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.

Subcutaneous Adipose Tissue Accumulation Is an Independent Risk Factor of Urinary Stone in Young People

BACKGROUND

Urinary stones usually start at a young age and tend to recur. Therefore, preventing stone occurrence and recurrence in young people is crucial. We aimed to investigate the association between subcutaneous adipose tissue, visceral adipose tissue, and stone episodes in young people.

METHODS

We retrospectively studied patients aged below 40 years with kidney or ureteral stones. Data on demographic and metabolic characteristics, urolithiasis history, subcutaneous fat area (SFA), and visceral fat area (VFA) were collected. We evaluated the association between SFA or VFA and the occurrence or recurrence of stone episodes using binary logistic regression and Poisson regression analyses.

RESULTS

In total, 120 patients were included. Abdominal obesity, overweight or obesity, dyslipidemia, metabolic syndrome, SFA, and VFA increased with the number of stone episodes (all p < 0.05). The increase in SFA was independently associated with episode occurrence (p = 0.015). Patients with an SFA > 97 cm² had a higher risk of episode occurrence. SFA and VFA accumulation were independently associated with episode recurrence (all p < 0.05), and SFA had a stronger association than VFA did.

CONCLUSIONS

In young people, SFA accumulation is an independent and early risk factor for the occurrence and recurrence of stone episodes. Subcutaneous fat could be a convenient and effective indicator to assess the risk of stone episodes before the development of metabolic disorders.

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.

Composition of uroliths in a tertiary hospital in South East Nigeria

Background

Urolithiasis affects primarily the urinary tract and complications as debilitating as renal failure may develop. Determining the chemical composition of uroliths can aid management and prevention of recurrence in patients.

Objective

To determine the chemical composition and anatomical distribution of uroliths in Nigeria.

Methods

This descriptive cross-sectional study was conducted between March 2014 and February 2016, in a tertiary hospital in Nigeria. We reviewed the outcomes of uroliths of adult patients sent to our laboratory for chemical analyses. Samples were analyzed using simple qualitative tests.

Results

52 adult patients were included with a mean age (SD) of 46.6 (12.6) years. Males (76.9%) were more affected than females (23.1%). For both sexes, highest occurrence of stones was in bladder (85.7%). Calcium-containing stones had the highest occurrence (85.2%) and predominated in the renal, ureter and urethra, followed by struvite stones (59.5%). In the bladder, struvite stones were predominant (85.8%), with calcium-containing stones accounting for 71.4%.

Conclusion

This study showed that struvite and calcium phosphate-containing stones constitute majority of uroliths in our setting with low occurrence of calcium oxalate stones. This indicates that urinary tract infection most likely plays a substantial role in the formation of uroliths in Nigerians. Modern methods of stone analysis is advocated to further define management options.

[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.

[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.

[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.

Elemental Content of Calcium Oxalate Stones from a Canine Model of Urinary Stone Disease

One of the most common types of urinary stones formed in humans and some other mammals is composed of calcium oxalate in ordered hydrated crystals. Many studies have reported a range of metals other than calcium in human stones, but few have looked at stones from animal models such as the dog. Therefore, we determined the elemental profile of canine calcium oxalate urinary stones and compared it to reported values from human stones. The content of 19 elements spanning 7-orders of magnitude was quantified in calcium oxalate stones from 53 dogs. The elemental profile of the canine stones was highly overlapping with human stones, indicating similar inorganic composition. Correlation and cluster analysis was then performed on the elemental profile from canine stones to evaluate associations between the elements and test for potential subgrouping based on elemental content. No correlations were observed with the most abundant metal calcium. However, magnesium and sulfur content correlated with the mineral hydration form, while phosphorous and zinc content correlated with the neuter status of the dog. Inter-elemental correlation analysis indicated strong associations between barium, phosphorous, and zinc content. Additionally, cluster analysis revealed subgroups within the stones that were also based primarily on barium, phosphorous, and zinc. These data support the use of the dog as a model to study the effects of trace metal homeostasis in urinary stone disease.

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.

[Hormonal and metabolic disorders as systemic factor for the formation of urinary calculi]

In patients suffering from urolithiasis, metabolic diagnostics often reveals abnormalities contributing to the formation of stones: hypocitraturia, hyper- and hypocalcemia, hypercalciuria, hypomagnesemia/hypomagnesuria, hyperoxalaturia, etc. Before surgery, complex biochemical examination of blood and 24-hourcollection urine in 82 patients with urolithiasis was performed. The analysis of the main laboratory parameters of carbohydrate, lipid, calcium and phosphorus and purine metabolism found the prevalence of violations of calcium and phosphorus metabolism in these patients. Dyslipidemia was diagnosed in 31 (37.8%) patients. There was a significant positive correlation between serum total cholesterol and serum total calcium (rs = 0.3315, P = 0.0103). Low serum calcium levels were associated with hyperoxalaturia (rs = -0.4270, P = 0.0295). There was a significant effect of natriuria on urinary excretion of oxalate (rs = 0.6107, P = 0.0001), Mg (rs = 0.4156, P = 0.0096) and K (rs = 0.5234, P = 0.00005). The study shows the role of magnesium in the prevention of recurrence and manifestation of urolithiasis. The combination of two or more types of hormonal and metabolic disorders increases the incidence of recurrent stones. Timely correction of hormonal-metabolic status allows to reduce the risk of stone formation, and hospitalization attributable to the complications associated.

