Xanthine Oxidoreductase Inhibitors Suppress the Onset of Exercise-Induced AKI in High HPRT Activity Urat1-Uox Double Knockout Mice.

BACKGROUND: Hereditary renal hypouricemia type 1 (RHUC1) is caused by URAT1/SLC22A12 dysfunction, resulting in urolithiasis and exercise-induced AKI (EIAKI). However, because there is no useful experimental RHUC1 animal model, the precise pathophysiologic mechanisms underlying EIAKI have yet to be elucidated. We established a high HPRT activity Urat1-Uox double knockout (DKO) mouse as a novel RHUC1 animal model for investigating the cause of EIAKI and the potential therapeutic effect of xanthine oxidoreductase inhibitors (XOIs). METHODS: The novel Urat1-Uox DKO mice were used in a forced swimming test as loading exercise to explore the onset mechanism of EIAKI and evaluate related purine metabolism and renal injury parameters. RESULTS: Urat1-Uox DKO mice had uricosuric effects and elevated levels of plasma creatinine and BUN as renal injury markers, and decreased creatinine clearance observed in a forced swimming test. In addition, Urat1-Uox DKO mice had increased NLRP3 inflammasome activity and downregulated levels of Na+-K+-ATPase protein in the kidney, as Western blot analysis showed. Finally, we demonstrated that topiroxostat and allopurinol, XOIs, improved renal injury and functional parameters of EIAKI. CONCLUSIONS: Urat1-Uox DKO mice are a useful experimental animal model for human RHUC1. The pathogenic mechanism of EIAKI was found to be due to increased levels of IL-1ß via NLRP3 inflammasome signaling and Na+-K+-ATPase dysfunction associated with excessive urinary urate excretion. In addition, XOIs appear to be a promising therapeutic agent for the treatment of EIAKI.

Plasma levels and urinary excretion of protein Z in patients with urolithiasis.

OBJECTIVES: Protein Z (PZ) is a γ-carboxyglutamic acid protein present in plasma that is involved in blood coagulation. Detailed analysis of urinary stones from patients with urolithiasis has revealed that PZ is often found in urinary stones composed of calcium oxalate monohydrate. In this study, we compared blood and urinary PZ concentrations between healthy individuals and patients with urolithiasis. METHODS: Plasma and urine were collected from healthy individuals and patients with urolithiasis who provided informed consent. PZ was detected as a urinary stone matrix protein in some of the patients. PZ was quantified by ELISA, creatinine was measured by the enzymatic method, and the total protein concentration was measured by the Bradford method. RESULTS: The plasma PZ level was 2.54 ± 1.02 µg/mL in healthy individuals and that in urolithiasis patients classified by stone history were from 1.16 ± 0.77 to 3.73 ± 1.09 µg/mL, which was not significantly different. The urinary excretion of PZ (PZ/creatinine) was also not different in patients with urolithiasis and in healthy individuals (from 54.1 ± 40.9 to 95.4 ± 69.4 ng/mg vs. 73.3 ± 36.0 ng/mg). A positive correlation was found between the plasma PZ level and creatinine-corrected urinary PZ concentration (r = 0.46). CONCLUSIONS: Both the plasma level and urinary excretion of PZ in urolithiasis patients were not significantly different with normal individuals. PZ detected in urinary stones as a matrix protein is thought to be incorporated into urinary stones regardless of blood and urine levels of PZ.

Metabolomic changes in cats with renal disease and calcium oxalate uroliths.

