Pediatric urolithiasis: etiology, specific pathogenesis and medical treatment

Pediatric urolithiasis is an endemic disease in certain parts of the world, namely Turkey and the Far East. As a recurrent pathology which may reveal functional as well and morphologic changes in the urinary tract, environmental factors together with urogenital abnormalities should be evaluated thoroughly in each patient. The aims of management should be complete clearance of stones, treatment of urinary tract infections, preservation of renal function and prevention of stone recurrence. In addition to certain minimally invasive stone removal procedures, treatment of pediatric urolithiasis requires a detailed metabolic evaluation in all patients on an individual basis. Obstructive pathologies have to be corrected immediately and children with a positive family history should be followed carefully with respect to a high likelihood of stone re-growth and recurrence. Although specific management of each metabolic abnormality seems to be the key factor in the medical management of stone disease, as general advice each child should be forced to adequate fluid intake which will reveal the urine volume increase in accordance with the body mass index. Moreover, medical therapeutic agents which increase urine citrate levels should be encouraged.

Renal tubular impairment in children with idiopathic hypercalciuria

Idiopathic hypercalciuria (IH) is defined as hypercalciuria that persists after correction of dietary inbalances and has no detectable cause. The excretion of urinary N-acetyl-beta-D-glucosaminidase (U-NAG), a marker of proximal tubular damage, has been previously reported as either increased or normal in children with IH. We evaluated U-NAG in 20 children (13 boys and 7 girls, mean age 10.3 years +/- 5.7 SD) with IH (urinary calcium excretion above 0.1 mmol/kg/24 hours, with no detectable cause) and with otherwise normal renal function tests. Ultrasound examination revealed urolithiasis (n=4) and nephrocalcinosis (n=1). The U-NAG values were evaluated in the spot urine collected from the second morning void and calculated as the urinary NAG/creatinine ratio (U-NAG/Cr) and expressed in nkat/mmol. The 24-hour urinary calcium excretion (U-Ca/24h) was assessed in a urinary sample from 24-hour collected urine and calculated in mmol/kg. The obtained results of U-Ca/24h and U-NAG/Cr were expressed as Z-scores. When compared to the reference data, the U-Ca/24h and U-NAG/Cr were significantly higher (p = 0.0004 and p = 0.006, respectively). There was no correlation between the U-NAG/Cr and U-Ca/24h (r = 0.18, p = 0.20). The U-NAG/Cr values were significantly higher in the 5 patients with urolithiasis/nephrocalcinosis, whether compared to the rest of the group (p = 0.02), or to the reference data (p = 0.01). The U-NAG/Cr activity was higher in 15 children without urolithiasis/nephrocalcinosis when compared to reference data (p < 0.01). There was no difference in U-Ca/24h between the children with and without urolithiasis/nephrocalcinosis (p = 0.58). These findings suggest that tubular impairment, as reflected by U-NAG/Cr, might occur in children with IH, especially in patients with urolithiasis/nephrocalcinosis. There doesn't seem to be a direct relationship between the U-NAG/Cr activity and the degree of calcium leakage.

Urolithiasis/nephrolithiasis: what's it all about?

Urolithiasis (urinary tract calculi or stones) and nephrolithiasis (kidney calculi or stones) are well-documented common occurrences in the general population of the United States. The etiology of this disorder is multifactorial and is strongly related to dietary lifestyle habits or practices. Proper management of calculi that occur along the urinary tract includes investigation into causative factors in an effort to prevent recurrences. Urinary calculi or stones are the most common cause of acute ureteral obstruction. Approximately 1 in 1,000 adults in the United States are hospitalized annually for treatment of urinary tract stones, resulting in medical costs of approximately dollar 2 billion per year (Ramello, Vitale, & Marangella, 2000; Tanagho & McAninch, 2004).

Oxalate stimulates IL-6 production in HK-2 cells, a line of human renal proximal tubular epithelial cells

BACKGROUND

Oxalate is a metabolic end product excreted primarily by the kidney and associated with several pathologic conditions. The most common pathologic condition involving oxalate is the formation of calcium oxalate stones in the kidney. Several stimuli have been implicated in the development of glomerular and tubular injury in various forms of immune-mediated renal diseases. The elevated level of interleukin-6 (IL-6) has been reported in the urine of kidney stone-forming patients. In the present study, we investigated the role of oxalate, a major constituent of calcium oxalate kidney stone disease, in the production of IL-6 in normal human HK-2 kidney cells.