Comparison of the metabolic profile of mixed calcium oxalate/uric acid stone formers to that of pure calcium oxalate and pure uric acid stone formers

OBJECTIVE

To compare the metabolic profile of patients who form mixed calcium oxalate (CaOx)/uric acid (UA) stones to those of pure CaOx and pure UA stone formers.

METHODS

We performed a retrospective review of 232 patients, with both stone composition analysis and 24-hour urine collection, seen between March 2002 and April 2012. Analysis of 24-hour urine constituents across the 3 stone groups (pure UA, pure CaOx, and mixed CaOx/UA) was performed using univariate analysis of variance and multivariate linear regression models adjusting for clinical and demographic factors and 24-hour urine collection elements.

RESULTS

A total of 27 patients (11.6%) had mixed CaOx/UA, 122 (52.6%) had pure CaOx, and 83 (35.8%) had pure UA calculi. Univariate analysis demonstrated significant differences between mixed CaOx/UA patients and pure CaOx patients for urine pH (mixed, 5.63 ± 0.49 vs pure, CaOx 5.93 ± 0.51; P = .009) and supersaturation (SS) UA (mixed, 1.84 ± 1.09 vs pure, CaOx 1.26 ± 0.93; P = .01), and a significant difference between mixed CaOx/UA patients and pure UA patients for SS CaOx (mixed, 7.18 ± 4.23 vs pure, UA 4.90 ± 2.96; P = .005). Multivariate analysis demonstrated that mixed CaOx/UA patients had no significant difference in SS CaOx as compared with pure CaOx patients (difference, -0.27; P = .66), whereas at the same time had no significant difference in SS UA as compared with pure UA patients (-0.07; P = .69).

CONCLUSION

The metabolic profile of patients who form mixed CaOx/UA stones demonstrates abnormalities that promote both CaOx and UA stone formation. Dietary and medical management for this group of patients should address treatment of both defects.

Purine disorders with hypouricemia

Hypouricemia is defined as a serum urate levels less than 2 mg/dL (119 µmol/L). Primary hypouricemia is caused by disorders of purine metabolism and transport. This laboratory finding is sometimes overlooked and, following two genetic defects, should be considered in differential diagnosis of unexplained hypouricemia. Hereditary xanthinuria is autosomal recessive and due to mutations in xanthine oxidase, leading to over-production of xanthine and minimal production of urate. Patients have very low serum urate levels and suffer from elevated levels of xanthine in the urine, leading to xanthine stones, haematuria, and sometimes occult chronic kidney failure. Hypouricemia is the key to diagnosis. Hereditary renal hypouricemia is a new genetic defect of renal transport of uric acid. Two types were distinguished: a) renal hypouricemia type 1, caused by the defects in the SLC22A12 gene coding the human urate transporter 1 (hURAT1) and b) renal hypouricemia type 2, caused by the defects in the SLC2A9 gene, which encodes GLUT9 transporter. This disorder predisposes patients to exercise-induced acute renal failure and/or nephrolithiasis. Diagnosis is based on two markers: hypouricemia (<119 µmol/L) and increased fractional excretion of uric acid (>10%). Over one hundred cases were identified in Japan and and this number is unique worldwide. Several patients were described in Macedonia. We were able to detect four Czech families with hereditary xanthinuria and eight cases of hereditary renal hypouricemia. In conclusion, hereditary xanthinuria and hereditary renal hypouricemia are still unrecognized conditions. Patients with unexplained hypouricemia need detailed purine metabolic investigations.

Determinants of brushite stone formation: a case-control study

Purpose

The occurrence of brushite stones has increased during recent years. However, the pathogenic factors driving the development of brushite stones remain unclear.

Methods

Twenty-eight brushite stone formers and 28 age-, sex- and BMI-matched healthy individuals were enrolled in this case-control study. Anthropometric, clinical, 24 h urinary parameters and dietary intake from 7-day weighed food records were assessed.

Results

Pure brushite stones were present in 46% of patients, while calcium oxalate was the major secondary stone component. Urinary pH and oxalate excretion were significantly higher, whereas urinary citrate was lower in patients as compared to healthy controls. Despite lower dietary intake, urinary calcium excretion was significantly higher in brushite stone patients. Binary logistic regression analysis revealed pH>6.50 (OR 7.296; p = 0.035), calcium>6.40 mmol/24 h (OR 25.213; p = 0.001) and citrate excretion <2.600 mmol/24 h (OR 15.352; p = 0.005) as urinary risk factors for brushite stone formation. A total of 56% of patients exhibited distal renal tubular acidosis (dRTA). Urinary pH, calcium and citrate excretion did not significantly differ between patients with or without dRTA.

Conclusions

Hypercalciuria, a diminished citrate excretion and an elevated pH turned out to be the major urinary determinants of brushite stone formation. Interestingly, urinary phosphate was not associated with urolithiasis. The increased urinary oxalate excretion, possibly due to decreased calcium intake, promotes the risk of mixed stone formation with calcium oxalate. Neither dietary factors nor dRTA can account as cause for hypercalciuria, higher urinary pH and diminished citrate excretion. Further research is needed to define the role of dRTA in brushite stone formation and to evaluate the hypothesis of an acquired acidification defect.

Acute kidney injury in two children caused by renal hypouricaemia type 2

BACKGROUND

Renal hypouricaemia is a heterogeneous inherited disorder characterized by impaired tubular uric acid transport with severe complications, such as acute kidney injury and nephrolithiasis. Type 1 is caused by a loss-of-function mutation in the SLC22A12 gene (OMIM #220150), while type 2 is caused by defects in the SLC2A9 gene (OMIM #612076).

