Understanding the Margins: Evaluation of Microwave Ablations Changes After Transarterial Embolization Utilizing Perfused Ex Vivo Human Kidneys

The combination of microwave ablation (MWA) and transarterial microsphere embolization (TAE) has been utilized to treat large renal tumors. This project aims to investigate the differences in size and shape of renal MWA with and without TAE utilizing a novel ex vivo human model.


Materials and Methods:

Under research consent, five human research kidneys declined for transplantation were obtained from three human deceased organ donors using standard surgical and transplant preservation techniques. Organs were connected to a fluoroscopic compatible ex vivo perfusion system consisting of pulsatile perfusion pump, membrane oxygenator, and warmer with continuous blood pressure and temperature monitoring. Perfusate solution was defibrinated red blood cells, normal saline, and glucose.

Two ablations—1 standard MWA, 1 TAE-MWA—were performed in each kidney at 2 minutes, 100 Watts using a MWA system (Solero Angiodynamics). An ablation was performed in the superior aspect of the kidney for standard MWA. Using standard technique, a 2.4-Fr microcatheter was then introduced into the inferior branch of the renal artery where 1 vial of LUMI M0 microspheres (Boston Scientific) was delivered to contrast stasis. Another MWA (2 min, 100W) was performed in the TAE region. Ablation zones of coagulative necrosis were sectioned along the long axis and segmented for maximal short axis diameter (SAD) and long axis diameter (LAD) measurements. Standard statistical analysis was performed. Histologic samples from each ablation zone were interpreted by a renal pathologist.



Results:

A total of 10 ablations (5 standard MWA, 5 TAE-MWA) were performed in five human kidneys. Average cold ischemic time was 44.5 hours (range 35 to 66 hours). Average mean arterial blood pressure was 170 ± 50 mmHg and 216 ± 77 mmHg after TAE (p = 0.29). Average flow rate was 1.7 + 0.4 mL/g/min. TAE-MWA resulted in significantly increased SAD, LAD, volume, and sphericity than standard MWA with average gross specimen comparisons as follows (5 standard MWA vs 5 TAE-MWA, two-tailed t-test): SAD, 1.8 ± 0.1 cm vs 2.5 ± 0.1 cm (p < 0.001); LAD, 2.9 ± 0.3 cm vs 3.2 ± 0.1 cm (p = 0.0385); volume, 5.0 ± 0.5 mL vs 11.0 ± 0.7 mL (p < 0.001); sphericity, 0.4 ± 0.2 vs 0.6 ± 0.1 (p = 0.049).  Histology demonstrated no significant differences in TAE-MWA other than concentrated microspheres. Tubular injury was identified in kidneys 1–4 MWA zones while severe diabetic glomerulosclerosis with tubular atrophy limited evaluation of kidney 5.



Conclusion:

In this ex vivo human model of renal MWA, TAE is an adjunctive treatment capable of increasing ablation margins and spherical shape.