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Objective: To assess the diagnostic accuracy and intra-observer agreement of endoscopic stone recognition (ESR) compared with formal stone analysis. Introduction: Stone analysis is a corner stone in the prevention of stone recurrence. Although X-ray diffraction (XRD) and infrared spectroscopy are the recommended techniques for reliable formal stone analysis, this is not always possible, and the process takes time and is costly. ESR could be an alternative, as it would give immediate information on stone composition. Materials and Methods: Fifteen endourologists predicted stone composition based on 100 videos from ureterorenoscopy. Diagnostic accuracy was evaluated by comparing the prediction from visual assessment with stone analysis by XRD. After 30 days, the videos were reviewed again in a random order to assess intra-observer agreement. Results: The median diagnostic accuracy for calcium oxalate monohydrate was 54% in questionnaire 1 (Q1) and 59% in questionnaire 2 (Q2), whereas calcium oxalate dihydrate had a median diagnostic accuracy of 75% in Q1 and 50% in Q2. The diagnostic accuracy for calcium hydroxyphosphate was 10% in Q1 and 13% in Q2. The median diagnostic accuracy for calcium hydrogen phosphate dihydrate and calcium magnesium phosphate was 0% in both questionnaires. The median diagnostic accuracy for magnesium ammonium phosphate was 20% in Q1 and 40% in Q2. The median diagnostic accuracy for uric acid was 22% in both questionnaires. Finally, there was a diagnostic accuracy of 60% in Q1 and 80% in Q2 for cystine. The intra-observer agreement ranged between 45% and 72%. Conclusion: Diagnostic accuracy of ESR is limited and intra-observer agreement is below the threshold of acceptable agreement.

Introduction: Relative supersaturation (SS) for calcium oxalate (CaOx), calcium phosphate (CaP), and uric acid (UA) has been used for assessing urinary crystallization and estimated by programs, in...

Kidney stone incidence has been known to vary with temperature and climate. However, little is known about any variation in the composition of kidney stones across different regions of the United States. We attempted to evaluate whether stone composition changes depending on region.We were given access to de-identified data from LABCORPs database of kidney stone composition from August 1, 2016, to October 24, 2016, for states in seven representative areas of the country: Virginia, Minnesota, Florida, Arizona, Colorado, California, and Texas. We analyzed each component of kidney stones with optical microscopy supplemented with Fourier-transform infrared spectroscopy (FT-IR) spectrometry using both the percentage of the stone that was composed of that component as well as a binary variable coded none vs any. Univariate associations between component and state were examined using chi-square or Fisher's exact test for the binary indicator, and analysis of variance for the continuous percentage. The same set of analyses was used for decade of age vs each component. The association between age and state was examined using analysis of variance.Data were available for 4335 kidney stones, from patients in the 7 states mentioned. The most common components across all stones were calcium oxalate monohydrate and calcium phosphate (both present in 93% of stones), calcium oxalate dihydrate (in 57% of stones), and uric acid (in 12% of stones). Stone composition did not vary widely across regions, except for uric acid stones, which were more prevalent in Florida compared to other states, with an odds ratio of 1.43 (95% confidence interval 1.12, 1.83).Kidney stone composition does not vary widely by region within the United States. Although temperature and humidity play a role in stone incidence, there does not appear to be a large variation between different climates, with the exception of uric acid stone formation in Florida.

