Seasonal variations in urinary calcium, volume, and vitamin d in kidney stone formers.

OBJECTIVES: To investigate the seasonal variations in urinary calcium, serum vitamin D, and urinary volume in patients with a history of nephrolithiasis. MATERIALS AND METHODS: Patients included were those who completed a 24-hour urine metabolic evaluation on two occasions; one in summer (June-Aug) and one in winter (Nov-Jan), and who had not started any medications or been instructed on dietary modifications in the interval between the two tests that may have impacted the results. Patients were excluded if they were on thiazide diuretics or were taking calcium and / or Vitamin D supplementation. Welch's t-test was used to compare the difference in average summer and winter values. Unpaired Student t-test was used to compare baseline parameters (age, BMI), and Paired Student t-test was used to compare average seasonal measurements in men vs. women. RESULTS: 136 patients were identified who were not taking calcium or vitamin D supplements or thiazide diuretics, and who were not instructed on dietary modifications in the interval between the two measured parameters. No significant differences were observed when comparing male to female baseline parameters of age or BMI (Table-1). Average 24-hour urine calcium was higher (226.60) in the winter than in summer (194.18) and was significant in males (p = 0.014) and females (p < 0.001). No significant seasonal difference was seen in 24-hour urine volume or serum vitamin D levels. CONCLUSIONS: Urinary calcium is higher in winter months compared to summer months. As such, tailoring medical preventative strategies to the time of year may be helpful.

Quality of life and urolithiasis: the patient - reported outcomes measurement information system (PROMIS).

BACKGROUND: With a high rate of recurrence, urolithiasis is a chronic disease that impacts quality of life. The Patient Reported Outcomes Measurement Information System is an NIH validated questionnaire to assess patient quality of life. We evaluated the impact of urolithiasis on quality of life using the NIH-sponsored PROMIS-43 questionnaire. MATERIALS AND METHODS: Patients reporting to the kidney stone clinic were interviewed to collect information on stone history and demographic information and were asked to complete the PROMIS-43 questionnaire. Quality of life scores were analyzed using gender and age matched groups for the general US population. Statistical comparisons were made based on demographic information and patient stone history. Statistical significance was P<0.05. RESULTS: 103 patients completed the survey. 36% of respondents were male, the average age of the group was 52 years old, with 58% primary income earners, and 35% primary caregivers. 7% had never passed a stone or had a procedure while 17% passed 10 or more stones in their lifetime. Overall, pain and physical function were worse in patients with urolithiasis. Primary income earners had better quality of life while primary caregivers and those with other chronic medical conditions were worse. Patients on dietary and medical therapy had better quality of life scores. CONCLUSIONS: Urolithiasis patients subjectively have worse pain and physical function than the general population. The impact of pain on quality of life was greatest in those patients who had more stone episodes, underscoring the importance of preventive measures. Stone prevention measures improve quality of life.

Dipstick Spot urine pH does not accurately represent 24 hour urine PH measured by an electrode.

OBJECTIVES: To determine whether spot urine pH measured by dipstick is an accurate representation of 24 hours urine pH measured by an electrode. MATERIALS AND METHODS: We retrospectively reviewed urine pH results of patients who presented to the urology stone clinic. For each patient we recorded the most recente pH result measured by dipstick from a spot urine sample that preceded the result of a 24-hour urine pH measured by the use of a pH electrode. Patients were excluded if there was a change in medications or dietary recommendations or if the two samples were more than 4 months apart. A difference of more than 0.5 pH was considered na inaccurate result. RESULTS: A total 600 patients were retrospectively reviewed for the pH results. The mean difference in pH between spot urine value and the 24 hours collection values was 0.52±0.45 pH. Higher pH was associated with lower accuracy (p<0.001). The accuracy of spot urine samples to predict 24-hour pH values of <5.5 was 68.9%, 68.2% for 5.5 to 6.5 and 35% for >6.5. Samples taken more than 75 days apart had only 49% the accuracy of more recent samples (p<0.002). The overall accuracy is lower than 80% (p<0.001). Influence of diurnal variation was not significant (p=0.588). CONCLUSIONS: Spot urine pH by dipstick is not an accurate method for evaluation of the patients with urolithiasis. Patients with alkaline urine are more prone to error with reliance on spot urine pH.