METHODS

Confluent cultures of HK-2 cells (a renal epithelial cell line of human origin) were exposed to various concentrations of oxalate (0.2 to 2.0 mmol/L) and lipopolysaccharide (LPS) (0.1 and 10 mug/mL) for various time points (4-24 h) under serum-free conditions. The conditioned mediums were collected, and an IL-6 protein level was measured by enzyme-linked immunosorbent assay (ELISA). The total cellular RNA was isolated from the cells and subjected to relative quantitative reverse transcription-polymerase chain reaction (RT-PCR) to determine the expression of IL-6 mRNA. The statistical analysis of the results was carried out using the Student t test.

RESULTS

HK-2 cells express IL-6 mRNA and protein. Oxalate increased the secretion of IL-6 protein in HK-2 cells in a concentration-dependent fashion. Oxalate exposure to HK-2 cells also induced transcriptional up-regulation of the IL-6 gene, as determined by the increased level of IL-6 mRNA expression following treatment with oxalate. Moreover, the effects of oxalate on IL-6 expression were time- and concentration-dependent. This is the first report demonstrating the regulation of IL-6 by oxalate.

CONCLUSION

This study provides the first direct evidence that oxalate up-regulates the expression and secretion of IL-6 in renal epithelial cells. The increased IL-6 expression and secretion by renal epithelial cells may play a critical role in the progression of urolithiasis in hyperoxaluric conditions.

Etiological and clinical patterns of childhood urolithiasis in Iraq

This study was conducted to evaluate the etiological and clinical characteristics of urolithiasis in Iraqi children. From 1999 to 2004, 204 children with renal calculi were evaluated. The age range of the patients was 4 months to 14 years, 61.3% of the patients were under 5 years. Male to female ratio was 2.8:1. The mean age at onset of symptoms was 3.2 years, and stone disease was diagnosed at a mean of 3.5 years. Hematuria (44.6%) and pain (28.4%) were the main clinical presentation. Of the 204 patients 45.1% had a family history of stones. Consanguinity was recorded in 72%; 75.5% had metabolic disorders. Stones were located at multiple sites in 80 patients, or 39.2%; 58 of these 80, or 72.5%, had metabolic disorders. Multiple stones were present in 47 (23%); 72.3% were related to metabolic disorders. In 126 patients, or 61.8%, both kidneys were involved equally. Bladder stones were found in 11.3%. Staghorn calculi occurred in 29 patients, or 14.2%; 27 of these had recurrent urinary tract infection (UTI). Nephrocalcinosis was diagnosed in 7, or 3.4%; all had metabolic disorders. Etiology of stone formation was established in 189 patients, or 92.6%, whereas 15, or 7.4%, had idiopathic stones. Metabolic disorders were the commonest cause in 106 patients (52%); 52 patients were classified as infective (25.5%). Anatomical defects were present in 25 (12.2%) and 6 children (2.9%) with primary endemic bladder calculi. Coexisting UTI was common (36.8%) in the metabolic group. We concluded that urolithiasis is a serious problem among Iraqi children, with early onset of presentation. Metabolic disorders were the major causes, but can be masked by associated UTI. Proper management of UTI with a careful metabolic assessment of young stone formers is valuable in combating urolithiasis.

Nonsurgical Management of Urolithiasis: An Overview of Expulsive Therapy

Although minimally invasive stone therapies such as shockwave lithotripsy, ureteroscopy, and percutaneous nephrolithotomy are efficacious, these techniques are not free of risks and are relatively expensive. Watchful waiting may be appropriate in patients without infection whose pain can be controlled with oral medication but is associated with pain, uncertainty, potential risks to renal function, and time lost from work. Hydroxyprogesterone, prostaglandin synthetase inhibitors, calcium-channel blockers such as nifedipine, alpha-1 blockers such as tamsulosin, and corticosteroids may have some beneficial effect. Future studies are likely to provide additional data in support of their use.