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

CT is a widely used imaging modality in the diagnosis of urolithiasis but subjects patients to ionizing radiation. Reduced dose protocols have recently gained wide acceptance. Stone density measurements have been used to predict composition and help guide treatment in standard dose CT (sCT) but not in reduced dose CT (RdCT). We aimed to compare density measurements obtained through RdCT

Understanding the factors affecting success of extracorporeal shockwave lithotripsy (SWL) would improve informed decision-making on the most appropriate treatment modality for an individual patient. Although stone size and skin-to-stone distance do correlate with fragmentation efficacy, it has been shown that stone composition and architecture, as reflected by structural heterogeneity on CT, are also important factors. This study aims to determine if CT texture analysis (CTTA), a novel, nondestructive, and objective tool that generates statistical metrics reflecting stone heterogeneity, could have utility in predicting likelihood of SWL success.Seven spontaneously passed, intact renal tract stones, were scanned ex vivo using standard CT KUB and micro-CT. The stones were then fragmented in vitro using a clinical lithotripter, after which, chemical composition analysis was performed. CTTA was used to generate a number of metrics that were correlated to the number of shocks needed to fragment the stone.CTTA metrics reflected stone characteristics and composition, and predicted ease of SWL fragmentation. The strongest correlation with number of shocks required to fragment the stone was mean Hounsfield unit (HU) density (r = 0.806, p = 0.028) and a CTTA metric measuring the entropy of the pixel distribution of the stone image (r = 0.804, p = 0.039). Using multiple linear regression analysis, the best model showed that CTTA metrics of entropy and kurtosis could predict 92% of the outcome of number of shocks needed to fragment the stone. This was superior to using stone volume or density.CTTA metrics entropy and kurtosis have been shown in this experimental ex vivo setting to strongly predict fragmentation by SWL. This warrants further investigation in a larger clinical study for the contribution of CT textural metrics as a measure of stone heterogeneity, along with other known clinical factors, to predict likelihood of SWL success.

The epidemiologic data regarding stone composition in Israel are based on anachronistic methods of stone analysis. Historically, Israel was noted for an unusually high percentage of uric acid stones. The aim of the study was to describe the current stone composition distribution in Israel, using modern techniques of urinary stone analysis. Age and sex correlations were investigated.In a bicenter study, using infrared spectroscopy and X-ray diffraction, stones from five hundred and thirty eight (538) patients were analyzed and demographic data recorded.The study cohort included 401 men (74.5%) and 137 women (25.5%) with a male to female ratio of 2.9:1 and a median age of 48 years (range 2-85 years). While calcium oxalate monohydrate was the predominant component in both sexes, it was lower in female patients (77.3% vs 65%). The rate of infection stones (struvite+carbonate apatite) was significantly higher in women (35.7% vs 10.2%). Uric acid stones were found in only 14.5% of the patients and increased with age. Conversely, the rate of calcium oxalate dihydrate decreased with age.Modern techniques of urinary stone analysis showed that the most frequent stone component in Israel is calcium oxalate monohydrate. In contrast to earlier reports and in accordance with reports from other countries, the overall frequency of uric acid is 14.5%. With age, the frequency of uric acid increases reaching 21% in persons60 years old. A significant sex difference was noted in the distribution of calcium oxalate stones and infection stones. The classic 3:1 ratio was maintained, however.

The purpose of our study was to determine, in vivo, whether single-energy noncontrast computed tomography (NCCT) can accurately predict the presence/percentage of struvite stone composition.We retrospectively searched for all patients with struvite components on stone composition analysis between January 2008 and March 2012. Inclusion criteria were NCCT prior to stone analysis and stone size ≥4 mm. A single urologist, blinded to stone composition, reviewed all NCCT to acquire stone location, dimensions, and Hounsfield unit (HU). HU density (HUD) was calculated by dividing mean HU by the stone's largest transverse diameter. Stone analysis was performed via Fourier transform infrared spectrometry. Independent sample Student's t-test and analysis of variance (ANOVA) were used to compare HU/HUD among groups. Spearman's correlation test was used to determine the correlation between HU and stone size and also HU/HUD to % of each component within the stone. Significance was considered if p0.05.Fourty-four patients met the inclusion criteria. Struvite was the most prevalent component with mean percentage of 50.1%±17.7%. Mean HU and HUD were 820.2±357.9 and 67.5±54.9, respectively. Struvite component analysis revealed a nonsignificant positive correlation with HU (R=0.017; p=0.912) and negative with HUD (R=-0.20; p=0.898). Overall, 3 (6.8%) had20% of struvite component; 11 (25%), 25 (56.8%), and 5 (11.4%) had 21% to 40%, 41% to 60%, and 61% to 80% of struvite, respectively. ANOVA revealed no difference among groups regarding HU (p=0.68) and HUD (p=0.37), with important overlaps. When comparing pure struvite stones (n=5) with other miscellaneous stones (n=39), no difference was found for HU (p=0.09) but HUD was significantly lower for pure stones (27.9±23.6 v 72.5±55.9, respectively; p=0.006). Again, significant overlaps were seen.Pure struvite stones have significantly lower HUD than mixed struvite stones, but overlap exists. A low HUD may increase the suspicion for a pure struvite calculus.

