Calcium Phosphate Stones Research Articles

Nephrocalcinosis in Calcium Stone Formers Who Do Not have Systemic Disease

Nephrocalcinosis is commonly present in primary hyperparathyroidism, distal renal tubular acidosis and medullary sponge kidney disease. To our knowledge it has not been studied in patients with calcium phosphate stones who do not have systemic disease. We studied patients undergoing percutaneous nephrolithotomy who had calcium phosphate or calcium oxalate stones and did not have hyperparathyroidism, distal renal tubular acidosis or medullary sponge kidney disease. On postoperative day 1 all patients underwent noncontrast computerized tomography. If there were no residual calcifications, the patient was categorized as not having nephrocalcinosis. If there were residual calcifications, the patient underwent secondary percutaneous nephrolithotomy. If the calcifications were found to be stones, the patient was categorized as not having nephrocalcinosis. If the calcifications were not stones, the patient was categorized as having nephrocalcinosis. Patients were grouped based on the type of stones that formed, including hydroxyapatite, brushite and idiopathic calcium oxalate. The extent of nephrocalcinosis was quantified as 0--absent nephrocalcinosis to 3--extensive nephrocalcinosis. Patients with residual calcifications on postoperative day 1 noncontrast computerized tomography who did not undergo secondary percutaneous nephrolithotomy were excluded from analysis. The presence or absence of nephrocalcinosis was correlated with metabolic studies. A total of 67 patients were studied, including 14 with hydroxyapatite, 19 with brushite and 34 with idiopathic calcium oxalate calculi. Nephrocalcinosis was present in 10 of 14 (71.4%), 11 of 19 (57.9%) and 6 of 34 patients (17.6%) in the hydroxyapatite, brushite and idiopathic calcium oxalate groups, respectively (chi-square p = 0.01). The mean extent of nephrocalcinosis per group was 1.98, 1.32 and 0.18 for hydroxyapatite, brushite and idiopathic calcium oxalate, respectively (p ≤0.001). The presence of nephrocalcinosis positively correlated with urine calcium excretion (mean ± SD 287.39 ± 112.49 vs 223.68 ± 100.67 mg per day, p = 0.03). Patients without systemic disease who form hydroxyapatite and brushite stones commonly have coexistent nephrocalcinosis. Nephrocalcinosis can occur in calcium oxalate stone formers but the quantity and frequency of nephrocalcinosis in this group are dramatically less.

Effect of Potassium Citrate on Calcium Phosphate Stones in a Model of Hypercalciuria.

Potassium citrate is prescribed to decrease stone recurrence in patients with calcium nephrolithiasis. Citrate binds intestinal and urine calcium and increases urine pH. Citrate, metabolized to bicarbonate, should decrease calcium excretion by reducing bone resorption and increasing renal calcium reabsorption. However, citrate binding to intestinal calcium may increase absorption and renal excretion of both phosphate and oxalate. Thus, the effect of potassium citrate on urine calcium oxalate and calcium phosphate supersaturation and stone formation is complex and difficult to predict. To study the effects of potassium citrate on urine supersaturation and stone formation, we utilized 95th-generation inbred genetic hypercalciuric stone-forming rats. Rats were fed a fixed amount of a normal calcium (1.2%) diet supplemented with potassium citrate or potassium chloride (each 4 mmol/d) for 18 weeks. Urine was collected at 6, 12, and 18 weeks. At 18 weeks, stone formation was visualized by radiography. Urine citrate, phosphate, oxalate, and pH levels were higher and urine calcium level was lower in rats fed potassium citrate. Furthermore, calcium oxalate and calcium phosphate supersaturation were higher with potassium citrate; however, uric acid supersaturation was lower. Both groups had similar numbers of exclusively calcium phosphate stones. Thus, potassium citrate effectively raises urine citrate levels and lowers urine calcium levels; however, the increases in urine pH, oxalate, and phosphate levels lead to increased calcium oxalate and calcium phosphate supersaturation. Potassium citrate induces complex changes in urine chemistries and resultant supersaturation, which may not be beneficial in preventing calcium phosphate stone formation.

MP80-17 DO 24-HOUR URINE SUPERSATURATIONS PREDICT STONE COMPOSITION?