CASE-DIAGNOSIS/TREATMENT

The cases of two children, a 12- and a 14-year-old boy with acute kidney injury (proband 1: urea 9.4 mmol/l, creatinine 226 μmol/l; proband 2: urea 11.7 mmol/l, creatinine 202 μmol/l) are described. Both are offspring of nonconsanguineous couples in the UK. The concentrations of serum uric acid were consistently below the normal range (0.03 and 0.04 mmol/l) and expressed as an increase in the fractional excretion of uric acid (46 and 93 %).

CONCLUSIONS

A sequencing analysis of the coding region of uric acid transporters SLC22A12 and SLC2A9 was performed. Analysis of genomic DNA revealed two unpublished missense transitions, p.G216R and p.N333S in the SLC2A9 gene. No sequence variants in SLC22A12 were found. Our findings suggest that homozygous and/or compound heterozygous loss-of-function mutations p.G216R and p.N333S cause renal hypouricaemia via loss of uric acid absorption and do lead to acute kidney injury.

[Effects of low-frequency magnetic field on urolith solubility in vitro]

A 27% increase in solubility of urolith substance was observed in water pretreated with alternating magnetic field (22 Hz, 25 mT) for 60 min compared to untreated water. Changed density of distilled water without concrement in response to the impact of alternating magnetic field does not influence qualitatively on solubility of urolith substance in the urolith placement in the pretreated water. Shift in wave length of maximums in spectra of solution absorption evidences for more intensive solution of organic components of uroliths in water pretreated with alternating magnetic field than in untreated water.

[Relationship between metabolic syndrome and urinary stone disease]

Epidemiologically, there are many same characteristics among patients with urolithiasis, life-style related diseases and metabolic syndrome. In a comparison with the major urological diseases, the patients with stone disease have the largest amount of visceral fat on computerized tomography. The patients who finally had a diagnosis of metabolic syndrome in urolithiasis were 43% of men and female 31%. The clinical features of the patients include increased urinary oxalate excretion, abnormal uric acid metabolism, and acidic urine. The basic studies by the animal experiments suggest that there is a close relationship between urolithiasis and metabolic syndrome. After the treatment of the urinary stone, it is very important to make a long-term follow-up by not only the prevention of recurrent stone episode but also life style management and medical treatment for metabolic syndrome.

[Diet therapy and life guidance to prevent calcium stones]

Urolithiasis patients have a low continuation rate with regard to visiting the hospital and undergoing periodic check-ups following therapy. The increased Westernization of diets has played a major role in its onset, and it is believed to be a lifestyle disease. Therefore, the prevention of relapse is difficult without improving the patients' lifestyle and eating habits, and it has been defined as a disease with an extremely high relapse rate. On the other hand, it is believed that the opportunity for periodic visits to the hospital and check-ups can be assured by continuously performing careful dietary interventions appropriate for each patient and by educating patients about the disease, thereby contributing to the prevention of relapses of urolithiasis.

[Pharmacotherapy for preventing calcium containing stone formation]

Many urinary tract stones consist of calcium, and has high relapse rate. Accordingly, it is very important to prevent calcium-containing stone formation. This paper describes about effects and mechanisms for Xanthine oxidase inhibitor, citrate formulation, magnesium formulation, thiazides, vitamin B(6), extract of Quercus salicina Blume and chorei-to (medical herb) . Recent new drugs and the elucidation of new metabolic pathways may lead to the development of prevention of urolithiasis.

Metabolic factors associated with urinary calculi in children

INTRODUCTION

We aimed to identify metabolic and anatomical abnormalities present in children with urinary calculi.

MATERIALS AND METHODS

Metabolic evaluation was done in 142 pediatric calculus formers. Evaluation included serum biochemistry; measurement of daily excretion of urinary calcium, uric acid, oxalate, citrate, and magnesium (in older children); and measurement of calcium, uric acid, oxalate, and creatinine in random urine samples in nontoilet-trained patients. Urinary tests for cystinuria were also performed. All of the patients underwent renal ultrasonography.

RESULTS

Sixty-one patients (42.7%) had metabolic abnormalities. Anatomical abnormalities were found in 12 patients (8.4%). Three children (2.1%) had infectious calculi, and 3(2.1%) had a combination of metabolic and anatomic abnormalities. In 66 children (46.2 %) we did not find any reasons for calculus formation (idiopathic). Urinalysis revealed hypercalciuria in 25 (17.6%), hyperuricosuria in 23 (16.1%), hyperoxaluria in 17 (11.9%), cystinuria in 9 (6.3%), hypocitraturia in 3 (2.1%), and low urinary magnesium level in 1 (0.7%) patients. Sixteen patients (11.2%) had mixed metabolic abnormalities.

CONCLUSIONS

Metabolic abnormalities are common in pediatric patients with urinary calculi. In our study, calcium and uric acid abnormalities were the most common, and vesicoureteral reflux seemed to be the most common urological abnormality which led to urinary stasis and calculus formation.

