Human kidney stones: a natural record of universal biomineralization.

GeoBioMed - a new transdisciplinary approach that integrates the fields of geology, biology and medicine - reveals that kidney stones composed of calcium-rich minerals precipitate from a continuum of repeated events of crystallization, dissolution and recrystallization that result from the same fundamental natural processes that have governed billions of years of biomineralization on Earth. This contextual change in our understanding of renal stone formation opens fundamentally new avenues of human kidney stone investigation that include analyses of crystalline structure and stratigraphy, diagenetic phase transitions, and paragenetic sequences across broad length scales from hundreds of nanometres to centimetres (five Powers of 10). This paradigm shift has also enabled the development of a new kidney stone classification scheme according to thermodynamic energetics and crystalline architecture. Evidence suggests that ≥50% of the total volume of individual stones have undergone repeated in vivo dissolution and recrystallization. Amorphous calcium phosphate and hydroxyapatite spherules coalesce to form planar concentric zoning and sector zones that indicate disequilibrium precipitation. In addition, calcium oxalate dihydrate and calcium oxalate monohydrate crystal aggregates exhibit high-frequency organic-matter-rich and mineral-rich nanolayering that is orders of magnitude higher than layering observed in analogous coral reef, Roman aqueduct, cave, deep subsurface and hot-spring deposits. This higher frequency nanolayering represents the unique microenvironment of the kidney in which potent crystallization promoters and inhibitors are working in opposition. These GeoBioMed insights identify previously unexplored strategies for development and testing of new clinical therapies for the prevention and treatment of kidney stones.

Evaluating outcomes of complete supine percutaneous nephrolithotomy for staghorn vs multiple non-staghorn renal stones: a 10-year study.

PURPOSE: To evaluate the outcomes of complete supine percutaneous nephrolithotomy (csPCNL) for staghorn stones and multiple large non-staghorn stones. METHODS: The records of 886 patients who underwent csPCNL from September 2009 to October 2019 were considered. Out of them, 201 cases met the eligibility criteria and they were divided into three groups: 63 cases of staghorn, 68 cases of multiple medium (20 mm < diameter ≤ 30 mm) non-staghorn and 70 cases of multiple large non-staghorn (> 30 mm) stones. Almost all outcomes and stone-related factors were analyzed. RESULTS: There was not any significant difference regarding age, body mass index, history of urinary tract infection, transfusion rate, complication rate, pre and post-surgery serum creatinine, hemoglobin drop and total hospital stay between the three groups. Stone free rate was 98.5% in multiple medium group, 97.1% in multiple large group and 84.1% in staghorn group (P = 0.001). The operation duration was significantly shorter for the multiple medium group (P < 0.001) but it was not significantly different between the multiple large non-staghorn and staghorn group. CONCLUSION: The results demonstrated that almost all outcomes were not significantly different between the three groups (especially between staghorn and larger non-staghorn ones). These findings reveal that surgeons could choose csPCNL for treatment of staghorn stones and multiple large non-staghorn stones and consider staghorn stones as challenging as multiple large (especially diameter > 30 mm) non-staghorn stones.

Classification of the renal papillary abnormalities by flexible ureteroscopy: evaluation of the 2016 version and update.

INTRODUCTION: To assess the use of the 2016 proposed classification of the renal papillary abnormalities during flexible ureteroscopy that aims to standardize their description. PATIENTS AND METHODS: We performed a prospective monocentric single operator collection of the data using this classification during 88 consecutive flexible ureteroscopies required for renal stones treatment. Outcome measurements and statistical analysis: data of stones analysis (microscopy and infrared spectrophotometry) and of serum and urines biochemical samples have been compared with the results of the classified endoscopic descriptions. RESULTS: Mean duration of description was 81.4 s. We reported that 83% of the patients had Randall plaques (RP), as only 4.5% of the patients had no abnormality. Concerning the papillary stones and anchored stones were observed in 30.7% and aspect of intraductal crystallization (Sc) in 15.9%. Erosions were present in 55.7% and extrophic papillae in 8%. Sa1 and Pa2 were significantly correlated to RP, anchored stones (Sa) to papillary erosions and calcium phosphate stones to intraductal crystallization. Hypercalciuria was significantly higher in Sa2 than Sa1 stones. CONCLUSIONS: The different descriptions in the 2016 classification were confirmed by the results of this study. Papillary abnormalities are consequences of stones development. Their descriptions could also improve the follow-up and the diagnosis of a metabolic lithogenesis. We recommend their systematic description during ureteroscopy. Some improvements are proposed to update this classification.

Pneumatic Lithotripsy versus Holmium Laser Lithotripsy in Percutaneous Nephrolithotomy for Patients with Guy's Stone Score Grade IV Kidney Stone.

