Guidewire type and prior use affects ureteral stent insertion force.

INTRODUCTION: To improve the success rate and safety of ureteral stent insertion, we sought to identify the effect of guidewire type and prior use upon the force needed to advance a 6Fr ureteral stent over various guidewires. MATERIALS AND METHODS: Two-hundred forty stent insertion trials were performed in an ex vivo porcine urinary tract model. Ten trials were randomly performed over 12 new and 12 used guidewires. For each trial, the force required to advance a 6Fr Cook double-pigtail ureteral stent was recorded. Guidewires included the Olympus Glidewire, Cook Fixed Core, and Boston Scientific Amplatz Super Stiff, Sensor, ZIPwire, and Zebra wire. RESULTS: The mean force needed for stent advancement was the lowest for the new Glidewire (0.18N) and ZIPwire (0.22N), with no significant difference to each other (p = 0.90). The following new wires required increasingly higher stent insertion forces compared to the Glidewire, the Zebra (0.60N; p < 0.01), Fixed Core (1.25N; p < 0.01), Sensor (1.43N; p < 0.01), and Amplatz Super Stiff wires (2.03N; p < 0.01). There was no statistical difference between new and used Glidewires (0.18N versus 0.29N; p = 0.14) and Zebra wires (0.59N versus 0.60N; p = 0.88). All other used wires required a significantly greater advancement force than their new counterparts (p < 0.01). CONCLUSIONS: For the same stent, the force required for stent advancement varies greatly between guidewire types. In addition, used guidewires typically required more force compared to new guidewires. In long or difficult cases, switching to a new wire may improve the ease of stent placement and reduce potential complications.

High-Frequency Dusting Versus Conventional Holmium Laser Lithotripsy for Intrarenal and Ureteral Calculi.

INTRODUCTION: The efficiency of holmium laser lithotripsy for urolithiasis depends upon several factors, including laser pulse energy and frequency and stone composition and retropulsion. This study investigates the complex interplay between these factors and quantifies lithotripsy efficiency using different laser settings in a benchtop kidney and ureter model. MATERIALS AND METHODS: In vitro caliceal and ex vivo porcine ureteral models were constructed. Calcium oxalate monohydrate stones were fragmented using a 200-µm laser fiber. In the caliceal model, stone fragmentation and vaporization rates at settings of 0.6 J/5 Hz, 0.2 J/15 Hz, and 0.2 J/50 Hz were compared. In the ureteral model, fragmentation time, retropulsion rate, fragmentation rate, and fragmented stone weight were compared at settings of 0.6 J/5 Hz and 0.2 J/15 Hz. Retropulsive forces generated at 0.6 J/5 Hz, 0.2 J/15 Hz, and 0.2 J/50 Hz settings were compared. Analysis was performed using Student's t-test and one-way ANOVA. RESULTS: In the caliceal model, the 0.6 J/5 Hz setting fragmented and vaporized stones at a higher rate than the 0.2 J/15 Hz setting (0.072 vs. 0.049 mg/s; p < 0.001). However, when the 0.2 J energy setting was combined with the 50 Hz frequency, the fragmentation rate (0.069 mg/s) was similar to the fragmentation rate at 0.6 J/5 Hz (0.072 mg/s; p = 0.677). In the ureteral model, the 0.6 J/5 Hz setting produced higher fragmentation rates (0.089 vs. 0.049 mg/s; p < 0.001), but resulted in significantly lower fragmented stone weight overall (16.815 vs. 25.485 mg; p = 0.009) due to higher retropulsion rates (0.732 vs. 0.213 mm/s; p < 0.001). Retropulsive forces decreased significantly when pulse energy decreased from 0.6 to 0.2 J (0.907 vs. 0.223 N; p < 0.001). Frequency did not affect retropulsive force at 15 and 50 Hz settings (0.223 vs. 0.288 N; p = 0.509). CONCLUSIONS: Laser lithotripsy of calcium oxalate monohydrate stones in the ureter should be performed using the low-energy, moderate-frequency dusting setting to minimize retropulsion and maximize efficiency. In the renal calix, the low-energy high-frequency setting performed similarly to the high-energy low-frequency setting.

Kidney, Ureter, and Bladder (KUB): A Novel Grading System for Encrusted Ureteral Stents.