Radiological imaging remains the cornerstone of follow-up of patients with urolithiasis. Plain abdominal X-ray (XRKUB) of these patients is largely becoming obsolete in favor of noncontrast computed tomography of the abdomen and pelvis (CTKUB), which offers superior sensitivity and specificity. Contentiousness exists, however, related to the radiation doses associated with CT. Calcium oxalate remains the most common stone composition across most populations. These calculi are radiopaque and thus follow-up with XRKUB may be appropriate in some settings, avoiding the higher radiation doses associated with standard protocol CT. With the emergence of low-dose CT, however, and the modest accuracy of XRKUB, the ongoing role for XRKUB in the management of urolithiasis is debatable. In this study, we assessed the proportion of pure calcium urolithiasis visible on XRKUB to assess the utility of XRKUB for follow-up of pure calcium urolithiasis. Hospital laboratory databases were analysed to identify patients who had undergone urological intervention and extraction of urolithiasis composed of pure calcium salts, who had undergone CTKUB and XRKUB during the same episode for diagnosis of the calculus. One hundred five calculi were included and the imaging for each patient analyzed. 79/105 calculi (75%) identified on CT were visible on XRKUB. The median calculus visible on XRKUB was 7.0 mm (interquartile range [IQR] 5.0-10.0 mm), the median calculus not seen was 4.25 mm (IQR 3.5-7.0 mm) as measured on CT (p 0.01). XRKUB accuracy varied according to calculus position within the renal tract. Calculi were most often visible in the renal pelvis and proximal ureter (86%), 50% of mid-ureteral and 72% of distal ureteral calculi were visible (p = 0.01). Until low-dose CT protocols become widely adopted, XRKUB still has a limited role in the management of pure calcium urolithiasis in selected patients. Due to its modest accuracy in many settings, this role is limited mainly to larger proximal urolithiasis.

Over the last 50 years, chemolysis as a primary or adjuvant treatment for urinary stones has fallen in and out of favor. We review the literature for a historical perspective on the origins and chronology of Renacidin therapy, focusing on landmark studies and impracticalities that have seemingly condemned it to history.A MEDLINE search was performed on the topic of chemolysis of urinary calculi. Historical literature was reviewed with regard to stone composition, treatment modalities, outcomes, and complications.A total of 61 articles were reviewed, 40 of which were case series, representing a total of 817 patients studied. Mulvaney first introduced Renacidin in 1959 as a modification of Suby and Albright's 1943 solution. Because of an overabundance of nonstandardized irrigation protocols, six deaths were reported in the early 1960s resulting in a Food and Drug Administration ban on the practice of upper urinary tract stone dissolution. Over time, Renacidin returned to the urologist's arsenal, appearing first as an adjunct to dissolve catheter and bladder calculi and later (1990) as an approved agent for renal pelvis and ureter use. This feat was almost single-handedly the result of a successful hemiacidrin case series published in 1971 by Nemoy and Stamey. By using daily urine cultures, prophylactic antibiotics, and meticulous intrarenal pressure monitoring, Nemoy and Stamey virtually eliminated all major irrigation complications, paving the way for a flurry of studies. More importantly, they established the link between residual struvite stones, persistent infection, and recurrent staghorn stone formation.Dissolution of urinary calculi by chemolysis has been shown to be safe and effective if performed with sterile urine cultures, prophylactic antibiotics, and low intrapelvic pressures. The pioneers of this therapy are remembered for their attempts to develop an alternative to open surgery, and, in the process, solidified the "stone-free" concept for infection-based stones.

