Upper urinary tract pressures in endourology: a systematic review of range, variables and implications

Ureteroscopic lithotripsy with pressure-measuring ureteral access sheath for large ureteral stones

INTRODUCTION

To evaluate the safety and efficacy of ureteroscopic lithotripsy with pressure-measuring ureteral access sheath (PM-UAS) for large ureteral stones.

MATERIAL AND METHODS

A total of 258 consecutive patients with large ureteral stones ≥15 mm was enrolled. They were treated by ureteroscopic lithotripsy with PM-UAS in the oblique supine lithotomy position. The technology can precisely monitor and automatically control cavity pressure. The cavity pressure control value was set at -15 mmHg∼-5 mmHg. The cavity pressure limit value was set at 30 mmHg. Infusion flow rate was set at 100-200 ml/min. Postoperative data such as stone-free rate and complications were analyzed.

RESULTS

PM-UAS was successfully implanted in 225 patients at one stage. Eighteen cases of patients who had failed the first surgery were successfully treated with a second operation. Fifty-one cases with stones migrating up to the kidney were converted to flexible lithotripsy. The other 15 cases were converted to percutaneous nephrolithotomy due to significant ureteral stenosis. The operative time was 49.5 ± 11.2 min. The stone-free rates after one month and three months were 87.2% (212/243) and 94.2% (229/243), respectively. Complications from grade I to II were observed in 25(10.3%) patients. No other complications from grade III to V were noted.

CONCLUSION

The ureteroscopic lithotripsy with PM-UAS is safe and efficacious for large ureteral stones.

Fluid absorption during flexible ureteroscopy with intelligent control of renal pelvic pressure: a randomized controlled trial

PURPOSE

To investigate fluid absorption and its influencing factors during flexible ureteroscopy with intelligent control of renal pelvic pressure (RPP).

METHODS

A total of 80 patients with upper urinary tract calculi underwent flexible ureteroscopy with intelligent control of RPP by pressure-measuring ureteral access sheath and were randomly divided into four groups. The RPP of Groups A, B, and C were set at - 5, 0 and 5 mmHg, respectively. Conventional flexible ureteroscopy with uncontrolled pressure served as control Group D. The perfusion flow rate was set at 100 ml/min in the four groups, with 20 patients in each group. The fluid absorption was measured by 1% ethanol every 10 min. Operation time, stone-free rate, and complications were recorded.

RESULT

Seventy-three patients were finally included in the RCT. The general and preoperative data of the patients were comparable between the groups. The fluid absorption of Groups A, B, and C was significantly less than that of Group D (P < 0.01). Fluid absorption and operation time were positively correlated, and the correlation coefficients R were 0.864, 0.896, 0.918, and 0.947, respectively (P < 0.01). The fluid absorption of patients with vomiting, fever and ureteral injury was greater than that of patients without complications in the four groups (P < 0.01). In different groups, fluid absorption was greater in patients with ureteral injury Post-Ureteroscopic Lesion Scale (PULS) 1-3 than in noninjured patients (P < 0.01).

CONCLUSION

Flexible ureteroscopy with intelligent control of RPP effectively reduces the absorption of perfusion fluid. Operation time and ureteral injury are also key factors affecting perfusion fluid absorption.

REGISTRATION NUMBER AND DATE

NCT05201599; August 11, 2021.

Intrarenal pressure detection during flexible ureteroscopy with fiber optic pressure sensor system in porcine model

To validate the feasibility of a fiber-optic pressure sensor-based pressure measurement device for monitoring intrarenal pressure and to analyze the effects of ureteral acess sheath (UAS) type, surgical location, perfusion flow rate, and measurement location on intrarenal pressure (IRP). The measurement deviations and response times to transient pressure changes were compared between a fiber-optic pressure sensing device and a urodynamic device IRP in an in vitro porcine kidney and in a water tank. Finally, pressure measurements were performed in anesthetized female pigs using fiber-optic pressure sensing device with different UAS, different perfusion flow rates, and different surgical positions at different renal calyces and ureteropelvic junctions (UPJ). According to our operation, the result is fiber optic pressure sensing devices are highly accurate and sensitive. Under the same conditions, IRP varied among different renal calyces and UPJ (P < 0.05). IRP was lowest at 50 ml/min and highest at 150 ml/min (P < 0.05). Surgical position had a significant effect on IRP (P < 0.05). 12/14 Fr UAS had a lower IRP than 11/13 Fr UAS. Therefore fiber optic pressure sensing devices are more advantageous for IRP measurements. In ureteroscopy, the type of ureteral sheath, the surgical position, the perfusion flow rate, and the location of the measurement all affect the intrarenal pressure value.

