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Mineral oil has been used to facilitate ureteral stone extraction and to treat selected patients with infected residual urine. The purpose of this study was to evaluate the effect of mineral oil on the urothelium. Twelve adult female farm pigs underwent bilateral ureteral catheter placement under general endotracheal anesthesia. Retrograde pyelograms were performed and the ureteral diameters measured. Using a randomization protocol, six animals underwent injection of 10 mL of normal saline into one ureteral catheter and 50 mL of normal saline instillation into the bladder. In the remaining six animals, 10 mL of mineral oil was injected into one ureteral catheter and 50 mL of mineral oil into the bladder. The instillation was maintained for 30 minutes, and then the catheters were removed. One week later, under general endotracheal anesthesia, cystoscopy and retrograde pyelography were performed to measure the diameter of the ureters, and the animals were euthanized. The bladder, ureters, and kidneys were harvested for macroscopic and histopathologic evaluation. There was no significant difference in the diameter of the ureters injected with normal saline, the uninjected ureters, or the mineral oil-injected ureters. The bladders, ureters, and kidneys were grossly normal in all animals. No significant histopathologic changes were noted in the ureteral or bladder urothelium or the renal parenchyma in the animals injected with mineral oil. In conclusion, the instillation of mineral oil within the urinary tract does not have any significant long-term functional or histopathologic effect on the urothelium.

To determine the acute tissue effects of endoscopic electrosurgery using different electrodes, smooth ball, smooth bar, vertically grooved bar, and horizontally fluted bar electrodes were applied to the epithelial surface of porcine bladders in vivo with electrosurgical cutting current supplied at 100, 150, and 200 W. A single pass was made on the surface of the tissue under endoscopic control with sorbitol irrigation using an excursion rate of 5 mm/sec. Each electrode was tested five times at each setting. The depths of electrosurgical vaporization and coagulation were measured by a pathologist blinded to the electrode and power setting. Depth of vaporization increased with the power setting of the generator and was greater with the non-smooth electrodes than the smooth electrodes. The depth of coagulation likewise was greater using the non-smooth electrodes but increased only minimally with increasing power settings. There were no differences in vaporization or coagulation depth between the small ball and smooth bar electrodes. The differences between the vertically grooved bar and horizontally fluted bar also were insignificant, except that in one-third of cases, the horizontally fluted bar created clefts undermining otherwise-undamaged areas of tissue. Non-smooth electrosurgical electrodes produce more vaporization and coagulation than smooth electrodes at a given power setting and therefore may be preferred for endoscopic applications. For use in tissues where precise control is required, the vertically grooved bar may be superior to the horizontally fluted bar because it provides similar vaporization and coagulation with a more uniform tissue effect.