You have accessJournal of UrologyStone Disease: Evaluation II1 Apr 2015MP80-17 DO 24-HOUR URINE SUPERSATURATIONS PREDICT STONE COMPOSITION? Mohamed Omar, Alaa El Mahdy, Ahmed Gamal, and Manoj Monga Mohamed OmarMohamed Omar More articles by this author , Alaa El MahdyAlaa El Mahdy More articles by this author , Ahmed GamalAhmed Gamal More articles by this author , and Manoj MongaManoj Monga More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.2853AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES To evaluate the correlation between 24 hour urine supersaturation levels and the crystalline stone composition. METHODS We retrospectively reviewed the results of stone analysis of 386 patients who had completed 24 hour urine stone risk profiles within 6 months of stone analysis. Patients were characterized as calcium oxalate, calcium phosphate or Uric acid stone formers based on the predominant component (>60%) of their stone. Patients with <50% of one stone composition were characterized as a mixed stone former. Sensitivity, specificity and accuracy of the 24-hour urine supersaturation for predicting the corresponding stone component were calculated. RESULTS The distribution of stone compositions was 235(61%) CAOX, 98(25%) CAPH, 35(9%) Uric acid and 18(5%) mixed stone group. The accuracy of supersaturation for predicting the predominant stone composition was 52.5% for CAOX, 70% for CAPH and 67% for Uric acid group. Even when the predominant stone composition exceeded 90%, the accuracy of supersaturation didn't change remarkably, coax (49 %, p=0.6641), cap (77%, p= 0.361) and uric acid (67%, p=0.9593) CONCLUSIONS 24-hour urine supersaturation has a poor accuracy to predict the predominant stone composition. Accuracy is highest for patients with calcium phosphate stone compositions. Bivariate comparison of 24-hour urine elements across stone type groups Demographics CaOx CaP Uric A Mixed P Value No. of patients (%) 235 (61%) 98 (25%) 35 (9%) 18 (5%) 386 Gender: Male 151 (64%) 31 (32%) 24 (69%) 10 (56%) <.0001 Gender: Female 84 (36%) 67 (68%) 11 (31%) 8 (44%) <.0001 Mean age 56±15 54±17 60±10 50±14 0.390 BMI 29±7.5 29.3±9.3 31.2±6.4 30.5±7.4 0.3781 pH 5.9±0.4 6.4±0.6 5.8±0.6 6.4±0.6 <.0001 Urine volume 2±0.9 2.1±1 1.9±0.8 1.9±1 0.6195 CaOx SS 6.74±3.6 6.6±3.7 5.9±3.7 5.6±3.2 0.3202 CaP SS 1±0.96 1.6±1.2 0.7±1.1 1.5±1.2 <.0001 Uric Acid SS 1±0.87 0.46±0.5 1.4±1 0.5±0.87 <.0001 Accuracy of supersaturation at different cut-off values of predominant stone composition Mineral Calcium oxalate Calcium phosphate Uric Acid >60% 52.5% 70% 67% >70% 54% 72% 67% >80% 54% 76% 67% >90% 49% 77% 67% © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e1025-e1026 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Mohamed Omar More articles by this author Alaa El Mahdy More articles by this author Ahmed Gamal More articles by this author Manoj Monga More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

MP40-19 METABOLIC STONE WORK-UP IN CHILDREN: WHAT DOES IT TELL US AND HOW IS IT UTILIZED?