INTRODUCTION: There is a significant incidence of cats with renal disease (RD) and calcium oxalate (CaOx) kidney uroliths in domesticated cats. Foods which aid in the management of these diseases may be enhanced through understanding the underlying metabolomic changes. OBJECTIVE: Assess the metabolomic profile with a view to identifying metabolomic targets which could aid in the management of renal disease and CaOx uroliths. METHOD: This is a retrospective investigation of 42 cats: 19 healthy kidney controls, 11 with RD, and 12 that formed CaOx nephroliths. Cats were evaluated as adults (2 through 7 years) and at the end of life for plasma metabolomics, body composition, and markers of renal dysfunction. Kidney sections were assessed by Pizzolato stain at the end of life for detection of CaOx crystals. CaOx stone presence was also assessed by analysis of stones removed from the kidney at the end of life. RESULTS: There were 791 metabolites identified with 91 having significant (p < 0.05, q < 0.1) changes between groups. Many changes in metabolite concentrations could be explained by the loss of renal function being most acute in the cats with RD while the cats with CaOx stones were intermediate between control and RD (e.g., urea, creatinine, pseudouridine, dimethylarginines). However, the concentrations of some metabolites differentiated RD from CaOx stone forming cats. These were either increased in the RD cats (e.g., cystathionine, dodecanedioate, 3-(3-amino-3-carboxypropyl) uridine, 5-methyl-2'-deoxycytidine) or comparatively increased in the CaOx stone forming cats (phenylpyruvate, 4-hydroxyphenylpyruvate, alpha-ketobutyrate, retinal). CONCLUSIONS: The metabolomic changes show specific metabolites which respond generally to both renal diseases while the metabolomic profile still differentiates cats with RD and cats with CaOx uroliths.

Diagnostic accuracy of dual-energy computed tomography (DECT) to differentiate uric acid from non-uric acid calculi: systematic review and meta-analysis.

BACKGROUND: Uric acid stone diagnosis is presently done primarily with in vitro analysis of stones. In vivo diagnosis with dual-energy CT (DECT) would allow earlier initiation of therapy with urine alkalinization and avoid surgical intervention. OBJECTIVE: To evaluate if DECT, using stone analysis as reference standard, is sufficiently accurate to replace stone analysis for diagnosis of uric acid stones. METHODS: Original studies in patients with urolithiasis examined with DECT with stone analysis as the reference standard were eligible for inclusion. MEDLINE (1946-2018), Embase (1947-2018), CENTRAL (August 2018), and multiple urology and radiology conferences were searched. QUADAS-2 was used to assess risk of bias and applicability. Meta-analyses were performed using a bivariate random-effects model. RESULTS: A total of 21 studies (1105 patients, 1442 stones) were included. Fourteen studies containing 662 patients (944 stones) were analyzed in the uric acid dominant target condition (majority of stone composition uric acid): mean sensitivity was 0.88 (95% CI 0.79-0.93) and specificity 0.98 (95% CI 0.96-0.99). Thirteen studies (674 patients, 760 stones) were analyzed in the uric acid-containing target condition (< majority of stone composition uric acid): mean sensitivity was 0.82 (95% CI 0.73-0.89) and specificity 0.97 (95% CI 0.94-0.98). Meta-regression showed no significant variability in test accuracy. Two studies had one or more domains at high risk of bias and there were no concerns regarding applicability. CONCLUSION: DECT is an accurate replacement test for diagnosis of uric acid calculi in vivo, such that stone analysis could be replaced in the diagnostic pathway. This would enable earlier initiation of urine alkalinization. KEY POINTS: • DECT for uric acid dominant stones has sensitivity of 0.88 (95% CI 0.79-0.93) and specificity of 0.98 (95% CI 0.96-0.99); uric acid-containing stones had mean sensitivity of 0.82 (95% CI 0.73-0.89) and specificity of 0.97 (95% CI 0.94-0.98). • Meta-regression did not identify any variables (study design, reference standard, dual-energy CT type, dose, risk of bias) that influenced test accuracy. • Only 2 of the 21 included studies had 1 or more domain considered to be at high risk of bias with the majority of domains considered at low risk of bias; there were no concerns regarding applicability in any of the included studies.

Dietary risk factors for urinary stones in children.