BACKGROUND AND OBJECTIVE: The aim of this study was to compare the efficacy and reliability of holmium (Ho:YAG) laser lithotripsy (HLL) and pneumatic lithotripsy (PL) in percutaneous nephrolithotomy (PCNL) in the treatment of patients with Grade IV kidney stones based on Guy's Stone Score. STUDY DESIGN/MATERIALS AND METHODS: This retrospective study included 103 patients with Grade IV kidney stones out of 440 patients who underwent PCNL through HLL and PL in Second Affiliated Hospital of Shantou University Medical College, China, from January 2016 to December 2018. We analyzed preoperative, intraoperative, and postoperative variables of the patients to evaluate the efficacy and reliability of PCNL procedures. RESULTS: Patients were categorized as Grade I, II, III, and IV, and the patients of each grade were 85 (19.32%), 39 (8.86%), 213 (48.41%), and 103 (23.41%), respectively. In Grade IV, the total operative time (min) for the PL and HLL groups was 137.7 ± 47.79 and 134.27 ± 53.38, respectively (p = 0.744). The variation in laboratory examination values including ΔHGB (g/L), ΔHCT, ΔPCT, and ΔCr (µmol/L) for PL and HLL groups was 19 ± 11.23/12 ± 15.42 (p = 0.012), 0.057 ± 0.034/0.038 ± 0.045 (0.009), 0.027 ± 0.034/0.026 ± 0.034 (0.702), and 3.07 ± 17.4/20.54 ± 65.93 (0.692), respectively. The postoperative hospitalization day was 8.94 ± 4.2 and 7.73 ± 2.75 (p = 0.015), respectively. As for the stone-free rate (SFR), the SFRs for PL and HLL were 48.15% (n = 39/81) and 59.09% (n = 13/22) (p = 0.363), respectively. CONCLUSIONS: HLL showed a comparable advantage of not only decreased postoperative hemoglobin and hematocrit but also fewer postoperative hospitalization days. Based on the results of our retrospective study, for those Grade IV kidney stone patients who have a risk of bleeding before PCNL operation, HLL can be a considerable treatment option. Besides, in consideration of reducing human care cost, HLL which showed fewer hospitalization days, would be more welcome by patients.

Determining the true burden of kidney stone disease.

The incidence and prevalence of kidney stones have increased over the past four decades. However, the diagnosis of 'kidney stone' can range from an incidental asymptomatic finding of limited clinical significance to multiple painful episodes of ureteral obstruction with eventual kidney failure. Some general strategies may be useful to prevent the recurrence of kidney stones. In particular, greater attention to kidney stone classification, approaches to assessing the risk of recurrence and individualized prevention strategies may improve the clinical care of stone formers. Although there have been some advances in approaches to predicting the recurrence of kidney stones, notable challenges remain. Studies of kidney stone prevalence, incidence and recurrence have reported inconsistent findings, in part because of the lack of a standardized stone classification system. A kidney stone classification system based on practical and clinically useful measures of stone disease may help to improve both the study and clinical care of stone formers. Any future kidney stone classification system should be aimed at distinguishing asymptomatic from symptomatic stones, clinically diagnosed symptomatic stone episodes from self-reported symptomatic stone episodes, symptomatic stone episodes that are confirmed from those that are suspected, symptomatic recurrence from radiographic recurrence (that is, with radiographic evidence of a new stone, stone growth or stone disappearance from presumed passage) and determine stone composition based on mutually exclusive categories.

Guy's Stone Score as a Predictor for Stone-Free Rate and Complications in Percutaneous Nephrolithotomy: A Single-Center Report from a Stone Belt Country.

OBJECTIVES: To evaluate Guy's Stone Score (GSS) as a grading system for the complexity of renal calculi before percutaneous nephrolithotomy (PCNL) and as a predictor for stone-free rate (SFR) and potential complications in the setting of a developing country with many cases of advanced complex stone disease. PATIENTS AND METHODS: We performed a prospective study on 115 patients with renal stones who had PCNL between August 2017 and October 2018. Stone complexity was classified according to GSS using preoperative imaging. The rates of perioperative complications were assessed using the Clavien grading system, and the SFR was assessed in the 3rd postoperative week by abdominal X-ray and renal ultrasound. The χ2 and one-way ANOVA tests were used for statistical analysis. A p value ≤0.05 was considered significant. RESULTS: The study included 115 patients (77 males) with a mean age of 50.2 (±13.3) years. Cases were classified according to GSS into 4 grades; there were 24 (20.9%) grade I, 48 (41.7%) grade II, 25 (21.7%) grade III, and 18 (15.7%) grade IV cases. There was a significant inverse correlation between GSS grade and SFR (p < 0.001). The rate of complications using the Clavien grading system were significantly higher in GSS grades III and IV (p = 0.002). So were the rates of blood transfusion, the need for >1 access tract, and the duration of hospitalization. CONCLUSION: GSS is a simple and easily reproducible system to classify the complexity of renal stones. In our setting, it also proved an excellent tool to predict SFR, perioperative complications, and associated ancillary procedures. Ultimately, it can help surgeons and, above all, patients to make a more informed decision about their surgery.

