Resistances of various renal instruments used in ureteral perfusion

Various needles, catheters, and tubes, which can be used in the kidney for percutaneous ureteral pressure-flow studies (Whitaker Test), were perfused at standard and high flow rates to determine their inherent resistances. Continuous pressure monitoring without subtraction of renal instrumental baseline can be performed only with the larger-bone instruments (1.7-2.7 mm internal diameter, depending on length) as these induce no measured pressure rise in the perfused system at flow rates up to 10 ml/minute.