Histotripsy Treatment of Benign Prostatic Enlargement Using the Vortx Rx System: Initial Human Safety and Efficacy Outcomes.

OBJECTIVE: To assess clinical safety (primary) and efficacy (secondary) of histotripsy for treatment of symptomatic benign prostatic enlargement in a first-in human study. METHODS: Twenty-five male subjects with moderate to severe lower urinary tract symptoms, prostate size between 30 and 80 g, and no evidence of prostate cancer were enrolled at 2 sites in a prospective, single-arm study. Treatment consisted of acoustic energy delivery through the perineum with integrated real-time transrectal ultrasound monitoring using the Vortx Rx system. Follow-up evaluations were performed on postoperative day 1 and 1, 3, and 6 months. RESULTS: Twenty-five men underwent histotripsy treatment with no serious intraoperative adverse events. Postoperatively, 3 cases of transient urinary retention (<3 days), 1 case of urinary retention (8 days in duration, defined as serious), a minor anal abrasion, and microscopic hematuria were considered device-related adverse events. Debulking of targeted prostate tissue was not observed with transrectal ultrasound imaging or with endoscopic visualization, and clinically meaningful improvement in uroflow or postvoid residual urine (PVR) did not occur. However, International Prostate Symptom Score improvement at 1 month was 12.5 (52.4%) ± 6.6 points (n = 25), at 3 months was 11.9 (50.8%) ± 7.6 points (n = 24), and at 6 months was 10.4 (44.0%) ± 7.6 points (n = 24) (P <.001). CONCLUSION: Prostate histotripsy was safe and well tolerated in this pilot human trial with improvement in lower urinary tract symptoms.

New metallic ureteral stents: improved tensile strength and resistance to extrinsic compression.

BACKGROUND AND PURPOSE: Extrinsic ureteral compression challenges a ureteral stent's ability to facilitate urinary drainage and to protect the kidney. Our purpose was to evaluate the performance of new metallic coil-based ureteral stents in terms of tensile strength and radial compression force. MATERIALS AND METHODS: Three stent designs tested from Prosurg Inc included Passage 7.0F, Snake 6.0F, and Snake 7.0F with the straight section covered with a biocompatible polymer tubing. A MTS Microbionix Testing System using Testworks II software, vibration isolation table, and a 5-N load cell were used to measure tensile and compressive strength. Stents were placed in hydraulic grips and stretched at a rate of 5 mm/s for 1 second under uniaxial tension. Extrinsic compression was exerted in 0.1-mm increments to maximum compression. The Young Modulus, E, was calculated from each trial using engineering stress. Data were analyzed using Mann-Whitney and t tests. RESULTS: The Passage, Snake 6F, and Snake 7F stents had tensile strengths of 27±3, 5±0.1, and 73±26 kPa, respectively. Mann-Whitney tests show statistically significant difference between stents (P<0.05). Elastic modulus needed to cause extrinsic compression was highest for Snake 6F (145,842±14332 Pa) compared with that of Passage (124,999±3182 Pa) and Snake 7F (126,132±19316 Pa), (P<0.05). CONCLUSION: The Snake 6F stent had the lowest tensile strength and was least resistant to extrinsic compression. The Snake 7F had the highest tensile strength and was most resistant to extrinsic compression. All three stents are more resistant to extrinsic compression than the Applied Silhouette or Cook Resonance, yet have lower tensile strengths.

Systematic evaluation of a novel foot-pump ureteroscopic irrigation system.