INTRODUCTION AND OBJECTIVES: Lower pole renal stones in children, usually present as an incidental finding. In general the need for intervention is rare but the precise frequency is unknown. Here in we evaluate the outcome of lower pole renal stones in children. METHODS: After Research Ethics Board (REB) approval, we performed a retrospective review of charts and renal ultrasounds of children with lower pole stones seen in Urology clinic at The Hospital for Sick Children over a period of 14 years. Complex renal malformations as horseshoe kidney, solitary kidney, solitary functioning kidney and cross-fused ectopia were excluded. Our goals are: 1) to determine factors that might predict the need for stone intervention (type of stones, underlying metabolic disease, size, and growth rate); 2) to calculate the success rate of non-operative management. RESULTS: One hundred and eight children with nephrolithiasis were initially screened. Forty six (42.6%) found to have lower pole stones. Mean age at presentation was 112.6 61.5 months. Twenty six patients (56.5%) were boys. Thirty six children (78.2%) had only 1 or 2 lower pole stones. Mean time of follow-up was 4.3 3.7 years. The difference between mean size of the lower pole stones in ultrasound (US) at presentation vs. last visit for patients followed conservatively was not statistically significant (6.9 3.2 mm vs. 7.38 4.5 mm, respectively ; ANOVA p1⁄40.1). Twenty one patients (45.6%) were symptomatic (renal colic and/or gross hematuria). From those, 10 passed stones (2 calcium phosphate, 5 calcium oxalate, 1 cystine, 1 uric acid, and 1 struvite). Twenty five (54.3%) children had surgery for stone removal (9 had extracorporeal shock wave lithotripsy, 14 ureteroscopy, 1 open nephrolithotomy and 1 nephrectomy). From those, 16 (64%) had stone growth over-time and significantly larger stones (10.6 5.5 mm) at baseline US. Five had percutaneous nephrolithotomy as second surgical procedure. Vast majority (90.9%) were calcium phosphate or calcium oxalate stones. CONCLUSIONS: Our data suggests that lower pole stones could be followed conservatively. Initial stone size greater than 10.6 5.5 mm and stone growth over-time are significant risk factors that might predict the need for surgical intervention.

Mechanism by which shock wave lithotripsy can promote formation of human calcium phosphate stones.

Human stone calcium phosphate (CaP) content correlates with higher urine CaP supersaturation (SS) and urine pH as well as with the number of shock wave lithotripsy (SWL) treatments. SWL does damage medullary collecting ducts and vasa recta, sites for urine pH regulation. We tested the hypothesis that SWL raises urine pH and therefore Cap SS, resulting in CaP nucleation and tubular plugging. The left kidney (T) of nine farm pigs was treated with SWL, and metabolic studies were performed using bilateral ureteral catheters for up to 70 days post-SWL. Some animals were given an NH4Cl load to sort out effects on urine pH of CD injury vs. increased HCO3 (-) delivery. Histopathological studies were performed at the end of the functional studies. The mean pH of the T kidneys exceeded that of the control (C) kidneys by 0.18 units in 14 experiments on 9 pigs. Increased HCO3 (-) delivery to CD is at least partly responsible for the pH difference because NH4Cl acidosis abolished it. The T kidneys excreted more Na, K, HCO3 (-), water, Ca, Mg, and Cl than C kidneys. A single nephron site that could produce losses of all of these is the thick ascending limb. Extensive injury was noted in medullary thick ascending limbs and collecting ducts. Linear bands showing nephron loss and fibrosis were found in the cortex and extended into the medulla. Thus SWL produces tubule cell injury easily observed histopathologically that leads to functional disturbances across a wide range of electrolyte metabolism including higher than control urine pH.

Uroliths of dogs in Switzerland from 2003 to 2009

Information on composition of uroliths collected between 2003 and 2009 from dogs in Switzerland and epidemiologic data of affected dogs are summarised in this paper. Of 490 stones analysed 44% were composed of calcium oxalate, 330% of struvite, 80% of silica, 7% of urate, 3% of cystine, 3% were mixed stones and 1% each were calcium phosphate and xanthine stones. Compared to other dogs, Norwich Terriers, Norfolk Terriers, Miniature Schnauzers, Miniature Pinscher and Yorkshire Terriers had a significantly increased risk to suffer from calcium oxalate stones, Dalmatians and Continental Bulldogs from urate stones and English Bulldogs from cystine stones. No breed had an increased risk of struvite or silica stones. Stones composed of silica were more prevalent in Switzerland compared to other countries and were more common in the eastern part than in the western part of Switzerland. This study shows that there are differences in occurrence and prevalence of uroliths between Switzerland and surveys of other countries.

Relationship between PatientÂ’s Demographics and Stone Composition in Men and Women

Purpose: To detect the differences in age, weight and height between three major stone groups. Materials and Methods: We retrospectively reviewed all patients with a diagnosis of nephrolithiasis in a large healthcare network from January 2000 to July 2014, for whom information on stone composition, age, sex, weight and height was available. Patients less than 18 years were excluded. Patients were characterized by gender and the major component of their stone analysis. We used Wilcoxon rank-sum test for continuous variables to detect the significant differences and multiple logistic regression analysis to evaluate the relative risk between stone groups. Results: 14,961 adult patients were identified. The Distribution of pure (≥ 90%) calcium oxalate, phosphate and uric acid stones in men, was (71%), (7%) and (22%) while in women it was (65%), (19%) and (16%) respectively. Males with calcium oxalate stones were taller than those with calcium phosphate by 2 cm (p=0.0006). Women with calcium phosphate stones were younger than those with calcium oxalate stones by 5 years (p=0.0001). Conclusions: Calcium phosphate stone composition is associated with a shorter stature in men and younger age in women in relation to those with calcium oxalate stones.