PURPOSE OF REVIEW: As the incidence of urinary stone disease in children is increasing, identifying dietary risk factors becomes vitally important, especially in the context of targeting interventions to reduce risk for stone formation. Indiscriminant dietary restrictions are not appropriate for paediatric patients. RECENT FINDINGS: Although large, prospective studies are still needed to better quantify dietary risk factors for paediatric stone formers, a number of smaller studies provide data to identify common risk factors to help prevent stone formation, while minimizing inappropriate dietary restrictions. SUMMARY: Interpretation of 24-h urine samples to identify individualized dietary risk factors is crucial for implementing a strategy for prevention of further urinary stone formation in children. Clinicians should avoid generalized dietary restrictions in stone-forming children uninformed by laboratory data.

Transplantation of a kidney with a heterozygous mutation in the SLC22A12 (URAT1) gene causing renal hypouricemia: a case report.

BACKGROUND: Renal hypouricemia (RHUC) is a genetic disorder caused by mutations in the SLC22A12 gene, which encodes the major uric acid (UA) transporter, URAT1. The clinical course of related, living donor-derived RHUC in patients undergoing kidney transplantation is poorly understood. Here, we report a case of kidney transplantation from a living relative who had an SLC22A12 mutation. After the transplantation, the recipient's fractional excretion of UA (FEUA) decreased, and chimeric tubular epithelium was observed. CASE PRESENTATION: A 40-year-old man underwent kidney transplantation. His sister was the kidney donor. Three weeks after the transplantation, he had low serum-UA, 148.7 µmol/L, and elevated FEUA, 20.8% (normal: < 10%). The patient's sister had low serum-UA (101.1 µmol/L) and high FEUA (15.8%) before transplant. Suspecting RHUC, we performed next-generation sequencing on a gene panel containing RHUC-associated genes. A heterozygous missense mutation in the SLC22A12 gene was detected in the donor, but not in the recipient. The recipient's serum-UA level increased from 148.7 µmol/L to 231.9 µmol/L 3 months after transplantation and was 226.0 µmol/L 1 year after transplantation. His FEUA decreased from 20.8 to 11.7% 3 months after transplantation and was 12.4% 1 year after transplantation. Fluorescence in situ hybridization of allograft biopsies performed 3 months and 1 year after transplantation showed the presence of Y chromosomes in the tubular epithelial cells, suggesting the recipient's elevated serum-UA levels were owing to a chimeric tubular epithelium. CONCLUSIONS: We reported on a kidney transplant recipient that developed RHUC owing to his donor possessing a heterozygous mutation in the SLC22A12 (URAT1) gene. Despite this mutation, the clinical course was not problematic. Thus, the presence of donor-recipient chimerism in the tubular epithelium might positively affect the clinical course, at least in the short-term.

Metabolic evaluation: who, when and how often.

PURPOSE OF REVIEW: To summarize recommendations of the guidelines of the American Urological Association and European Association of Urology, and our opinion on which urinary tract stone disease patients should be metabolically evaluated at which moment and how often. RECENT FINDINGS: A standard metabolic evaluation should be performed in all stone formers to prevent recurrent disease. This includes a medical and lifestyle history, physical examination, basic urine and blood analysis, radiological examination and stone analysis. The latter should already be performed during surgery, especially when only a couple of fragments are sent for analysis. Supplementary, performing a 24-h urine analysis should be supported in all patients to understand the lithogenic process that will guide the according follow-up. When risk factors are found, an extended individualized metabolic evaluation should be performed to exclude underlying metabolic diseases and to start stone-specific recurrence prevention. SUMMARY: Urologists should be trained in perioperative stone characterization, because it contains information of urinary environment at the times of stone formation and growth. The extensiveness and frequency of metabolic work-up and follow-up of stone formers should be tailored to the type of stone, severity of the disease, patient's comorbidities and medications.

The Impact of Glycosylation of Osteopontin on Urinary Stone Formation.