INTRODUCTION: To evaluate forces exerted on a stone with different ureteroscopic irrigation systems. METHODS: A 3 mm steel simulated stone was welded to a 3F stone basket and inserted into the working channel of a 4.5F Wolf semirigid ureteroscope. The basket shaft was attached to a 50 g load cell. The urterescope was placed in a ureteral model (14F silicon tubing). Simulated blood (McCormick™ Red Dye, 1 dye drop/15 mL H(2)O) was dripped adjacent to the stone at 12 drops/min. Endoirrigation devices were attached to the ureterscope and irrigation was applied at a rate sufficient to maintain visualization of the stone. Force on the stone was measured with the following endoirrigation systems: Boston Scientific™ Single-Action-Pump System (SAP) hand-pump and NuVista Medical™ Flo-Assist(®) foot-pump. RESULTS: No significant difference (p=0.19) in the number of pumps required to maintain a clear endoscopic field was found between the SAP (0.20±0.075/second) and Flo-Assist device (0.25±0.056/second). The pump duration of the Flo-Assist was found to be less (1.12±0.40 seconds) than the SAP (1.35±0.31 seconds), but not significantly different (p=0.24). The average maximum impulse was significantly lower (p=0.0002) for the SAP (8.34×10(-5) Ns) than the Flo-Assist (1.96×10(-3) Ns). Total maximum impulse (2.02×10(-5) Ns) for the SAP and total average impulse (5.51×10(-6) Ns) were found to be lower than the Flo-Assist device. The Flo-Assist had a total maximum impulse of 4.49×10(-4) Ns and total average impulse of 8.85×10(-6) Ns, however, these differences were not statistically significant. CONCLUSION: The hand-pump (SAP) and foot-pump (Flo-Assist) irrigation devices tested require comparable amounts of pumps for similar durations of time to maintain endoscopic visualization. Overall, the SAP device exerts less average maximum force on the stone than the Flo-Assist device.

Systematic evaluation of hybrid guidewires: shaft stiffness, lubricity, and tip configuration.

OBJECTIVE: To conduct a comparison of physical and mechanical properties for 5 commonly used guidewires to assess advantages of wires for specific applications. METHODS: Tests on guidewires (0.035" diameter; straight, flexible tip) included tip bending, shaft buckling, lubricity, and tip puncture measurements. Guidewires included 2 hybrid wires: the U-Nite (Bard Urological, Covington, GA) and the Sensor (Boston Scientific, Natick, MA). Our aim was to compare the stiffness of these hybrid wires with the standard Amplatz SuperStiff (Boston Scientific). Our second aim was to compare the hydrophilic tip of the hybrid wires with 2 traditional hydrophilic guidewires: the NiCore (Bard Urological) and RadiFocus glidewire (Boston Scientific). RESULTS: The Amplatz SuperStiff had a significantly stiffer shaft than either hybrid wire, with a buckling force of 1.81 ± 0.91 N compared with the Sensor (0.80 ± 0.29 N, P = .0002) and the U-Nite (0.77 ± 0.29 N, P < .0001). The Boston Scientific guidewire tips were less stiff than the Bard guidewires, requiring up to 48% less force to bend when encountering resistance (P < .0001). The U-Nite had the highest lubricity (0.09 ± 0.03 N, P < .0001) and roundest tip of all the guidewires tested. The RadiFocus required the greatest puncture force (1.80 ± 0.27 N, P < .0001) of all the guidewires tested. CONCLUSION: Hybrid wires offer a combination of a stiffer shaft and hydrophilic tip. The Amplatz SuperStiff remains the stiffest wire and as such is best suited for placement of ureteral access sheaths or larger stents. The Boston Scientific wires require less force to "bend" around a point of obstruction compared with the Bard wires. The Boston Scientific RadiFocus requires the greatest force to puncture aluminum foil.

Small-diameter nitinol stone baskets: radial dilation force and dynamics of opening.