Prone vs supine percutaneous nephrolithotomy: does position affect renal pelvic pressures?

The purpose of this study was to measure and compare renal pelvic pressure (RPP) between prone and supine percutaneous nephrolithotomy (PCNL) in a benchtop model. Six identical silicone kidney models were placed into anatomically correct prone or supine torsos constructed from patient CT scans in the corresponding positions. A 30-Fr renal access sheath was placed in either the upper, middle, or lower pole calyx for both prone and supine positions. Two 9-mm BegoStones were placed in the respective calyx and RPPs were measured at baseline, irrigating with a rigid nephroscope, and irrigating with a flexible nephroscope. Five trials were conducted for each access in both prone and supine positions. The average baseline RPP in the prone position was significantly higher than the supine position (9.1 vs 2.7 mmHg; p < 0.001). Similarly, the average RPP in prone was significantly higher than supine when using both the rigid and flexible nephroscopes. When comparing RPPs for upper, middle, and lower pole access sites, there was no significant difference in pressures in either prone or supine positions (p > 0.05 for all). Overall, when combining all pressures at baseline and with irrigation, with all access sites and types of scopes, the mean RPP was significantly higher in the prone position compared to the supine position (14.0 vs 3.2 mmHg; p < 0.001). RPPs were significantly higher in the prone position compared to the supine position in all conditions tested. These differences in RPPs between prone and supine PCNL could in part explain the different clinical outcomes, including postoperative fever and stone-free rates.

Safety and feasability of ureteroscopy for pediatric stone, in children under 5 Years (SFUPA 5): A French multicentric study

INTRODUCTION

Ureteroscopy (URS) can be proposed as first-line therapy for the management of pelvic stones from 10 to 20 mm and for lower ureteric stones in children. However, little is known about the success and the morbidity of URS in young children. Ureteroscopic treatment may present matters in young children because of the small size of the pediatric kidney and the small size of the collecting system.

OBJECTIVE

To assess safety and efficacy of URS for the treatment of urinary stones in children aged of 5 years or less.

STUDY DESIGN

After the institutional ethical board approval was obtained, we conducted a retrospective, analytic, multicentric study that included all URS performed between January 2016 and April 2022 in children aged of 5 years or less. In this non-comparative case series, anonymized pooled data were collected from 7 tertiary care centers of pediatric patients. Endpoints were the one-session SFR at 3 months and per and postoperatives complications. Descriptive statistics were applied to describe the cohort.

RESULTS

Eighty-three patients were included. For them, 96 procedures were performed at the median age of 3.5 years (IQR: 0.8-5) and median weight of 14 Kg (6.3-23). Median stone size was 13 mm (4-45). There were 65 (67 %) renal stones treated with flexible URS, most of which were in the renal pelvis (30 %) and in the lower calix (33 %). A ureteral access sheath was used in 91 % procedures. Preoperative ureteral stent was placed in 52 (54 %) of patients. None of patients had ureteral dilatation. The single-session SFR was 67.4 % (56.3 and 89.2 % for flexible URS and semi-rigid URS respectively) and children require 1.4 procedures to achieve complete stone clearance. The overall complication rate was 18.7 %, most of them were minor (Clavien I-II). Intraoperative perirenal extravasation (Clavien IIIb) due to forniceal rupture was documented in 6.2 % of cases, related to an increased intrapelvic pressure (IPP) performed in a closed pelvicalyceal system.

DISCUSSION

Pediatric urologists should be aware of forniceal rupture based on the presence of extravasation of contrast during endourological procedures especially when they have difficulties to reach lower caliceal stone in small patient.

CONCLUSION

URS in patients aged of 5 years or less, is a complex minimally invasive procedure with reasonable efficacy and low morbidity. Intrarenal stones treated by RIRS in young children carries the risk of additional procedures to complete stone clearance.