Cystinuria: the South Indian experience

Cystinuria is reportedly a rare condition affecting the stone patients in India. This paper presents the occurrence of cystine-related abnormality in the population of stone patients reporting to the hospitals in South India. Two thousand and eight hundred urine samples from 1,300 patients attending the urinary stone clinic during the period 2004-2008 were assessed for cystinuria by performing the nitroprusside test on the early morning urine and random samples on the day of attendance. Urinary deposits were also studied in all the patients. Stones retrieved from 800 stone patients were analysed qualitatively and by Fourier Transform infra red (FTIR) spectroscopy. Cystinuria was identified in only three patients. None of these patients showed cystine crystals. Three other patients out of the 1,300 showed presence of cystine crystals in the urine deposit. FTIR spectroscopy of the stones retrieved from the patients showed presence of cystine in 19 out of the 800 stones analysed (2.375%). None of the patients with cystine in the stones had either cystine crystals in the urine or positive nitroprusside test for cystine. All the patients who had positive cystine, cystine crystals or cystine in stone analysis had other biochemical abnormalities. They were medically managed with appropriate biochemical corrective chemotherapy and had control of stone disease process. All the patients were advised purine restriction in the diet. It is concluded from the study that cystinuria is a rare entity in South India. It, however, exists in a small percentage of stone patients. Specific treatment with D-penicillamine was not administered to the patients in view of the high cost, nonavailability and possible toxicity. The patients considered above did not have intractable stone disease which was not amenable to usual modalities of directed medical therapy.

Drug dosage protocol for calcium oxalate stone

In earlier studies, we have confirmed that in most patients with calcium oxalate stone formation, a combination of allopurinol and pyridoxine is best suited for treatment and prevention of the stone forming process. The objective of this study is to identify the most effective directed medical treatment of urinary stones. The drug dose adjustment was based on clinical, radiological, biochemical, and microscopic parameters. 444 patients with proved calcium oxalate stone disease who were getting a combination of allopurinol and pyridoxine for a minimum period of 36 months were enrolled in this prospective study. The dosage schedule of these patients was recorded. Dosage adjustment was made depending upon the various clinical, biochemical, microscopic, and radiological changes during the study period. The dosage schedules were in six categories, namely very high dose chemotherapy (VHDC), i.e. allopurinol 600 mg/day and pyridoxine 240 mg/day, high-dose chemotherapy (HDC), i.e. allopurinol 300 mg/day and pyridoxine 120 mg/day, moderate dose prophylaxis (MDP), i.e. allopurinol 200 mg/day and pyridoxine 80 mg/day, low-dose prophylaxis (LDP), i.e. allopurinol 100 mg/day and pyridoxine 40 mg/day, and very low-dose prophylaxis (VLDP), i.e. allopurinol 50 mg/day and pyridoxine 20 mg/day and intermittent VLDP, wherein the VLDP was given on alternate months and still later at longer intervals. The temporary risk was assessed at each visit and dosage adjustment was made. The effect of the intervention was assessed during the next visit. All the patients involved in the study needed dose adjustment. The following schedules were initiated: VHDC (12) 3.5%, HDC (103) 23.2%, MDP (78) 17.57%, or LDP (251) 56.53%. Patients who defaulted for more than a month were excluded from the study. During each visit for follow up, all patients were advised change over of dose depending upon the clinical situation at the time of review. Patients on VHDC were advised reduction to lower doses systematically. On passage of stones, the dose was immediately reduced to LDP in all situations unless prevented by the presence of significant crystalluria or severe pain. All patients on MDP had reduction of dose to LDP subsequently. Patients started on LDP needed elevation in dose in 63 (16.8%) to HDC and 23 patients (12.87%) to MDP. Dose of 247 patients could be reduced to VLDP (55.63%) and later on to intermittent VLDP 85 (19.14%). 74 (16.7%) patients continued to be on LDP throughout the period of study. It is concluded that in managing the stone patient, the clinical, radiological, microscopic and biochemical parameters should be taken into consideration in deciding the reduction/increase in the dose of drugs. The principle of giving chemotherapy/chemoprophylaxis should be to administer the least number of drugs in the least dosage depending upon the requirement of the disease.

Medical therapy of stone disease: from prevention to promotion of passage options

Medical therapy has been used for many years in the prevention of urinary stones. Medications directed at correcting urinary metabolic abnormalities responsible for promoting stone formation include thiazide diuretics, citrate salts, and allopurinol. All have proven to be efficacious. In addition, intake of citrate-rich juices, such as lemonade, may help to reduce urinary stone formation. More recently, there has been increasing interest in and use of medical therapy to aide in the passage of ureteral stones. Medical expulsive therapy (MET) has been shown to be cost effective compared with observation followed by treatment. Alpha-adrenergic receptor blockers are most commonly prescribed to promote passage of ureteral stones. They are able to facilitate stone passage, reduce time to passage, and decrease pain. Calcium-channel blockers also increase stone-passage rates. Steroids are useful adjuncts in MET.

[Percentage of uric acid calculus and its metabolic character in Dongjiang River valley]

OBJECTIVE

To study the percentage of uric acid calculus in uroliths and its metabolic character in Dongjiang River valley.

METHODS

To analyze the chemical composition of 290 urinary stones by infrared (IR) spectroscopy and study the ratio changes of uric acid calculus. Uric acid calculus patients and healthy people were studied. Personal characteristics, dietary habits were collected. Conditional logistic regression was used for data analysis and studied the dietary risk factors of uric acid calculus. Patients with uric acid calculus, calcium oxalate and those without urinary calculus were undergone metabolic evaluation analysis. The results of uric acid calculus patients compared to another two groups to analysis the relations between the formation of uric acid calculus and metabolism factors.