PURPOSE: To evaluate the radial dilation force and basket opening dynamics of three small (<1.5F) stone baskets. MATERIALS AND METHODS: Boston Scientific OptiFlex (1.3F), Cook N-Circle Nitinol Tipless Stone Extractor (1.5F), and Sacred Heart Medical Halo (1.5F) baskets were tested for radial dilation force in 10 repetitions using a floating block atop a stationary block secured to a digital scale. The floating block, attached to a plastic frame and base, pressed down on the scale to measure the radial dilation of the open basket while being passed through the cylindrical opening between the blocks. These same baskets were tested in triplicate for basket width in 0.5- to 2-mm length increments using a mechanical caliper under optical light microscope visualization to evaluate the linearity of basket opening and length at which target basket width (5 mm) was reached. RESULTS: The Sacred Heart Medical Halo had the best radial dilation (2.97 ± 0.22 g), followed by the Cook N-Circle (1.29 ± 0.04 g), and finally Boston Scientific OptiFlex (1.19 ± 0.12 g). The N-Circle was the only basket to exhibit linear opening, while the Halo exhibited an exponential curve. The OptiFlex exhibited a polynomial curve, with linear opening across the midrange of the basket length. From these curve equations, the target basket width (5 mm) was calculated. The N-Circle and the OptiFlex reached the target basket width at a basket length of 9.4 mm and 9.6 mm, respectively. The Halo reached the target basket width at a basket length of 11.5 mm. CONCLUSIONS: The radial dilation force differs significantly among commercial baskets and may affect ureteral stone extraction. Linear basket opening may provide the physician more control in stone retrieval.

Comparison of small diameter stone baskets in an in vitro caliceal and ureteral model.

BACKGROUND AND PURPOSE: Three small diameter (<1.5F) stone baskets have recently been introduced. Our objective was to evaluate the stone capture rate of these baskets in an in vitro ureteral model and an in vitro caliceal model using novice, resident, and expert operators. MATERIALS AND METHODS: Sacred Heart Medical Halo™ (1.5F), Cook N-Circle(®) Nitinol Tipless Stone Extractor (1.5F), and Boston Scientific OptiFlex(®) (1.3F) stone baskets were tested in an in vitro ureteral and a caliceal model by three novices, three residents, and three experts. The caliceal model consisted of a 7-cm length of 10-mm O.D. plastic tubing with a convex base. Each operator was timed during removal of a 3-mm calculus from each model with three repetitions for each basket. Data were analyzed by analysis of variance single factor tests and t tests assuming unequal variances. RESULTS: In the ureteral model, the Halo had the fastest average rate of stone extraction for experts and novices (0:02 ± 0:01 and 0:08 ± 0:04 min, respectively), as well as the overall fastest average stone extraction rate (0:08 ± 0:06 min). No statistical significant differences in extraction times between baskets were identified in the resident group. In the novice group, the Halo stone extraction rate was significantly faster than the OptiFlex (P=0.029). In the expert group, the OptiFlex had statistically significant slower average extraction rates compared with the Halo (P=0.005) and the N-Circle (P=0.017). In the caliceal model, no statistically significant differences were noted. CONCLUSION: While no significant differences were noted in extraction times for the caliceal model, the extraction times for the ureteral model were slowest with the OptiFlex basket. Other variables important in selection of the appropriate basket include operator preference, clinical setting, and cost.

Resistance to extrinsic compression and maintenance of intraluminal flow in coil-reinforced stents (Silhouette Scaffold Device): an in vitro study.

INTRODUCTION: Stenting is the best approach to manage ureteral extrinsic compression and depends on intraluminal patency, which is mainly determined by cross-sectional stability. We evaluated the resistance to extrinsic compression of the Silhouette Scaffold Device and its ability to simultaneously maintain intraluminal flow. MATERIALS AND METHODS: Four 8 F Silhouette stents of different lengths were evaluated for radial compression and intraluminal flow by an MTS Micro Bionix Testing System using Testworks II software. Compression was exerted in 0.2 mm increment cycles until a maximum load cell of 5 N was reached. The Young's modulus, E, was calculated from each trial using engineering stress. Flow rates were compared with the 10.2 F Cook Amplatz. Analysis of variance was used to detect differences between Scaffold stents, and Student's t-test for differences between baseline flow rates. A level of significance of p < 0.05 was used. RESULTS: Cross-sectional area and E did not differ throughout different length Scaffold stents (average 28,856 +/- 2592; 95% confidence interval 27,447, 30,265; p = 0.426). The inner lumen of the 10.2 F Cook Amplatz was larger by 0.125 mm. Baseline flow rate of the Cook Amplatz was significantly higher than that of the Silhouette Scaffold (1.089 vs. 0.660 mL/second, p = 0.001), but the drop in the flow rate was four times faster for the Amplatz. CONCLUSION: The resistance of 8 F Silhouette Scaffold Device is extremely higher than that of previously tested stents, and it is uniform along the shaft and does not vary with length. The Cook Amplatz 10.2 F stent has higher flow at baseline and 2 mm compression, but its flow rate drops four times faster than the Silhouette Scaffold.