Urolithiasis and obesity: metabolic and technical considerations

PURPOSE OF REVIEW

The increasing prevalence of obesity poses a challenge to urologists in the diagnosis and treatment of urolithiasis. This review summarizes the new evidence linking obesity and urolithiasis, and the technical considerations and modifications necessary in the diagnosis and treatment of stone disease in obese patients.

RECENT FINDINGS

Recent studies have confirmed the epidemiological link between obesity and urolithiasis, and have provided some possible explanations for its underlying cause. New clinical series have demonstrated that flexible ureterorenoscopy and adapted percutaneous nephrolithotomy techniques can result in similar stone clearance rates and morbidity to the non-obese patient. New data, however, suggest that obesity may be an independent predictor of extracorporeal shock wave lithotripsy treatment failure for ureteric stones. Evidence of the efficacy of dietary modification and medical treatment of metabolic abnormalities has been reported in obese stone formers.

SUMMARY

Urolithiasis can be safely and effectively managed in obese patients with minor modifications to the established surgical techniques. Increased understanding of the underlying metabolic abnormalities in obese patients with urolithiasis may improve prevention strategies in the future.

Efficacy of the Duet lithotripter using two energy sources for stone fragmentation by shockwaves: an in vitro study

PURPOSE

To evaluate the efficacy of the Duet lithotripter's novel design of two independent spark-plug generator/reflector systems focused at a common F2. The apparatus allows either simultaneous delivery of shockwaves from both generators (resulting in a per-shock energy delivery at F2 equal to that delivered by its single generator at about 24 kV), alternating (between the two generators), or single-generator delivery of shockwaves at various energy levels and rates.

MATERIALS AND METHODS

Eighty-five phantom gypsum stones (volume 786 mm3 each) were placed in a net-like basket and immersed in a specially designed waterbath coupled with the Duet lithotripter (Direx Medical Systems Ltd., Petach Tikva, Israel). Shockwaves were delivered at rates of either 60 or 120 per minute and at intensities of 16 or 22.8 kV (electrohydraulic). Energy was delivered either separately from each generator, in an alternating mode, or simultaneously from both generators. The number of shocks required to fragment the stones sufficiently to allow all of the pieces to fall through the basket holes (complete fragmentation) was recorded.

RESULTS

The number of shocks required for complete fragmentation in the alternate mode (120 shocks/min, each generator rate 60/min; 22.8kV) was lower than with the single generator, 112 +/- 19 v 134 +/- 18 (at a rate of 120/min; 22.8 kV). The simultaneous mode of dual generator shockwave delivery was more effective than the traditional single generator (114 +/- 28 shocks at a rate of 120/min, 16 kV v 159 +/- 40 shocks at a rate 120/min; 22.8kV).

CONCLUSION

The Duet lithotripter is more effective when used in a simultaneous or alternating mode than is the classical single mode of shock delivery, with the added benefit of shorter treatment time.

Regulation of renal calcium receptor gene expression by 1,25-dihydroxyvitamin D3 in genetic hypercalciuric stone-forming rats

Hypercalciuria in inbred genetic hypercalciuric stone-forming (GHS) rats is due, in part, to a decrease in renal tubule Ca reabsorption. Activation of the renal Ca receptor (CaR) may decrease renal tubule Ca reabsorption and cause hypercalciuria through suppression of Ca-sensitive potassium channel activity. Because the rat renal CaR gene is regulated by extracellular calcium and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and GHS rats have increased renal vitamin D receptor content, the current study was undertaken to determine the level of CaR gene expression in GHS rat kidney and whether CaR gene expression is regulated by 1,25(OH)2D3. Male GHS and normal control (NC) rats were fed a Ca-sufficient diet (0.6% Ca). Western blotting revealed a four-fold increase in CaR protein in GHS rat renal tissue, and 1,25(OH)2D3 administration increased renal CaR in both GHS and NC rats. Northern blot analysis of extracts of renal cortical tissue from GHS and NC rats revealed a major 7-kb transcript of CaR and a more modest 4-kb transcript, both of which were readily detectable. Both Northern blotting and real-time reverse transcription-PCR revealed increased basal CaR mRNA expression levels in GHS rat kidney. 1,25(OH)2D3 administration increased renal CaR mRNA levels 2.0- and 3.3-fold in GHS and NC rats, respectively. Despite the greater incremental increase by 1,25(OH)2D3 in NC rats, CaR mRNA levels remained higher in GHS rat kidney, and the elevation was more sustained. 1,25(OH)2D3 increased CaR mRNA through both elevated CaR gene expression and prolonged tissue half-life. These results demonstrate that GHS rats have high levels of CaR gene expression and CaR protein that may contribute to the hypercalciuria and calcium nephrolithiasis.