RESULTS

Uric acid calculi were found in 53 cases (18.3%). The multiple logistic regression analysis suggested that low daily water intake, eating more salted and animal food, less vegetable were very closely associated with uric acid calculus. Comparing to calcium oxalate patients, the urine volume, the value of pH, urine calcium, urine oxalic acid were lower, but uric acid was higher than it. The value of pH, urine oxalic acid and citric acid were lower than them, but uric acid and urine calcium were higher than none urinary calculus peoples. Blood potassium and magnesium were lower than them.

CONCLUSIONS

The percentage of uric acid stones had obvious advanced. Less daily water intake, eating salted food, eating more animal food, less vegetables and daily orange juice intake, eating sea food are the mainly dietary risk factors to the formation of uric acid calculus. Urine volume, the value of pH, citric acid, urine calcium, urine uric acid and the blood natrium, potassium, magnesium, calcium, uric acid have significant influence to the information of uric acid stones.

Enteric oxalate secretion is not directly mediated by the human CFTR chloride channel

The secretion of the oxalate anion by intestinal epithelia is a functionally significant component of oxalate homeostasis and hence a relevant factor in the etiology and management of calcium oxalate urolithiasis. To test the hypothesis that human cystic fibrosis transmembrane conductance regulator (hCFTR) can directly mediate the efflux of the oxalate anion, we compared cAMP-stimulated 36Cl-, 14C-oxalate, and 35SO(4)2- efflux from Xenopus oocytes expressing hCFTR with water-injected control oocytes. hCFTR-expressing oocytes exhibited a large, reversible cAMP-dependent increase in whole cell conductance measured using a two-electrode voltage clamp and a 13-fold increase in rate of cAMP-stimulated 36Cl- efflux. In contrast, the rate constants of oxalate and sulfate efflux were low and unaffected by cAMP in either control or hCFTR-expressing oocytes. We conclude that the human CFTR gene product does not directly mediate oxalate efflux in secretory epithelia and hence is not directly involved in oxalate homeostasis in humans.

[Expression of calbindin-D28k in genetic hypercalciuric stone-forming rats kidney and its role in pathogenesis of idiopathic hypercalciuria]

OBJECTIVE

To study the expression level of calbindin-D28k, a kind of calcium binding protein, in the kidneys of genetic hypercalciuric stone-forming (GHS) rats and to investigate its role in idiopathic hypercalciuria (IH).

METHODS

Kidneys were taken out from 16 GHS rats and 6 normal control (NC) rats. Western blotting and real time quantitative PCR were used to detect the protein and mRNA expression levels of calbindin-D28k respectively.

RESULTS

Western blotting showed that the A value of calbindin-D28k of the GHS rats was 0.49 +/- 0.02, significantly higher than that of the NC rats (0.20 +/- 0.01, P < 0.05). The 2(-(delta delta CT)) value of mRNA of calbindin-D28k of the GHS rats was 1.21, remarkably higher than that of the NC rats [with the of 2(-(delta delta CT)) value of 1.0]. There was not significant difference in the delta CT value between the two groups (P > 0.05).

CONCLUSION

The up-regulation of calbindin-D28k in the GHS rats is possibly caused by hyperexpression of VDR and hypercalcinuria, and plays an important role in urine calcium reabsorption; however, it is not the key protein that results in IH.

The concentration of Zn, Mg and Mn in calcium oxalate monohydrate stones appears to interfere with their fragility in ESWL therapy

Extracorporeal shockwave lithotripsy (SWL) has remained the preferred method of treatment of urinary stones since its introduction in 1980. Although SWL is classified as a potential first-line treatment for renal stones smaller than 2 cm and its overall success rate is higher than 85% for stone clearance, not all renal calculi are successfully fragmented after SWL. Among the urinary stones, calcium oxalate monohydrate (COM) stone is one of the hardest stones to fragment. Several factors interfering with stone fragility are known to exist. In addition to technical properties for SWL to increase the quality and rate of stone disintegration, the composition of stones such as trace element levels may also interfere with the efficacy of SWL. Therefore, in the present study, we aimed to elucidate the correlation, if it exists, between fragmentation of renal stones and their trace element (Cu, Zn, Mg, Fe, Pb, Mn, Cr) concentrations. For this purpose, the patients admitted to our department who were identified with urinary stones (740 patients) and underwent SWL sessions were evaluated prospectively. Patients having 5-20 mm of solitary COM stone in the renal pelvis were included in this study. The trace element concentrations of renal stones that were successfully fragmented with SWL (SWL-S) were compared with those that were unsuccessfully fragmented after three SWL sessions (SWL-US) and removed surgically. Our measurements showed that the concentrations of Cu, Fe, Pb, and Cr were similar in both groups; by contrast, the concentration of Zn, Mg and Mn was significantly lower in SWL-US renal stones. The present results suggest that low concentrations of Zn, Mg and Mn in COM stones appear to make them resistant to SWL fragmentation and may offer a critical distinction for the choice of a treatment program.

