Presented by: Ron Marom MD
University of Michigan

Introduction

High irrigation rates are commonly used during high-power laser lithotripsy and can in some cases increase intrarenal pressure (IRP) substantially. In addition to pyelovenous backflow and associated risks of infection and sepsis, concerns have been raised that elevated IRP may also diminish renal artery flow and perfusion of the kidney.  In this study we sought to investigate changes in renal artery blood flow in response to elevation of IRP during ureteroscopy in an in-vivo porcine model.

Materials

After laparotomy, the renal hilum was exposed and an ultrasonic flow cuff was placed on the renal artery. Ureteroscopy was performed on three kidney units of two porcine subjects using a prototype ureteroscope with a pressure sensor at its tip. A modified ureteral access sheath was used to adjust the outlet resistance and allowed control of IRP.  Saline irrigation was delivered at two rates to induce IRPs of approximately 30 mmHg and 100 mmHg alternately for periods of two minutes for up to 15 cycles for each kidney unit. Irrigation rate, IRP, and arterial blood flow were recorded in real-time. Using MATLAB, the data streams were aligned, and the arterial flow was measured in response to the IRP. To account for systemic variation in blood flow, the percentage reduction in renal artery flow at high IRP was calculated with respect to the arterial flow value at low IRP, derived from the average of the two adjacent cycles.

A control data set was obtained by placing the ultrasonic flow cuff on one kidney while performing ureteroscopy with the same experimental conditions on the contralateral side.

Results

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At elevated IRP (100 mmHg) renal artery blood flow was reduced in all three renal units (Fig A) by 10-20% but not in the control (Fig B).

Conclusion

-  Renal artery blood flow decreased 10-20% when IRP was increased from 30 to 100 mmHg in the porcine model.  This decreased renal blood flow is unlikely to have an appreciable effect on tissue oxygenation or heat sink capacity during ureteroscopy.

Funding

Research grant from Boston Scientific

Disclaimer: The prototype ureteroscope used in this study was a concept device/technology which was not available for sale at the time the study was conducted. Pre-clinical study results may not necessarily be indicative of clinical performance.

Lead Authors

William W. Roberts, MD
University of Michigan

Co-Authors

Julie J. Dau, DVM
University of Michigan

Timothy L. Hall, PhD
University of Michigan

Khurshid R. Ghani, MBChB, MS, FRCS
University of Michigan