Does 24-Hour Urine Supersaturation Predict Stone Composition?

Background: The aim of the study was to evaluate the correlation between 24-hour urine supersaturation (SS) levels and the crystalline stone composition. Methods: We retrospectively reviewed the results of stone analysis of 386 patients who had completed 24-hour urine stone risk profiles within 2 months of stone analysis. Patients were characterized as calcium oxalate (CAOX), calcium phosphate (CAPH) or uric acid (UA) stone formers based on the predominant component (> 60%) of their stone. Patients with < 50% of one stone composition were characterized as a mixed stone former. Sensitivity, specificity and accuracy of the 24-hour urine SS for predicting the corresponding stone component were calculated. Results: The distribution of stone compositions was 235 (61%) CAOX, 98 (25%) CAPH, 35 (9%) UA and 18 (5%) mixed stone group. At predominant stone mineral concentration ? 60%, the accuracy of 24-hour urine SS for predicting the predominant stone composition was 52.5% for CAOX, 70% for CAPH and 67% for UA group. Even when the predominant stone mineral concentration was ? 90%, the accuracy of SS did not improve: COAX (49%, P = 0.6641), CAPH (77%, P = 0.361) and UA (67%, P = 0.9593). Conclusions: Twenty-four-hour urine SS has a poor accuracy to predict the predominant stone composition. Accuracy is highest for patients with CAPH stones. World J Nephrol Urol. 2015;4(1):169-172 doi: http://dx.doi.org/10.14740/wjnu206w

Calcium Phosphate Stone Morphology Can Reliably Predict Distal Renal Tubular Acidosis

Calcium stones represent 85% to 90% of all urinary calculi, including various crystalline compositions and etiological conditions. Calcium phosphate accounts for 10% to 15% of cases. These stones are mainly related to 3 groups of risk factors, including calcium or phosphate metabolism disturbance, renal acidification defects and urinary tract infection. Identifying the stone etiology often requires extensive metabolic evaluation. We assessed whether stone analysis including morphological typing in addition to stone composition could be a valuable help for diagnosis. Of 60,564 stones analyzed by morphological examination and infrared spectroscopy at our laboratory 6,439 (10.6%) were mainly composed of carbapatite. Of these stone 1,093 patients were included in study who had an available etiological diagnosis and stones containing at least 70% of calcium phosphate without struvite. Of the 1,093 calcium phosphate stones 12.8% showed a peculiar morphology termed IVa2, characterized by a smooth aspect and a glazed brown-yellow appearance with tiny cracks. IVa2 morphology was observed in 96.1% of stones associated with inherited distal renal tubular acidosis. In contrast, the other stones of similar composition but different morphology were related to distal renal tubular acidosis in only 3.9% of cases. In addition, IVa2 stones were found in 65% of calcium phosphate stone formers associated with Sjögren syndrome and in 35% of calcium phosphate stones in patients with medullary sponge kidney. These 2 conditions are related to a mild to moderate distal acidification defect. Identifying IVa2 stone morphology is clinically relevant because it should prompt clinicians to search for complete or incomplete distal acidosis and initiate specific therapy to decrease recurrence.

Stone Size Limits the Use of Hounsfield Units for Prediction of Calcium Oxalate Stone Composition