Renal inter-alpha-trypsin inhibitor heavy chain 3 increases in calcium oxalate stone-forming patients

Inter-alpha-trypsin inhibitor heavy-chain proteins bind to the protease inhibitor bikunin and to hyaluronan, stabilizes extracellular matrix in various tissues, and also inhibits calcium oxalate crystallization in vitro. In both normal and stone-forming patients, we found heavy chain 3 and hyaluronan in the interstitial matrix of the kidney. Osteopontin was found in the collecting duct, thin loop of Henle, and urothelial cells. In stone formers, heavy chain 3 was also present in collecting duct, thin loop, and interstitial cells. Heavy chain 3 and osteopontin colocalized in plaque matrix and urothelial cells. Within individual plaque spherules, heavy chain 3 was found in the matrix layer while osteopontin was located along the crystal-matrix interface. Bikunin was present only in the collecting duct apical membranes and the loop cell cytoplasm of stone formers colocalizing with osteopontin and heavy chain 3. Widespread heavy chain 3 was only present in stone formers, whereas osteopontin was similarly expressed in normal and stone-forming subjects except for its localization in plaques of the stone formers. This is consistent with studies linking inter-alpha-trypsin inhibitor components to human stone disease, although their role is still unclear. Heavy chain 3 may also play a role in stabilizing hyaluronan in the renal interstitial matrix.

Prevention of Stone Disease

In recent years stone disease has become more widespread in developed countries. At present the prevalence is 5.2 and 15% of men and 6% of women are affected. The increase is linked to changes in lifestyle, eating patterns and obesity which has become very common. The 'metabolic syndrome' includes all the diseases, e.g. hypertension, lipid imbalances, type 2 diabetes mellitus, gout and cardiovascular disease, which are concomitant in the majority of stone formers. Dietary patterns, besides leading to stone formation, also determine stone chemistry. With a diet that is rich in oxalates, calcium oxalate will constitute 75% of stones, struvite 10-20%, uric acid 5-6% and cystine 1%. As approximately 50% of patients with stones suffer recurrences, metabolic and/or pharmacological prophylaxis is recommended.

[The most important factor for active urinary stone formation in patients with urolithiasis]

INTRODUCTION

Urolithiasis, which affects 1-5% of western world population causing significant morbidity, is heterogeneous disorder with varying pathophysiologic milieu. Patients with recurrent stone formation are the particular problem because the understanding of the risk factors for active stone formation is deficient. The aim of the present study was to determine the most important metabolic and clinical parameters for active stone formation in order to recommend the best preventive therapies.

MATERIALS AND METHODS

In this study 134 consecutive outpatients (57 males, 46.9+/-14.4 years old) were referred and evaluated for urinary stone disease at our Institute. Clinical and metabolic parameters were determined by standardized procedures of questionnaire, serum biochemical profiles and urinalyses. An active stone former group was defined by an increase in the size or number of stones, or a recurrent stone event within 2 years.

RESULTS

In the evaluated cohort, 51 patients (38.1%) created the active stone former group. These patients were younger in the moment of the first stone elimination, had higher serum creatinine concentration, lower urine citrate concentration, as well as citrate/calcium ratio, higher urine pH and more frequently had clinical important urine sediment with eritrocituria and lenkocituria compared to the non-active stone group. Significant positive correlations were found between the active stone former and serum creatine concentration (r=0.227), urine pH (r=0.223), urine sediment (r=0.255) but negative with urine citrate (r=-0.275) and citrate/calcium ratio (r=-0.227). However, multivariate analysis indicated that clinical important urine sediment with eritrocituria and leuokocituria (p=0.033) and low urine citrate (p=0.04) were the only determinants of active urinary stone formation.

CONCLUSION

Further study is required to investigate efficacy of alkaline citrate substitution and rigorous diagnosis and treatment of infections in order to prevent urinary stone recurrence.

Ammonium acid urate urolithiasis in Japan

AIM

Ammonium acid urate (AAU) calculi are a rare urolithiasis in developed countries but are endemic in developing countries. We assessed the features of AAU urolithiasis in Japanese patients.

METHODS

We reviewed hospital charts of patients with urolithiasis who were treated with extracorporeal shock wave lithotripsy and endourological procedures at Sagamidai Hospital (Kanagawa, Japan) from January 1992 to December 2001. On the basis of the results of stone analysis with an infrared spectrophotometer, AAU stones were found.

RESULTS

Of 8664 urolithiasis that we reviewed, 33 calculi (0.38%) from 29 patients contained AAU crystals. From crystallographic findings, we defined two types of AAU-containing stones: pure and mixed AAU urolithiasis. Pure AAU urolithiasis were seen in 13 stones from 10 patients and mixed AAU in 20 stones from 19 patients. We found significant differences between the groups: the pure AAU group predominantly consisted of young, thin women and the mixed group consisted of middle-aged men. Laboratory findings showed trends of low levels of serum protein, potassium, and urine pH in the pure AAU group.

CONCLUSIONS

Because each type of AAU urolithiasis is associated with different patient characteristics and pathophysiological features, it is important to understand the type of AAU urolithiasis in patients with calculi.

Rat strains differ in susceptibility to Ureaplasma parvum-induced urinary tract infection and struvite stone formation

Individuals with struvite uroliths are susceptible to recurrent urinary tract infections (UTI), sepsis, and renal disease. Unfortunately, little is known about the host-specific factors that predispose to this disease. In order to develop a rodent model that can address this problem, we inoculated female Fischer 344 (F344), Lewis (LEW), Sprague-Dawley (SD), and Wistar (WIS) rats with a host-adapted strain of Ureaplasma parvum. Animals were necropsied at 2 weeks postinoculation; 100% of F344, 42% of SD, 10% of LEW, and 10% of WIS rats remained infected. Severe bladder lesions and struvite calculi were seen in 64% of F344 rats; in other rat strains, bladder lesions were mild or absent. F344 rats with struvite uroliths had the highest urinary levels of proinflammatory cytokines, such as GRO/KC, interleukin-1alpha (IL-1alpha), and IL-1beta. F344 rats without struvite stones at necropsy had milder bladder lesions and significantly lower urinary levels of proinflammatory cytokines but a more prominent inflammatory response than did other rat strains. Based on our results, struvite stone formation is linked to a robust inflammatory response that does not resolve UTI but instead promotes damage to surrounding tissues.

