Development of new experimental kidney model for in vitro study of retrograde intrarenal surgery: The “T-box”

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.

Examining the Impact of Different Properties of Ureteral Access Sheaths in Reducing Insertion Force during Retrograde Intrarenal Surgery: An In Vitro Study

BACKGROUND AND PURPOSE

This study aimed to evaluate the characteristics of ureteral access sheaths (UASs) that can reduce the insertion force while accessing the upper urinary tract.

MATERIALS AND METHODS

Six different types of 12/14-Fr UASs were used. We evaluated the properties of UASs such as the diameter of the outer sheath, length of the inner dilator tip exposed from the outer sheath, sheath flexibility (assessed in terms of bending force of the tip or base), flexibility ratio (i.e., bending force value of tip-to-base ratio), and frictional force of the outer sheath surface. We measured the force required for inserting the UAS into an artificial ureteral model and examined the correlation between the relevant characteristics and insertion force for each UAS.

RESULTS

Overall, a lower tip-to-base flexibility ratio (r = 0.66) and a lower frictional force (r = 0.50) were inversely correlated with insertion force. The force of insertion into the bifurcation was associated with the flexibility of the base (r = -0.64), flexibility ratio (r = 0.79), and frictional force (r = 0.66). Moreover, a shorter dilator tip (r = 0.52), lower flexibility ratio (r = 0.52), and lower frictional force (r = 0.50) were correlated with a lower insertion force at the proximal ureter.

CONCLUSION

A UAS with a rigid base and flexible tip parts, a smoother surface, and a shorter dilator tip would be preferable for reducing the insertion force. These findings may be crucial for selecting or developing an ideal UAS that can decrease the risk of ureteral injury.

Photodynamic Diagnosis with Oral 5-Aminolevulinic Acid for Upper Urinary Tract Carcinoma: A Prospective Clinical Trial

Background and Purpose: In this study, we evaluated the effectiveness and safety of photodynamic diagnosis (PDD) of upper urinary tract carcinoma (UTUC) using oral 5-aminolevulinic acid (5-ALA). Materials and Methods: Consecutive adult patients with suspected UTUC based on imaging and urine cytology findings were prospectively enrolled from May 2018 to January 2019. 5-ALA (20 mg/kg) was orally administered 2 to 3 hours before diagnostic ureteroscopy (URS). Sixty-three biopsy samples were collected from 20 eligible patients using white light (WL) and PDD-URS. The primary endpoint was sensitivity, and the secondary endpoints were specificity, positive predictive value (PPV) and negative predictive value (NPV), diagnostic accuracy, and safety. Results: The sensitivity of photodynamic URS was significantly higher than that of WL-URS (93.8% vs 62.5%, p = 0.0025). Although the specificity and PPV were not different between the two procedures, PDD-URS showed a significantly higher NPV (92.3% vs 69.2%, p = 0.027) and accuracy (0.86 vs 0.75, p = 0.0297) than WL-URS. With respect to safety, no grade ≥3 adverse events related to 5-ALA administration occurred in any patients. Conclusion: We found that PDD-URS with oral 5-ALA is a safe and superior diagnostic tool for detection of UTUC compared with conventional WL-URS.

Current Status of Simulation Training in Urology: A Non-Systematic Review

Simulation has emerged as an effective solution to increasing modern constraints in surgical training. It is recognized that a larger proportion of surgical complications occur during the surgeon's initial learning curve. The simulation takes the learning curve out of the operating theatre and facilitates training in a safe and pressure-free environment whilst focusing on patient safety. The cost of simulation is not insignificant and requires commitment in funding, human resources and logistics. It is therefore important for trainers to have evidence when selecting various simulators or devices. Our non-systematic review aims to provide a comprehensive up-to-date picture on urology simulators and the evidence for their validity. It also discusses emerging technologies and future directions. Urologists should embed evidence-based simulation in training programs to shorten learning curves while maintaining patient safety and work should be directed toward a validated and agreed curriculum.