute freeze-thaw-freeze protocol

To determine the lethal cryoablation size of a single 15-minute freeze protocol and compare it with that of the conventional 10-minute freeze, 8-minute active thaw, 10-minute freeze cycle (10-8-10) in swine liver and kidney. Percutaneous CT-guided cryoablation was performed in 5 swine livers and kidneys. In each organ, one ablation (2 probes) was performed utilizing the 10-8-10 minute cycle and a second utilizing the single 15-minute cycle. When the “ice-ball” was maximal, 10 cc of India Ink was arterially infused into the organ. The two ablations were timed to end simultaneously so that the unfrozen tissue surrounding both ablation zones was stained at maximal ablation volume. Histologic analysis was performed by a pathologist. The ablation length (long axis of the cryoprobe tract) and maximum width (perpendicular to the cryoprobe track) were measured and the tissues were fixed in formalin. Histopathologically determined ablation length in the 10-8-10 samples was 5.00 ± 0.75 cm and 6.55 ± 0.55 cm for kidney and liver tissue, respectively. For the 15-minute single cycle the respective sizes were 4.96 ± 0.32 cm and 6.85 ± 0.49 cm. Similarly, ablation width in the 10-8-10 samples was 3.95 ± 0.17 cm and 4.5 ± 0.3 cm for kidney and liver, respectively, in the 10-8-10 samples and 4.00 ± 0.44 cm and 4.3 ± 0.28 cm, for kidney and liver, respectively, in the 15-minute samples. Neither ablation length nor width (and consequently volume) were significantly different between the cryoablation protocols. In addition, this was true in both kidney and liver tissue. However, ablation length and width were significantly smaller in the kidney when compared to the liver, for each cryoablation protocol. This observation can be explained by the higher tissue perfusion in the kidney compared to the liver (fourfold), and the role this perfusion plays in heat exchange within the tissue (the heat pump effect). An abbreviated, single 15-minute cryoablation results in an identical ablation size to that of the conventional 10-8-10 minute protocol, regardless of tissue. A larger cryoablation zone observed in hepatic tissue can potentially be explained by differences in tissue perfusion.

Renal atrophy and arterial stenosis. A prospective study with duplex ultrasound.

Renal artery disease is an important cause of both renal failure and hypertension. Duplex ultrasound is a reliable noninvasive method for classifying the severity of renal artery lesions and can be repeated to follow the course of the disease over time. The purpose of this study was to determine the changes in kidney size associated with various degrees of renal artery disease. Serial kidney lengths were measured as part of a prospective duplex ultrasound study of patients with renal artery narrowing. Fifty-four patients (22 men, 32 women; mean age, 65.8 years) with 101 renal artery and kidney sides eligible for follow-up were evaluated at 6-month intervals for an average of 14.4 months (range, 4 to 24 months). No kidneys with renal arteries classified as normal or less than 60% diameter stenosis by duplex criteria were found to have a decrease in length of greater than 1 cm during follow-up. In kidneys with a high-grade renal artery stenosis (> or = 60% diameter reduction), 26% (13 of 49 sides) were found to have a decrease in length of greater than 1 cm. The average decrease in length was 1.9 cm (range, 1.2 to 3.4 cm). By life table analysis, the estimated risk of a decrease in length of greater than 1 cm for kidneys with 60% stenosis or greater was 19% at 1 year. Loss of renal mass, as documented by ultrasound measurement of kidney length, is an important consequence of high-grade renal artery stenosis.