Concurrent stone stabilization improves ultrasonic and pneumatic efficacy during cystolithopaxy: an in vitro analysis.

OBJECTIVE: To identify whether stabilization of larger bladder stones would improve the efficacy of combination (ultrasonic/pneumatic) lithotripsy in a phantom bladder stone model for percutaneous cystolithopaxy. MATERIALS AND METHODS: Using 1cm phantom Bego stones, a spherical model bladder was used to simulate percutaneous bladder access. A UroNet (US Endoscopy, USA) was placed alongside a Swiss Lithoclast probe through the working channel of a Storz 26Fr rigid nephroscope. Using a 30Fr working sheath, the stone was captured, and fragmented for 60 seconds. Resulting fragments and irrigation were filtered through a 1mm strainer, and recorded. Five trials were performed with and without the UN. Durability was then assessed by measuring net defects, and residual grasp strength of each instrument. Descriptive statistics (mean, standard deviations) were used to summarize the data, and Student's t-tests (alpha < 0.05) were used to compare trials. RESULTS: The mean time to stone capture was 12s (8-45s). After fragmentation with UN stabilization, there were significant improvements in the amount of residual stone (22% dry weight reduction vs 8.1% without UN, p < 0.001), number of fragments (17.5 vs 5.0 frag/stone, p=0.0029), and fragment size (3.6mm vs. 7.05 mm, p=0.035). Mesh defects were noted in all nets, ranging from 2-14 mm, though all but one net retained their original grip strength (36.8N). CONCLUSIONS: Bladder stone stabilization improved fragmentation when used in conjunction with ultrasonic/pneumatic lithotripsy. However, due to limitations in maneuverability and durability of the UN, other tools need to identified for this indication.

Dyslipidemia and kidney stone risk.

PURPOSE: We studied the impact of dyslipidemia on 24-hour urinalysis and stone composition. MATERIALS AND METHODS: We retrospectively identified patients with nephrolithiasis who underwent 24-hour urinalysis and lipid profile evaluation within 3 months. Patients were divided into groups based on total cholesterol, high density lipoprotein, nonhigh density lipoprotein and triglycerides. The groups were compared based on demographic data, diabetes, hypertension and each component of 24-hour urinalysis and stone composition. Multivariate analysis and linear regression were performed to control for potential confounders, including age, gender, body mass index, diabetes and hypertension. RESULTS: A total of 2,442 patients with a mean age of 51.1 years were included in study. On multivariate analysis patients with high total cholesterol had significantly higher urinary potassium and calcium, those with low high density lipoprotein or high triglycerides had significantly higher urinary sodium, oxalate and uric acid with lower pH, and those with high nonhigh density lipoprotein had higher urinary sodium and uric acid. Regarding stone composition, high total cholesterol and triglycerides were significantly associated with a higher uric acid stone rate (p = 0.006 and <0.001, respectively). Linear regression showed a significant association of nonhigh density lipoprotein with higher urinary sodium (p = 0.011) and uric acid (p <0.001) as well as triglycerides and higher uric acid (p = 0.017), and lower urinary pH (p = 0.005). CONCLUSIONS: There is a link between dyslipidemia and kidney stone risk that is independent of other components of metabolic syndrome such as diabetes and obesity. Specific alterations in the patient lipid profiles may portend unique aberrations in urine physicochemistry and stone risk.

Gout, stone composition and urinary stone risk: a matched case comparative study.

