Carl Sarkissian

Patient Decision Making for Asymptomatic Renal Calculi: Balancing Benefit and Risk

OBJECTIVEnTo evaluate which variables affect patients decisions on the management of asymptomatic renal calculi.nnnMATERIALS AND METHODSnWe 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.nnnRESULTSnOf 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.nnnCONCLUSIONnPrevious 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.

Dyslipidemia and Kidney Stone Risk

PURPOSEnWe studied the impact of dyslipidemia on 24-hour urinalysis and stone composition.nnnMATERIALS AND METHODSnWe 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.nnnRESULTSnA 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).nnnCONCLUSIONSnThere 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.

Systematic Evaluation of Hybrid Guidewires: Shaft Stiffness, Lubricity, and Tip Configuration

OBJECTIVEnTo conduct a comparison of physical and mechanical properties for 5 commonly used guidewires to assess advantages of wires for specific applications.nnnMETHODSnTests 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).nnnRESULTSnThe 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.nnnCONCLUSIONnHybrid 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.

Gout, Stone Composition and Urinary Stone Risk: A Matched Case Comparative Study

PURPOSEnWe established the most common stone composition, and serum and urinary biochemical features in patients with gout and urolithiasis.nnnMATERIALS AND METHODSnWe 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.nnnRESULTSnFor 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.nnnCONCLUSIONSnUric 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.

Type-2 Diabetes and Kidney Stones: Impact of Diabetes Medications and Glycemic Control

OBJECTIVEnTo evaluate the impact of diabetic medications and glycemic control on the urine pH, 24-hour urine stone risk profile, and stone composition.nnnPATIENTS AND METHODSnWe 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.nnnRESULTSnWe 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.nnnCONCLUSIONnUrine 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.

Hydrophilic Guidewires: Evaluation and Comparison of Their Properties and Safety

OBJECTIVEnTo compare physical and mechanical properties of 10 commercially available hydrophilic guidewires.nnnMETHODSnIn 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.nnnRESULTSnThe 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.nnnCONCLUSIONnEach 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.

New ureteral access sheaths: a double standard.

OBJECTIVEnTo investigate the functional characteristics of the traditional and new single-wire ureteral access sheath (UAS) configurations relating to insertion, positioning, tissue injury, and durability.nnnMATERIALS AND METHODSnFour 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.nnnRESULTSnThe Navigator HD had the largest external diameter (13.02F). Re-Trace had the longest (51xa0mm) and most flexible tip (0.942 lb, Pxa0<.001). Flexor-R had the shortest (23.2xa0mm) 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, Pxa0<.001) and caused the least damage (4.95xa0mm) when advanced against tissue. Navigator HD had the least frictional resistance (0.14 lb, Pxa0<.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; Pxa0<.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; Pxa0<.001). The differences in kinking forces and radiopacity were not significant.nnnCONCLUSIONnThe 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.

OBJECTIVEnTo evaluate regional differences in adaptation of best practice recommendations for extracorporeal shock wave lithotripsy (SWL) across 4 distinct geographic regions.nnnMETHODSnA 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.nnnRESULTSnData 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).nnnCONCLUSIONnThe 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.

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

OBJECTIVEnTo 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.nnnMETHODSnWe 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.nnnRESULTSnThe percentage UA stone composition increased as patients became older (Pxa0= .05) or heavier (Pxa0<.001). Gender did not impact the percentage of UA in stones. Although a higher serum UA level was associated with higher UA stone composition (Pxa0<.0006), urinary UA levels did not correlate (Pxa0= .1). In contrast, urinary pH correlated significantly with higher UA stone composition (Pxa0= .03).nnnCONCLUSIONnOlder 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.

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

OBJECTIVEnTo 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.nnnMATERIALS AND METHODSnThree 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.nnnRESULTSnSelf-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.nnnCONCLUSIONnAwareness 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.