Biomineralogy of human urinary calculi (kidney stones) from some geographic regions of Sri Lanka

Kidney stones (urinary calculi) have become a global scourge since it has been recognized as one of the most painful medical problems. Primary causative factors for the formation of these stones are not clearly understood, though they are suspected to have a direct relationship to the composition of urine, which is mainly governed by diet and drinking water. Sixty nine urinary calculi samples which were collected from stone removal surgeries were analyzed chemically for their Na, K, Ca, Mg, Cu, Zn, Pb, Fe and phosphate contents. Structural and mineralogical properties of stones were studied by XRD and FT-IR methods. The mean contents of trace elements were 1348 mg kg(-1) (Na); 294 mg kg(-1) (K); 32% (Ca); 1426 mg kg(-1) (Mg); 8.39 mg kg(-1) (Mn); 258 mg kg(-1) (Fe); 67 mg kg(-1) (Cu); 675 mg kg(-1) (Zn); 69 mg kg(-1) (Pb); and 1.93% (PO (4) (3-) ). The major crystalline constituent in the calculi of Sri Lanka is calcium oxalate monohydrate. Principal component analysis was used to identify the multi element relationships in kidney stones. Three components were extracted and the first component represents positively correlated Na-K-Mg-PO (4) (3-) whereas the second components represent the larger positively weighted Fe-Cu-Pb. Ca-Zn correlated positively in the third component in which Mn-Cu correlated negatively. This study indicates that during the crystallization of human urinary stones, Ca shows more affinity towards oxalates whereas other alkali and alkaline earths precipitate with phosphates.

In vitro and in vivo study of effect of lemon juice on urinary lithogenesis

OBJECTIVES

The diversity of experimental results obtained in the study of the effect of citrus juice on urinary lithogenicity moved us to study the effect of these substances in vitro and in-vivo. The in-vitro study is based on the turbidimetric method on calcium oxalate crystallization. In vivo, we studied the effect of lemon juice consumption on urinary chemistry and we tested it on calcium oxalate crystallization in natural urine.

METHODS

The formation of crystals is induced by the addition of the oxalate and calcium solution. Optical density (OD) is measured in a closed system at physiological conditions. The effects of the various juices of lemon, was evaluated by the addition of 50 ml of juice. A male volunteer with no history of kidney stone participated in this study, by lemon juice ingestion. The pH, concentration of oxalate, calcium and citrate were determined before and after ingestion and urine was freshly analyzed by microscopy.

RESULTS AND CONCLUSIONS

In synthetic urine, the inhibition rate of calcium oxalate crystallization increases gradually with the lemon juice concentration. In natural urine, we noted that the kinetics of crystallization of calcium oxalate, before and after ingestion of lemon juice, are comparable. In vivo, after ingestion, a small increase in mean urinary pH (from 6.7 +/- 0.1 to 6.9 +/- 0.1) was noted. Indeed, oxalate calcium means and citrate excretion increased during this period with 33.41%, 6.85% and 3.53% respectively. This increase in the oxalate excretion is probably explained by the conversion of the exogenous ascorbic acid contained in the lemon juice. These results show that the lemon juice presents an important inhibitory effect in vitro. The ingestion of the lemon juice seems to dissipate a effect of great quantity of citrates which in turn increases the excretion of oxalates. The presence of these two elements simultaneously: citrate and oxalate compensate for their opposite effect.

Intestinal Oxalate Absorption is Higher in Idiopathic Calcium Oxalate Stone Formers Than in Healthy Controls: Measurements With the [13C2]Oxalate Absorption Test

PURPOSE

We assessed the importance of oxalate hyperabsorption for idiopathic calcium oxalate urolithiasis, oxalate absorption in healthy volunteers and recurrent calcium oxalate stone formers was compared.

MATERIALS AND METHODS

The [(13)C2]oxalate absorption test, a standardized, radioactivity-free test, was performed. On 2 days 24-hour urine was collected and an identical standard diet containing 800 mg Ca daily was maintained. On the morning of day 2 a capsule containing 0.37 mmol sodium [(13)C2]oxalate was ingested. A total of 120 healthy volunteers (60 women and 60 men) and 120 patients (30 women and 90 men) with idiopathic CaOx urolithiasis (60% or greater CaOx) were tested.

RESULTS

Mean intestinal oxalate absorption in the volunteers was 8.0 +/- 4.4%, and in the patients was 10.2 +/- 5.2% (p <0.001). There was no significant difference in mean absorption values between men and women within both groups. A high overlap between the absorption values of volunteers and patients was found. Only in the patient group did absorption values greater than 20% occur. Oxalate absorption correlated with oxalate excretion in the patients, r = 0.529 (p <0.01) and in the volunteers, r = 0.307 (p <0.01).

CONCLUSIONS

In high oxalate absorbers dietary oxalate has a significant role in oxalate excretion and, therefore, increases the risk of calcium oxalate stone formation.