Ureteral obstruction: is the full metallic double-pigtail stent the way to go?

BACKGROUND: The Resonance metallic ureteral stent (Cook Medical, Bloomington, Indiana, USA) has been introduced for the management of extrinsic-etiology ureteral obstruction for time periods up to 12 mo. OBJECTIVE: The current study aims to determine short- and medium-term effectiveness of the Resonance stent in malignant and benign ureteral obstruction. DESIGN, SETTING, AND PARTICIPANTS: In total, 50 patients with extrinsic malignant obstruction (n=25), benign ureteral obstruction (n=18), and previously obstructed mesh metal stents (n=7) were prospectively evaluated. INTERVENTION: All patients were treated by Resonance stent insertion. Twenty stents were inserted in antegrade fashion, and the remaining stents were inserted in a retrograde approach. No patient dropped out of the study. The follow-up evaluation included biochemical and imaging modalities. MEASUREMENTS: We evaluated the technical success rate, stricture patency rate, complications, and the presence and type of encrustation. RESULTS AND LIMITATIONS: The technical success rate of transversal and stenting of the strictures was 100%. In 19 patients, balloon dilatation was performed prior to stenting. The mean follow-up period was 8.5 mo. The stricture patency rate in patients with extrinsic malignant ureteral obstruction was 100% and in patients with benign ureteral obstruction 44%. Failure of Resonance stents in all cases of obstructed metal stents was observed shortly after the procedure (2-12 d). In nine cases, stent exchange was demanding. Encrustation was present in 12 out of 54 stents. CONCLUSIONS: The Resonance stent provides safe and sufficient management of malignant extrinsic ureteral obstruction. Resonance stent use in benign disease needs further evaluation, considering the untoward results of the present study.

Next generation biodegradable ureteral stent in a yucatan pig model.

PURPOSE: Ureteral stents are commonly used to facilitate kidney drainage but they may produce significant stent symptoms and morbidity, and require a secondary procedure for removal. Previous biodegradable stents showed bio-incompatibility or inconsistent degradation, requiring extra procedures to remove undegraded stent fragments. We previously reported a first generation biodegradable stent composed of suture-like material that required placement through the lumen of a sheath and degraded by 10 weeks. We now report second and third generation biodegradable stents that degrade more rapidly and can be placed directly over a polytetrafluoroethylene guidewire. MATERIALS AND METHODS: Two groups of 16 Yucatan pigs each were unilaterally stented endoscopically with a control nondegradable (biostable) stent or a second generation degradable Uriprene stent. Blood studies, renal ultrasound and excretory urography were done throughout the study to determine renal function, hydronephrosis and stent degradation. Genitourinary organs were harvested at necropsy for pathological analysis. A third generation stent designed to improve degradation time was bilaterally implanted endoscopically into 4 Yorkshire Farm pigs (total of 8 stents), followed by excretory urography weekly to assess degradation and kidney function. Biomaterial parameters were tested. RESULTS: Second generation stents began degrading at 2 weeks and were completely degraded by 10 weeks. All third generation stents were degraded by 4 weeks. Hydronephrosis was considerably less in the Uriprene group than in control biostable stented kidneys. Biostable stented ureters showed an average higher degree of inflammation, uropathy and nephropathy. Physical characteristics indicate that Uriprene stents are significantly more resistant to stent compression and have markedly higher tensile strength and coil strength comparable to that of other commercially available plastic stents. CONCLUSIONS: Our study confirms that Uriprene stents are biocompatible and provide good renal drainage. They hold promise for decreasing the need for a secondary procedure and stent related morbidity, such as infection and irritative symptoms.

Uropathogen interaction with the surface of urological stents using different surface properties.