The optimal ratio of endoscope-sheath diameter with negative-pressure ureteral access sheath: an in vitro research

PURPOSE

To maintain safe intrarenal pelvic pressure (IPP), the combination of flexible ureteroscope (fURS) and traditional ureteral access sheath (T-UAS) should maintain a basic rule that is the ratio of endoscope-sheath diameter (RESD) ≤ 0.75. However, the negative-pressure ureteral access sheath (NP-UAS) may break the rule of negative pressure suction. This study aimed to examine the effect of NP-UAS on IPP and flow rate (FR) with varying RESD.

METHODS

In a 3D-printed renal model, flexible ureteroscopy lithotripsy (fURL) was replicated. Six sizes of fURS paired with 12Fr T-UAS and NP-UAS resulted in six distinct RESDs of 0.63, 0.78, 0.87, 0.89, 0.90, and 0.91. While the irrigation pressure (IRP) was set between 100 and 800 cmH2O and the sucking pressure (SP) was set between 0 and 800 cmH2O, the IPP and FR were measured in each RESD.

RESULTS

NP-UASs can reduce the IPP and increase the FR at the same RESD compared to T-UASs. The IPP decreased with increasing SP with NP-UAS. When RESD ≤ 0.78, T-UAS and NP-UAS can maintain IPP < 40 cmH2O in most circumstances. When RESD = 0.87, it is challenging for T-UAS to sustain IPP < 40 cmH2O; however, NP-UAS can do so. When RESD ≥ 0.89, it is difficult to maintain an IPP < 40 cmH2O even with NP-UAS.

CONCLUSION

NP-UAS can decrease IPP and increase FR compared with T-UAS. To maintain a safe IPP, it is recommended that RESD < 0.85 when utilizing NP-UAS.

Experimental study of a new technique for minimally invasive percutaneous nephrolithotomy: intelligent pressure-controlled minimally invasive percutaneous nephrolithotomy

BACKGROUND

To test the reliability and safety of a newly invented technique for minimally invasive percutaneous nephrolithotomy, intelligent pressure-controlled minimally invasive percutaneous nephrolithotomy (IPC-MPCNL).

METHODS

Eighteen kidneys of nine female pigs were randomly divided into three groups. Those in Groups A and B underwent IPC-MPCNL through the new system composed of a pressure-measuring MPCNL suctioning sheath and an irrigation and suctioning platform with pressure feedback control. The infusion flow rate was 500 ml/min in Group A and 750 ml/min in Group B. Those in Group C underwent MPCNL at an infusion flow rate of 500 ml/min. The renal pelvic pressure (RPP) monitored by a ureteral catheter and that monitored by the pressure-measuring sheath in Groups A and B were compared. The RPP in Group C was monitored by a ureteral catheter.

RESULTS

The RPP measured by the pressure-measuring sheath and that measured by the ureteral catheter in Group A was - 5.59 ± 1.95 mmHg and 4.46 ± 2.08 mmHg, respectively. The RPP measured by the pressure-measuring sheath and that measured by the ureteral catheter in Group B was - 4.00 ± 2.01 mmHg and 5.92 ± 2.05 mmHg, respectively. Hence, the RPPs measured by the pressure-measuring sheath in Groups A and B were consistent with those measured by the ureteral catheter. The RPP in Group C was 27.75 ± 5.98 mmHg (large fluctuations).

CONCLUSIONS

IPC-MPCNL can be used to accurately monitor the RPP and maintain it within a preset safe range via suction. The new technique and the new system are safe and reliable.

In vitro comparison of simulated intrapelvic pressure in an artificial kidney model during retrograde intrarenal surgery among various single-use ureteroscopes

OBJECTIVES

This study compares intrapelvic pressure (IPP) during retrograde intrarenal surgery with various single-use flexible ureteroscopes (f-URS) in an artificial kidney model.

METHODS

We created an artificial kidney model with a pressure sensor using a bladder evacuation device. The model was completely closed and the only backflow was on the side of the ureteroscope inside the ureteral access sheath (UAS). We tested five single-use f-URSs (LithoVue, Wiscope, PU3022A, PU3033A, and AXIS) with six different types of UAS (9.5/11.5-14/16 Fr). Using the automatic irrigation system, 30 s of irrigation was performed at various pressures (40-180 mmHg) and steady-state IPP was recorded. IPP was compared between the five single-use f-URSs. IPP cutoff value was determined at 30 mmHg. The diameter of the endoscope tip and the curved and shaft parts were also measured and recorded.