We read with great interest the paper by York and colleagues [1] entitled "Randomized controlled trial comparing three different modalities of lithotrites for intracorporeal lithotripsy in PCNL". This study showed that the safety and efficacy of Cyberwand, Lithoclast Select, and the StoneBreaker lithotripters are similar and comparable. They stated that "the clearance rate of “hard” stones (defined as brushite, cystine, and uric acid stones) was comparable across the 3 groups). We would like to point out that this statement is one side of the coin. It is possible that the clearance rate of "soft” stones was different. This paper did not perform analysis between "soft" stone compositions. Previous studies with higher sample size showed that stone composition is an important factor that affect stone clearance rate of different types of lithotripters [2]. Furthermore, we want to make a minor criticism of this study: the low sample size of this study may be responsible for this non-significant finding.

To compare the efficiency and cost effectiveness of a combined pneumatic and ultrasonic lithotrite (Lithoclast Ultra) and a standard ultrasonic lithotrite, (LUS-1) during percutaneous nephrolithotomy.In a prospective randomized trial, 30 patients undergoing percutaneous nephrolithotomy (PCNL) were randomized to PCNL with either the combined pneumatic and ultrasonic lithotrite (PUL) or a standard ultrasonic lithotrite (SUL). Patient demographics, stone composition, location, pre- and post-operative stone burden, fragmentation rates, and device failures were compared.There were 13 patients in the PUL group and 17 patients in the SUL group. Stone burden and location were equal. Overall, 64% of the PUL group had hard stones (defined as stones that were either pure or a mixture of cystine [3], calcium oxalate monohydrate [CaOxMono; 2], and calcium phosphate [CaPO4; 2]), and four had soft stones (3 struvite and 1 uric acid [UA]). In the SUL group, there were eight hard stones (5 CaOxMono and 3 CaPO4), and six soft stones (4 calcium oxalate dihydrate [CaOxDi] and 2 UA) (P = 0.51). Stone composition data were unavailable for five patients. Fragmentation time for the PAL was 37 minutes versus 31.5 minutes for the SUL (P = 0.22). Stone retrieval and mean operative times were similar for both groups. There were a total of three (23.1%) device-related problems in the PUL group, and eight (47%) in the SUL group. There was one (7.7%) device malfunction in the PUL group due to probe fracture. There were two (11.7%) device failures in the SUL group; one failure required the device to be reset every 30 minutes, and the second was an electrical failure. Suction tubing obstruction occurred twice (15.3%) in the PUL group and 35.3% in the SU group (P = 0.35). The stone-free rates for the PUL and SUL were 46% and 66.7%, respectively (P = 0.26).Although the PUL was more costly, stone ablation and clearance rates were similar for both the combined pneumatic and ultrasonic device and the standard ultrasonic device. When stratified with respect to stone composition, the PUL was more efficient for harder stones, and the SUL was more efficient for softer stones.

