Working Channel Of Ureteroscope Research Articles

Endoscopic Forceps for Ureteroscopy: A Comparative In Vitro Analysis

To evaluate the functional characteristics of different ureteroscopic graspers. The Captura (2.8F, Cook Medical, Bloomington, IN), Platinum (3.0F, Bard Urological, Covington, GA), TriClaw (2.4F, UroGyn Medical, Inc., Valapraiso, IN), Graspit (2.6F, Boston Scientific, Natick, MA), and Boston Scientific Tricep (2.4F, 3.0F, and 3.0F non-retracting) graspers were tested. Opening dynamics were evaluated using high-resolution images. Grip strength was determined by measuring the maximum tensional force applied while grasping stone models attached to an inline load cell. Safety profile was evaluated by the maximum force required to perforate aluminum foil. Impact on ureteroscope deflection was assessed by measurement of maximum deflection (baseline = 247°) and bending radius after advancing each grasper through a flexible ureteroscope working channel. The Tukey test for inequality assuming unequal variance with Bonferroni adjustment was used to compare grip strength and perforation forces. The Tricep (2.4F, 3.0F NR, and 3.0F) and Captura graspers required the least distance (7.9-8.1 mm) to attain a grasping width of 5 mm. When compared across all stone models, the TriClaw and Graspit had greater grip strengths than all other devices. The Captura (1.92 ± 0.43 N) and Tricep 2.4F (1.72 ± 0.88 N) required the greatest forces to perforate aluminum foil. Ureteroscope deflection was least impacted by the Tricep 2.4F (213°, 1.35 cm radius), Graspit (207°, 1.35 cm radius), TriClaw (206°, 1.3 cm radius), and all graspers could be deployed and operated at maximum deflection. There are significant differences in opening dynamics, grip strength, perforation forces, and ureteroscope deflection among ureteroscopic graspers that may predict clinical performance capabilities.

Double-J stent placement with grasping forceps through ureteroscope working channel: a novel technique

To report a new technique for the retrograde placement of a double-J stent with grasping forceps through the ureteroscope working channel. Materials and methods: In our technique, the ureteroscope is advanced to the renal pelvis or proximal location of the obstruction in the ureteral lumen; a double-J stent is then introduced into the ureteroscope working channel. The double-J stent is pushed forward until its proximal tip is seen; then the clamp over the distal tip of the pusher is opened and the guide-wire and pusher are removed from the channel, respectively. The grasping forceps is inserted into the working channel until it is touching the stent; the ureteroscope is removed from the ureter by pulling it over the stent and grasping forceps. Thus, the stent is placed in the ureteral lumen. Results: This technique was successful in 17 patients: 16 retrograde ureteroscopies for stone extraction and 1 retrograde ureteroscopy with ureteropelvic junction obstruction. No complications occurred during follow-up. Conclusion: Our simple technique may be safely used to place double-J stent in cases of ureteral obstruction. It may reduce procedure time and it avoids the potential complications of blind catheter placement.

Irrigant Flow and Intrarenal Pressure During Flexible Ureteroscopy: The Effect of Different Access Sheaths, Working Channel Instruments, and Hydrostatic Pressure

Our aim was to determine the optimal size of access sheath for ureteroscopy and stone lasertripsy to achieve good irrigant flow while maintaining the lowest possible intrarenal pressure. We used an in vitro anatomic model into which a pressure transducer was incorporated. Cook Peel-Away 10F, Flexor 12F, 14F, 16F single lumen, and a new 14F Flexor dual-lumen sheath were tested. Irrigant flow and intrarenal pressure were measured with an empty ureteroscope working channel and with a 1.4F or 2.4F basket within the working channel with a hydrostatic pressure of 1 m and 2 m, respectively. For the dual-lumen sheath, the irrigation was either connected to the scope or the second channel of the access sheath. Two other configurations were tested: 4F ureteral catheter placed alongside a 10F sheath (configuration 1) or a 5F ureteral catheter within a 16F access sheath (configuration 2). With an empty working channel, irrigant flow increased with sheath diameter. The presence of a 1.4F or 2.4F basket, however, reduced flow up to 65% and 90%, respectively. Increasing the hydrostatic column to 2 m height improved the irrigant flow but with a predisposition to a higher intrarenal pressure. Using configurations 1 and 2, the flow rates improved by 250% and 700%, respectively, with a 2.4F basket in the working channel, and could also be used with a 2 m hydrostatic column without raising the intrarenal pressure. Increased access sheath diameter does not improve flow when the working channel of a flexible ureteroscope is occupied. Our proposed configuration of a ureteral access catheter placed inside or alongside the access sheath provides by far the highest flow rates without a rise in the intrarenal pressure.