RESULTS

The diameters of all parts were significantly different between single-use f-URSs. The maximum IPP tended to be higher in ureteroscopes with larger diameters of the proximal parts (curved part/shaft part). In LithoVue and Uscope PU3022A f-URSs, the maximum IPP did not exceed 30 mmHg when UAS ≥12/14 Fr was used. In AXIS and Wiscope f-URSs, it did not exceed the cutoff value when the UAS ≥11/13 Fr was used. In Uscope PU3033A f-URS, it did not exceed 30 mmHg when the UAS ≥10/12 Fr was used.

CONCLUSIONS

Maximum IPP tended to be higher in f-URSs with larger diameters of the proximal part and the appropriate size of the UAS differed between various single-use f-URSs.

Intrarenal pressures during flexible ureteroscopy: an insight into safer endourology

OBJECTIVES

To assess intrarenal pressures (IRPs) and complication rates after flexible ureteroscopy (fURS), and to assess factors that contribute to raised IRPs and postoperative complications.

PATIENTS AND METHODS

After informed consent patients underwent fURS under general anaesthesia. The transducer of a 0.3556 mm (0.014″) pressure guidewire was placed in the renal pelvis for live recording of IRPs. The fURS procedures were performed in a routine manner under antibiotic cover with the aim of dusting the calculus to completion. The operating surgeon was blinded to the live-recorded IRPs.

RESULTS

A total of 40 fURS procedures were performed in 37 patients (26 male and 11 female). The mean age was 50.5 years. As a cohort, the mean of average IRPs was 34.8 mmHg and the mean of maximal IRPs was 128.8 mmHg. Pearson's correlation showed a significant inverse correlation between the mean IRP and age (r[38]: -0.391, P = 0.013). Three cases experienced postoperative deviations from uncomplicated recovery, with two being hypotensive and one case being both hypotensive and hypoxic. Three cases returned to the emergency department within 30 days of surgery, with two cases of flank pain and one case of urosepsis with positive urine cultures. The patient presenting with urosepsis had exhibited IRPs exceeding the mean.

CONCLUSION

The IRPs changed significantly from normal baseline levels during routine fURS. The mean IRP during fURS correlates with patient age, but not with other factors. The IRP may be related to increased complication rates at fURS. Understanding factors that influence IRP will allow urologists to better manage this intraoperatively.

In vivo ureteroscopic intrarenal pressures and clinical outcomes: a multi-institutional analysis of 120 consecutive patients

OBJECTIVES

To evaluate the pressure range generated in the human renal collecting system during ureteroscopy (URS), in a large patient sample, and to investigate a relationship between intrarenal pressure (IRP) and outcome.

PATIENTS AND METHODS

A prospective multi-institutional study was conducted, with ethics board approval; February 2022-March 2023. Recruitment was of 120 consecutive consenting adult patients undergoing semi-rigid URS and/or flexible ureterorenoscopy (FURS) for urolithiasis or diagnostic purposes. Retrograde, fluoroscopy-guided insertion of a 0.036-cm (0.014″) pressure guidewire (COMET™ II, Boston Scientific, Marlborough, MA, USA) to the renal pelvis was performed. Baseline and continuous ureteroscopic IRP was recorded, alongside relevant operative variables. A 30-day follow-up was completed. Descriptive statistics were applied to IRP traces, with mean (sd) and maximum values and variance reported. Relationships between IRP and technical variables, and IRP and clinical outcome were interrogated using the chi-square test and independent samples t-test.

RESULTS

A total of 430 pressure traces were analysed from 120 patient episodes. The mean (sd) baseline IRP was 16.45 (5.99) mmHg and the intraoperative IRP varied by technique. The mean (sd) IRP during semi-rigid URS with gravity irrigation was 34.93 (11.66) mmHg. FURS resulted in variable IRP values: from a mean (sd) of 26.78 (5.84) mmHg (gravity irrigation; 12/14-F ureteric access sheath [UAS]) to 87.27 (66.85) mmHg (200 mmHg pressurised-bag irrigation; 11/13-F UAS). The highest single pressure peak was 334.2 mmHg, during retrograde pyelography. Six patients (5%) developed postoperative urosepsis; these patients had significantly higher IRPs during FURS (mean [sd] 81.7 [49.52] mmHg) than controls (38.53 [22.6] mmHg; P < 0.001).