Evaluation of Nephrolithometric Scoring Systems to Predict Outcomes of Retrograde Intrarenal Surgery.

PURPOSE: The aim of the study was to evaluate the predictive value of nephrolithometric scoring systems used to predict the complexity of renal stones for the outcomes of retrograde intrarenal surgery (RIRS). MATERIALS AND METHODS: A total of 81 patients who underwent RIRS for nephrolithiasis between January 2013 and October 2017 were reviewed in this retrospective study. Guy's Stone Score (GSS), the S.T.O.N.E., Clinical Research Office of the Endourologic Society (CROES), and Seoul National University Renal Stone Complexity (S-ReSC) nephrolithometry scores were assessed by same researcher for each patient from preoperative non-contrast enhanced computed tomography scans. These nephrolithometric scores, stone characteristics and complications were compared in patients with/without residual stone. RESULTS: The median (IQR) age of patients (37 female/44 male) was 45 (20) years. The median (IQR) stone burden was 139.4 (125.4) mm2 and the mean Hounsfield unit (HU) value was 1034.46 ± 239.56. The stone burden, S.T.O.N.E. and S-ReSC scores were statistically significantly higher and the CROES score was significantly lower in patients with a residual stone (p < 0.001, for all). The incidence of residual stones was statistically significantly higher in patients with Grade 3 GSS (p = 0.018). While S.T.O.N.E., S-ReSC and CROES were significantly correlated with stone-free rates, GSS failed to correlate with stone-free status. According to the receiver operating characteristic (ROC) curve analysis, the predictive value of stone burden was higher for residual stones, compared to S-ReSC scoring (p < 0.05). CONCLUSION: Nephrolithometric scoring systems nomograms used to predict the PCNL success were not superior to stone burden in predicting the RIRS success.

Detection of Renal Calculi in Ultrasound Image Using Meta-Heuristic Support Vector Machine.

Typically, the acquired renal ultrasound image includes a course of speckle noises. This paper primarily investigates an approach for the detection of renal calculi by processing those raw US images with the help of a meta-heuristic SVM classifier. One of the major downsides of involving Ultrasound images in medical analysis is the prevalence of Speckle Noises. An Adaptive Mean Median Filter approach has been introduced in the work to get rid of the speckle noises to the maximum extent ever in the literature. Segmentation is performed by employing conventional K-Means and GLCM features were extracted for classification using a meta-heuristic SVM classifier. The proposed methodology investigates with a Real-time Acquired Dataset of Mithra Scans, Tamilnadu, India comprises of 250 clinical Ultra-Sound Kidney Images of which 150 are having Calculi and the rest are Healthy. With the experimental results, the proposed meta-heuristic SVM classifier have performed better in noisy images while comparing with other conventional methods considered in the literature. It exhibits an Accuracy of 98.8% with a FAR rate of 1.8 for FRR as high as 3.3. The results clearly proposed that the novel AMM-PSO-SVM could be a promising technique for object or foreign body detection in a medical imaging application that uses ultrasound imaging.

Microwave dielectric property based classification of renal calculi: Application of a kNN algorithm.

The proper management of renal lithiasis presents a challenge, with the recurrence rate of the disease being as high as 46%. To prevent recurrence, the first step is the accurate categorization of the discarded renal calculi. Currently, the discarded renal calculi type is determined with the X-ray powder diffraction method which requires a cumbersome sample preparation. This work presents a new approach that can enable fast and accurate classification of discarded renal calculi with minimal sample preparation requirements. To do so, first, the measurements of the dielectric properties of naturally formed renal calculi are collected with the open-ended contact probe technique between 500 MHz and 6 GHz with 100 MHz intervals. Cole-Cole parameters are fitted to the measured dielectric properties with the generalized Newton-Raphson method. The renal calculi types are classified based on their Cole-Cole parameters as calcium oxalate, cystine, or struvite. The classification is performed using k-nearest neighbors (kNN) machine learning algorithm with the 10 nearest neighbors, where accuracy as high as 98.17% is achieved.

Predictive ability of Guy's stone score in pediatric patients undergoing percutaneous nephrolithotomy.