Osteopontin (OPN) is a matrix glycoprotein of urinary calculi. This study aims to identify the role of aberrant glycosylation of OPN in urolithiasis. We retrospectively measured urinary glycosylated OPN normalized by urinary full-length-OPN levels in 110 urolithiasis patients and 157 healthy volunteers and 21 patients were prospectively longitudinal follow-up during stone treatment. The urinary full-length-OPN levels were measured using enzyme-linked immunosorbent assay and glycosylated OPN was measured using a lectin array and lectin blotting. The assays were evaluated using the area under the receiver operating characteristics curve to discriminate stone forming urolithiasis patients. In the retrospective cohort, urinary Gal3C-S lectin reactive- (Gal3C-S-) OPN/full-length-OPN, was significantly higher in the stone forming urolithiasis patients than in the healthy volunteers (p < 0.0001), with good discrimination (AUC, 0.953), 90% sensitivity, and 92% specificity. The Lycopersicon esculentum lectin analysis of urinary full-length-OPN showed that urinary full-length-OPN in stone forming urolithiasis patients had a polyLacNAc structure that was not observed in healthy volunteers. In the prospective longitudinal follow-up study, 92.8% of the stone-free urolithiasis group had Gal3C-S-OPN/full-length-OPN levels below the cutoff value after ureteroscopic lithotripsy (URS), whereas 71.4% of the residual-stone urolithiasis group did not show decreased levels after URS. Therefore, Gal3C-S-OPN/full-length-OPN levels could be used as a urolithiasis biomarker.

Renal hypouricemia caused by novel compound heterozygous mutations in the SLC22A12 gene: a case report with literature review.

BACKGROUND: Renal hypouricemia (RHUC) is a heterogeneous genetic disorder that is characterized by decreased serum uric acid concentration and increased fractional excretion of uric acid. Previous reports have revealed many functional mutations in two urate transporter genes, SLC22A12 and/or SLC2A9, to be the causative genetic factors of this disorder. However, there are still unresolved patients, suggesting the existence of other causal genes or new mutations. Here, we report an RHUC patient with novel compound heterozygous mutations in the SLC22A12 gene. CASE PRESENTATION: A 27-year-old female presenting with recurrent hypouricemia during routine checkups was referred to our hospital. After obtaining the patient's consent, both the patient and her healthy parents were analyzed using whole-exome sequencing (WES) and Sanger sequencing to discover and validate causal mutations, respectively. The prioritization protocol of WES screened out two mutations of c.269G > A/p.R90H and c.1289_1290insGG/p.M430fsX466, which are both located in the SLC22A12 gene, in the patient. Sanger sequencing further confirmed that the patient's heterozygous c.269G > A/p.R90H mutation, which has been reported previously, derived from her mother, and the heterozygous c.1289_1290insGG/p.M430fsX466 mutation, which was found for the first time, derived from her father. p.R90H, which is highly conserved among different species, may decrease the stability of this domain and was considered to be almost damaging in silicon analysis. p.M430fsX466 lacks the last three transmembrane domains, including the tripeptide motif (S/T)XΦ (X = any amino acid and Φ = hydrophobic residue), at the C-terminal, which interact with scaffolding protein PDZK1 and thus will possibly lead to weak functioning of urate transport through the disruption of the "transporter complex" that is formed by URAT1 and PDZK1. CONCLUSIONS: We report a Chinese patient with RHUC, which was caused by compound heterozygous mutations of the SLC22A12 gene, using WES and Sanger sequencing for the first time. Mutation-induced structural instability or malfunction of the urate transporter complex may be the main mechanisms for this hereditary disorder.

Urinary tract stones in cystic fibrosis.

Urinary tract stones are a common problem in a general population but increasingly so in cystic fibrosis (CF) patients as survival improves. Mechanisms of stone formation are discussed, particularly those unique to CF patients. Modalities of treatment and the decision making process in this choice is outlined as well as possible future preventative strategies.

Recurrent stone-forming patients have high visceral fat ratio based on computed tomography images compared to first-time stone-forming patients.