OBJECTIVE: To introduce a grading system (kidney, ureter, and bladder [KUB]) to identify encrusted stents that may require multiple surgeries, multimodal surgery, and operative time > 180 minutes for successful removal. METHODS: One hundred ten retained encrusted ureteral stents were retrospectively scored using the KUB grading system and this score was correlated with operative time, need for multiple surgeries or multimodal surgery, and stone-free rate. Data analysis was performed with t test, Mann-Whitney U test, and chi-square tests. A P value of <0.05 was considered statistically significant. RESULTS: Average indwelling stent time was 17.2 months (0.7-139.0). There were 83.6% of stents removed in a single surgery, with 63.0% of these requiring multimodal surgery. K score ≥ 3 was associated with multiple surgeries (odds ratio [OR] 3.59, P = .006), multimodal surgery (OR 2.44, P = .04), operative time > 180 minutes (OR 3.80, P = .001), and lower stone-free rate (OR 0.23, P = .02). U score ≥ 3 was associated with operative time > 180 minutes (OR 3.28, P = .003). B score ≥ 3 was associated with lower stone-free rate (OR 0.23, P = .020). Total score ≥ 9 was associated with multiple surgeries (OR 4.19, P = .001), operative time > 180 minutes (OR 3.45, P = .002), and lower stone-free rate (OR 0.13, P = .001). CONCLUSION: The KUB system identifies stents at risk for requiring multiple surgeries, multimodal surgery, and operative time > 180 minutes. It also correlates with stone-free rate. This grading system can help surgeons manage patient expectations and predict surgical complexity.

Direct Endoscopic Visualization Combined with Ultrasound Guided Access during Percutaneous Nephrolithotomy: A Feasibility Study and Comparison to a Conventional Cohort.

PURPOSE: Percutaneous nephrolithotomy access may be technically challenging and result in significant radiation exposure. In an attempt to reduce percutaneous nephrolithotomy radiation exposure, a novel technique combining ultrasound and direct ureteroscopic visualization was developed and reviewed. MATERIALS AND METHODS: Ureteroscopy without fluoroscopy was used to determine the optimal calyx for access, which was punctured with a Chiba needle under percutaneous ultrasound guidance. Next a wire was passed into the collecting system and ureteroscopically pulled into the ureter using a basket. Tract dilation and sheath and nephrostomy tube placement were performed under direct ureteroscopic visualization. Twenty consecutive patients undergoing this novel technique were reviewed and compared to 20 matched patients treated with conventional percutaneous nephrolithotomy. Mann-Whitney U and Pearson chi-square tests were used for comparisons with p <0.05 considered significant. RESULTS: Using this novel technique mean fluoroscopy access time was 3.5 seconds (range 0 to 27.9) and mean total fluoroscopic time was 8.8 seconds (range 0 to 47.1). Mean operative time was 232 minutes (range 87 to 533), estimated blood loss was 111 ml, the stone-free rate was 65% and the complication rate was 25%. Compared to 20 matched conventional percutaneous nephrolithotomy cases, there was no difference in operative time (p=0.76), estimated blood loss (p=0.64), stone-free rate (p=0.50) or complications (p=1.00). However, the novel technique resulted in a significant reduction in fluoroscopy access time (3.5 vs 915.5 seconds, p <0.001) and total fluoroscopy time (8.8 vs 1,028.7 seconds, p <0.001). CONCLUSIONS: This study demonstrates the feasibility of combined ultrasound and ureteroscopic assisted access for percutaneous nephrolithotomy. A greater than 99% reduction in fluoroscopy time was achieved using this technique.

Percutaneous Externally Assembled Laparoscopic Instruments: Creation of a New Surgical Paradigm.

OBJECTIVES: Laparoendoscopic single-site surgery (LESS) and natural orifice transluminal endoscopic surgery (NOTES) produce excellent cosmetic outcomes, but are technically challenging. The objective of this study was to test the functionality and feasibility of a novel minimally invasive surgical paradigm, which maintains triangulation but uses special externally assembled instruments to minimize the postoperative cosmetic impact. METHODS: Percutaneous Externally Assembled Laparoscopic (PEAL) instruments have specialized 2.96-mm shafts with interchangeable 5-mm working tips that are assembled externally. First, 5-mm laparoscopic, PEAL, and 2-mm needlescopic instruments were tested to determine piercing force on fresh human cadaver organs. In a bench-top study, 20 subjects assembled and used PEAL instruments in five different skills tests that were also compared with the same tasks using conventional laparoscopic instruments. Finally, PEAL instrument functionality was tested in a four-porcine nephrectomy feasibility study. RESULTS: PEAL (2.80 lbF) and 5-mm laparoscopic instruments (2.28 lbF) had a significantly higher mean organ piercing perforation force compared with needlescopic instruments (1.39 lbF, p < 0.05). Average assembly time of PEAL instruments was 31.08 seconds (range: 19.83-43.85). There were no significant differences in the amount of time needed for completion of the bench-top tasks between laparoscopic and PEAL instruments (p > 0.05 for all tasks). Four-porcine PEAL nephrectomies were completed with no complications and minimal blood loss (mean 7.5 mL). Mean operative time was 98.25 minutes (range 79-116). CONCLUSION: PEAL tools are easily assembled, have similar safety and efficacy compared with standard laparoscopic tools, and are less likely to injure organs compared with needlescopic instruments. They function well during laparoscopic nephrectomy and may decrease the invasiveness of conventional laparoscopic instrumentation.