PURPOSE: We established the most common stone composition, and serum and urinary biochemical features in patients with gout and urolithiasis. MATERIALS AND METHODS: We retrospectively searched for the records of patients diagnosed with gout among all those in our stone registry. A matched case cohort of stone formers was generated from our registry who had the same age, gender and body mass index. Primary end points were baseline 24-hour urinary metabolic panels and stone composition. Medications were considered. Groups were compared using the Student t and chi-square/Fisher exact tests with significance considered at p <0.05. RESULTS: For stone panel evaluation 181 patients met our inclusion criteria. There was no significant difference in 24-hour uric acid between the nongout and gout cohorts but hyperoxaluria was more common in patients with gout (74% vs 61%, p = 0.009). For stone composition analysis 393 patients were included. The gout cohort had lower calcium oxalate monohydrate (39.4% vs 54.7%), calcium oxalate dihydrate (6.0% vs 11.2%) and calcium phosphate (9.6% vs 14.1%) but higher uric acid (42.7% vs 18.2%, each p <0.001). Pure uric acid stones were more common in patients with gout (52.2% vs 22.3%, p <0.001), while calcium oxalate monohydrate (45.2% vs 68.6%, p <0.001), calcium oxalate dihydrate (0.6% vs 3.5%, p = 0.017) and calcium phosphate (1.6% vs 4.9%, p = 0.033) were more common in nongout cases. Patients with gout who were on allopurinol had fewer pure uric acid stones (30.4% vs 56.4%) and more calcium oxalate monohydrate stones (69.6% vs 40.7%, each p <0.001) than those without medication. CONCLUSIONS: Uric acid stones are the most common pure stone composition in patients with gout but 48% have nonuric acid stones. Allopurinol changes the stone composition distribution in patients with gout to a pattern similar to that in stone formers without gout.

Does stone entrapment with ″Uro-Net″ improve Ho:YAG laser lithotripsy efficiency in percutaneous nephrolithotomy and cystolithopaxy?: an in vitro study.

PURPOSE: to test the effect of stone entrapment on laser lithotripsy efficiency. MATERIALS AND METHODS: Spherical stone phantoms were created using the BegoStone® plaster. Lithotripsy of one stone (1.0 g) per test jar was performed with Ho:YAG laser (365 µm fiber; 1 minute/trial). Four laser settings were tested: I-0.8 J,8 Hz; II-0.2J,50 Hz; III-0.5 J,50 Hz; IV-1.5 J,40 Hz. Uro-Net (US Endoscopy) deployment was used in 3/9 trials. Post-treatment, stone fragments were strained though a 1mm sieve; after a 7-day drying period fragments and unfragmented stone were weighed. Uro-Net nylon mesh and wire frame resistance were tested (laser fired for 30s). All nets used were evaluated for functionality and strength (compared to 10 new nets). Student's T test was used to compare the studied parameters; significance was set at p < 0.05. RESULTS: Laser settings I and II caused less damage to the net overall; the mesh and wire frame had worst injuries with setting IV; setting III had an intermediate outcome; 42% of nets were rendered unusable and excluded from strength analysis. There was no difference in mean strength between used functional nets and non-used devices (8.05 vs. 7.45 lbs, respectively; p = 0.14). Setting IV was the most efficient for lithotripsy (1.9 ± 0.6 mg/s; p < 0.001) with or without net stabilization; setting III was superior to I and II only if a net was not used. CONCLUSIONS: Laser lithotripsy is not optimized by stone entrapment with a net retrieval device which may be damaged by high energy laser settings.

Catheter design for effective manual bladder irrigation.