FlexGuardTM: a new laser insertion sheath: functional aspects in ureterorenoscopy (URS)

The evolution of flexible ureteroscopes led to a widespread use for the management of upper urinary tract abnormalities. The cost of purchase, maintenance and the durability of these instruments has become a major issue. This work describes a new device to avoid damages due to incorrect use of the Holmium laser during insertion of the laser fibre. A laser fibre with an optical core of 271 and 430 muicrom outside diameter was slid inside the FlexGuard laser fibre insertion sheath (LISA laser products, Germany). The outside diameter of the sheath measures 2.7 F (0.9 mm) and 2.1 F (0.7 mm) luminal diameter. The distal fibre tip was brought up to a position app. 2 mm inside the distal end of the sheath. The loaded sheath was pushed through the working channel of various ureteroscopes which were in maximum deflection. With the insertion sheath protruding about 2 mm from the distal tip of the URS the fibre was effortless forwarded out of the sheath to approach the stone. Once the laser fibre was in position, the sheath was removed, to increase the volume of irrigation fluid during laser lithotripsy. The radius of curvature (ROC) of the URS in maximum deflection and the integrity of the working channel was investigated. Using the insertion sheath the laser fibre reached the working position without any recognition of scratching or resistance. The integrity of the ureterorenoscopes was checked thoroughly be manually operated manometry. No damage of the inner surface of the working channel occurred. The ROC of the instrument did not change significantly during this procedure. After removal of the sheath the ROC remained stable. With the extended use of ureteroscopy, durability and repair costs are of concern. Damage resulting from incorrect use of laser fibres is a major issue in this respect. FlexGuard proved to avoid this damage in all flexible ureteroscopes investigated without limiting their mobility.

Durability of Working Channel in Flexible Ureteroscopes When Inserting Ureteroscopic Devices

We studied the physical damage to the working channel of flexible ureteroscopes caused by insertion of various accessories. A procedure was developed to avoid channel damage. An experimental model representing a flexible ureteroscope was prepared, and damage to its working channel was evaluated by inserting instruments through it. Deflection angles of the channel were changed from 0 degrees to 120 degrees, and each device was inserted and removed 100 times for each selected angle of the channel. Any induced pinholes were identified by an air-leak test. Also, the inside of the channel was inspected with an extremely fine fiberscope. Insertions of 3F biopsy forceps or a 2.4F Nitinol stone-retrieval device caused only slight damage to the model channel, even when the deflection angle was 120 degrees. However, the tips of 200- or 250-microm holmium laser fibers shaved the inner surface of the channel at 60 degrees of deflection, and at 120 degrees, the laser fiber either penetrated the channel or could not be advanced because of resistance by the channel wall. When the laser fiber was inserted within a protective tube, the channel was never damaged, even when the deflection angle was 120 degrees. When devices are inserted into the working channel of a flexible ureteroscope, damage to the wall depends on the kind of device and deflection angle. Harm could be avoided by inserting the devices, especially laser probes, within a protective tube.

Alteration in Irrigant Flow and Deflection of Flexible Ureteroscopes with Nitinol Baskets

Introduction of an instrument into the working channel of ureteroscopes adversely affects flow and deflection. We evaluated the alterations in ureteroscope channel flow and deflection caused by available Nitinol(R) baskets. We compared the effects of 11 Nitinol baskets on irrigation flow and deflection of three flexible ureteroscopes (Olympus P3, ACMI DUR8, and ACMI DUR8 Elite). ANOVA was used to compare the loss of flow and deflection for each basket, with P values adjusted for multiple comparisons by the Tukey method. Ureteroscope flow and deflection were progressively adversely affected by all baskets as their diameter increased. The average baseline irrigant flow (46.6 mL/min) was decreased significantly: by 78.5% (to 9.9 mL/min), with the smaller baskets (Microvasive 1.9F and Cook 2.2F) and by 99.1% (to 0.4 mL/min) with the larger baskets (ACMI 3.0F and Microvasive 3.0F). Similarly, the mean baseline upward deflection (162 degrees) decreased by 2 degrees (1.2%) for the Cook 2.4F N-Compass and by 20 degrees (12.3%) for the ACMI 3.0F. Loss of downward deflection from baseline (170 degrees) ranged from 6 degrees (3.5%) for the Microvasive 1.9F to 17 degrees (10%) for the Microvasive 2.6F grasping forceps. The least deterioration in flow and deflection occurred with the two smallest baskets (Microvasive 1.9F and Cook 2.2F). Ureteroscope irrigation flow and deflection deteriorate progressively with larger-caliber Nitinol baskets. The Microvasive 1.9F and Cook 2.2F baskets resulted in the least deterioration of irrigation and deflection metrics. However, basket size is not the only factor responsible for changes in flow and ureteroscope deflection.