Urolithiasis in adolescent children

Idiopathic urolithiasis in children has become more frequent in the past few decades as a result of increasing affluence and rapid change in our society's dietary habits. In Western societies, calcium stones in the kidney and ureter predominate. Pediatric urolithiases, unlike the adult form, require a comprehensive metabolic evaluation, because metabolic and enzymatic derangements play an important role in their pathogenesis. The recent advancements in endoscopic procedures, interventional radiology, and lithotripsy have allowed children to be managed effectively without open surgery. Pediatric urolithiasis requires a close working relationship between the urologist for acute surgical management of urolithiasis and the nephrologists for prevention of stone formation. In many children and adolescents with urolithiasis, a nonpharmacologic approach involving the adoption of healthy nutrition habits may suffice.

EFFECTS OF URINARY PROTHROMBIN FRAGMENT 1 IN THE FORMATION OF CALCIUM OXALATE CALCULUS

PURPOSE

We investigated the effects of urinary prothrombin fragment 1 in the formation of calcium oxalate urolithiasis.

MATERIALS AND METHODS

Fresh urine and renal parenchyma from patients with calcium oxalate calculus and normal controls were collected. Urinary prothrombin fragment 1 was isolated and purified from urine. It was identified by sodium dodecyl sulfide-polyacrylamide gel electrophoresis and analysis of its first 13 N-amino acids. The inhibitory activity of urinary prothrombin fragment 1 on calcium oxalate crystal growth was tested by the seeded crystallization technique. Meanwhile, the gamma-carboxyglutamic acid composition of urinary prothrombin fragment 1 was analyzed by a previously described method and genetic mutation of the gamma-carboxyglutamic acid domain of urinary prothrombin fragment 1 from renal parenchyma was detected by polymerase chain reaction-single strand conformational polymorphism sequencing.

RESULTS

The gamma-carboxyglutamic acid composition of urinary prothrombin fragment 1 was significantly decreased from normal (24.4 to 1.7 mol/1,000 amino acids) in patients with calcium oxalate calculus. The mean growth index +/- SD of urinary prothrombin fragment 1 to calcium oxalate crystals was 42.3 +/- 4.2 compared with the normal index of 19.2 +/- 2.8 (p <0.01). The polymerase chain reaction-single strand conformational polymorphism sequencing technique revealed no genetic mutation of the gamma-carboxyglutamic acid domain of urinary prothrombin fragment 1 in patients with calcium oxalate calculus.

CONCLUSIONS

The gamma-carboxyglutamic acid composition of urinary prothrombin fragment 1 as well as its ability to inhibit calcium oxalate crystal growth was significantly decreased in patients with calcium oxalate calculus. This was not caused by genetic mutation of the gamma-carboxyglutamic acid domain of urinary prothrombin fragment 1. It is important to elucidate the mechanisms of calcium oxalate stones in view of urinary prothrombin fragment 1.

Progress in the Use of Helical CT for Imaging Urinary Calculi

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

Metabolic evaluation of urolithiasis patients from eastern Croatia

Metabolic parameters were determined in fasting blood serum, fasting first morning urine, and 24-hour urine of male patients with recurrent calcium oxalate stones (N = 26, age 39.1 +/- 6.2 years) as well as in male healthy controls (N = 18, age 35.0 +/- 7.1 years), recruited from the eastern part of Croatia. The 24-hour urinary calcium excretion was significantly higher (p < 0.01) for patients (5.6 +/- 2.5 mmol) than for controls (3.7 +/- 1.9 mmol), but potassium excretion was higher (p < 0.01) for controls (74.5 +/- 33.8 mmol) than for patients (49.2 +/- 15.7 mmol). The mean ionic activity product of calcium and oxalate ions, IAP(CaOx), calculated from the fasting first morning urine parameters, was 25% higher for patients than for controls, but the difference was not statistically significant (p > 0.05). Very strong correlation (r = 0.97) was obtained between IAP(CaOx) values and calculated Ogawa indices that were recommended for estimating the potential risk for calcium oxalate stone formation.