PURPOSE: We compared the efficiency of clearance of a simulated clot from a bladder model using a 6-hole irrigation catheter, a traditional Malecot catheter and a modified Malecot catheter with additional side holes. MATERIALS AND METHODS: Latex balloons 12 inches in diameter served as the bladder model. They were filled with 300 cc Jell-O® gelatin, which had been partially solidified for 8 hours at 36F. Five manual irrigation/aspiration cycles with a 60 cc catheter tip syringe were performed to remove simulated clot from the bladder models and the amount of clot removed was measured. Five bladder models were used to test the efficiency of clot removal for each 22Fr catheter design, including a standard 22Fr Model 361222 Malecot latex 4-wing catheter (Rusch, High Wycombe, United Kingdom) and a 22Fr Bardex® Model 606118-22 latex 6-hole catheter. Two modified versions of the Malecot catheter design involving 2 and 4 additional holes were also tested to determine the effect of a hybrid 6-hole/Malecot design. RESULTS: The 6-hole catheter was more efficient for clot evacuation than the Malecot catheter (p = 0.014). The modified Malecot catheter with 4 additional holes was more efficient than the original Malecot catheter (p = 0.020). However, it was not significantly better than the 6-hole catheter. After 5 irrigation/aspiration cycles 77.0% of residual clot remained in the bladder with the Malecot catheter compared to 60.4% and 54.0% for the 6-hole and modified 4-hole Malecot catheters, respectively. CONCLUSIONS: The 6-hole catheter showed an advantage in clot removal over the Malecot catheter design. The enhanced ability of the 6-hole design to remove simulated clot may be attributable to the larger area covered by the holes at the catheter tip. Further investigation to determine the effect of spacing between the holes and the number of holes on the ability to break apart and remove clot is recommended for a more thorough understanding of differences among catheter models and methods of improvement.

Continuation of Renin-Angiotensin-Aldosterone Inhibitors Does Not Impact Renal Function Among Patients Undergoing Percutaneous Nephrolithotomy.

OBJECTIVE: In the perioperative period, renin-angiotensin-aldosterone system (RAAS) inhibitors may result in cardiovascular and renal functional changes. We sought to determine the acute and chronic renal functional and blood pressure effects of continuing or withdrawing angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARBs) after percutaneous nephrolithotomy (PCNL). MATERIALS AND METHODS: This was a retrospective review of all patients undergoing PCNL at our institution from 2002 to 2013. Patients on either an ACE-I and/or ARB who received an ACE-I and/or ARB during their surgical hospitalization were matched based on sex, age, and body mass index to patients who had their medication withheld during the postoperative period. The two groups were compared. RESULTS: A total of 2784 patients underwent PCNL during the study period. At the time of PCNL, 15.2% (423/2784) of patients and 6.5% (181/2784) were prescribed an ACE-I and an ARB, respectively. Fifty-nine percent (248/423) of patients on an ACE-I and 66.9% (121/181) on an ARB received their medication during their postoperative hospitalization. There was no significant difference in average length of stay (2 days vs 2 days), perioperative change in glomerular filtration rate, glomerular filtration rate (GFR) (-0.50 mL/min/1.73 m2 vs -2.34 mL/min/1.73 m2, p = 0.267), change in GFR at 1 month postoperatively (-4.63 mL/min/1.73 m2 vs -5.90 mL/min/1.73 m2, p = 0.748), or change in GFR at 1 year (-2.08 mL/min/1.73 m2 vs -0.13 mL/min/1.73 m2, p = 0.267) between patients who received vs withheld their medication during the postoperative stay. CONCLUSION: It is safe to continue RAAS inhibitors in patients undergoing PCNL during their operative hospitalization.

Predictors of Reporting Success With Increased Fluid Intake Among Kidney Stone Patients.

OBJECTIVE: To determine how kidney stone patients' knowledge, behaviors, and preferences toward fluid intake differed from those reporting being successful or unsuccessful at increasing fluid intake for prevention. MATERIALS AND METHODS: Three hundred two kidney stone patients filled out a survey on stone history, fluid intake success, and knowledge, behaviors, and preferences toward fluid intake. Responses were compared between those reporting being very successful at fluid intake and those reporting being not successful or only somewhat successful. Self-reported fluid intake success was correlated in a subset of 41 subjects using 24-hour urine volumes. RESULTS: Self-reported fluid intake success correlated significantly with 24-hour urine volumes. Unsuccessful fluid drinkers were less likely to be aware of their future stone risk and were less likely to be counseled on prevention by a urologist. Successful fluid drinkers reported the fewest barriers per person, were more likely to prefer water for fluid intake, and were more likely to like the "taste" of water. Strategies used for remembering to drink varied significantly with those unsuccessful most often reporting "just tried to remember" and those successful at fluid intake most likely to carry a water bottle. All groups reported similar perceived severity from stones, perceived benefits of drinking fluids, and preference for using urine color to monitor hydration. CONCLUSION: Awareness of future stone risk, preference for water, counseling on stone prevention by a urologist, and specific strategies used for increasing fluid intake varied between patients who were successful or unsuccessful with fluid intake. Addressing these differences may help improve fluid intake success.