To evaluate the role of stone size in predicting urinary calculus composition using Hounsfield units on noncontrasted computed tomography (CT) scan. A retrospective review was performed for all patients who underwent ureteroscopy or percutaneous nephrolithotomy during a 1-year period, had a stone analysis performed, and had CT imaging available for review. All CT scans were reviewed by a board-certified radiologist. Variables evaluated included age, sex, body mass index, stone size, stone location, Hounsfield units (HUs), and stone composition. We identified a total of 91 patients (41 men and 50 women) with CT imaging and stone analysis available for review. Stone analysis showed 41 calcium oxalate monohydrate (CaOxMH), 13 calcium oxalate dihydrate, 29 calcium phosphate, 5 uric acid, 2 struvite, and 1 cystine stone. Average age was 46 years, and average body mass index was 32 kg/m2. Measured HUs varied significantly with size for CaOxMH and calcium oxalate dihydrate stones (P values <.05), but not for calcium phosphate stones (P = .126). Using a CaOxMH identification value of 700-1000 HUs, 28 of 41 stone compositions (68%) would not have been correctly identified, including all 10 (100%) small (<5 mm) stones, 13 of 22 (59%) medium (5-10 mm) stones, and 5 of 9 large (>10 mm) stones (55%). For calcium stones, the ability of CT HUs to predict stone composition was limited, likely due to the mixed stone composition. Within a cohort of CaOxMH stone formers, measured HUs varied linearly with stone size. All stones <5 mm were below thresholds for CaOxMH composition.

Trace elements in urinary stones: a preliminary investigation in Fars province, Iran.

In view of the high incidence rate of urinary stones in the south and southwest of Iran, this paper investigates trace elements content including heavy metals in 39 urinary stones, collected from patients in Fars province, Iran. The mineralogy of the stones is investigated using X-ray diffractometry. The samples are classified into five mineral groups (calcium oxalate, uric acid, cystine, calcium phosphate and mixed stone). Major and trace elements in each group were determined using ICP-MS method. P and Ca constitute the main elements in urinary stones with Ca being more affine to oxalates while other alkali and alkaline earths precipitate with phosphate. Significant amounts of trace elements, especially Zn and Sr, were found in urinary calculi (calcium oxalate and phosphates) relative to biominerals (uric acid and cystine). Among urinary calculi, calcium phosphate contains greater amounts of trace metal than calcium oxalate. Phosphates seem to be the most important metal-bearing phases in urinary stones. Results indicate that concentrations of elements in urinary stones depend on the type of mineral phases. Significant differences in elements content across various mineralogical groups were found by applying statistical methods. Kruskal-Wallis test reveals significant difference between Ca, P, K, Na, Mg, S, Zn, Sr, Se, Cd, and Co content in different investigated mineral groups. Moreover, Mann-Whitney test differentiates Ca, Na, Zn, Sr, Co, and Ni between minerals in oxalate and uric acid stones. This study shows that urinary stone can provide complementary information on human exposure to elements and estimate the environmental risks involved in urinary stones formation.

Association of serum biochemical metabolic panel with stone composition.

To determine the association of the basic metabolic panel with stone type. The present study was a retrospective review of 492 stone formers with both stone composition analysis and basic metabolic panel available. Analysis of a basic metabolic panel across stone types was carried out using Fisher's exact test and analysis of variance. Multinomial logistic regression was used to predict stone type based on a basic metabolic panel. A total of 272 (55%) patients had predominantly calcium oxalate stones, 100 (21%) had uric acid stones, 93 (19%) had calcium phosphate stones, 16 (3%) had mixed stones and 11 (2%) had other types of stones. Uric acid stone formers had the highest serum glucose, blood urea nitrogen and creatinine levels. Calcium oxalate stone formers had the highest serum sodium. No significant differences in mean serum calcium levels across different stone types were identified. The predicted risk of uric acid stone over the other stone types increased with an increase in serum glucose and decreased with an increase in carbon dioxide levels. The predicted risk of calcium oxalate stones increased with an increase in serum sodium and chloride levels. The predicted risk of calcium phosphate and oxalate stones over the other stone types increased with an increase in serum calcium levels. The overall accuracy of the basic metabolic panel alone to predict stone type was 59%. A basic metabolic panel alone or in combination with 24-h urinalysis and demographics does not accurately predict stone type. However, it can be used in combination with other variables to predict stone composition.

Metabolic disorders: stones as first clinical manifestation of significant diseases.

Metabolic syndrome, type 2 diabetes, and primary hyperparathyroidism are metabolic disorders that should deserve a special focus in renal stone patients as a pathogenic link is established with some stone components. Indeed, an acidic urinary pH due to a decreased ammonium bioavailability explains the high prevalence of uric acid stones in patients with metabolic syndrome or diabetes and, primary hyperparathyroidism induced hypercalciuria increases the risk of calcium phosphate stones. We report here four clinical cases of renal stone patientswith metabolic disorders encountered in a daily practice.Clinical andmetabolicfindings altogether with stone analysis componentspresented here,illustrate relevant pathophysiological links. 24 hours urine evaluation and stone analysis which includes both morphological typingand infrared spectroscopy, are key diagnostic steps for early recognition of metabolic disorders. Metabolic screening allows diet related stone identification, points out stone risk factors and identifies patients'comorbidity. The occurrence of nephrocalcinosis with or without chronic renal failure should require a more detailed metabolic evaluation in order to identify uncommon etiologies such as renal tubular acidosis.