The goal of this study was to analyze the effect of stone composition on the efficacy of retrograde intrarenal surgery (RIRS) with kidney stones of 1-3 cm, 1-2 cm, and 2-3 cm in diameter.We undertook a retrospective analysis of 74 patients with kidney stones who underwent RIRS. The patients were divided into two groups based on stone composition: Group I (n=47) (calcium oxalate monohydrate and calcium phosphate) was the hard to fragment stone group and group II (n=27) (calcium oxalate dihydrate, magnesium ammonium phosphate, and uric acid) was the easy to fragment stone group. Forty-six patients with kidney stones 1 to 2 cm in diameter were divided into group A (n=30) (smaller than 20 mm, hard to fragment stones) and group B (n=16) (smaller than 20 mm, easy to fragment stones). Twenty-eight patients with stones 2 to 3 cm in diameter were divided into group C (n=17) (larger than 20 mm, hard to fragment stones) and group D (n=11) (larger than 20 mm, easy-to-crush stones).The stone clearance rates of group I and group II were 66.0% and 88.9%, respectively (P0.05). The stone clearance rates of group A and group B were 73.3% and 100% (P0.05). The stone clearance rates of group C and group D were 52.9% and 72.7%, respectively.Stone composition has a significant impact on the efficacy of RIRS in the management of 1 to 3 cm kidney stones. For 2-3 cm calcium oxalate dihydrate stones, uric acid stones, and magnesium ammonium phosphate stones, the outcome of RIRS treatment was relatively good, and RIRS is recommended.

Stone analysis is not always available, and recent studies reveal interlaboratory reporting differences, suggesting inaccurate reports. We sought to determine whether appropriate medical therapy could be made without stone analysis when imaging, history, and laboratory data were available.One hundred stone formers (SFs) were categorized as calcium oxalate, calcium phosphate, uric acid, or struvite based on a single analysis. Age, gender, body mass index, comorbidities, serum chemistries, 24-hour urine, and imaging information were incorporated into a "Megaprofile." Radiographic details about patients' stones were recorded. Attenuation: Size ratios were calculated to predict stone composition. Stone composition data were then withheld and three urologists (S.L.B., S.S., and S.Y.N.) evaluated each Megaprofile, making nutritional and pharmacologic recommendations. Next, a repeat evaluation ensued with stone analyses. Recommendations were compared with the gold standard being those made using stone composition data.Without stone analysis, the panel recommended targeted nutrition therapy in 91% of cases, which remained unchanged once composition was revealed. Medication was prescribed in 68% of cases. Overall, therapy based on the Megaprofile without stone composition data was appropriate 93% of the time. In 7% of cases, therapy was changed after stone composition was revealed. In 21% of patients with recurrent urinary tract infections (UTIs), knowledge of stone composition altered therapy.Medical, laboratory, and radiographic data provide sufficient information to direct both nutritional and pharmacologic therapy in most SFs (93%), but those with recurrent UTIs may derive more benefit from stone analysis prior to directed medical therapy.

Noncontrast computed tomography (NCCT) has high sensitivity, specificity, and is able to predict stone composition using Hounsfield units (HU) but is associated with high radiation exposure. In an attempt to reduce radiation exposure, low-dose stone protocols have been developed that provide excellent detection of stones. It is not known, however, whether these protocols are equally effective in determining HU stone density. The purpose of this study is to compare stone HU attenuation between low- and conventional-dose NCCT.In this prospective randomized, single blinded study, 7-mm calcium oxalate stones were placed randomly into nine intact urinary systems and scanned in three different cadaveric vehicles. Holding other parameters constant, NCCT was performed at varying mAs levels ranging from 5 to 140. Identical magnified images at each mAs setting were reviewed in a blinded fashion to determine HU attenuation. Statistical analyses were performed using a Kruskal-Wallis test and the Levene test, with P0.05 considered significant.In 19 different stone configurations with 133 stones, median attenuation levels were 614, 674, 681, 669, 670, 674, and 667 HU at 5, 7.5, 15, 30, 50, 70, and 140 mAs, respectively. The differences in median attenuation levels were not significantly different (P=0.998). An increasing trend of attenuation variability was noticed as the radiation dose decreased; however, this was not significant (P=1.0).Low-dose NCCT results in similar HU attenuation compared with conventional-dose NCCT. Although there is a slight increase in variability, low-dose NCCT provides similar information to assist in determining stone composition as conventional-dose NCCT.