OBJECTIVES: To compare various fat parameters based on computed tomography images between recurrent stone-forming patients and patients forming stones for the first time. METHODS: Included in the present study were 300 patients with upper urinary tract calculi who had undergone active stone removal in our hospital. Using pretreatment computed tomography images, we measured visceral fat area and volume, subcutaneous fat area and volume, visceral fat area ratio and visceral fat volume ratio. We compared patient backgrounds and these fat parameters between those who recurrently formed stones and those who formed stones for the first time. We also performed logistic regression analysis to identify factors that contribute to severe stones. RESULTS: A total of 148 (49.3%) patients were recurrent stone-forming patients. Recurrent stone-forming patients were statistically significantly younger (P < 0.01) and there were more male patients (P < 0.01). In addition, visceral fat area ratio and visceral fat volume ratio in recurrent stone-forming patients were significantly higher than those in first-time stone-forming patients (P = 0.03 and P = 0.01, respectively). On the other hand, there was no significant difference in visceral fat area (P = 0.32), subcutaneous fat area (P = 0.36), visceral fat volume (P = 0.38) or subcutaneous fat volume (P = 0.23). Receiver operating characteristics analysis showed that area under the curve of visceral fat volume ratio (0.583) for recurrent stones was larger than that of visceral fat area ratio (0.571). In multivariate analysis, increasing visceral fat volume ratio was an independent significant predictor of recurrent stones (P = 0.04). CONCLUSIONS: Recurrent stone-forming patients have high visceral fat ratios compared to first-time stone-forming patients, shown here for the first time.

Renal Calcium Oxalate Deposits Induce a Pro-Atherosclerotic and Pro-Osteoporotic Response in Mice.

Urinary stone disease (USD) is increasing in adult and pediatric populations. Adult and pediatric studies have demonstrated decreased bone mineral density and increased fracture rates. USD has also been independently linked to increased rates of myocardial infarction and cerebral vascular accidents. Although USD is a multisystem disorder involving the kidneys, bone, and vasculature, the molecular mechanisms linking these three organs remain unknown. Calcium oxalate nephropathy was induced in C57BL/6J mice with intra-peritoneal (ip) injection of sodium glyoxolate. Half of each kidney underwent Pizzalato staining and half was snap frozen for RNA extraction. RT2 Profiler Mouse Atherosclerosis, Osteoporosis, and Calcium Signaling PCR Arrays (Qiagen) were performed. Only results that passed quality checks in PCR array reproducibility and genomic DNA contamination were included. Genes had to show at least fourfold differential expression and P < 0.01 to be considered significant. Atherosclerosis array showed upregulation of 19 genes by fourfold, 10 of which were ≥10-fold. All 19 had P ≤ 0.002. The Osteoporosis array showed fourfold upregulation of 10 genes, five showed >10-fold increase. All 10 have P ≤ 0.003. The calcium signaling array showed significant fourfold upregulation of 10 genes, four of which were ≥10-fold. All 10 have P ≤ 0.03. We have demonstrated that calcium oxalate nephropathy can induce upregulation of atherosclerotic, metabolic bone, and calcium homeostasis genes in a murine model. This may be and initial step in identifying the molecular mechanisms linking stone, bone, and cardiovascular disease. J. Cell. Biochem. 118: 2744-2751, 2017. © 2017 Wiley Periodicals, Inc.

[Mineralogical composition of urinary stones, risk factors and metabolic disturbances in patients with calcium-oxalate urolithiasis].

AIM: To identify the most likely metabolic disturbances and risk factors for stone formation in a group of patients with calcium oxalate urolithiasis, and to establish the relationship between the mineralogical composition of calculi and impaired excretion of inhibitors and promoters of stone formation. MATERIALS AND METHODS: Fifty patients with calcium oxalate urolithiasis were tested using a complex of physicochemical methods. Patients assessment included evaluation of quantitative mineralogical composition of calculi, daily urine pH profile and daily urinary excretion of urates, calcium, magnesium, oxalate, phosphate and citrate ions. RESULTS: The main mineralogical phase of the stones in over 80% of patients was calcium oxalate monohydrate; none of the patients had pure dihydrate stones. The most frequent metabolic disorders were hypocitraturia, hypercalciuria and hyperuricosuria. Predominant risk factors were excessive body weight and insufficient fluid intake. Only one patient had an idiopathic stone formation. It was established for the first time that patients with calcium oxalate stones, containing 10 or more mass percent of apatites had statistically significantly lower daily urinary calcium and oxalate excretion and simultaneously increased phosphate excretion. CONCLUSIONS: The study findings showed that patients with calculi based on calcium oxalate dihydrate should undergo testing for daily urinary excretion of calcium and citrate while pa-tients with calcium oxalate stones containing 10 or more mass percent of apatites should also be tested for daily phosphate excretion and urine pH-profile. Daily urinary citrate excretion was reduced in all study patients, and urate excretion was significantly increased, apparently due to an imbalanced diet and excessive intake of animal protein. Menopausal and postmenopausal women are at a particular risk due to low urinary citrate excretion and high urinary calcium excretion regardless of stone composition.