Renal Vascular Clamp Placement: A Potential Cause of Incomplete Hilar Control during Partial Nephrectomy.

PURPOSE: Previous benchtop studies have shown that robotic bulldog clamps provide incomplete vascular control of a Penrose drain. We determined the efficacy of robotic and laparoscopic bulldog clamps to ensure hemostasis on the human renal artery. The effect of clamp position on vascular control was also examined. MATERIALS AND METHODS: Fresh human cadaveric renal arteries were used to determine the leak point pressure of 7 bulldog clamps from a total of 3 manufacturers. Five trials were performed per clamp at 4 locations, including the fulcrum, proximal, middle and distal positions. Comparison was done using the Kruskal-Wallis test with p <0.05 considered significant. RESULTS: None of the bulldog clamps leaked at a pressure less than 215 mm Hg when applied at the proximal, middle or distal position. In general leak point pressure decreased as the artery was positioned more distal along the clamp. The exception was when the vessel was placed at the fulcrum position. At that position 80% to 100% of trials with the Klein laparoscopic, 100% with the Klein robotic (Klein Robotic, San Antonio, Texas) and 60% to 80% with the Scanlan robotic (Scanlan International, Saint Paul, Minnesota) clamp leaked at pressure below 215 mm Hg. CONCLUSIONS: Each vascular clamp adequately occluded flow at physiological pressure when placed at the proximal, middle or distal position. Furthermore, these results demonstrate that there is leakage at physiological pressure when the artery is placed at the fulcrum of certain clamp types. These results suggest that applying a bulldog clamp at the fulcrum could potentially lead to inadequate vessel occlusion and intraoperative bleeding.

Techniques for Minimizing Radiation Exposure During Evaluation, Surgical Treatment, and Follow-up of Urinary Lithiasis.

Patients receive significant radiation exposure during the diagnosis, treatment, and follow-up of urinary stone disease. This radiation exposure may result in patient harm and is believed to contribute to the risk for malignancy. This review will present current information to allow surgeons to optimize their diagnostic, treatment, and follow-up regimens to allow optimal care of stone disease patients at the lowest radiation dose possible.

Ureteroscopy Without Fluoroscopy: A Feasibility Study and Comparison with Conventional Ureteroscopy.

INTRODUCTION AND OBJECTIVES: Patients with urolithiasis are exposed to significant amounts of radiation during their initial work-up, surgical treatment, and follow-up. The purpose of this study was to determine the feasibility of performing ureteroscopy without fluoroscopy. In addition, we compared patients treated using a completely fluoroless ureteroscopic technique with a cohort of conventional ureteroscopies performed using fluoroscopy. MATERIALS AND METHODS: A retrospective review of 50 consecutive patients undergoing fluoroless ureteroscopy was performed. These procedures were performed by inserting guidewires and instruments using tactile feedback, direct visualization, and external visual cues to substitute for fluoroscopy. In addition, this cohort was compared with 50 conventional, fluoroscopy-guided ureteroscopies performed in the same time period. RESULTS: Fifty ureteroscopies were performed without image guidance. For this cohort, the mean operative time was 59.2 minutes, overall stone burden was 91.53 mm(2), complication rate was 4%, and repeat procedure rate was 8%. Compared with conventional ureteroscopy the fluoroless ureteroscopy patients had a larger stone burden (p=0.042; 91.53 vs 56.58 mm(2)), but similar age, gender, American Society of Anesthesiologists (ASA) score, body-mass index, operative time, complication rate, and repeat procedure rate. CONCLUSIONS: This study demonstrates the feasibility and efficacy of the completely fluoroless ureteroscopic treatment of calculi throughout the entire upper urinary tract while completely removing radiation exposure to the patients and staff. Although this fluoroless technique may be most applicable in patients at highest risk for radiation exposure, such as pregnant women, children, and recurrent stone formers, it offers an alternative for reduction of radiation in all patients.