Renal stone analysis: why and how?

Upper urinary tract stone disease is widespread in the developed world. On both clinical and economic grounds it is now accepted that evidence-based medical intervention is the only approach likely to make a significant impact on the incidence, and more importantly, the recurrence rates of this disease. Targeted medical prophylaxis requires reliable information on stone type which, when combined with relevant blood and urine analyses, allows identification of treatable risk factors. Data from an external quality assurance scheme indicate that stone analysis is poorly performed in many laboratories, and it is probable that this results in ill-informed patterns of investigation, inappropriate therapy, missed diagnoses of rarer causative disorders and wasteful further investigation of 'non-renal' stone artefacts. Renal stone analysis is a specialist investigation requiring appropriate analytical and interpretative expertise if the information is to be used to enhance patient care. For those laboratories not able to offer this, for whatever reason, referral is the only defensible approach to service provision. The methods currently employed in many departments have no place in modern clinical biochemistry practice.

Rationale Diagnostik der Urolithiasis in der täglichen Praxis

Patients with renal colic are usually treated in emergency care units or by their family doctors and require immediate diagnosis and treatment. The life-time risk is up to 10 %. The prevalence amounts to 4.7 % in Germany. In addition to confirming the diagnosis and inducing an adequate pain therapy it is very important for patients to be directed correctly and, above all, prevention is important, too. Without treatment the recurrence rate ranges between 50 and 100 %. Particularly, these principals should give useful advice, wherever patients are treated without urological department.

IN VITRO COMPARISON OF FRAGMENTATION EFFICIENCY OF FLEXIBLE PNEUMATIC LITHOTRIPSY USING 2 FLEXIBLE URETEROSCOPES

PURPOSE

Pneumatic lithotripsy has been shown to be an effective and safe intracorporeal lithotripsy modality for renal and ureteral calculi, capable of fragmenting stones of all compositions. We determined the in vitro stone fragmentation abilities of the 0.5 mm flexible pneumatic lithotripsy probe when inserted through the working channel of 2, 7.5Fr flexible ureteroscope designs (straight working channel and offset working channel at approximately 30 degrees from the long axis of the endoscope). The velocity and displacement of the pneumatic probe tip were also evaluated with the probe inserted through each endoscope.

MATERIALS AND METHODS

The 0.5 mm (1.5Fr) stainless steel probe was tested at 5 deflection angles, namely 0, 12, 24, 33 and 48 degrees, at a pneumatic pressure of 2.5 bar when inserted through the offset and straight working channel ureteroscopes. A noncontact optical laser system was used to measure or calculate the displacement and velocity of the 0.5 mm probe tip at each angle of deflection with the 2 ureteroscopes. Fragmentation at all deflection angles was assessed using plaster of Paris stone phantoms with the pneumatic device on continuous mode at 2.5 bar pressure for 30 seconds. Stones were weighed after each fragmentation cycle and the percent weight lost was determined. Comparisons were made between the 2 ureteroscopes at each angle.

RESULTS

Probe tip displacement was significantly better through the straight channel ureteroscope with 30% improvement at all angles tested compared to the offset channel. Moreover, a substantial decrement in tip displacement was noted as the angle of deflection increased regardless of the endoscope used. Conversely tip velocity was relatively unchanged throughout the study and it was equivalent from straight to offset channel measurements. Phantom stone fragmentation correlated inversely with the severity of the deflection angle. An approximately 80% loss of fragmentation ability was noted as the angle increased from 0 to 48 degrees. Although the pneumatic device performed better through the straight channel scope, a similar percent loss in fragmentation from 0 to 48 degrees was seen when using either endoscope.