[The role of the Randalls plaques in the pathogenesis of recurrent urolitasis].

The aim of the work was to present current concept of the pathogenesis of urolithiasis. Treatment and prevention of this disease a challenging issue. The article presents basic information about Randalls plaques that are described as calcium salt deposits on the surface of the transitional cell epithelium. The cause of Randalls plaques was the subject of many studies and is still not completely clear. To date, we can state that the deposit formation starts in the pelvicalyceal system and is directly linked to recurrent urolithiasis. The discovery of Randall plaques in the 1940s transformed the conception of stone formation, but there are even more questions about the pathogenesis of urolithiasis. In that respect, we consider it important to analyze the studies on Randalls plaques.

[Quantitative mineralogical analysis and structure of urinary stones in patients living in Ivanovo region].

This paper focuses on developing and implementing a method of quantitative mineralogical analysis of urinary stones based on powder diffraction data analysis using 4 Topas (Bruker) software. Mineralogical composition of 100 urinary stones from urolithiasis patients living in Ivanovo region was examined. More than 70% of stones consisted of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD), and their mixtures with hydroxylapatite. Forty four percent of urinary stones consisted of one component (COM, uric acid (UA) or, less frequently, hydroxyapatite (HA); 56% of urinary stones comprised two, three or four components. The most common mineral was COM (more than 70% of cases), the rarest were calcium oxalate trihydrate (CT), brushite and newberrite. The most common combinations of minerals in mixed stones were COM+HA, COM+COD and COM+COD+HA. The texture, the surface composition and its changes in the course of chemolysis in different types of stones were examined using scanning electron microscopy (SEM) and X-ray microanalysis (XRM). Implications for using analytical chemical and physical techniques for the diagnosis and treatment of urolithiasis were discussed.

Provider variation in the quality of metabolic stone management.

PURPOSE: Urinary stone disease is a chronic condition for which secondary prevention (dietary and medical therapy guided by 24-hour urine collection results) has an important role. Assessing the response to these interventions with followup testing is recommended and yet to our knowledge provider compliance with these guidelines is unknown. MATERIALS AND METHODS: Using Litholink® files from 1995 to 2013 we identified adults with urinary stone disease who underwent metabolic evaluation and the providers who ordered the evaluation. By focusing on patients with an abnormality on the initial collection we determined the proportion who underwent a followup test within 6 months of the initial test. Multilevel modeling was done to quantify variation in followup testing among providers after accounting for various patient and provider factors. RESULTS: A total of 208,125 patients had an abnormality on the initial collection, of whom only 33,413 (16.1%) performed a repeat collection within 6 months. While most variation in followup testing was attributable to the patient, the provider contribution was nontrivial (18.0%). The specialty of the ordering provider was important. Patients who saw a urologist had 24% lower odds of repeat testing compared to those who saw a primary care physician (OR 0.76, 95% CI 0.67-0.86, p <0.001). CONCLUSIONS: Followup testing is uncommon in patients with an abnormal initial 24-hour urine collection. Given the observed provider variation, efforts to educate providers on the value of followup testing are likely to have salutary effects on patients with metabolic stone disease.

Metabolic evaluation of urinary lithiasis: what urologists should know and do.

