Shubha De

Flexible Ureteroscopy With a Ureteral Access Sheath: When to Stent?

OBJECTIVE To compare intra- and postoperative data of patients who underwent ureterorenoscopy (URS) with an access sheath, with and without postoperative stenting. METHODS We retrospectively identified patients who underwent flexible URS with a ureteral access sheath between January 2102 and January 2013. Two surgeons performed all cases; one who routinely stents after flexible ureteroscopy and a second who selectively stents. Fifty-one patients who were stented and 51 patients not stented after URS were enrolled in this study. Patients were matched by operative time as a surrogate measure of complexity of the procedure. Intra- and postoperative data were compared. We also analyzed if preoperative stenting or sheath diameter had any effect on postoperative pain score for each group. RESULTS Patients in the stented group were older (P <.001), had larger ureteral access sheaths (P <.001), and greater stone burden (P <.001). Despite this, the stented group had lower pain scores (4.5 ± 3.2 vs 8.9 ± 3.2; P = .025) and were less likely to seek medical assistance for pain than the unstented patients (26.3% vs 3.9%; P = .007). Patients who were prestented before ureteroscopy had lower pain scores than those who were not prestented in the group that did not receive a postoperative stent (4.2 ± 3.4 vs 6.6 ± 2.8; P = .047). CONCLUSION Postoperative stenting after flexible URS with a ureteral access sheath seems to decrease postoperative pain. Patients might be selected for no ureteral stent if they were prestented before the procedure, and the URS was uneventful.

Detection of Urolithiasis: Comparison of 100% Tube Exposure Images Reconstructed with Filtered Back Projection and 50% Tube Exposure Images Reconstructed with Sinogram-affirmed Iterative Reconstruction

PURPOSE To compare images acquired with 50% tube exposure with a dual-source computed tomographic (CT) scanner and reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE) with 100% exposure images reconstructed with filtered back projection (FBP) for reader ability to detect stones, reader confidence, and findings outside the urinary tract. MATERIALS AND METHODS In this HIPAA-compliant, institutional review board-approved study, imaging examinations in 99 patients with urolithiasis were assessed. Data from both tubes were reconstructed with FBP; data from the primary tube only were reconstructed with SAFIRE. Seven readers evaluated randomized studies for calculi in nine regions. Reader confidence was scored by using a five-point scale. Ancillary findings were noted. Nonparametric methods for clustered data were used to estimate the area under the receiver operating characteristic curves with 95% confidence intervals to test for noninferiority of 50% exposure with SAFIRE. RESULTS Calculi were found in 113 locations (pyelocalyceal ureter, 86; proximal ureter, seven; midureter, four; distal ureter, 15; bladder, one) and not found in 752 locations. Mean area under the receiver operating characteristic curve for FBP was 0.879 (range, 0.607-0.967) and for SAFIRE, 0.883 (range, 0.646-0.971; 95% confidence interval: -0.025, 0.031). The SAFIRE images were not significantly inferior to FBP images (P = .001). Reader confidence levels for images with stones were similar with FBP and SAFIRE (P = .963). For the 52 patients who had extraurinary findings, readers reported them correctly in 74.4% (271 of 364) and 72.0% (262 of 364) of cases (P = .215) for FBP and SAFIRE, respectively. For the nine patients with potentially important findings per the reference standard, the detection rates were 44% (28 of 63) and 33% (21 of 63, P = .024), respectively. For the 43 patients with unimportant or likely unimportant findings, the false detection rates were 15% (44 of 301) and 14% (43 of 301, P = .756), respectively. CONCLUSION The 50% tube exposure CT images reconstructed with SAFIRE were not inferior to 100% exposure images reconstructed with FBP for diagnosis of urolithiasis, without decreases in reader confidence.

Accuracy of ultrasonography for renal stone detection and size determination: is it good enough for management decisions?

To determine the sensitivity and specificity of ultrasonography (US) for detecting renal calculi and to assess the accuracy of US for determining the size of calculi and how this can affect counselling decisions.

Changing trends in the American diet and the rising prevalence of kidney stones.

OBJECTIVE To evaluate the trends in the American diet over the last 40 years (1974-2010), during which time the National Health and Nutrition Examination Survey data set has documented an increase in stone prevalence from 3.8% to 8.8%. MATERIALS AND METHODS We used the National Health and Nutrition Examination Survey reported rates for stone disease (1974-2010) to compare the United States Department of Agricultures food distribution data during the same period. Three data points for prevalence were used from the literature. We correlated these to changing lithogenic food distributions using linear models to interpolate annual changes in prevalence. Spearman correlations were performed (P ≤.05) using SAS 9.2 (SAS Institute, Cary, NC). RESULTS Increased total daily calories (rho, 0.96; P <.001), fat (rho, 0.79; P <.001), protein (rho, 0.85; P <.001), fruit (rho, 0.6; P = .01), and vegetables (rho, 0.73; P <.001) correlated strongly with increasing stone prevalence. Dark green vegetables, flour or cereal products, fish or shellfish, corn products (including high fructose corn syrup), and added sugars also showed strong correlations with stone prevalence. Citrus fruits were negatively correlated to stone disease (rho, -0.18; P = .31). Protein, fruits and vegetables, and added sugars actually decreased in proportion to daily caloric per capita increases. CONCLUSION Increases in caloric intake and several lithogenic foods correlate temporally with increasing stone prevalence. The nature of this relationship is difficult to determine from this data; although, clearly, American diets have changed over the last 4 decades.

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.

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.

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.

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.

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 60seconds. 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.

Accurately Diagnosing Uric Acid Stones from Conventional Computerized Tomography Imaging: Development and Preliminary Assessment of a Pixel Mapping Software

Purpose: Preoperative determination of uric acid stones from computerized tomography imaging would be of tremendous clinical use. We sought to design a software algorithm that could apply data from noncontrast computerized tomography to predict the presence of uric acid stones. Materials and Methods: Patients with pure uric acid and calcium oxalate stones were identified from our stone registry. Only stones greater than 4 mm which were clearly traceable from initial computerized tomography to final composition were included in analysis. A semiautomated computer algorithm was used to process image data. Average and maximum HU, eccentricity (deviation from a circle) and kurtosis (peakedness vs flatness) were automatically generated. These parameters were examined in several mathematical models to predict the presence of uric acid stones. Results: A total of 100 patients, of whom 52 had calcium oxalate and 48 had uric acid stones, were included in the final analysis. Uric acid stones were significantly larger (12.2 vs 9.0 mm, p = 0.03) but calcium oxalate stones had higher mean attenuation (457 vs 315 HU, p = 0.001) and maximum attenuation (918 vs 553 HU, p <0.001). Kurtosis was significantly higher in each axis for calcium oxalate stones (each p <0.001). A composite algorithm using attenuation distribution pattern, average attenuation and stone size had overall 89% sensitivity, 91% specificity, 91% positive predictive value and 89% negative predictive value to predict uric acid stones. Conclusions: A combination of stone size, attenuation intensity and attenuation pattern from conventional computerized tomography can distinguish uric acid stones from calcium oxalate stones with high sensitivity and specificity.