CONCLUSIONS

The flexible pneumatic 0.5 mm lithotripsy probe appears to be best used through a straight channel flexible ureteroscope, out performing use through the offset channel scope at all angles of deflection. Tip displacement and fragmentation ability were inversely related to the degree of active deflection as the angle increased from 0 to 48 degrees. Use of the flexible pneumatic probe to aid in managing renal or proximal ureteral calculi may be limited until an improved probe can be developed, allowing complete and unencumbered fragmentation throughout all angles of deflection.

Epidemiology of nephrolithiasis today

The epidemiology of nephrolithiasis differs according to geographical area and socio-economic conditions. In Italy the prevalence of the disease in 1993 was 17.2/1,000 inhabitants, most patients are men and elderly. The relative risk increased in subjects with family history for calculosis, with the tendency to eat protein-rich food and with overweight and body mass index (MBI) >32 kg/m2. Calcium oxalate and/or phosphate stones account for almost 70% of all renal stones observed in economically developed countries.

Predictive medicine in non-malignant urological disorders

The potential of disease prediction in non-malignant disorders should not be undervalued. Such disorders present several characteristics which make them suitable for disease prediction: they can be wide-spread, strongly affect the patients' quality of life, lead to a heavy burden on social health expenses and have a protracted clinical course. Moreover, people who present a high risk for non-malignant disease can be successfully introduced to long-term preventive measures such as lifestyle modifications, dietary changes and improvement in hygienic conditions. There is a growing demand for developing predictive medical strategies in urology. While urological cancers are the main focus of interest, we analyse the potentialities and challenges of predictive medicine in non-malignant urological disorders, with particular attention to benign prostate hyperplasia and urolithiasis.

Calcium urolithiasis, blood pressure and salt intake

OBJECTIVES

To determine whether stone-formers have higher BP than controls drawn from the general population and matched for age, sex and ethnic origin and to compare the relationship between sodium and calcium excretion in the two groups.

PATIENTS AND METHODS

Thirty-six patients [mean (+/-standard deviation, SD) = 49.0 +/- 11.7 years; range 27-70 years] with kidney or ureteric stones and 108 controls (mean age of 49.6 +/- 6.8 years; range 39-61 years), matched for gender, ethnic origin and age group were studied. Patients and controls underwent physical measurements, a venous blood sample and they were asked to collect a 24-h urine sample for sodium, potassium, calcium and creatinine.

RESULTS

Stone-formers were significantly heavier and had higher BP than age-, sex- and ethnic-matched population controls. Whilst the difference in systolic BP was independent of the difference in body mass index [16.8 mmHg (7.2-26.4 mmHg), p = 0.001), the difference in diastolic BP was attenuated after adjustment for body mass [1.8 (-3.4 to 7.1), p = 0.49]. Stone-formers passed less urine than controls [-438 ml/day (95% CI -852 to -25), p = 0.038]. They had higher urinary calcium than controls [+3.7 mmol/day (2.8-4.6 mmol/day), p < 0.001], even when expressed as ratio to creatinine [+0.20 (0.11-0.29), p < 0.001]. Sodium excretion was positively associated with urinary calcium in both stone-formers and in controls. The slopes were comparable (0.92 vs 0.98 mmol Ca/100 mmol Na) so that for any level of sodium excretion (or salt intake), stone-formers had a higher calcium excretion than controls.

CONCLUSIONS

In stone-formers, the BP is higher than in controls. Stone-formers excrete more calcium than controls do. In stone-formers and controls, the relationship between urinary sodium and calcium is similar. Since this relationship results from an effect of sodium on calcium, a reduction in salt intake may be a useful method of reducing urinary calcium excretion in stone-formers. However, the "relative" hypercalciuria seen in stone-formers is independent of salt intake and may well reflect an underlying genetic predisposition.