BACKGROUND: Several authors have evaluated, in a number of external validation and predominantly adult studies, Guy's stone score (GSS) as a predictive tool for the assessment of stone clearance after percutaneous nephrolithotomy (PCNL). However, there are limited and conflicting data investigating whether GSS could be a potential independent factor associated with residual stone rates and complications of PCNL for children. OBJECTIVE: The aim of the current study was to evaluate the ability of GSS, as an independent factor, to predict residual stone rates and complications in pediatric patients undergoing PCNL. STUDY DESIGN: The records of the pediatric patients who had undergone PCNL for stone disease at the current department were retrospectively reviewed. Variables included patient, stone, and treatment parameters. The GSS was used for assessment of stone complexity. Univariate and multivariate analyses were performed to evaluate factors associated with residual stone rates and complications of pediatric PCNL. RESULTS: The study group consisted of 114 children (63 boys and 51 girls) with a median (interquartile range) age of 6 (3-11) years and who had undergone 122 PCNLs (eight bilateral). Multivariate logistic regression analysis (Summary Table) demonstrated that the independent risk factors for increased residual stone rate following pediatric PCNL monotherapy were GSS (OR 3.14, 95% CI 1.31-7.49, P = 0.01) and number of calyces involved (OR 4.02, 95% CI 1.11-14.53, P = 0.033). Multivariate logistic regression analysis demonstrated that the independent risk factors for complications following pediatric PCNL were surgical experience (OR 2.72, 95% CI 1.09-6.82, P = 0.032), and operation time (OR 1.01, 95% CI 1.00-1.03, P = 0.040). DISCUSSION: A prediction model is needed to pre-operatively counsel patients and evaluate outcomes for measuring treatment success of PCNL. The GSS provides a simple, reliable and reproducible tool for describing the complexity of PCNL while predicting postoperative stone-free status, despite its limitations. However, little research has been conducted on the applicability of GSS in pediatric patients undergoing PCNL. In addition, conflicting results have been reported about its association with complications of pediatric PCNL. CONCLUSIONS: The current study found that although GSS had a significant predictive ability for residual stone rates after pediatric PCNL revealed by multivariate logistic regression, the results did not conclude that complexity of GSS was directly proportional to complications of pediatric PCNL. The factors, including calyceal involvement and surgeon experience, may need to be incorporated in GSS to further improve its ability to predict outcomes of pediatric PCNL. IRB APPROVED PROTOCOL NUMBER: 1422.

Litiasis urinaria: epidemiología y clasificación del cálculo urinario / Urinary lithiasis: epidemiology and classification of urinary calculus / Urolitíase: epidemiologia e classificação dos cálculos renais

Se estima que la incidencia de cálculos renales en España se ha incrementado en los últimos años. En este trabajo se realizó una aproximación epidemiológica de la litiasis urinaria, y se estableció una clasificación de los cálculos urinarios analizados durante un año. Se ha creado una base de datos con los cálculos analizados mediante espectroscopía de infrarrojos con Transformada de Fourier, considerando edad, sexo, recidivas y parámetros bioquímicos, en orina de 24 horas. La influencia del sexo en la litiasis urinaria es muy marcada y el número de cálculos en el varón es muy superior. Además, el factor edad incrementa la litiasis desde 5% a los 30 años hasta 25% a los 60. Estos datos se refieren a los cálculos totales y no diferencian su composición química. Si se diferencian según la composición, se ha encontrado una tendencia similar en hombres y mujeres en los cálculos de oxalato cálcico monohidratado, pero muy distinta en los de oxalato cálcico dihidratado y fosfocarbonato cálcico. La incidencia en menores de 20 años es muy baja, y prevalece en los niños en la primera década y en las niñas en la segunda década de vida. Además, se ha observado una mayor prevalencia de cálculos en los meses de verano asociada a mayores valores séricos de vitamina D. Por lo tanto, es imprescindible partir de unos criterios taxativos de clasificación de los cálculos urinarios para la realización de estudios epidemiológicos. En los últimos años la proporción entre las diferentes composiciones ha cambiado y se ha producido un aumento en los cálculos de oxalato.

The incidence of renal calculus in Spain has been increased in recent years. In this work, an epidemiological approach of urinary lithiasis has been made, establishing a classification of the urinary calculi analyzed during a year. A database has been created with the analyzed calculi by Fourier Transform Infrared Spectroscopy, collecting age, sex, recurrences and biochemical parameters obtained from 24-hour urine. The influence of sex on urinary lithiasis is very marked and the number of stones in the male in much higher. In addition, the age factor increases lithiasis from 5% at 30 years of age to 25% at 60 years of age. These data refer to the total calculi, without differentiating their chemical composition. If differentiation is made according to the composition, a similar tendency is found in men and women in the monohydrate calcium oxalate calculi, but very different in those of dihydrate calcium oxalate and calcium phosphocarbonate. The incidence in children under 20 years of age is very low; males have more calculi in the first decade of life and girls in the second decade of life. In addition, a higher prevalence of stones has been observed in the summer months associated with higher serum levels of vitamin D. Thus, it is essential to stablish classification criteria of urinary calculi for epidemiological studies. In recent years, the ratio of the different compositions has changed, resulting in an increase of oxalate calculi.