100% uric acid stone formers: what makes them different?

OBJECTIVE: To identify what risk factors on 24-hour urinalysis, if any, predispose patients to have higher percentages of uric acid (UA) stone composition in their stones, with specific emphasis on patients with pure UA stones. METHODS: We retrospectively identified 308 patients from review of a kidney stone analysis database. Patients were grouped according to the percentage UA composition: 10%-20%, 30%-50%, 60%-90%, and 100% UA. Data were extracted from 24-hour urine collections and serum chemistries. Patients taking allopurinol, citrates, or thiazide diuretics were excluded. RESULTS: The percentage UA stone composition increased as patients became older (P = .05) or heavier (P <.001). Gender did not impact the percentage of UA in stones. Although a higher serum UA level was associated with higher UA stone composition (P <.0006), urinary UA levels did not correlate (P = .1). In contrast, urinary pH correlated significantly with higher UA stone composition (P = .03). CONCLUSION: Older and heavier patients with higher serum UA levels are more likely to have a pure UA stone. This information combined with traditional predictors (urine pH, radiopacity of stone, and Hounsfield units) may help identify those most likely to respond to dissolution therapy.

Tissue damage from ultrasonic, pneumatic, and combination lithotripsy.

PURPOSE: To conduct a comparative evaluation of ultrasonic, pneumatic, and dual ultrasonic (DUS) lithotripsy to predict the safety of probes on urinary tract tissue. MATERIALS AND METHODS: The Swiss Lithoclast Ultra (ultrasonic-only [US] and ultrasonic-pneumatic combination [US+P]) and the Gyrus ACMI Cyberwand (DUS) were evaluated. Fresh porcine ureter, bladder, and renal pelvis tissues were used with a hands-free setup to vertically apply 0, 400, or 700 g of force with each probe for a duration of 3 seconds, 5 seconds, or 3 minutes (or until perforation occurred). Data collection included whether perforation occurred and time to perforation. Histological analysis of nonperforated samples was used to compare the anatomical depth to which damage occurred. RESULTS: The total percentage of trials resulting in perforation for all tissue types, contact durations, and forces was found to be 8.5% (10/117) for US, 13.7% (16/117) for US+P, and 26.4% (31/117) for DUS. No perforations occurred with light contact (0 g) of probe force, regardless of tissue type, lithotripsy mode, or contact duration. Overall, the renal pelvis was most resistant to perforation (p=0.0004), while no difference was found between the bladder and ureter tissue (p=0.32). Force beyond 400 g and contact greater than 5 seconds increased risk for damage. CONCLUSIONS: Mode of lithotripsy, tissue type, probe force, and probe-tissue contact duration all significantly impacted the extent of damage and likelihood for perforation to occur. All devices and tissue types provided a reasonable margin of safety for probe-tissue contact times of 3 and 5 seconds with no more than 400 g of force.

New ureteral access sheaths: a double standard.