PURPOSE: Ureteral stents commonly become infected or encrusted. Various coatings have been developed to decrease bacterial adherence. To our knowledge there has been no in vitro testing of coating with heparin to date. We determined the effects of heparin coating on bacterial adherence of common uropathogens and physical stent properties. MATERIALS AND METHODS: Heparin coated Radiance ureteral stents (Cook) and noncoated Endo-Sof control stents were tested against triclosan eluting Triumph(R) stents and noneluting Polaris control stents for adherence of Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Staphylococcus aureus and Pseudomonas aeruginosa for 7 days. Adherent bacteria were determined and biofilms were visualized using fluorescent dyes. Radial, tensile and coil strength of the Radiance and Polaris stents was compared to determine the effect of heparin coating on physical stent characteristics. RESULTS: Heparin coating did not decrease bacterial adhesion compared to its control. E. coli adhesion was limited by all stents tested. The Polaris stent showed significantly greater resistance to bacterial adherence for Klebsiella, Pseudomonas and Enterococcus than the Endo-Sof and Radiance stents but was more susceptible to S. aureus adherence. The Triumph stent resisted all bacteria except Pseudomonas and Enterococcus. Mature biofilms were observed on all stents with lower viability on the Triumph stent. Radiance stents showed higher tensile and lower compression strength than its control. CONCLUSIONS: Heparin coating does not decrease bacterial adherence to ureteral stents. Drug eluting antimicrobials have an inhibitory effect on bacterial adherence and the Polaris stent showed the least bacterial adherence of the nondrug eluting ureteral stents tested.

Celecoxib in the management of acute renal colic: a randomized controlled clinical trial.

OBJECTIVES: To evaluate the efficacy of celecoxib as an analgesic and medical expulsive agent in acute renal colic. METHODS: A prospective randomized double-blind study was conducted on patients presenting with an obstructing ureteral calculus < 10 mm in largest diameter. Patients were randomized to 400 mg of celecoxib, followed by 200 mg every 12 hours for 10 days, or to placebo. Patients with a solitary kidney, renal insufficiency (CR > 1.8), urinary tract infection, or significant cardiovascular disease were excluded. RESULTS: A total of 57 patients provided consent of which 53 completed the study. Four patients were excluded from the analysis because of stone passage or withdrawal of consent before the first dose of study medication. No significant difference was noted in the spontaneous stone passage rate (celecoxib 55.2%, placebo 54.2%) and between celecoxib and placebo with regard to days to stone passage (7.0 vs 9.0, P = .6) or size of stone passed (3.9 vs 4.6 mm, P = .18). No significant difference was noted in pain analog scores (2.6 vs 3.5, P = .71) or narcotic doses (13.2 vs 13.6, P = .74). Furthermore, a 25% decrease in narcotic use (or 19 mg based on placebo mean) was outside the 80% one-sided confidence interval for the change in mean narcotic use between the 2 groups. Thus, it is unlikely (< 20%) that we missed a clinically significant beneficial effect of celecoxib on narcotic consumption because of sample size. CONCLUSIONS: Celecoxib does not facilitate stone passage or decrease narcotic requirements in patients with acute renal colic.

Foley catheter characteristics: predicting problems.

PURPOSE: To evaluate the physical properties of urethral catheters that are predictive of ease of placement and risk of urethral trauma: Stiffness, buckling, and friction forces. MATERIALS AND METHODS: Eleven Bard Lubri-Sil and 10 Kendall Dover 16F Foley catheters were tested using a linear motion stage driven by a stepper motor with a resolution of 5 microns/step or by hand. Force was measured at a sampling rate of 5 Hz with a Wagner FDIX digital force gauge. Friction force was measured by pulling each Foley catheter at a rate of 2.5 mm/s through a 15.6F hole drilled in 36-mm thick biologic material (Oscar Meyer Beef Light bologna 12 oz package). Ease of advancement was measured by the force necessary to maneuver a catheter around a 90-degree turn in a bulbar urethra modeled by 5/16 inch inner diameter silicone tubing and lubricant. Buckling forces were measured at the tip (8 mm), from the distal end of the balloon to the tip (30 mm), and along a 20 cm section of the shaft using the appropriate size force gauge. RESULTS: No significant difference was noted for friction force. The Kendall catheters (0.0686 +/- 0.102 lb(f)) took more force to advance around a 90-degree turn, compared with the Bard (0.602 +/- 0.110 lb(f), P = 0.003). Buckling force along the shaft and from the balloon to the tip was significantly greater for the Bard (0.051 +/- 0.02 lb(f), P < 0.001 and 0.892 +/- 0.166 lb(f), P < 0.001) compared with the Kendall (0.027 +/- 0.007 lb(f) and 0.803 +/- 0.129 lb(f)) catheters. Stiffness of the tip was significantly greater for the Kendall (2.644 +/- 0.552 lb(f), P < 0.001) compared with the Bard (2.101 +/- 0.437 lb(f)) Foley catheters. CONCLUSIONS: Traumatic catheterization is a major cause of urethral stricture. Catheter stiffness may increase the risk of urethral injury and subsequent stricture formation. Ease of advancement and tip stiffness may be important at predicting clinical performance of urethral catheters.