Is calcium oxalate nucleation in postprandial urine of males with idiopathic recurrent calcium urolithiasis related to calcium phosphate nucleation and the intensity of stone formation? Studies allowing insight into a possible role of urinary free citrate and protein

In idiopathic recurrent urolithiasis (IRCU) calcium oxalate and calcium phosphate are components of stones. It is not sufficiently known whether in urine the nucleation (liquid-solid transition) of each salt requires a different environment, if so which environment, and whether there is an impact on stone formation. Nucleation was induced by in vitro addition of oxalate or calcium to post-test meal load whole urine of male stone patients (n=48), showing normal daily and baseline fasting oxaluria. The maximally tolerated (until visible precipitates occur) concentration of oxalate (T-Ox) or calcium (T-Ca) was determined; additionally evaluated were other variables in urine, including total, complexed and free citrate (F-Cit), protein (albumin, non-albumin protein) and the clinical intensity (synonymous metabolic activity; MA) of IRCU. In the first of three trials the accumulation of substances in stone-forming urine was verified (trial-V); in the second (clinical trial 1) two strata of T-Ox (Low, High) were compared; in the third (clinical trial 2) IRCU patients (n=27) and a control group (n=13) were included to clarify whether in stone-forming urine the first crystal formed was calcium oxalate or calcium phosphate, and to identify the state of F-Cit. T-Ox was studied at the original pH (average<6.0), T-Ca at prefixed pH 6.0; the precipitates were subjected to electron microscopy and element analysis. Trial-V: Among the urinary substances accumulating at the indicated pHs were calcium, oxalate and phosphate, and the crystal-urine ratios were compatible with the nucleation of calcium oxalate, calcium-poor and calcium-rich calcium phosphate; citrate, protein and potassium also accumulated. Clinical trial 1: the two strata exhibited an inverse change of T-Ox and T-Ca, the ratio T-Ox/T-Ca and MA. The initial (before induction of Ox or Ca excess) supersaturation of calcium oxalate and brushite were unchanged, with the difference of proteinuria being borderline. Several correlations were significant (p≤0.05): urine pH with citrate and volume, protein with volume and MA, T-Ox with T-Ca and MA. Clinical trial 2: in patients with reduced urine volume and moderate urine calcium excess, the first precipitate appeared to be calcium oxalate, followed by amorphous calcium phosphate. Conversely, when the calcium excess was extreme, calcium-rich hydroxyapatite developed, followed by calcium oxalate; F-Cit, not total and complexed citrate, was decreased in IRCU vs. male controls; F-Cit rose pH-dependently, and the ratio F-Cit at original pH vs. F-Cit at pH 6.0 correlated inversely with the nucleation index T-Ox/T-Ca; MA correlated inversely with the ratio F-Cit at pH 6.0, respectively, original pH, but directly with the urinary albumin/non-albumin protein ratio. In summary 1) to study calcium oxalate and calcium phosphate nucleation in whole urine of IRCU patients is feasible; 2) at this crystallization stage the two substances, dominant in calcium stones, appear intimately linked, 3) in stone-forming urine, calcium phosphate may be ubiquitously present, likely as particles <0.22 μm; 4) together with co-precipitation of calcium oxalate and calcium phosphate, low F-Cit and alteration of proteinuria may act in concert and accelerate stones.

[B-mode and color Doppler sonography of kidneys in healthy lambs and lambs with urolithiasis]

The objectives of this study were to determine some morphological characteristics of kidneys and resistive index (RI) changes in renal interlobar artery using B-Mode and color coded doppler sonography in lambs with urolithiasis. The study was performed in 14 male lambs (8 patients, 6 healthy) aged between 2-2.5 months in the same herd. The kidneys had a mean length of 55.6 +/- 1.6 mm, a width of 31.8 +/- 1.2 mm and a parenchymal width of 10.6 +/- 0.6 mm in healthy lambs. These values were 95.4 +/- 3.6., 52.4 +/- 1.3 and 8.75 +/- 0.5 mm, respectively in lambs with urolithiasis. These differences between both groups were significant. Furthermore, the mean resistive index values in lambs with urolithiasis (0.81 +/- 0.017 m/sn) were significantly higher than controls (0.62 +/- 0.013 m/sn). It was concluded that B-Mode and color coded doppler sonography might provide useful information for detection of changes in kidneys of lambs with urolithiasis like hydronephrosis and renal swelling as well as elevated resistance in the renal interlobar artery.