Evaluation of Hounsfield Units as a predictive factor for the outcome of extracorporeal shock wave lithotripsy and stone composition.

The objective of this study was to evaluate the utility of the Hounsfield Unit (HU) values as a predictive factor of extracorporeal shock wave lithotripsy outcome for ureteral and renal stones. We also assessed the possibility that HU values could be used to predict stone composition. A retrospective study was performed to measure stone HU values in 260 patients who underwent extracorporeal shock wave lithotripsy (ESWL) for solitary renal and ureteral stones from July 2007 to January 2012. Stone volume, location, skin-to-stone distance, stone HU values, and stone composition were assessed. Success of ESWL was defined as: (1) being stone-free or (2) residual stone fragments <4 mm after 3 months by radiography. Of the 260 assessed patients, 141 (54.2%) were stone-free, 32 (12.3%) had residual stone fragments <4 mm (clinically insignificant stone fragments), and 87 (33.5%) had residual stone fragments ≥4 mm after one round of ESWL. Multivariate analysis revealed that stone location and mean HU were significant predictors of ESWL success. Receiver operating characteristic curves defined cutoff values for predicting treatment outcome. Treatment success rates were significantly higher for stones <815 HU than with stones >815 HU (P < 0.0265). HU of calcium oxalate and calcium phosphate stones were higher than those of uric acid stones, but we could not differentiate between calcium oxalate monohydrate and calcium oxalate dihydrate stones. Evaluation of stone HU values prior to ESWL can predict treatment outcome and aid in the development of treatment strategies.

Sulfate but not thiosulfate reduces calculated and measured urinary ionized calcium and supersaturation: implications for the treatment of calcium renal stones.

BackgroundUrinary sulfate (SO4 2−) and thiosulfate (S2O3 2−) can potentially bind with calcium and decrease kidney stone risk. We modeled the effects of these species on the concentration of ionized calcium (iCa) and on supersaturation (SS) of calcium oxalate (CaOx) and calcium phosphate (CaP), and measured their in vitro effects on iCa and the upper limit of stability (ULM) of these salts.MethodsUrine data from 4 different types of stone patients were obtained from the Mayo Nephrology Clinic (Model 1). A second data set was obtained from healthy controls and hypercalciuric stone formers in the literature who had been treated with sodium thiosulfate (STS) (Model 2). The Joint Expert Speciation System (JESS) was used to calculate iCa and SS. In Model 1, these parameters were calculated as a function of sulfate and thiosulfate concentrations. In Model 2, data from pre- and post STS urines were analyzed. ULM and iCa were determined in human urine as a function of sulfate and thiosulfate concentrations.ResultsCalculated iCa and SS values for all calcium salts decreased with increasing sulfate concentration. Thiosulfate had no effect on these parameters. In Model 2, calculated iCa and CaOx SS increased after STS treatment, but CaP SS decreased, perhaps due to a decrease in pH after STS treatment. In confirmatory in vitro experiments supplemental sulfate, but not thiosulfate, significantly increased the calcium needed to achieve the ULM of CaP and tended to increase the oxalate needed to reach the ULM of CaOx. Sulfate also significantly decreased iCa in human urine, while thiosulfate had no effect.ConclusionIncreasing urinary sulfate could theoretically reduce CaOx and CaP stone risk. Although STS may reduce CaP stone risk by decreasing urinary pH, it might also paradoxically increase iCa and CaOx SS. As such, STS may not be a viable treatment option for stone disease.

