In Vitro Evaluation of Stone Fragment Evacuation by Suction

Optimizing Outcomes in Flexible Ureteroscopy: A Narrative Review of Suction Techniques

OBJECTIVE

The aim of this review is to summarize the existing suction systems in flexible ureteroscopy (fURS) and to evaluate their effectiveness and safety.

METHODS

A narrative review was performed using the Pubmed and Web of Science Core Collection (WoSCC) databases. Additionally, we conducted a search on the Twitter platform. Studies including suctions systems in fURS were included. Editorials, letters and studies reporting intervention with semirigid ureteroscopy, PCNL and mPCNL were excluded.

RESULTS

A total of 12 studies were included in this review. These studies comprised one in vitro study, one ex vivo study, one experimental study and eight cohort studies. The Pubmed and WoSCC searches identified three suction techniques (Irrigation/Suctioning system with control of pressure, suction ureteral access sheath (sUAS) and direct in scope suction (DISS)), and the Twitter search identified four of them. The overall results showed that suction is an effective and safe technique that improves stone-free rates, reduces operative time and limits complication rates after fURS.

CONCLUSIONS

The use of suctioning during common endourological procedures has been shown to improve safety and efficacy in several indications. However, randomized controlled trials are needed to confirm this.

Instrumental dead space and proximal working channel connector design in flexible ureteroscopy: a new concept

Objective

The objective of this study was to evaluate a new concept in flexible ureteroscopy: instrumental dead space (IDS). For this purpose, various proximal working channel connector designs, as well as the impact of ancillary devices occupying the working channel were evaluated in currently available flexible ureteroscopes.

Design and methods

IDS was defined as the volume of saline irrigation needed to inject at the proximal connector for delivery at the distal working channel tip. Because IDS is related to working channel diameter and length, proximal connector design, as well as occupation of working channel by ancillary devices, these parameters were also reviewed.

Results

IDS significantly varied between flexible ureteroscope models, ranging from 1.1 ml for the Pusen bare scopes, to 2.3 ml for Olympus scopes with their 4-way connector (p < 0.001). Proximal connector designs showed a high degree of variability in the number of available Luer locks, valves, seals, angles, and rotative characteristics. The measured length of the working channel of bare scopes ranged between 739 and 854 mm and significantly correlated with measured IDS (R² = 0.82, p < 0.001). The coupling of scopes with an alternative ancillary proximal connector and the insertion of ancillary devices into the working channel significantly reduced IDS (mean IDS reduction of 0.1 to 0.5 ml; p < 0.001).

Conclusions

IDS appears as a new parameter that should be considered for future applications of flexible ureteroscopes. A low IDS seems desirable for several clinical applications. The main factors impacting IDS are working channel and proximal connector design, as well as ancillary devices inserted into the working channel. Future studies should clarify how reducing IDS may affect irrigation flow, intrarenal pressure, and direct in-scope suction, as well as evaluate the most desirable proximal connector design properties.

Retrograde Cystonephroscopy for Complex Renal Calculi Using Novel Dual Action Aspiration, Irrigation Cystoscope: Initial Case Series

Introduction Percutaneous nephrolithotomy (PCNL) is the gold standard treatment for kidney stones ≥ 2 cm; however, it remains an invasive procedure with significant risks especially in individuals with severe medical co-morbidities. In contrast, while ureteroscopy is far less morbid, a major impediment to its use for larger calculi is the inability to evacuate the many fragments created during laser lithotripsy. Herein, we describe two patients with large volume calculi and a third high risk patient with a smaller stone that were treated with cystonephroscopy using a recently released, 16Fr flexible cystoscope equipped with dual aspiration and irrigation capabilities. Materials and Methods Three consecutive female patients underwent retrograde cystonephroscopy from June 2021 to July 2021 with a novel 16Fr aspiration enabled flexible cystoscope. Demographic data were collected. Pre-operative and post-operative CT-scan images were reviewed to determine linear stone dimensions and scalene ellipsoid volume. Results The three female patients had an average age of 72.3 years and an American Society of Anesthesiologists (ASA) physical status score of 3. The mean preoperative stone volume was 4950 mm³. The average post-cystonephroscopy stone volume was 217 mm³ resulting in a total stone clearance rate of 97%. No major complications occurred. Average procedure time was 176 minutes. Conclusions Among three high risk female patients, two with large volume calculi, retrograde cystonephroscopy with a novel aspiration-enabled cystoscope allowed for the procedure to be successfully completed solely via a retrograde approach.

The Life and Death of Percutaneous Stone Removal: "Looking Back-Looking Forward"

Although percutaneous nephrolithotomy (PCNL) is less morbid than open surgery, it still carries risks of significant complications as well as injury to the renal parenchyma. Flexible ureteroscopic stone removal, although causes no appreciable damage to the renal parenchyma, has limitations, most notably, a lower stone-free rate than PCNL. Advances in our knowledge regarding ureteral physiology combined with technical developments applied to ureteral access sheath deployment and size may well propel retrograde intrarenal surgery to the forefront of kidney stone removal, regardless of stone size or location.

Ex-vivo Renal Stone Dusting: Impact of Laser Modality, Ureteral Access Sheath, and Suction on Total Stone Clearance

INTRODUCTION AND OBJECTIVES

Conventional renal stone dusting is challenging; the holmium laser (Ho:YAG) and holmium with MOSES Effect (Ho:YAG-MOSES) fail to uniformly produce fragments <100 microns (i.e. dust). The superpulse thulium fiber laser (sTFL) may more effectively render uroliths into "dust," and may thus improve stone free rates. Accordingly, we performed ex-vivo evaluations with all three laser modalities, assessing stone fragments and stone clearance.

METHODS

Seventy-two ex-vivo porcine kidney-ureter models were divided into 12 groups of six: laser type (Ho:YAG, Ho:YAG-MOSES, sTFL), ureteroscope (URS) with and without applied suction, and presence or absence of a 14Fr ureteral access sheath (UAS). Calcium oxalate stones were pre-weighed and implanted into each kidney via a pyelotomy. Stones were treated at 16 watts using dusting settings of 0.4Jx40Hz (Ho:YAG) 0.2Jx80Hz (Ho:YAG-MOSES), and 0.2Jx80Hz (sTFL) for up to 20 minutes. No stone basketing was performed. Kidneys were bi-valved and residual fragments were collected, dried, weighed, and sieved to determine fragment size and stone clearance.

RESULTS

Initial stone mass (mg), procedure time (sec), and laser energy expenditure (kJ) were similar in all 12 groups. The greatest stone clearance was seen with sTFL+suction+UAS (94%) compared to a conventional technique (Ho:YAG+no suction+no UAS) (65%, p<0.01). The use of sTFL provided greater stone clearance than Ho:YAG or Ho:YAG-MOSES. Aspiration improved stone clearance for sTFL (p=0.01) but not for Ho:YAG or Ho:YAG-MOSES, consistent with the creation of smaller fragments with sTFL. Presence of a 14F UAS improved stone clearance in all scenarios (p<0.01).

CONCLUSIONS

In this ex-vivo study, stone clearance was optimized under the following conditions: sTFL laser, 14F ureteral access sheath, and aspiration. This combination resulted in 94% of stone fragments cleared; the 6% remaining fragments were all <2 mm. In all scenarios, deployment of a 14Fr UAS improved stone clearance.