Estima-se que a incidência de cálculos renais na Espanha tem aumentado nos últimos anos. Este trabalho foi realizado com uma abordagem epidemiológica da litíase urinária, estabelecendo uma classificação de cálculos urinários analisados durante um ano. Foi criado um banco de dados com os cálculos analisados por espectroscopia de infravermelho com Transformada de Fourier, considerando idade, gênero, recidivas e parâmetros bioquímicos na urina de 24 horas. A influência do gênero na litíase urinária é muito acentuada e o número de cálculos em homens é muito maior. Além disso, o fator idade aumenta a litíase de 5% aos 30 anos para 25% aos 60 anos. Estes dados referem-se os cálculos totais e não diferenciam sua composição química. Diferenciam-se de acordo com a composição, foi encontrada uma tendência semelhante em homens e mulheres nos cálculos de oxalato de cálcio mono-hidratado, mas muito diferente em oxalato de cálcio di-hidratado e fosfo-carbonato de cálcio. A incidência em pessoas menores de 20 anos é muito baixa, prevalecendo em meninos na primeira década e em meninas na segunda década de vida. Além disso, foi observada maior prevalência de cálculos nos meses de verão associada a maiores níveis séricos de vitamina D. Portanto, é essencial a partir de critérios taxativos de classificação dos cálculos urinários para realizar exames epidemiológicos. Nos últimos anos, a proporção entre as diferentes composições tem mudado, resultando num aumento dos cálculos de oxalato.

Comparison of STONE, CROES and Guy's nephrolithometry scoring systems for predicting stone-free status and complication rates after percutaneous nephrolithotomy in obese patients.

In this study, we aim to evaluate the accuracy of STONE (stone size, tract length, obstruction, number of involved calyces, and essence/stone density), Clinical Research Office of the Endourological Society (CROES), and Guy's nephrolithometry scoring systems (NSS) in obese patients. The charts of patients who underwent percutaneous nephrolithotomy (PNL) between June 2008 and June 2016 were retrospectively analyzed. Calculations of the STONE, CROES, and Guy's NSS were performed by a resident who was well informed regarding each NSS. Patients were classified under nine scores according to STONE, four grades according to CROES, and four grades according to Guy's NSS. In total, 248 obese patients were enrolled in the study. Stone size was significantly higher in patients without stone-free status (p = 0.001). In patients who were stone-free and those with residual stones, the mean STONE score was 9.71 and 9.23 (p = 0.160), CROES was 172 and 129 (p = 0.001), and Guy's NSS was 1.67 and 2.75 (p = 0.001). Multivariate regression analysis identified the CROES and Guy's NSS were independent factors for PNL success in obese patients (p = 0.01 and p = 0.01, respectively). The CROES and Guy's NSS showed good accuracy with PNL success (AUC = 0.777 and AUC = 0.844, respectively). None of the three NSS systems were statically associated with a complication rate (p = 0.23 for STONE, p = 0.14 for CROES, and p = 0.51 for Guy's NSS). Our study demonstrated that CROES and Guy's NSS were independent predictors of stone-free rate following PNL in obese patients. Our study also revealed that three of the NSSs were not useful for predicting PNL complications in obese patients.

A novel method for predicting kidney stone type using ensemble learning.

The high morbidity rate associated with kidney stone disease, which is a silent killer, is one of the main concerns in healthcare systems all over the world. Advanced data mining techniques such as classification can help in the early prediction of this disease and reduce its incidence and associated costs. The objective of the present study is to derive a model for the early detection of the type of kidney stone and the most influential parameters with the aim of providing a decision-support system. Information was collected from 936 patients with nephrolithiasis at the kidney center of the Razi Hospital in Rasht from 2012 through 2016. The prepared dataset included 42 features. Data pre-processing was the first step toward extracting the relevant features. The collected data was analyzed with Weka software, and various data mining models were used to prepare a predictive model. Various data mining algorithms such as the Bayesian model, different types of Decision Trees, Artificial Neural Networks, and Rule-based classifiers were used in these models. We also proposed four models based on ensemble learning to improve the accuracy of each learning algorithm. In addition, a novel technique for combining individual classifiers in ensemble learning was proposed. In this technique, for each individual classifier, a weight is assigned based on our proposed genetic algorithm based method. The generated knowledge was evaluated using a 10-fold cross-validation technique based on standard measures. However, the assessment of each feature for building a predictive model was another significant challenge. The predictive strength of each feature for creating a reproducible outcome was also investigated. Regarding the applied models, parameters such as sex, acid uric condition, calcium level, hypertension, diabetes, nausea and vomiting, flank pain, and urinary tract infection (UTI) were the most vital parameters for predicting the chance of nephrolithiasis. The final ensemble-based model (with an accuracy of 97.1%) was a robust one and could be safely applied to future studies to predict the chances of developing nephrolithiasis. This model provides a novel way to study stone disease by deciphering the complex interaction among different biological variables, thus helping in an early identification and reduction in diagnosis time.