We present our experience with micropercutaneous cystolithotripsy (mPCCL) using transillumination-guided access in children with bladder stones and evaluate the safety and efficacy of this procedure.Twelve children who underwent mPCCL for bladder stone removal in our department between January 2011 and September 2013 were included in this study. Percutaneous access was performed using the transillumination technique. The chief complaint, age and sex of the patients, stone size, operative time, complications, stone-free rate, and stone composition as determined by radiography diffraction analysis were recorded.The mean age of the patients was 2.6 (1-7) years. One out of 12 patients was a girl. The mean stone size was 14 mm (7-32 mm). The mean mPCCL procedure time was 38.7 (15-65) minutes. The mean hospital stay was 1.4 (0.5-4) days. The stone-free rate after one mPCCL intervention was 91.6% and increased to 100% after two sessions of mPCCL. The notable complications were transient macroscopic hematuria in one patient, acute urinary retention in one patient, and the need for a second session of mPCCL in another patient. The stones were composed of calcium oxalate (3), ammonium acid urate (1), calcium phosphate (1), cystine (1), struvite (1), and unknown (5).Transillumination-guided mPCCL is a safe and effective technique, does not require the use of ionizing radiation, is technically easy, and is a minimally invasive alternative for the management of bladder stones. It has many advantages, especially in pediatric patients, such as decreased urethral injury, no need for postoperative catheter insertion in most cases, and shorter operative time.

Stone composition, as reflected in radiographic appearance, is important to help choose between SWL and percutaneous/endoscopic procedures. Predicting a stone's composition accurately from a plain radiograph would be a useful tool in clinical decision-making. However, the ability of physicians to predict composition has not been adequately assessed. A prospective study was designed to quantify the accuracy of a panel of physicians who routinely deal with stones in classifying stone composition solely from radiographs.A panel of six members was created to review 100 plain-film radiographs from patients with renal stones of known composition. The panel consisted of two urologists, two radiologists, and two nephrologists, all of whom have expertise in stone disease. If the composition guessed was at least 40% of the total stone composition, the response was deemed correct.Overall, there was an average 39% correct response score among the six panelists. When the stones were divided by size, 35% were1 cm, and 65% were larger. The accuracy of chemical composition determination did not improve with greater stone size, nor was there a difference in accuracy for pure and mixed stones. The most frequently misclassified stone was calcium phosphate, with only 14% being correctly diagnosed.With a random sampling of plain radiographs, a panel of physicians specializing in stone disease correctly diagnosed the composition of renal calculi less than half of the time without being given clinical information.

Purpose: We examined the stone composition, 24-hour urinary risk factors, and insurance status in patients evaluated in two regional stone clinics to further investigate the relationship between the socioeconomic status and kidney stone formation.We performed a retrospective review of stone formers who completed a 24-hour urinalysis as part of a metabolic evaluation for nephrolithiasis. Insurance status was determined by billing records and those with state-assisted insurance (SAI) were compared to patients with private insurance (PI). Multivariate analyses were performed adjusting for known risk factors for stones.Three hundred forty-six patients were included. Patients with SAI (16%) were significantly more likely to be female (55% vs.38%, p=0.026) and younger (43.5 vs.49.2, p=0.003). Among those with stone composition data (n=200), SAI patients were as likely to form calcium phosphate (CaPhos) as calcium oxalate (CaOx) stones (46.9% vs.31.3%, p=0.44). PI patients were significantly less likely to form CaPhos than CaOx stones (10.1% vs.77.4%, p0.001). On multivariate analysis, among those with calcium stones, the odds of forming CaPhos stones over CaOx stones were ten times higher among SAI patients compared to PI, odds ratio 10.2 (95% CI 3.6, 28.6, p0.001). Further, patients with SAI had significantly higher urine sodium, pH, and supersaturation of CaPhos, and a lower supersaturation of uric acid compared to patients with PI.SAI was associated with a greater likelihood of a CaPhos stone composition and increased urinary risk factors for CaPhos stones. These findings may reflect dietary or other unmeasured differences, and have important implications for resource allocation and counseling, as treatment may differ for these groups.