Characterization of histone (H1B) oxalate binding protein in experimental urolithiasis and bioinformatics approach to study its oxalate interaction

The rat kidney H1 oxalate binding protein was isolated and purified. Oxalate binds exclusively with H1B fraction of H1 histone. Oxalate binding activity is inhibited by lysine group modifiers such as 4',4'-diisothiostilbene-2,2-disulfonic acid (DIDS) and pyridoxal phosphate and reduced in presence of ATP and ADP. RNA has no effect on oxalate binding activity of H1B whereas DNA inhibits oxalate binding activity. Equilibrium dialysis method showed that H1B oxalate binding protein has two binding sites for oxalate, one with high affinity, other with low affinity. Histone H1B was modeled in silico using Modeller8v1 software tool since experimental structure is not available. In silico interaction studies predict that histone H1B-oxalate interaction take place through lysine121, lysine139, and leucine68. H1B oxalate binding protein is found to be a promoter of calcium oxalate crystal (CaOx) growth. A 10% increase in the promoting activity is observed in hyperoxaluric rat kidney H1B. Interaction of H1B oxalate binding protein with CaOx crystals favors the formation of intertwined calcium oxalate dehydrate (COD) crystals as studied by light microscopy. Intertwined COD crystals and aggregates of COD crystals were more pronounced in the presence of hyperoxalauric H1B.

Impact of hypoxia and hypercapnia on calcium oxalate toxicity in renal epithelial and interstitial cells

Although there is an ongoing controversy about the primary site of calcium oxalate stone (CaOx) formation, there is some evidence for extratubular crystallization. However, the mechanisms leading to such interstitial calcifications are not clear. Anatomical studies have demonstrated a close association between the renal vasculature and renal tubules. It has been hypothesized that disorders of the vasculature may contribute to renal stone formation. The exceptional papillary environment with low oxygen and high carbon dioxide is of interest in this context and its impact on CaOx toxicity to renal cells has to be evaluated. LLC-PK1, Madin-Darby canine kidney (MDCK), human umbilical vein endothelial (HUVEC) and fibroblast cell lines were exposed to hypoxia (3% O2) alone, hypercapnia combined with hypoxia (3% O2, 18% CO2) or standard culture conditions (20% O2) for 72 h. Cell survival rates were determined microscopically after 4 h of incubation with CaOx at final concentrations of 1, 2 and 4 mM. DAPI staining and western blot were used to evaluate the induction of apoptosis. We confirmed that CaOx leads to concentration-dependent effects on the viability of the cell lines. HUVECs were most vulnerable to CaOx among the four cell lines. Incubation under hypoxia alone had no impact on CaOx toxicity to any of the cell lines in terms of survival. However, under combined hypoxic and hypercapnic conditions, all cell lines displayed a significant reduction of cell survival compared to room air incubation. Again, this effect was most pronounced for HUVECs. The induction of apoptosis could not be demonstrated in any experimental setting. Combined hypoxia and hypercapnia clearly aggravate CaOx toxicity to renal cell lines. As we could not demonstrate the induction of apoptosis, this effect may be a result of toxic necrosis. Especially the CaOx effect on interstitial cell lines might be of interest in the chronic ischemic papillary environment. An increased toxicity may lead to recurrent stone formation, and vice versa, diseases of the vasculature, like arteriosclerosis, may further promote stone formation by induction of local ischemia. This issue has to be clarified by further studies.

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.

[Application and research progress of composition analysis of urinary calculi]

The analyses of compositions of urinary stones can provide significant reference to the treatment and prevention of recurrence of urolithiasis. In the present paper, the application and research progress of composition analyses of various urinary stones such as calcium oxalates, phosphates, uric acid, urates, cystine etc. by means of modern instruments are summarized. These techniques include Raman spectroscopy, thermogravimetry analysis/differential thermal analysis (TGA/DTA), nuclear magnetic resonance (NMR), high-performance liquid chromatography (HPLC), Fourier infrared (FTIR) spectroscopy, etc.

Randall's plaque: Pathogenesis and role in calcium oxalate nephrolithiasis

The purpose of these studies was to test the hypothesis that Randall's plaque develops in unique anatomical sites of the kidney and their formation is conditioned by specific stone-forming pathophysiologies. We performed intraoperative papillary biopsies from kidneys of idiopathic-calcium oxalate (CaOx), intestinal bypass for obesity, brushite (BR) and cystine stone formers (SF) during percutaneous nephrolithotomy. Tissues were examined by infrared analysis and light and electron microscopy. Our analysis revealed a distinct pattern of mineral deposition and papillary pathology for each type of SF. CaOx SF had interstitial apatite crystals beginning at thin loops of Henle. These deposits termed Randall's plaque are thought to serve as sites for stone attachment. No tubular injury was noted. Intestinal bypass patients possessed intraluminal apatite deposits in inner medullary collecting ducts (IMCD) with associated cell injury. BR SF showed the most severe form of cortical and medullary changes with sites of Randall's plaque, and yellowish intraluminal deposits of apatite in IMCD. Cystine SF had plugging of ducts of Bellini with cystine crystals and apatite deposits in IMCD and loops of Henle. Intratubular sites of crystalline deposits were always associated to adjacent regions of interstitial fibrosis. The metabolic, anatomic, and surgical pathologic findings in four distinct groups of SF clearly show that 'the histology of the renal papilla from a stone former, is particular to the clinical setting'. We believe our approach to studying stone disease will provide insights into the pathogenesis of stone formation for each type of SF that will lead to improved clinical treatment.