Clinical utility of computed tomography Hounsfield characterization for percutaneous nephrolithotomy: a cross-sectional study.

BACKGROUND: Computed Tomography (CT) is considered the gold-standard for the pre-operative evaluation of urolithiasis. However, no Hounsfield (HU) variable capable of differentiating stone types has been clearly identified. The aim of this study is to assess the predictive value of HU parameters on CT for determining stone composition and outcomes in percutaneous nephrolithotomy (PCNL). METHODS: Seventy seven consecutive cases of PCNL between 2011 and 2016 were divided into 4 groups: 40 (52%) calcium, 26 (34%) uric acid, 5 (6%) struvite and 6 (8%) cystine stones. All images were reviewed by a single urologist using abdomen/bone windows to evaluate: stone volume, core (HUC), periphery HU and their absolute difference. HU density (HUD) was defined as the ratio between mean HU and the stone's largest diameter. ROC curves assessed the predictive power of HU for determining stone composition/stone-free rate (SFR). RESULTS: No differences were found based on the viewing window (abdomen vs bone). Struvite stones had values halfway between hyperdense (calcium) and low-density (cystine/uric acid) calculi for all parameters except HUD, which was the lowest. All HU variables for medium-high density stones were greater than low-density stones (p < 0.001). HUC differentiated the two groups (cut-off 825 HU; specificity 90.6%, sensitivity 88.9%). HUD distinguished calcium from struvite (mean ± SD 51 ± 16 and 28 ± 12 respectively; p = 0.02) with high sensitivity (82.5%) and specificity (80%) at a cut-off of 35 HU/mm. Multivariate analysis revealed HUD ≥ 38.5 HU/mm to be an independent predictor of SFR (OR = 3.1, p = 0.03). No relationship was found between HU values and complication rate. CONCLUSIONS: HU parameters help predict stone composition to select patients for oral chemolysis. HUD is an independent predictor of residual fragments after PCNL and may be fundamental to categorize it, driving the imaging choice at follow-up.

Profile of metabolic and infectious stone-formers in a contemporary PCNL cohort.

INTRODUCTION: To identify factors associated with stone composition in patients undergoing percutaneous nephrolithotomy (PCNL). MATERIAL AND METHODS: A retrospective analysis of patients who underwent PCNL at two academic institutions between 2002 and 2014. Stone composition, stone characteristics based on non-contrast computer tomography (NCCT), patient demographics, and the S.T.O.N.E nephrolithometry scores were compared. Stones were characterized as either infection or metabolic. Metabolic stones were classified as calcium phosphate-containing and all others. RESULTS: A total of 192 renal units underwent PCNL. Retrieved stones were found to be 75% (144) metabolic and 25% (48) infection by stone analysis. Of the metabolic stones, 51% (73) were phosphate-containing calculi. Overall, infection stones were found to have a significantly higher S.T.O.N.E nephrolithometry score than metabolic stones (9.2 versus 8.1, p < 0.001). Average Hounsfield units (HU) were significantly lower in infection stones (765 versus 899, p < 0.05). Sixty-three percent of patients with infection stones were female as compared to 46% of patients with metabolic stones. Patients with phosphate-containing stones in the metabolic group were significantly more likely to be female (56% versus 35%, p < 0.01), younger (mean 49 versus 60 years of age, p < 0.02), and have lower BMI's (30 versus 32, p < 0.02) compared with other metabolic stones. CONCLUSIONS: Patient demographics including age, sex and BMI differ between patients with phosphate and non-phosphate containing metabolic stones. Higher S.T.O.N.E nephrolithometry scores were found in infection stones. These findings may serve as useful tools in the identification of stone compositions that are being seen more frequently in large and complicated stones undergoing PCNL.

[Etiopathogenic factors of the different types of urinary litiasis.] / Factores etiopatogénicos de los diferentes tipos de urolitiasis.