OBJECTIVE: To investigate the functional characteristics of the traditional and new single-wire ureteral access sheath (UAS) configurations relating to insertion, positioning, tissue injury, and durability. MATERIALS AND METHODS: Four UAS were tested: Navigator HD (11/13F, Boston Scientific), Re-Trace (10/12F, Coloplast), Flexor-Parallel (P), and Flexor-Regular (R; 9.5/11.5F, Cook Medical). UASs were evaluated for sharpness-(1) foil perforation, (2) tissue skiving (advancing sheath/dilator against fixed foil or bologna models); rigidity-(3) tip bending, (4) sheath buckling; (5) lubricity (dynamic friction through bologna), (6) dilator removal force, (7) kinking forces (side wall compressive forces), and (8) radiopacity. New UASs were used for each trial. A motorized sliding stage was used, and continuous force measurements were recorded with a Mark-10 digital force gauge. RESULTS: The Navigator HD had the largest external diameter (13.02F). Re-Trace had the longest (51 mm) and most flexible tip (0.942 lb, P <.001). Flexor-R had the shortest (23.2 mm) and stiffest tip (7.48 lb). The Cook tip perforation forces were highest (0.807 lb), whereas the sheath required the most force (0.25 lb, P <.001) and caused the least damage (4.95 mm) when advanced against tissue. Navigator HD had the least frictional resistance (0.14 lb, P <.001). The single-wire systems had the lowest buckling forces (Navigator HD, 0.41 lb; Flexor-R, 0.827 lb; Flexor-P, 0.445 lb; Re-Trace, 1.014 lb; P <.001) and the highest dilator removal forces compared with classic systems (Flexor-P, 1.39 lb; Re-Trace, 1.9 lb; Navigator HD, 0.190 lb; Flexor-R, 0.194 lb; P <.001). The differences in kinking forces and radiopacity were not significant. CONCLUSION: The Navigator HD was the most slippery and rigid sheath, whereas the single-wire systems had lower buckling forces and required more force to remove their dilators. Cook sheaths appeared the least traumatic.

Best practices in shock wave lithotripsy: a comparison of regional practice patterns.

OBJECTIVE: To evaluate regional differences in adaptation of best practice recommendations for extracorporeal shock wave lithotripsy (SWL) across 4 distinct geographic regions. METHODS: A retrospective study was performed using a prospective database maintained by a mobile lithotripsy provider (ForTec Medical, Streetsboro, OH). SWL cases performed in Ohio, Northern Illinois/Southern Wisconsin, Florida, and New York were included. Treatment parameters evaluated included treatment rate, use of a power ramp-up protocol, use of a pretreatment pause after the initial 100 shocks, ancillary procedures, and need for retreatment. Regional and physician-specific patterns were examined. Statistical analyses using chi-square and analysis of variance were performed with a significance of P <.05. RESULTS: Data from 2240 SWL procedures were included in the study. Overall adaptation of power ramp-up protocols and treatment rates were high (93% and 93%), whereas use of pause was lower (75%, P <.001). Retreatment rates were low (4.3%), although ancillary procedures were performed in 34% of patients, and 8.3% of patients received stents for stones <1 cm. Regional differences were present in all parameters: Florida physicians used power ramp-up less (83%, P <.001) but had good use of pretreatment pause (98%, P <.001), both Wisconsin/Illinois and New York were less likely to use slow rate (87% and 84%, respectively, P <.001). CONCLUSION: The recommendations for slower shock wave rates and power ramp protocols have reached high penetration in urologic practices; however, the more recent recommendation for a pause after the initial 100 shocks has been less uniformly implemented. Inconsistencies in regional adaptation of best practices may identify opportunities for further education.

Can obese stone formers follow dietary recommendations?

