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

Flexible 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.

We 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.

Flow 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).

A 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.