A novel dual-diameter ureteroscope working channel: Impact on irrigant flow

ObjectivesTo compare irrigant flow characteristics through standard working channels (3.6F to 4.5F) and a dual-diameter working channel. Irrigant flow is critical for adequate visualization during endoscopic procedures. MethodsWorking channels were created out of 80 cm of light wall polytetrafluoroethylene (PTFE) tubing (inner diameter 3.6F, 4.0F, and 4.5F) with a male Luer connector attached to one end by epoxy resin. The dual-diameter working channel was created with a 70-cm segment of PTFE (4.5F inner diameter, 0.059 in.) and a 10-cm segment of PTFE (3.6F inner diameter, 0.047 in.) with a male Luer connector attached to the free end of the 4.5F tubing. Stone basket shafts (100 cm in length, outer diameter 1.9F, 2.4F, and 3.0F) were created out of unmodified polyimide tubing with a 0.018-in.-diameter nitinol mandrel epoxy core for stability. Irrigant flow was measured at 100 mm Hg pressure for 1 minute with an empty channel and with stone basket shafts in the channel. ResultsThe flow rates were significantly greater with the dual-diameter working channel than with the standard flexible ureteroscope (3.6F) working channel using an empty channel (79.2 versus 44.1 mL/min, P = 0.0001), 1.9F basket (35.9 versus 10.0 mL/min, P = 0.003), 2.4F basket (20.7 versus 4.3 mL/min, P = 0.002), and 3.0F basket (6.0 versus 0.7 mL/min, P = 0.0002) sheath. ConclusionsA dual-diameter working channel may optimize irrigant flow characteristics for flexible ureteroscopes while maintaining a small distal tip diameter.

Morphological and Physiological Changes in the Urinary Tract Associated With Ureteral Dilation and Ureteropyeloscopy: An Experimental Study

The gross and microscopic effects of four common modes of ureteral dilation and ureteroscopy were examined in 26 renoureterai units in 13 minipigs. Acutely, ureters subjected to mechanical (bougie, Teflon, or balloon) ureteral dilation and ureteropyeloscopy (UPS) demonstrated active mucosal bleeding with multiple sites of perforation, whereas ureters subjected to hydraulic dilation and UPS were significantly less traumatized. Two weeks after mechanical ureteral dilation and UPS, 3 of 6 ureters were obstructed radiographically, whereas all 7 hydraulically dilated ureters were unobstructed. By 6 weeks, all radiographic evidence of obstruction had resolved in the mechanically dilated group. While 5 of 6 mechanically dilated ureters showed extensive scarring with muscle loss 4 to 6 weeks after dilation, no scarring was seen in those ureters dilated hydraulically.Renal pelvic pressure (RPP) was measured continuously with a nephrostomy catheter in vivo during (bougie, Teflon, balloon and hydraulic) ureteral dilation and UPS. Renal pelvic pressure during rigid ureteroscopy approximated the resting pelvic pressure plus the irrigant height above the kidney or set pressure on a hydraulic pump, plus a “scope effect” which was characterized by a 20 to 25mm. Hg increase in RPP produced by moving the endoscope in the ureter without flow. The effects on RPP of continuous bladder drainage with a urethral catheter and renal pelvic decompression with an open-ended ureteral catheter passed into the renal pelvis through the ureteroscope working channel were also examined. The maximum RPP was evaluated in vitro in a separate group of 16 freshly harvested pig kidneys of similar weight examined immediately after sacrifice and was found to be 439mm. Hg.We also studied the immediate and long-term effects of low (<120cm. H20 or 90mm. Hg) versus high (>200cm. H20 or 150mm. Hg) RPP on renal histology. Acutely, high pressure caused diffuse denudation and flattening of the caliceal urothelium, submucosal edema and congestion not seen in calyces subjected to low irrigant pressure. Four to six weeks later, there was a higher incidence of columnar metaplasia, subepithelial nests and pericalyceal vasculitis in calyces subjected to high pressure as compared with those subjected to low irrigant pressure. Acutely, renal tubules subjected to high irrigant pressure demonstrated marked vacuolization and degeneration, whereas tubules subjected to low pressure appeared normal. At 4 to 6 weeks, focal scarring was seen in 5 of 7 kidneys subjected to high irrigant pressure, whereas no scarring was noted in all 6 kidneys subjected to low irrigant pressure.In summary, it seems that hydraulic intramural ureteral dilation is less traumatic than mechanical modes of dilation with less potential for ureteral scarring and stricture. Prolonged exposure of the minipig kidney to high RPP (>200cm. H20) during UPS resulted in renal scarring and inflammation not seen following low pressure (<120cm. H20) irrigation. Because the human kidney is anatomically and physiologically similar to the minipig kidney, it may respond to high renal pelvic pressures in a similar fashion.