Urinary nephrocalcin excretion in children with urolithiasis

The aim of this study was to investigate the role of nephrocalcin in childhood urolithiasis. Forty-one patients with urinary stones and 25 age- and sex-matched healthy controls were admitted to the study. Blood and timed urine samples were taken from both patient and control groups for biochemical analysis. Serum and urine creatinine (Cr) and urinary nephrocalcin (NC) were measured. NC excretion was expressed as a NC/Cr (mg/g) ratio. NC-PreA/Cr and NC-D/Cr ratios were found to be significantly higher in patients than in the control group. No statistically significant differences were found in NC-A/Cr, NC-B/Cr, NC-C/Cr ratios between the patient and control groups. The high NC-PreA/Cr ratio (p = 0.012) observed in stone-forming patients indicates that this ratio may also be an important stimulatory factor for urinary stone disease.

[Effects of water diuresis on the urinary ph of patients under relapsing lithiasis]

INTRODUCTION

It has been observed that in healthy individuals the increase in urinary flow induced by water overload may be enough to alter the urinary Ph to obtain values considered safe in the prophylaxis of lithogenesis. The aim of the present paper is to determine the effects of water diuresis on the urinary Ph of patients suffering from relapsing lithiasis.

MATERIAL AND METHOD

26 patients were included in the present study. The urinary Ph of all patients was measured along two consecutive days, at 8.30 and again at 12.30, under normal conditions (the first day) and once they had received a water load equivalent to 1.5% of their weight (the second day).

RESULTS

The altered mean value of the Ph induced on the first day by the circadian rhythm showed a mean of 0.13 units of Ph, which lacks statistical significance (p > 0.05). However, on the second day we obtained a value of 0.42, which is statistically significant (p < 0.01). The normal tendency after the water overload was towards a positive increase of the Ph in those patients whose urine showed a preload Ph value < 6.1, whereas those individuals with a preload Ph value > 6.48 suffered negative increases.

CONCLUSIONS

The increase of diuresis induced by water load proved enough to provoke an increase of urinary Ph when its baseline value is < 6.1, or either a decrease when its baseline value is > 6.48. In both cases, Ph values ranged between 6-6.5 which are considered safe values in the prophylaxis of lithogenesis. The more separated the baseline urinary Ph is from the 6.1-6.48 range, the greater the effect of the water load.

Calcium oxalate aggregation in whole urine, new aspects of calcium stone formation and metaphylaxis

OBJECTIVES

To assess the influence of pH, Ca(2+)-concentration, hydroxyapatite (HAP) and preformed calcium oxalate (CaOx) aggregates on the aggregation (AGN) of CaOx crystals directly produced in unpretreated whole urine (U) by oxalate loads (OL).

METHODS

After OL at pH 5.0 and pH 6.5 minimal sedimentation time of precipitates (ST = minutes for 0.05 optical density [OD] decrease) was measured in 40 U of 5 healthy men by spectrophotometry. An ST(P) (< or =2.8) was taken as indicator for primary AGN and an ST(S) (< or =1.4) as one for secondary AGN. In 20 U Ca(2+) was determined initially, Ca(2+) at pH 6.5 was readjusted by adding CaCl(2) to the value measured at pH 5.0 and an OL of 1.5mM performed. OL of 0.25-0.75 mM were given to 20 U either with 0.05 mg/ml HAP or after a primary OL of 2mM.

RESULTS

Alkalinization of U from pH 5.0 to 6.5 decreased Ca(2+) by 44+/-15% (mean+/-S.D.) and, in U with total Ca <3mM, below a crucial value of 1mM where no ST(P) was observed. At identical Ca(2+), pH had no influence on ST. With HAP, an ST(P) was found after an OL of 0.5mM in 10% and of 0.75 mM in 35%, predominantly at pH 5.0. An ST(S) was observed after a second OL of 0.5mM in 55% and of 0.7 5mM in 75% of experiments.

CONCLUSIONS

Provided that AGN is important for stone formation, calcium nephrolithiasis might be initiated at high urinary Ox and low pH by HAP of kidney calcifications, prevented at moderate calciuria by alkali treatment and augmented during relative hyperoxaluria by secondary AGN.