INTRODUCTION: Obese patients have an increased risk of kidney stones, and several studies have identified specific urinary derangements on 24-hour collections. The objective of this study was to assess obese and super-obese stone formers, and their compliance with dietary modifications over time, based on 24-hour urine outcomes. PATIENTS AND METHODS: A retrospective review was performed searching for all stone formers who completed a 24-hour urine collection before and after dietary counseling for stone prevention. Patients were excluded if placed on medical therapy in addition to dietary therapy. Patients were divided in three main groups according to their body mass index (BMI): 30, 30-40, and >40 kg/m(2). Demographic data and 24-hour urine stone risk parameters (volume, sodium, uric acid, citrate, and oxalate) were assessed. Initial 24-hour urine results were compared to follow-up results after dietary counseling. Then, the outcomes from each group were compared to each other. RESULTS: Two hundred and fourteen stone formers (67% male) were identified with a mean age of 49.5±15.0 years. One hundred twenty-eight (59.8%) patients had BMI <30 kg/m(2), 61 (28.5%) between 30-40 kg/m(2), and 25 (11.7%) >40 kg/m(2). Among patients with BMI <30 kg/m(2), there were significant improvements in all urinary parameters (p<0.001) as well as in the group with BMI between 30 to 40 kg/m(2) (p=0.02 for oxalate, p<0.001 for other parameters). Among super-obese patients, there were significant improvements in the urinary volume (p=0.03), sodium (p<0.001), uric acid (p=0.001), and oxalate (p<0.001). There were no significant differences in the improvements observed in the urinary volume (p=0.69), sodium (p=0.08), uric acid (p=0.17), and citrate levels (p=0.97) between the groups. CONCLUSION: Dietary recommendations can be an equally effective strategy in decreasing the risk or stone recurrence in obese and super-obese kidney stone formers as it is in those who are not obese.

Evaluating the automated Thermedx Fluid Management System in a ureteroscopy model.

INTRODUCTION: The Thermedx Fluid Management System (TFMS) is an automated pressurized irrigation system that allows concurrent temperature control. Developed for use in multiple surgical specialties, it provides settings specific to several endoscopic urologic procedures. The objective of this study was to critically appraise the functional characteristics and precision of the device regarding irrigation warming, pressurization, and flow during semirigid ureteroscopy. METHODS: Using an in vitro model, the TFMS was assessed using the proprietary urology tubing with and without a short semirigid ureteroscopy/ureteroscope (URS) (7.4F/35 cm Wolf 425612). Pressures and temperatures were measured using continuous digital sensors (Meriam m1550-gi0015, and Taylor Digital Thermometer 9842). Stepwise increases in settings were measured with and without the ureteroscope (from 100 to 200 mm Hg), and with and without the included pressure release valve (preset for 150 mm Hg). Continuous measures (60/min) were recorded and compared with values recorded by the internal unit sensors. RESULTS: At room temperature (18.1°C), the starting irrigation temperature was 19.5°C, increasing to 35.5°C after 7.2 minutes at maximum settings (40°C). Irrigation returned to baseline temperature after 6.7 minutes with the heater disabled. The irrigation temperature was not affected by changes in pressure settings and flow rates. The unit's display readings were 4°C-6°C higher than measured at the tip of the ureteroscope. Flow rates detected at the tip of the URS were 2%-8% less than the unit reported. Pressures were between 8%-17% higher using URS than that reported by the unit, and highest values were encountered when the physical safety pop-off valve was removed from the tubing. CONCLUSIONS: The TFMS provides a pressurized/warmed irrigation strategy for many endoscopic procedures. It is important to note that the system underestimates pressures at the tip of the endoscope, while overestimating the flow rates and temperatures delivered from the scope when utilizing the device.

Type-2 diabetes and kidney stones: impact of diabetes medications and glycemic control.

OBJECTIVE: To evaluate the impact of diabetic medications and glycemic control on the urine pH, 24-hour urine stone risk profile, and stone composition. PATIENTS AND METHODS: We retrospectively reviewed our database searching for type-2 diabetic patients with kidney stones from July 2002 to January 2013. Patients were divided in 2 groups according to their diabetic medications: insulin vs oral antihyperglycemics. Patients were compared based on their urine collections and stone composition. A linear regression was done to assess which variables could predict a low urine pH. In a subgroup analysis, patients on thiazolidinediones (ie, pioglitazone) were compared with patients on other oral antihyperglycemics. RESULTS: We analyzed 1831 type-2 diabetic patients with stone disease; 375 (20.5%) were included in the insulin group and 1456 (79.5%) in the antihyperglycemics group. Linear regression revealed male gender (P = .011) and insulin therapy (P <.001) as protective factors of low urine pH, whereas HbA1c level (P <.001) was inversely related to the urine pH (odds ratio, -0.066; 95% confidence interval, -0.096 to -0.036; P <.001). There were no significant differences in other 24-h urine stone risk parameters or stone composition between the groups. There were also no significant differences in the subgroup analysis. CONCLUSION: Urine pH is inversely related to HbA1c level. Insulin therapy is associated with higher urine pH than oral antihyperglycemic agents despite higher HbA1c suggesting that insulin may modify urine pH independent of glycemic control.