Obesity has been identified as a limitation of extracorporeal shockwave lithotripsy (SWL). The obesity metrics of body mass index (BMI) and skin-to-stone distance (SSD) have been evaluated as predictors of SWL success. While SSD has demonstrated a strong correlation with success, BMI has not. Bioimpedance analysis (BIA) is an accurate way of determining body adiposity. We evaluated fat mass percentage (FMP) as measured by BIA as a predictor of SWL success.We prospectively collected body composition data using the Imp-DF50 Body Impedance Analyzer on consecutive patients undergoing SWL. All generated variables, including FMP, along with demographics, BMI, stone size, and stone composition, were analyzed. Patients were evaluated for success, defined as no evidence of stones on radiography of the kidneys, ureters, and bladder at follow-up.Fifty-two consecutive patients were enrolled in the study, of which 37 had the necessary metrics to be included in the analysis. Twenty-three (62.2%) patients were stone free while 14 (37.8%) were found to have residual stone at follow-up. There was no difference in sex, stone laterality, mean age, and stone size between the groups. For the success and failure groups, the mean BMI was 25.8 kg/m(2) and 29.8 kg/m(2) (P=0.0091), and mean FMP 24.6% and 32.2% (P=0.0034). On mirrored multivariable analysis, both BMI (OR=0.735, P=0.026) and FMP (OR=0.806, P=0.010) were associated with success. Patients with a FMP ≥35% had a reduced success rate compared with those with a FMP35% (14% vs 73%, respectively, P=0.0028).Both BMI and FMP both appear to be independent predictors of success. Based on these findings, a large study examining the relationship between BMI, FMP, SSD, and SWL success is warranted. A preoperative FMP ≥35% is associated with a 14% success rate, and alternative treatment strategies for urolithiasis should be considered.

Helical CT has become the preferred method to diagnose urinary calculi in patients presenting with abdominal or flank pain. Recent in vitro studies have shown that CT also can display the internal structure in stones with remarkable detail. Because some stones respond better to SWL than others, knowing stone structure at diagnosis could be helpful in choosing among treatment options. This paper examines the potential for CT to be used in this way. Older CT technology proved to be problematic, in that all studies using low-resolution CT will suffer from an artifact in which stone size affects apparent CT attenuation values. Thus, the observation that stones with low measured CT attenuation break more easily than stones with high attenuation could be attributable entirely to an artifact of stone size. Most stones are composed of more than one mineral, and heterogeneity of composition may contribute to variability in stone response to SWL. Older technology is not useful in evaluating stone composition, but current and emerging CT machines have sufficient resolution to determine the composition and structure of stones inside the patient, provided proper viewing windows are used. Continuing improvement in image resolution in helical CT promises to provide information about stone composition and structure that will ultimately lead to better care for patients with stone disease.

The choice of the most efficient treatment modality for renal calculi could be facilitated by determining the precise chemical stone composition before treatment. We investigated the possibility of using conventional X-ray imaging to determine stone composition and to find a simple method of predicting stone fragility for treatment planning.The X-ray density of 92 stones with known infrared spectroscopy analyses (calcium oxalate monohydrate, calcium oxalate dihydrate, struvite, and calcium phosphate) was retrospectively investigated by scanning the films with a digital camera. The data analysis was done using a commercially available graphics program to compare the total gray-scale levels of the stones.There was a significant difference in the mean gray-scale level of calcium phosphate and calcium oxalate stones (P0.01). The mean gray-scale difference between calcium oxalate dihydrate and calcium oxalate monohydrate was also significant (p0.02). All calcium oxalate, struvite, and calcium phosphate stones were correctly identified. Of the calcium oxalate monohydrate and calcium oxalate dihydrate stones, 98.4% and 66.6%, respectively, were correctly identified.The method allows a reliable diagnosis of stone composition from radiographs, which can be useful in stone treatment planning.

