Intrarenal pressure and irrigation flow with commonly used ureteric access sheaths and instruments

Abstract

IntroductionFlexible ureterorenoscopy is becoming a first-line treatment for many intrarenal stones. Ureteric access sheaths are commonly used to aid access, stone removal and reduce intrarenal pressure. We evaluated the effects of two commonly used access sheaths on irrigation flow and intrarenal pressure during flexible ureterorenoscopy. We measured the effect of scope instrumentation on flow and pressure.Material and methodsWe utilized a 10/12F and 12/14F, 35 cm Re-Trace™ access sheath with a FlexX2 scope in a cadaveric porcine kidney. We evaluated the effect of four Nitinol baskets (1.3F, 1.5F, 1.9F, 2.2F), three different 200 µm laser fibres and a hand-held pump. Measurements of irrigation flow and intrarenal pressure were recorded and compared between the different sized access sheaths.ResultsFlow rates varied widely between access sheaths. Without instrumentation, mean flow was 17 mls/min (10/12F access sheath), versus 33 mls/min (12/14F sheath) (p <0.0001). Increasing basket size produced a gradual reduction in flow and pressure in both access sheaths. Reassuringly, pressures were low overall (<40 cm H2O). Pressures were significantly reduced when using the larger 12/14F sheath, with and without all instrumentations (p <0.0001). Hand-held pump devices have a marked effect on flow and pressure in both sheaths; with pressures rising up to 121 cm H2O with a 10/12F sheath, versus 29 cm H2O (12/14F) (p <0.0001).ConclusionsA 12/14F access sheath offered significantly improved irrigation whilst maintaining significantly lower intrarenal pressure, when compared to a 10/12F access sheath in a cadaveric porcine model. Scope instrumentation affects irrigation flow and pressure in both sized sheaths. Furthermore, there should be caution with hand-held pump devices, especially with smaller sized sheaths, as intrarenal pressure can be very high.

Determinants of outflow rate during flexible ureteroscopy: an experimental in vivo study in an anesthetized porcine model

“…We also decided to perform all the experiments with a laser ber in the working channel because most of the time in fURS is spent with the ber inserted and it is during lithotripsy that ow is most required. It has been shown that increasing the size of instruments inside the working channel reduces the ow as it reduces the irrigation in ow [19,20]. In our study, the use of a 200 µm instead of 272 µm laser ber only increased ow when the ureteroscope was in the upper calyx and a 14/16Fr UAS was being used.…”

“…They have found that using a UAS kept IPP low even with high irrigation pressure. Later, these ndings have been sustained by in vitro [19], ex vivo [20], animal in vivo [5] and human in vivo [12] studies. Fang L, et al [21] established the concept of ratio endoscope-sheath diameter (RESD) and proposed that RESD < 0.75 should be considered safe, as it prevented IPP above 13 cm H 2 O in their porcine model.…”

The Role of 12/14F Ureteral Access Sheath in Flexible Ureteroscopy for Moderate Nephrolithiasis

“…Reduced bacterial backflow to the venous system due to lower intrarenal pressure while using UAS causes a reduction in bacteria transport into the circulatory system, which has been suggested as a rationale for employing a UAS in SIRS and sepsis prevention [18,19]. We were unable to prove any protective role of using a UAS for SIRS prevention in this study.…”

The dilemma of 12/14F ureteral access sheath (UAS) usage: a case control study

“…The reduction of bacterial backflow to the venous system due to lowered intrarenal pressure during ureteroscopy has been proposed as a rationale for UAS usage in sepsis prevention [ 18 , 19 ]. Adversely, we recorded a trend towards the development of SIRS in overall analysis of the patients operated on with the help of 12/14F UAS.…”