A newly designed amplatz sheath decreases intrapelvic irrigation pressure during mini-percutaneous nephrolitholapaxy: an in-vitro pressure-measurement and microscopic study.

BACKGROUND AND
PURPOSE: In recent years, mini-percutaneous nephrolitholapaxy (mini-PCNL) has gained popularity because of its reduced invasiveness. To improve clinical outcomes further, research is ongoing in selected centers. Important areas of interest include extravasation into the retroperitoneal space, acute absorption syndrome, and septicemia. The aim of this experimental study was to test a new 18F nephroscope sheath specially designed to decrease intrapelvic pressure during mini-PCNL whatever the irrigation pressure. In addition, the hydrodynamic effects of this device can be used for suction and removal of the stone fragments, in contrast to a standard Amplatz sheath.
MATERIALS AND METHODS: In a fresh, perfused cadaveric porcine kidney model, the new sheath was compared with a conventional sheath (control) with closed and open Luer-Lok outflow under increasing irrigation pressure. Intrarenal pressure peaks were measured with a urodynamic workstation. The irrigation fluid was marked with an ink that stains only endoluminal surfaces, and a post-measurement histopathologic work-up was performed to evaluate the changes on a morphologic level.
RESULTS: Closing of the control sheath resulted in an increase in the intrapelvic pressure to a maximum of 136 cm H2O. Using the new sheath with a constant output flow made possible by its open proximal end, the maximal intrapelvic pressure remained low at 20 cm H2O, even when the inflow pressure reached 125 cm H2O. The ink distribution on the hematoxylin and eosin-stained slides reflected the results of the pressure measurements.
CONCLUSIONS: Newly designed nephroscope sheaths with an open proximal end, such as the one described here, decrease the intrapelvic pressure compared with a closed outflow system. As a result, strict fluid control during the intervention is not necessary.