The Relationship Between Urinary Stone Components and Visceral Adipose Tissue Using Computed Tomography–based Fat Delineation

To determine the relationship between body mass index (BMI), visceral adipose tissue (VAT), and stone components. A cross-sectional study has been done for urinary stone cohort between 2010 and 2012. Data on patient's age, gender, BMI, urinary pH, stone components, and VAT using computed tomography-based delineation were collected. Obesity was defined as BMI≥25 kg/m2 or as VAT≥100 cm2. To compare the differences between the types of stones, multinomial logistic regression analyses were conducted. Of 203 cases, 49.3% patients were obese based on BMI, and 65.5% were obese using VAT criteria. Multinomial logistic regression analysis revealed that obesity defined by VAT was found to be associated with uric acid stones compared with calcium phosphate stones (odds ratio [OR] 6.544, 95% confidence interval [CI], P=.030) and mixed calcium oxalate phosphate stones (OR 5.582, 95% CI, P=.038). Similar results were observed in calcium oxalate stones over calcium phosphate stones (OR 2.984, 95% CI, P=.032) and calcium oxalate phosphate stones (OR 2.542, 95% CI, P=.041). On the contrary, obesity defined based on BMI has no correlation over all types of urinary stone components. This result implies that VAT has a more important role in uric acid and calcium oxalate stone formation than total body fat, represented by BMI.

Nephrocalcinosis in primary Sjogren's syndrome

A 29-year-old woman presented with a known nephrocalcinosis that had developed nine years earlier. Her past medical history was remarkable for a cardiac arrest secondary to a profound hypokalaemia (1.7 mEq/L) in the post-operative period following a complicated appendicular peritonitis at 19 years of age. Her on-going treatment included potassium citrate supplementation and increased fluid intake to induce hyperdiuresis. There was no relevant family history. On admission, pertinent laboratory data were as follows: hypokalaemia (3.4 mEq/L), normal anion gap hyperchloraemic metabolic acidosis (plasma 21 mEq/L), inappropriately high urine pH (7.0), positive urinary anion gap (þ21 mEq/L), tubular proteinuria 0.5 g per 24 h and chronic kidney disease (serum creatinine, 1.4 mg/dL. CKD Epi MDRD creatinine clearance, 72 mL/min). A urine pH of >5.3 in the presence of metabolic acidosis suggests distal renal tubular acidosis. On bicarbonate loading, was <5%, with a low (urinary–blood) DpCO2 (13 mmHg), suggesting defective H+ secretion by alpha-intercalated cells. A CT scan imaging (Figure 1A) and plain X-ray of the abdomen (Figure 1B) showed macroscopic bilateral nephrocalcinosis. Biochemical analysis of the kidney stone revealed a calcium phosphate stone type suggestive of distal renal tubular acidosis (dRTA). She had polyclonal hypergammaglobulinaemia and positive antinuclear antibodies (1/1600) of anti-Ro/SS-A type. Accessory salivary gland biopsy showed Grade 2 inflammatory infiltrates on the Chisholm–Mason scale. The kidney biopsy revealed mild inflammatory cell infiltrates, with interstitial fibrosis. Fig. 1. (A) Bilateral macroscopic nephrocalcinosis. (B) Plain X-ray. Distal RTA is the most common cause of nephrocalcinosis due to hypercalciuria without hypercalcaemia. The reported prevalence of nephrocalcinosis in patients with dRTA ranges from 60 to 80%. Distal renal tubular acidosis (dRTA) related to Sjogren's syndrome occurred in up to 33%. Primary Sjogren's syndrome may manifest itself as dRTA-associated nephrocalcinosis by autoantibodies directed against the A-type intercalated cells in the collecting tubules leading to a defect in hydrogen ion secretion.

Can 24-Hour Urine Stone Risk Profiles Predict Urinary Stone Composition?

Distinguishing calcium oxalate from uric acid stones is critical to identify those patients who may benefit from dissolution therapy and can also help direct preventive measures for stone growth. We aim to study whether 24-hour urine analysis may predict the urinary stone composition. We retrospectively identified patients with calcium oxalate and uric acid stone compositions who also had a 24-hour urine collection within 3 months of stone analysis. Patients with calcium phosphate, cystine, and other stone compositions were excluded. Subjects were divided based on their stone type (calcium oxalate vs uric acid stones) and were compared according to demographic data and 24-hour urine analysis. Logistic regression analysis was performed to assess the association between stone composition and covariates. A nomogram was then constructed to predict uric acid stones over calcium oxalate stones. Of the 1163 patients identified, 1054 (90.6%) had calcium oxalate stones and 109 (9.4%) had uric acid stones. On logistic regression, body mass index (BMI) (odds ratio [OR] 1.351, 95% confidence interval [CI] 1.133-1.609; P<0.001), urinary sodium (OR 1.021, 95% CI 1.004-1.037; P=0.013), calcium (OR 0.987, 95% CI 0.979-0.996; P=0.003), oxalate (OR 0.890, 95% CI 0.804-0.985; P=0.024), and uric acid (OR 0.989, 95% CI 0.982-0.997; P=0.005) were significant predictors for urinary stone composition. The nomogram with the highest concordance index (c-index=0.855) was obtained using age, BMI, urinary sodium, calcium, oxalate, and uric acid as variables. Distinguishing uric acid from calcium oxalate stones can be performed with relative accuracy using parameters from the 24-hour urine stone risk profile and the patient's BMI and age.