Radial dilation of nephrostomy balloons: a comparative analysis.

PURPOSE: The dynamics of percutaneous balloon expansion may differ with increasing extrinsic compressive forces and increasing inflation pressures. This study compares the ability of percutaneous balloons to expand under different radial constrictive forces. MATERIALS AND METHODS: Three 30F nephrostomy balloons were tested: Bard X-Force, Boston Scientific Microvasive Amplatz Tractmaster, and Cook Ultraxx. With a super stiff guidewire in place, the balloon tip was secured by elevated vice grips on either side of the balloon. A string was wrapped around the balloon center once, and incremental increases in load were added (2g, 42g, 82g, and 122g) to represent increasing extrinsic compression. The balloon was inflated with a contrast agent and circumference changes were measured at increments of 4 ATM, 10 ATM, and burst pressure. Balloons were tested in triplicate for each load. RESULTS: All balloons were unable to reach 90% of their expected diameter with larger constrictive loads (122g) at low (4 ATM) and nominal (10 ATM) inflation pressures. Only the Bard and Cook balloons reached at least 90% of the expected diameter with a coefficient of variance (CV) less than 10% at burst pressure under the larger constrictive load (122g), 94.3% +/- 6.7%, CV 7.1% and 96.3% +/- 2.9%, CV 3.0% respectively. All balloons performed well under low constriction forces and reached at least 80% of the expected diameter by 10 ATM under all constrictive loads. CONCLUSIONS: The Bard X-Force and Cook Ultraxx percutaneous nephrostomy balloons achieved the most reliable radial dilation against large constrictive forces simulating fascial or retroperitoneal scar tissue.

Radial dilation of nephrostomy balloons: a comparative analysis

PURPOSE: The dynamics of percutaneous balloon expansion may differ with increasing extrinsic compressive forces and increasing inflation pressures. This study compares the ability of percutaneous balloons to expand under different radial constrictive forces. MATERIALS AND METHODS: Three 30F nephrostomy balloons were tested: Bard X-Force™, Boston Scientific Microvasive Amplatz Tractmaster™, and Cook Ultraxx™. With a super stiff guidewire in place, the balloon tip was secured by elevated vice grips on either side of the balloon. A string was wrapped around the balloon center once, and incremental increases in load were added (2g, 42g, 82g, and 122g) to represent increasing extrinsic compression. The balloon was inflated with a contrast agent and circumference changes were measured at increments of 4 ATM, 10 ATM, and burst pressure. Balloons were tested in triplicate for each load. RESULTS: All balloons were unable to reach 90 percent of their expected diameter with larger constrictive loads (122g) at low (4 ATM) and nominal (10 ATM) inflation pressures. Only the Bard and Cook balloons reached at least 90 percent of the expected diameter with a coefficient of variance (CV) less than 10 percent at burst pressure under the larger constrictive load (122g), 94.3 percent ± 6.7 percent, CV 7.1 percent and 96.3 percent ± 2.9 percent, CV 3.0 percent respectively. All balloons performed well under low constriction forces and reached at least 80 percent of the expected diameter by 10 ATM under all constrictive loads. CONCLUSIONS: The Bard X-Force and Cook Ultraxx percutaneous nephrostomy balloons achieved the most reliable radial dilation against large constrictive forces simulating fascial or retroperitoneal scar tissue.