In this review, we analyze the etiopathogenic principles of urinary lithiasis formation. In the kidney, calcifications that may cause renal lithiasis are produced as a consequence of processes that injury the urothelium at the papilla and Bellini's ducts. With the improvement of imaging techniques, mainly micro CT scan, it is possible to detect them and we may be able to anticipate to the formation of lithiasis. As we well know, there are different factors that influence the formation of the calculi depending on their composition. In calcium lithiasis it is key to review the modification of the categories of hypercalciuria, we currently distinguish two types instead of three, thanks to the fasting calcium/ creatinine ratio, differentiating absorptive hypercalciuria and fasting hypercalciuria. In the fasting hypercalciuria, it is important to emphasize the relationship between this factor and the loss of bone mineral density in patients with recurrent renal calcic lithiasis, so that in this kind of patients it is compulsory the study of bone metabolism by bone remodelling markers and bone densitometry. Regarding the other factors that participate in the formation of calcium lithiasis we should specially emphasize on hypercalciuria and its growing increase because of its relationship with obesity and metabolic syndrome, as well as hipocitraturia, present in an important percentage of patients and related in some cases with metabolic acidosis and osteopenia-osteoporosis too. In relation to uric acid lithiasis it should be highlighted that urinary pH is the most determinant factor and, therefore, its control and modifications would be paramount for prevention of this type of lithiasis. In the infectious lithiasis, the presence of germs that split urea is mandatory. They generate ammonia ions with the ability to injure the urothelium and to form magnesium ammonium phosphate lithiasis mainly. Regarding cystine lithiasis, rare, it was classically divided in three types and now passed to be classified in type A and B depending on the muted gene, and it is more useful to perform direct 24-hour urine measurement than screening tests which have low sensitivity. In general, we tried to give a comprehensive view of the various types of lithiasis emphasizing the most interesting clinical points for the urologist.

¿Se puede realmente prevenir la litiasis renal? Nuevas tendencias y Herramientas terapéuticas / May renal lithiasis be really prevented? New trends and therapeutic tools

Los cálculos renales se forman en general como consecuencia de la combinación de determinados factores, algunos relacionados con la composición de la orina (concentración de sustancias litógenas, déficit de inhibidores de la cristalización, presencia de nucleantes heterogéneos) y otros con la morfoanatomía renal (estasis urinaria, cavidades de baja eficacia urodinámica, deformaciones morfoanatómicas, lesiones del tejido papilar renal). De hecho, la composición, macroestructura y microestructura del cálculo dependerán claramente de los factores que lo han inducido. Por esta razón, disponer del cálculo renal convenientemente estudiado y clasificado simplifica el diagnóstico y posibilita un enfoque terapéutico más eficaz ya que se dirige directamente a corregir los factores etiológicos responsables de la litiasis. En esta publicación revisamos los principales factores etiológicos implicados en la formación de cada tipo de cálculo y las medidas profilácticas que pueden adoptarse para su adecuada corrección. Los cálculos renales más frecuentes se han clasificado en los siguientes tipos: cálculos de oxalato cálcico monohidrato papilares, cálculos de oxalato cálcico monohidrato de cavidad, cálculos de oxalato cálcico dihidrato, cálculos mixtos de hidroxiapatita/oxalato cálcico, cálculos de carboxiapatita/hidroxiapatita, cálculos de brushita, cálculos de estruvita/carboxiapatita, cálculos de ácido úrico, cálculos de ácido úrico/oxalato cálcico monohidrato y cálculos de cistina. En ocasiones, sin embargo, no se dispone del cálculo para su estudio, en cuyo caso el único camino a seguir consiste en utilizar toda la información disponible (historial clínico, hábitos de vida, datos radiológicos), junto con la información bioquímica urinaria básica, para identificar y corregir cuantos factores etiológicos relacionados con la litiasis renal se hayan identificado

Renal calculi are generally formed as a result of the combination of certain factors, some related to urine composition (concentration of lithogenic substances, deficiency of crystallization inhibitors, presence of heterogeneous nucleants) and others with renal morphology and anatomy (urinary tract stasis, low urodynamic efficiency cavities, morpho-anatomic deformations, renal papillary tissue lesions). In fact, the composition, macrostructure and microstructure of the calculus will clearly depend on the factors that have induced it. For this reason, the appropriate study and classification of the renal calculi simplifies the diagnosis and allows a more effective therapeutic approach since it can be oriented to directly correct the etiological factors responsible for stone formation. In this article, we review the main etiological factors involved in the formation of each type of calculus and the prophylactic measures that can be adopted for proper correction. The most frequent kidney stones have been classified into the following types: calcium oxalate monohydrate papillary calculi, calcium oxalate monohydrate non-papillary calculi, calcium oxalate dihydrate calculi, mixed hydroxyapatite/ calcium oxalate calculi, carboxyapatite/hydroxyapatite calculi, brushite calculi, struvite/carboxyapatite calculi, uric acid calculi, uric acid/calcium oxalate monohydrate calculi, and cystine calculi. Occasionally, however, the calculus is not available for study, in which case the only way forward is to use all available information (clinical history, life habits, radiological data), together with basic biochemical information, to identify and correct all etiological factors related to renal lithiasis that have been identified

The osteopontin-controlled switching of calcium oxalate monohydrate morphologies in artificial urine provides insights into the formation of papillary kidney stones.

