Intrarenal pressures during flexible ureteroscopy: an insight into safer endourology

Manual manipulation and ex vivo flexible ureteroscopic lithotripsy to salvage deceased donor kidneys with renal stones: a case series

BACKGROUND

Nephrolithiasis is generally considered a relative contraindication for kidney donation. This study aimed to evaluate the feasibility and effectiveness of a surgical technique designed to salvage deceased donor kidneys with renal stones. The technique involves manual manipulation of the recovered kidney combined with flexible ureteroscopic lithotripsy (MM-FURSL) to clear the stones prior to transplantation.

CASE PRESENTATION

A total of nine kidneys were recovered from six deceased donors. The recipients (66.7% female; mean age 43.9 ± 12.2 years) had been on dialysis for an average of 2.6 years before undergoing renal transplantation with MM-FURSL. Donor kidneys contained 1 to 4 stones each, with a mean maximum stone diameter of 15.1 ± 10.6 mm and an average CT density of 942.0 ± 106.6 HU. The mean warm and cold ischemia times were 5 min and 480 ± 108.2 min, respectively. The average total operative duration was 57.0 ± 63.4 min. The first patient to undergo MM-FURSL had the longest operative and cold ischemia times due to the use of a reusable flexible ureteroscope, which was damaged during the procedure. She was the only patient to experience acute tubular necrosis (ATN), but her creatinine levels normalized within three weeks. No other complications were observed during a mean follow-up period of 11.7 ± 8.2 months.

CONCLUSION

MM-FURSL is an effective method for removing renal stones in donor kidneys. Short-term outcomes were favorable, suggesting that this technique could be a viable approach to expand the donor pool by salvaging kidneys with nephrolithiasis. However, prolonged cold ischemia time may increase the risk of ATN and should be minimized.

Current utility, instruments, and future directions for intra-renal pressure management during ureteroscopy: scoping review by global research in intra-renal pressure collaborative group initiative

Background

Technical advancements and intrarenal pressure are synergistic in improving perioperative outcomes during flexible ureteroscopy (FURS). Mismanaged intra-renal pressure (IRP) has negative consequences and it is associated with an increased risk of sepsis, bleeding, pelvicalyceal fluid extravasation, and even collecting system injuries and acute as well as chronic renal failure. The cornerstone of a safe FURS is the ability to continuously monitor IRP to avoid elevation of IRP above the normal range of 10 mmHg.

Objectives

This scoping review aims to report the current state of real-time IRP monitoring in in vivo clinical studies and the various monitoring methods and technology to understand how this may be best used in daily clinical practice.

Eligibility criteria

A systematic literature search was conducted. Only in vivo clinical studies published in English documenting IRP measurement methodologies during semirigid or flexible ureteroscopy for urolithiasis management were included.

Results

Out of 1326 retrieved papers, 17 studies met the inclusion criteria, comprising 2 randomized controlled trials, 2 retrospective studies, and 13 observational studies. Current noninvasive IRP monitoring devices include ureteric catheters placed retrogradely or via percutaneous tubing and connected to pressure transducers, amplified by cardiology-used pressure sensing systems or urodynamic systems, automated pressure-regulating systems, pressure sensing guidewires, and IRP sensing flexible ureteroscopes. The review revealed significant variations in IRP measurement methods, reporting units, and irrigation techniques. Notably, elevated IRP above 30 mmHg was consistently associated with increased postoperative complications, including sepsis.

Conclusion

Current clinical studies have only ascertained that increased IRP above 40 mmHg positively correlates with infectious complications and postoperative pain. No standardized values are available to predefine safe thresholds in practice. With the availability of noninvasive tools for IRP monitoring, future research should focus on multicenter studies to establish reference ranges and best practices for IRP management, ultimately improving patient outcomes in endourological procedures.

Automatic irrigation system with a fiber-optic pressure sensor regulating intrapelvic pressure for flexible ureteroscopy

Increased intrapelvic pressure (IPP) due to irrigation during flexible ureteroscopy (f-URS) can pose a risk of postoperative severe urinary tract infection associated with pyelovenous backflow. An automatic regulation system for maintaining safe IPP levels could enable surgeons to perform f-URS safely without postoperative complications. This study aimed to assess the measurement accuracy of an ultra-miniature fiber-optic pressure sensor incorporated into a small-caliper ureteroscope for assessing IPP and to develop an automatic irrigation system linked to this sensor. A porcine kidney was used for the ex vivo experiment. The nephrostomy catheter, connected to the conventional pressure transducer, was placed on the renal pelvis to evaluate the actual IPP (a-IPP). For measuring IPP using the fiber-optic pressure sensor (fo-IPP) built into the f-URS, a diaphragm pressure sensor of Φ250 μm was used. To establish an irrigation system, the optimal proportional-integral-derivative (PID) controller was explored to accurately adjust the irrigation pump flow rate. A high correlation between a-IPP and fo-IPP was confirmed across irrigation pressure values of 60-180 mbar (all, r ≥ 0.7, p < 0.001). When performing bolus irrigation, although fo-IPP showed relatively a higher peak value than a-IPP, the response time of fo-IPP was equivalent to that of a-IPP. After PID parameter optimization, our automatic irrigation system based on fo-IPP smoothly and accurately regulated the intended IPP set in the 5-20 mmHg range without overshooting. We successfully developed and demonstrated an automatic irrigation system regulating IPP based on the PID controller for f-URS, utilizing a fiber-optic pressure sensor. Further research, including in vivo studies, will be needed to assess clinical feasibility.