INTRODUCTION: Urolithiasis is a complex medical entity and regroups several different types of stones, each caused by a multitude of dietary imbalances or metabolic anomalies. In order to better assess the stone-forming patient, urologists should be competent in performing a thorough metabolic work-up. MATERIALS AND METHODS: We reviewed the litterature in order to provide an appropriate overview of the various components of the metabolic evaluation, including stone analysis, biochemistry tests, and urine collection. CONCLUSION: Performing a metabolic evaluation allows precise intervention in order to treat and mainly prevent stone disease.

Calcium oxalate urolithiasis in mice lacking anion transporter Slc26a6.

Urolithiasis is one of the most common urologic diseases in industrialized societies. Calcium oxalate is the predominant component in 70-80% of kidney stones, and small changes in urinary oxalate concentration affect the risk of stone formation. SLC26A6 is an anion exchanger expressed on the apical membrane in many epithelial tissues, including kidney and intestine. Among its transport activities, SLC26A6 mediates Cl(-)-oxalate exchange. Here we show that mutant mice lacking Slc26a6 develop a high incidence of calcium oxalate urolithiasis. Slc26a6-null mice have significant hyperoxaluria and elevation in plasma oxalate concentration that is greatly attenuated by dietary oxalate restriction. In vitro flux studies indicated that mice lacking Slc26a6 have a defect in intestinal oxalate secretion resulting in enhanced net absorption of oxalate. We conclude that the anion exchanger SLC26A6 has a major constitutive role in limiting net intestinal absorption of oxalate, thereby preventing hyperoxaluria and calcium oxalate urolithiasis.

In vitro studies of epithelium-associated crystallization caused by uropathogens during urinary calculi development.

Infectious urinary stones account for about 10% of all urinary stones. In 50% of cases urolithiasis is a recurrent illness, which can lead to the loss of a kidney if not properly treated. One of the reasons for recurrence of the disease may be the ability of bacteria to invade urothelial cells, persist in the host cells and serve as potential reservoirs for infection. Various uropathogens are associated with the formation of bacteria-induced urinary stones but Proteus mirabilis is the most commonly isolated (70%). An in vitro model was used in this study to analyze intracellular growth and crystallization in the presence of P. mirabilis, Klebsiella pneumoniae and Escherichia coli. Human ureter (Hu 609) and bladder (HCV 29) epithelial cell lines were infected with bacteria and incubated (3-72 h) in the presence of synthetic urine and amikacin to prevent extracellular bacterial growth. During the incubation the number of bacteria (CFU/ml) inside epithelial cells and the intensity of crystallization were established. Crystallization was determined as an amount of a calcium radioisotope. The chosen strains of uropathogens were able to invade both types of epithelial cells but the Hu 609 cells were invaded to a higher extent. However, crystallization occurred only in the presence of P. mirabilis strains which were invasive and urease-positive. The highest intensity of cell-associated crystallization was observed when the number of bacteria within the urothelium remained stable during the time of incubation. These results show that P. mirabilis has an ability to form crystals inside the host cells. Under these conditions bacteria are protected from antibiotic killing, which leads to persistent and recurrent infections. We also suspect that this phenomenon may be an important stage of kidney stones formation.

Bilateral urinary calculi with discordant stone composition.

OBJECTIVES: To describe a cohort of bilateral stone formers with significantly different compositions between renal units. METHODS: Patients treated for bilateral nephrolithiasis over a 4-year period (2007-2010) were identified. Stones were categorized by dominant (≥50%) mineralogical component. Patients with significant compositional differences between renal units (discordant stone formers) were compared to patients with a similar stone type in each kidney. RESULTS: Fifteen of the 59 bilateral stone formers (25.4%) were discordant stone formers with significant differences in stone composition between renal units. Forty-four of the 59 patients (74.6%) had the same stone composition on each side. Thirty percent of discordant stones had calcium phosphate as the dominant stone component. Discordant stone formers were younger, had better renal function, and tended to have a larger stone burden (p < 0.05). CONCLUSIONS: A significant minority of bilateral stone formers form a different type of stone in each kidney. Local or micro-environmental etiologies may explain this phenomenon and may also account for failure of preventive therapy in some patients.