The protein osteopontin (OPN) plays an important role in preventing the formation of calcium oxalate monohydrate (COM) kidney stones. To gain insight into these mechanisms, crystallization was induced by addition of human kidney OPN to artificial urine (ionic strength comparable to urine; without citrate), and the OPN-COM interaction studied using a combination of scanning electron (SEM) and confocal microscopy. By SEM, we found that increasing OPN concentrations formed large monoclinic penetration twins (no protein added) and, at higher concentrations (1-, 2µg/ml OPN), super and hyper twins with crystal habits not found in previous studies. For instance, the hyper twins indicate well-facetted gearwheel-like habits with "teeth" developed in all crystallographic directions. At OPN concentrations ≥2µg/ml, a switching to small dumbbell-shaped COM habits with fine-textured surfaces occurred. Confocal microscopy of these dumbbells indicates protein incorporation in almost the entire crystal structure (in contrast to facetted COM), proposing a threshold concentration of ∼2µg/ml OPN for the facetted to the non-facetted habit transformation. Both the gearwheel-like and the dumbbell-shaped habit are again found side-by-side (presumably triggered by OPN concentration gradients within the sample) in in-vitro formed conglomerates, which resemble cross-sections of papillary kidney stones. The abrupt transformation from facetted to non-facetted habits and the unique compliance of the two in-vitro formed habits with the two main morphologies found in papillary kidney stones propose that OPN is a main effector in direct stone-forming processes. Moreover, stone structures which exhibit these two morphologies side-by-side might serve as a novel indicator for OPN concentrations surrounding those structures.

Endoscopic description of renal papillary abnormalities in stone disease by flexible ureteroscopy: a proposed classification of severity and type.

INTRODUCTION: The goal of this original work was to describe papillary abnormalities using flexible ureteroscopy into a new classification and to assess their relation with stone composition. PATIENTS AND METHODS: We performed a prospective monocentric single-operator study aiming to describe various aspects of renal papillae. Data have been prospectively collected during consecutive 164 sequential flexible ureterorenoscopies required for the treatment of renal stones from May 2011 to March 2015. The collected stones have been examined by microscopy and infrared spectrometry. Serum and urine biochemical samples have been systematically analyzed. RESULTS: A total of 74 patients (45.1 %) had renal papillary abnormalities on at least one papilla, excluding typical Randall's deposits alone. Various abnormalities were reported, some of them being present in the same patient: tip papillary erosions (51.3 %), anchored papillae calculi (47.3 %), subepithelial stones (18.9 %), cryptic papillae (10.8 %), extrophic papillae (9.46 %) and intraductal deposits (2.7 %). Associations between papillary abnormalities and stone types were found. Intraductal deposits were systematically associated with carbonate apatite IVa2 stones and hypocitraturia. A "first step" classification has been established to standardize the description of these papillary abnormalities for future reports and studies. CONCLUSIONS: This study highlights the necessity of papillary abnormalities description in further multicentric studies and ureteroscopy's reports. The established classification needs multicentric evaluation and validation. The endoscopic observation and knowledge of pathological aspects of the papillae should help to better understand pathogenesis of nephrolithiasis. Medical or surgical treatments of some abnormalities should be also discussed and evaluated to improve the prevention of stone recurrence.

Treatment Response in Patients with Stones, and Low Urinary pH and Hypocitraturia Stratified by Body Mass Index.

PURPOSE: Obesity has been shown to be a risk factor for kidney stone formation. Obesity leads to insulin resistance which subsequently leads to low urinary pH. Low urinary pH is typically treated with potassium citrate. We determined if the response to potassium citrate for the treatment of low urinary pH and hypocitraturia varied when patients were stratified by body mass index. MATERIALS AND METHODS: We retrospectively reviewed the records of patients with urolithiasis and concomitant hypocitraturia and low urinary pH as unique abnormalities upon metabolic evaluation treated exclusively with potassium citrate. Based on body mass index the cohort was divided into the 4 groups of normal weight, overweight, obese and morbidly obese. Metabolic data were compared among the 4 groups at baseline and subsequent followup visits up to 2 years. We compared urinary pH and citrate in absolute values and the relative changes in these parameters from baseline. Similarly, we compared the rates of potassium citrate treatment failure. RESULTS: A total of 125 patients with hypocitraturia and low urinary pH were included in this study. Median patient age was 61 years, 80 patients were male and median body mass index was 30.4 kg/m(2). Patients with a higher body mass index tended to be younger (p=0.010), and had a lower urinary citrate but higher sodium, oxalate and uric acid levels. Urinary pH was similar across body mass index groups. pH values and their absolute changes from baseline were lower as body mass index increased (p ≤0.001). Similarly, we noted an association between increasing body mass index category and lower urinary citrate levels accompanied by a statistically significant trend indicating lower absolute changes in citrate with increasing body mass index (p ≤0.001). Potassium citrate dose was increased more frequently among the higher body mass index groups. CONCLUSIONS: Patients with a higher body mass index presented with a lower increase in citrate excretion and urinary pH levels after they were started on potassium citrate, and they needed more frequent adjustments to their therapy.