Evidence-based instrumentation for flexible ureteroscopy: a review.

Instrumentation is the key to success in endourology. Indeed, endourology could be redefined as "enginurology," as the marriage between engineering and urology, and developing instrumentation to improve patient outcomes is the key facilitator in the advancement of minimally-invasive techniques. This review article will identify the evidence base that supports our current recommendations for equipment used during ureteroscopy.

Alfuzosin stone expulsion therapy for distal ureteral calculi: a double-blind, placebo controlled study.

PURPOSE: We evaluated the efficacy of alfuzosin as medical expulsive therapy for distal ureteral stone passage. MATERIALS AND METHODS: A total of 76 patients with a distal ureteral calculus provided consent for the study. Patients were randomized between placebo and study medication, and investigators and patients were blinded to the randomization scheme. Followup was done on a weekly basis and continued until the patient was rendered stone-free. The patient blood pressure, discomfort level, stone position on imaging, number of remaining pills and any adverse events were assessed. Statistical analysis was performed with the Student t test with p <0.05 considered significant. RESULTS: The overall spontaneous stone passage rate was 75%, including 77.1% for placebo and 73.5% for alfuzosin (p = 0.83). Mean +/- SD time needed to pass the stone was 8.54 +/- 6.99 days for placebo vs 5.19 +/- 4.82 days for alfuzosin. (p = 0.003). There was no difference in the size or volume of stones that passed spontaneously between the placebo and alfuzosin arms, as measured on baseline computerized tomography (4.08 +/- 1.17 and 3.83 +/- 0.95 mm, p = 0.46) and by a digital caliper after stone expulsion (3.86 +/- 1.76 and 3.91 +/- 1.06 mm, respectively, p = 0.57). When comparing the improvement from the baseline pain score, the alfuzosin arm experienced a greater decrease in pain score in the days after the initial emergency department visit to the date of stone passage (p = 0.0005). CONCLUSIONS: Alfuzosin improves the patient discomfort associated with stone passage and decreases the time to distal ureteral stone passage but it does not increase the rate of spontaneous stone passage.

Impact of irrigation systems on stone migration.

PURPOSE: To evaluate forces exerted on a stone with different ureteroscopic irrigation systems that could impact stone migration during ureteroscopy. MATERIALS AND METHODS: A 3-mm steel simulated stone was welded to a 3F stone basket. The basket wire was then backloaded into the working channel of a 4.5F Wolf semirigid ureteroscope. The basket shaft was attached to a 50 g load cell. The ureteroscope was placed in a ureteral model (14F silicon tubing). Simulated blood was dripped adjacent to the stone at 12 drops/min. Endo-irrigation devices were attached to the ureteroscope, and irrigation was applied at a rate sufficient to maintain visualization of the stone. Force on the stone was measured with the following endo-irrigation systems: Gravity (183 cm H2O); pressurized irrigation (150 mm Hg, 300 mm Hg); Kosin Technology Universal Piggyback Irrigation System (UPIS) at gravity (183 cm H2O), 150 mm Hg and 300 mm Hg; EMS Medical Peditrol Foot Pump; Cook Ureteroscopy Irrigation System; ACMI Irri-Flo Irrigation Delivery System; and Boston Scientific Single-Action-Pump System (SAPS). RESULTS: SAP required the least number of pumps (0.35/sec) to maintain a clear endoscopic field while the Peditrol device required the most (1.88/sec). Pulse duration was longest for the ACMI (1.6 sec) and shortest for pressurized gravity and UPIS (<0.3 sec). The average total maximum impulse during a pump was significantly greater with the Cook (0.017 Ns) and ACMI (0.027 Ns) systems. On average, gravity-based systems applied the least amount of force, < or =0.0006 Ns, maximum impulse at any given time. CONCLUSIONS: Gravity-based systems exert less force than hand-held and foot-pump devices. Of the hand-held devices, the SAP exerted the least average maximum impulse on the stone.

