[Evaluation of the effects of microwave tissue coagulation, radiofrequency ablation or ultrasonically-activated scalpel on renal tissue as a minimally invasive therapy].

Purpose: The objective of this study was to optimize least invasive techniques, like microwave tissue coagulation (MCT), radiofrequency ablation (RFA) or ultrasonically-activated scalpel (USS) for the electric and thermal conduction in kidney.
Materials and Methods: Needle electrode of MCT, RFA or USS were inserted into pig's kidney, under general anesthesia. We examined if the interruption of renal artery or cooling of renal parenchyma by irrigation in the renal pelvis had an effect on the tissue temperature distribution and area of tissue degeneration. The tissue parenchyma temperatures were measured at regular intervals of area (each 2.5-5.0 mm) from needle electrode or hook probe and of time (each 10 sec) using by needle temperature sensor, and pathological investigations on the tissue degeneration of the renal parenchyma were done.
Results: By MCT, interruption of renal artery had no effect on the distribution of tissue temperature and the area of tissue degeneration. Cooling of renal parenchyma by irrigation in the renal pelvis did not affect the area of tissue degeneration but the tissue temperature was elevated significantly. By RFA, particular interest, interruption of renal artery and cooling of renal parenchyma enhanced to increase both the tissue temperature and the area of tissue degeneration. By USS, interruption of renal artery enhanced to increase both the tissue temperature and the area of tissue degeneration. Cooling of renal parenchyma by irrigation in the renal pelvis had no effect on the distribution of temperature and the area of tissue degeneration. We also examined weather cooling of renal parenchyma by several irrigation solutions which have different electric conductivity (EC) such as normal saline solution (EC: 15,800 microS/cm), tap water (EC: 133 microS/cm) and glucose solution (EC: 8.6 microS/cm) in the renal pelvis using ureteral catheter would effect on the distribution of temperature and the area of tissue degeneration. In MCT and USS, these solutions did not have any effect, but in RFA the degree of tissue temperature elevation by normal saline, tap water and glucose solution were high, intermediate and low, respectively.
Conclusion: As RFA and USS tend to be affected by the surrounding environment, electric and thermal conductivity should be applied with caution, while using these techniques.