Age-dependent Association Between Dickkopf-1 and Calcium-containing Urolithiasis

To evaluate the serum Dickkopf-1 (DKK1) level in patients with calcium-containing upper urinary tract stones (Ca-UUTS). The study retrospectively enrolled 184 patients with Ca-UUTS and 46 age-matched controls. The serum DKK1 level and urine calcium/creatinine ratio were detected in both groups. The mean serum DKK1 level in the controls was 321.7 ± 284.1 pg/mL, which was significantly lower than that of the patients with calcium oxalate and calcium phosphate (CaOx + CaP), CaOx, and CaP stones (687.8 ± 600.2, 640.5 ± 721.5, and 857.9 ± 913.2 pg/mL, respectively). The mean urine calcium/creatinine ratio, an indicator of hypercalciuria, was higher in the Ca-UUTS patients with CaOx + CaP (0.10 ± 0.06), CaOx (0.13 ± 0.07), and CaP (0.12 ± 0.07) stones than in the controls (0.08 ± 0.04). Statistical significance was noted only in the patients with CaOx (P = .005) and CaP (P = .037) stones. A significant positive association was found between the serum DKK1 level and age in the control group but not in the Ca-UUTS patients. In subjects aged younger than 50 years, the serum DKK1 level in the Ca-UUTS group was significantly higher than in the control group (605.3 ± 514.4 vs 274 ± 229.8 pg/mL, P = .0003). The serum DKK1 level was not associated with stone size. Serum DKK1, an inhibitor of the Wnt signaling pathway, was positively associated with the formation of Ca-UUTS, especially in patients aged younger than 50 years.

Determinants of Holmium:Yttrium–aluminum-garnet Laser Time and Energy During Ureteroscopic Laser Lithotripsy

To evaluate the association of preoperative noncontrast computed tomography stone characteristics, laser settings, and stone composition with cumulative holmium:yttrium-aluminum-garnet (Ho:YAG) laser time/energy. We retrospectively reviewed patients who underwent semirigid/flexible ureteroscopy and Ho:YAG laser lithotripsy (200 or 365 μm laser fiber; 0.8-1.0 J energy; and 8-10 Hz rate) at 2 tertiary care centers (April 2010-May 2012). Studied parameters were as follows: patient's characteristics; stone characteristics (location, burden, hardness, and composition); total laser time and energy; and surgical outcomes. One hundred patients met our inclusion criteria. Mean stone size was 1.01 ± 0.42 cm and volume 0.33 ± 0.04 cm(3). Mean stone radiodensity was 990 ± 296 HU, and Hounsfield units density 13.8 ± 6.0 HU/mm. All patients were considered stone free. Stone size and volume had a significant positive correlation with laser energy (R = 0.516, P <.001; R = 0.621, P <.001) and laser time (R = 0.477, P <.001; R = 0.567, P <.001). When controlling for stone size, only the correlation between HU and laser time was significant (R = 0.262, P = .011). In the multivariate analysis, with exception of stone composition (P = .103), all parameters significantly increased laser energy (R(2) = 0.524). Multivariate analysis revealed a positive significant association of laser time with stone volume (P <.001) and Hounsfield units density (P <.001; R(2) = 0.512). In multivariate analysis for laser energy, only calcium phosphate stones required less energy to fragment compared with uric acid stones. No significant differences were found in the multivariate laser time model. Ho:YAG laser cumulative energy and total time are significantly affected by stone dimensions, hardness location, fiber size, and power. Kidney location, laser fiber size, and laser power have more influence on the final laser energy than on the total laser time. Calcium phosphate stones require less laser energy to fragment.