Endoscopic forceps for ureteroscopy: a comparative in vitro analysis.

OBJECTIVE: To evaluate the functional characteristics of different ureteroscopic graspers. METHODS: 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. RESULTS: 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. CONCLUSION: There are significant differences in opening dynamics, grip strength, perforation forces, and ureteroscope deflection among ureteroscopic graspers that may predict clinical performance capabilities.

Patient decision making for asymptomatic renal calculi: balancing benefit and risk.

OBJECTIVE: To evaluate which variables affect patients' decisions on the management of asymptomatic renal calculi. MATERIALS AND METHODS: We hypothesized that patients who had experienced greater pain, passed larger or more stones, or passed stones more recently would be more likely to choose surgical intervention (ureteroscopy [URS] or shock wave lithotripsy [ESWL]) instead of observation (OBS). The survey was distributed to 101 patients in our stone clinic. The patients were given a hypothetical scenario of an asymptomatic 8-mm lower pole stone and descriptions for OBS (annual radiography, 40% chance of growth >10 mm within 4 years, 20% chance of passage), ESWL (65% success rate), and URS (90% success rate, with stent placement for 1 week). The patients were also asked whether they would rather defer the decision to their physician. RESULTS: Of the patients, 22.8% chose OBS, 29.7% chose URS, and 47.5% chose ESWL. The patients who had passed larger stones (P = .029) were less likely to choose OBS over surgery. Of the 78 patients who chose intervention, 61.5% preferred ESWL. The patients were more likely to choose URS if they had previously undergone URS (P = .0064) and stent placement (P = .048), and the patients were more likely to choose ESWL if they had a previously undergone ESWL (P = .019). Surgical choice was not affect by size of the largest stone passed (P = .46), date of last passage (P = .080), previous pain intensity (P = .11), previous percutaneous nephrolithotomy (P = .73), or number of stones passed (P = .51). Finally, 56.4% of patients deferred the decision of the treatment approach to the physician. CONCLUSION: Previous stone experience and treatment significantly affected treatment choice. Patients rely on their physician to educate them on the alternatives and play an active role in selecting the treatment approach.

Hydrophilic guidewires: evaluation and comparison of their properties and safety.

OBJECTIVE: To compare physical and mechanical properties of 10 commercially available hydrophilic guidewires. METHODS: In vitro testing was performed to evaluate 10 different straight hydrophilic guidewires (5 regular and 5 stiff wires): Glidewire, NiCore, EZ Glider, Hiwire, and Zipwire. The forces required for tip perforation, tip bending, shaft bending, and friction during movement were measured for all 10 wires. The tip contour was measured using high power light microscopy. RESULTS: The Glidewire required the greatest force to perforate our model (P = .01). The EZ Glider, Zipwire, and Glidewire had the lowest tip bending forces (P <.001). The Glidewire had the stiffest shaft (P <.001). The EZ Glider and Glidewire required the greatest forces in the friction test (P <.001). Regarding the stiff guidewires, the GlidewireS required the greatest force in the perforation test (P ≤.05). The GlidewireS and EZ GliderS required the lowest tip bending force (P ≤.004). The ZipwireS and NiCoreS had the stiffest shafts (P ≤.01). The GlidewireS required the greatest force in the friction test (P <.001). Measurement of the tip contour showed the Zipwire, HiwireS, and EZ GliderS had the roundest tips. CONCLUSION: Each wire has unique properties with advantages and disadvantages. The Glidewires (both stiff and regular) have the lowest potential for perforation, although they are less slippery. The Glidewire and EZ Glider required the least tip force to bend around a point of obstruction.