Comprehensive metabolic evaluation has become an important aspect of the management of recurrent nephrolithiasis, yet the role of stone analysis is often neglected or perhaps underestimated. The purpose of this study was to determine the role of stone analysis in medical decision making in patients with recurrent nephrolithiasis.We evaluated 100 consecutive stone-forming patients who had undergone compositional stone analysis as well as comprehensive metabolic evaluation at our institution. An analysis of stone composition in relation to metabolic disturbances was performed. Patients were stratified into two groups: calcium and non-calcium stone formers.Patients having non-calcium stones were found to have a metabolic analysis reflecting specific metabolic disorders. Alternatively, patients with calcium stones were heterogeneous with regard to metabolic disorders, but there was a significant likelihood of renal tubular acidosis in those patients with calcium phosphate calculi. On the basis of these results, a simplified metabolic evaluation and nonselective medical therapy based on stone composition was formulated to facilitate assessment, management, and monitoring of stone disease.Compositional stone analysis should be an integral part of the metabolic evaluation of patients with nephrolithiasis. Moreover, stone analysis alone may provide guidance for therapeutic treatment and obviate a formal metabolic evaluation.

Informed selection of treatment requires knowledge of the size and composition of a calculus. Spiral CT has a growing role in the detection of calculi, with an overall accuracy in excess of 95%. Moreover, the margin of error in determining stone size does not exceed 3.6%, and stone volume is underestimated by

It is almost impossible to estimate a stone's composition preoperatively, yet there is no question that it plays a great role in the difficulty of an endoscopic lithotripsy. One hundred and sixty patients have been treated with endoscopic access to their upper urinary tract and laser lithotripsy. All calculi were fragmented successfully with the pulsed-dye laser (Pulsolith). In 59 consecutive patients, an estimate of calculus composition was made endoscopically, in 46 of whom sufficient stone fragments were retrieved for crystallographic analysis. Twentytwo patients were felt to have either pure (>90%) or mixed (>50%) calcium oxalate monohydrate stone exteriors at the time of endoscopy, and in all these patients, the final stone analysis agreed with the endoscopic assessment. Endoscopic assessment of calcium oxalate dihydrate, uric acid, and struvite/calcium oxalate phosphate stones was also found to be accurate on final stone analysis. Overall, there was a 89% success rate in estimating stone composition...

With the development of small-caliber ureteroscopes and lithotripsy devices, it is now possible to perform intracorporeal stone fragmentation without dilatation of the ureteral orifice. Ureteral stones are typically fragmented into small particles that can be difficult to retrieve for stone analysis. Infrared spectroscopy (IRS) of the precipitate from urine after intracorporeal lithotripsy represents a method for obtaining stone analysis.A total of 69 patients underwent ureteroscopic lithotripsy with the holmium laser or the electrohydraulic probe for stones in the ureter (N = 65) or kidney (N = 4). Each patient's bladder was then drained and the urine filtered. The resulting precipitate was analyzed using IRS.The amount of material for analysis wasor =1 mg in 56 patients (82%). Stone composition was positively identified in 44 patients (64%). Material suitable for analysis was recovered from 73% of patients when the bladder was drained with a cystoscope sheath compared with 43% when a urethral catheter was used (P = 0.03). There was no significant difference in pretreatment stone size in the patients who had a positive v a negative result (11.7 mm v 10.9 mm; P = 0.06). Similarly, the stone location was not significantly related to the likelihood of positive analysis (P = 0.29).Straining the urine after ureteroscopic intracorporeal lithotripsy and analyzing the precipitate with IRS is able to identify stone composition in the majority of patients. This method is especially useful in the setting of holmium laser lithotripsy, in which the majority of the stone is converted to spontaneously passable particles.