CONCLUSIONS

A dynamic IRP profile is observed during human in vivo URS, with IRP frequently exceeding expected thresholds. A relationship appears to exist between elevated IRP and postoperative urosepsis.

Mechanism of urosepsis: relationship between intrarenal pressures and pyelovenous backflow

To document the histological changes observed in renal units subjected to elevated intrarenal pressures (IRPs) and postulate the possible mechanisms of infectious complications after ureteroscopy.

MATERIALS AND METHODS

Ex vivo studies were performed on porcine renal models. Each ureter was cannulated with a 10-F dual-lumen ureteric catheter. A pressure-sensing wire was inserted through one lumen and with the sensor positioned in the renal pelvis for IRP measurement. Undiluted India ink stain was irrigated through the second lumen. Each renal unit was subjected to ink irrigation at target IRPs of 5 (control), 30, 60, 90, 120, 150, and 200 mmHg. Three renal units were subjected to each target IRP. After irrigation, each renal unit was processed by a uropathologist. Macroscopically, the amount of renal cortex stained by ink was calculated as a percentage of the total perimeter. Microscopically, presence of ink reflux into collecting ducts or distal convoluted tubules, and pressure-related features, was noted at each IRP.

RESULTS

Signs of pressure, as represented by collecting duct dilatation, was first observed at 60 mmHg. Ink staining was consistently observed in the distal convoluted tubules at IRPs ≥60 mmHg, and all renal units above this pressure showed renal cortex involvement. At ≥90 mmHg, ink staining was observed in venous structures. At 200 mmHg, ink staining was observed in supportive tissue, venous tributaries in the sinus fat, peritubular capillaries, and glomerular capillaries.

CONCLUSION

Using an ex vivo porcine model, pyelovenous backflow occurred at IRPs of ≥90 mmHg. Pyelotubular backflow occurred when irrigation IRPs were ≥60 mmHg. These findings have implications for the development of complications after flexible intrarenal surgery.

Retrograde vacuum-assisted MiniPCNL system for large distal ureteric calculus removal: A case report

Large ureteral calculi are commonly associated with severe colic pain, complex urinary tract infections, severe hematuria, hydronephrosis, and renal deterioration, often requiring immediate surgical intervention. Ureteroscopy is a favored treatment due to its higher stone-free rates; however, it encounters difficulties in cases of a high burden of distal ureteral stones. We present a case where a patient with a significant ureteral calculus was effectively treated with a vacuum-assisted mini-percutaneous nephrolithotomy system in retrograde approach. This intervention enabled the complete removal of the stone, leading to the patient's full recovery without complications.

Real Time Intrarenal Pressure Control during Flexible Ureterorrenscopy Using a Vascular PressureWire: Pilot Study

(1) Introduction: To evaluate the feasibility of measuring the intrapelvic pressure (IPP) during flexible ureterorenoscopy (f-URS) with a PressureWire and to optimize safety by assessing IPP during surgery. (2) Methods: Patients undergoing f-URS for different treatments were recruited. A PressureWire (0.014", St. Jude Medical, Little Canada, MN, USA) was placed into the renal cavities to measure IPP. Gravity irrigation at 40 cmH₂O over the patient and a hand-assisted irrigation system were used. Pressures were monitored in real time and recorded for analysis. Fluid balance and postoperative urinary tract infection (UTI) were documented. (3) Results: Twenty patients undergoing f-URS were included with successful IPP monitoring. The median baseline IPP was 13.6 (6.8-47.6) cmH₂O. After the placement of the UAS, the median IPP was 17 (8-44.6) cmH₂O. With irrigation pressure set at 40 cmH₂O without forced irrigation, the median IPP was 34 (19-81.6) cmH₂O. Median IPP during laser lithotripsy, with and without the use of on-demand forced irrigation, was 61.2 (27.2-149.5) cmH₂O. The maximum pressure peaks recorded during forced irrigation ranged from 54.4 to 236.6 cmH₂O. After the surgery, 3 patients (15%) presented UTI; 2 of them had a positive preoperative urine culture, previously treated, and a positive fluid balance observed after the surgery. (4) Conclusion: Based on our experience, continuous monitoring of IPP with a wire is easy to reproduce, effective, and safe. In addition, it allows us to identify and avoid high IPPs, which may affect surgery-related complications.