Wire-based ureteral stents: impact on tensile strength and compression.

OBJECTIVES: To evaluate the performance of coil-based ureteral stents in terms of tensile strength and the radial compression force. METHODS: Three Cook Resonance (RES) metallic coil stents and three coil-reinforced Applied Medical Silhouette (SIL) ureteral stents were tested. An MTS MicroBionix Testing System using Testworks II software, vibration isolation table, and 5-N load cell were used to measure tensile and compressive strength. Stents were placed in hydraulic grips spaced 24 cm apart and stretched at a rate of 5 mm/s for 1 second under uniaxial tension. Extrinsic compression was exerted in 0.2-mm increments to maximum compression. The Young's modulus, E, was calculated for each trial using the engineering stress. Comparisons were made with the Cook C-flex, which in previous studies was shown to be stiffer and more resistant to compression than other traditional polymer stents. RESULTS: The RES and SIL stents demonstrated tensile strengths of 936 +/- 485 kPa and 770 +/- 82 kPa, respectively (P = 0.02). The elastic modulus required to cause extrinsic compression was lower for the RES (63,248 +/- 3218 Pa) than for the SIL (105,664 +/- 11,529 Pa) (P <0.001). Both stents were more resistant to stent compression than previously tested stents without coil-reinforcement, the strongest of which was the Cook C-Flex (E = 30,355 +/- 910 Pa; P <0.001). CONCLUSIONS: Both the Cook Resonance and Applied Medical Silhouette stents are more resistant to extrinsic stent compression than ureteral stents that are not coil-reinforced. The Cook Resonance has a higher tensile strength, whereas the Applied Medical Silhouette is more resistant to extrinsic compression.

Lateral deflection to release a stone: a simple method.

We describe and demonstrate a simple method to release a stone from a basket that emphasizes the importance of lateral deflection of the ureteroscope while opening and advancing the basket. This technique works well with semirigid and flexible ureteroscopes and all stone baskets, although some difficulty may be encountered with flat-wire baskets.

Physical characteristics of next-generation ureteral access sheaths: buckling and kinking.

OBJECTIVE: To evaluate physical characteristics of next-generation access sheaths that impact clinical failure. METHODS: Testing of the Cook Flexor (12/14 Fr x 35 cm, Cook), ACMI UroPass (12/14 Fr x 38 cm, ACMI), Bard Aquaguide (11/13 Fr x 35 cm Bard), and Boston Scientific Navigator (11/13 Fr x 36 cm BSCI-11, 13/15 Fr x 36 cm BSCI-13) was performed on a linear motion stage driven by a stepper motor with a resolution of 5 microm per step. Force was measured at a sampling rate of 5 Hz with a Wagner FDIX digital force gauge. Friction force was measured by pulling sheaths at 2.5 mm/s through 2.78 mm (8.3 Fr) holes drilled in 36 mm thick biologic material. Buckling force was measured as the force required to compress a 25-cm length of sheath in a clamp-clamp configuration during a 30 mm move. Kinking was measured as the slope of the force-deflection curve for wall compression over a deflection of 2 mm. RESULTS: No significant difference was noted in the friction force of the Cook (1.2 N), Bard (1.3 N), BSCI-11 (1.0 N), and BSCI-13 (1.0 N). Buckling force was significantly greater for the Cook (5.1 +/- 0.49 N) than the Bard (2.8 +/- 0.31 N), BSCI-11 (2.0 +/- 0.25 N), ACMI (3.2 +/- 0.33 N), and BSCI-13 (2.9 +/- 0.31 N). Kinking force was significantly lower with the Bard (9 N/mm) than the Cook (42 N/mm), BSCI-11 (41 N/mm), and BSCI-13 (30 N/mm), and significantly higher with the ACMI (83 N/mm). CONCLUSIONS: The Cook Flexor sheath is most resistant to buckling forces that would predict failure to advance up the ureter. The Bard Aquaglide is most likely to kink after removal of the inner obturator, whereas the ACMI Uropass is most resistant to kinking.