Tadeusz Porowski

An association between kidney stone composition and urinary metabolic disturbances in children

OBJECTIVE To determine kidney stone composition in children and to correlate stone fractions with urinary pH and metabolic urinary risk factors. PATIENTS AND METHODS We studied 135 pediatric patients with upper urinary tract lithiasis in whom excreted or extracted stones were available for analyses. Composition of stones was analyzed. A 24-hour urine assessment included volume, pH and daily excretions of calcium, oxalate, uric acid, cystine, creatinine, phosphate, magnesium and citrate. RESULTS Calcium oxalate was the major component of 73% stones, followed by struvite (13%) and calcium phosphate (9%). Uric acid was present in almost half of stones, but in rudimentary amounts. The calcium oxalate content in calculi showed a strong relationship with calciuria, and moderate association with oxaluria, magnesuria and acidification of urine. The percent content of struvite presented reverse and lower correlations with regard to the above parameters. Calcium phosphate stone proportion had low associations with urinary risk factors. CONCLUSIONS Calciuria, oxaluria, magnesuria and low urine pH exerted the biggest influence on calcium oxalate content in pediatric renal stones. Relationships of urinary risk factors with calculi calcium phosphate content were of unclear significance. Urinary citrate excretion did not significantly correlate with kidney stone composition in children.

Does obesity or hyperuricemia influence lithogenic risk profile in children with urolithiasis

BackgroundThere are indications that obesity and hyperuricemia may influence the formation and composition of urinary stones. The aim of our study was to determine the effect of obesity and hyperuricemia on the urinary lithogenic risk profile in a large cohort of pediatric patients.MethodsThe study population comprised 478 children with urolithiasis and 517 healthy children (reference group). We studied the effects of obesity on the lithogenic profile by dividing the patients with urolithiasis into two groups based on body mass index Z-score (patients who were overweight/obese vs. those with normal weight for age) and comparing the two groups. To study the effect of hyperuricemia on the lithogenic profile, we divided the patients with urolithiasis into two groups based on the presence or not of hyperuricemia (110 patients with urolithiasis accompanied by hyperuricemia vs. 368 patients with urolithiasis and normal serum uric acid levels) and compared the groups.ResultsAmong the children and adolescents with urolithiasis and hyperuricemia, there was a significantly lower excretion of crystallization inhibitors (citrates, magnesium). We also found significantly negative correlations between serum uric acid levels and the urine citrate/creatinine ratio (citrate/cr.; r = −0.30, p < 0.01), as well as the magnesium/cr. ratio (Mg/cr.; r = −0.33, p < 0.01). There was no statistically significant differences in the urinary excretion of oxalates, citrates, calcium, phosphorus, magnesium and uric acid between children with urolithiasis who were either overweight or obese and children with urolithiasis who had a normal body weight.ConclusionsIn our pediatric patient cohort, hyperuricemia was associated with a decrease in the excretion of crystallization inhibitors in the urine, but the clinical relevance of this observation needs to be confirmed in future studies. Obesity and overweight had no direct influence on the lithogenic risk profile in the urinary stone formers in our study, but there was an indication that higher serum uric acid may be associated with impairment in renal function, which in turn could influence the excretion of lithogenic parameters.

Correspondence between Ca2+ and calciuria, citrate level and pH of urine in pediatric urolithiasis

BackgroundHypercalciuria and hypocitraturia are considered the most important risk factors for urolithiasis. Citrate binds to urinary calcium to form a soluble complex which decreases the availability of ionized calcium (Ca2+) necessary for calcium oxalate formation and phosphate crystallization. The aims of this study were to assess the Ca2+ fraction in relation to total calciuria, citraturia and urinary pH and to determine whether urinary Ca2+ concentration is a helpful biomarker in metabolic evaluation of children with urolithiasis.MethodsWe collected 24-h urine samples from 123 stone-forming children and adolescents with hypocitraturia and from 424 healthy controls. Total calciuria (total calcium, Catotal), Ca2+, pH, citrate, oxalate and Bonn Risk Index (BRI) were assessed and compared between the two groups.ResultsTotal calciuria and Ca2+ content were higher in stone-formers than in the healthy children. In both stone-formers and controls, Ca2+ content was inversely related to citraturia and urinary pH, whereas the Ca2+/Catotal ratio differed slightly between the groups. A large variability in Ca2+ level was found across individuals in both groups. The BRI increased with increasing calciuria and urine acidity.ConclusionsCompared to controls, stone-formers with hypocitraturia demonstrated a higher urinary Ca2+ concentration, but this was proportional to calciuria. The large individual variability in urinary Ca2+ content limits its practical use in metabolic evaluation of children with urolithiasis. However, the Ca/Citrate ratio may be a useful clinical tool in evaluating children with urolithiasis.

Isolation, purification, and characterization of glucosamine-6-phosphate-N-acetylase from pig liver

The procedure of isolation, purification, and characterization of glucosamine-6-phosphate acetylase from the pig liver is described. The steps of purification were as follows: adsorption on hydroxylapatite, fractionation with ammonium sulfate, chromatography on cellulose phosphate, electrofocusing, and preparative gel electrophoresis. A highly purified (about 3000-fold) preparation of GlcN-6-P acetylase, with a yield of 23%, was obtained. It was found that GlcN-6-P acetylase from pig liver is heterogeneous and exists in two active forms. The characteristic features of the preparation were established: Mr, about 24 kDa; temperature optimum at 37 degrees; pH optimum at 7.45; and Km (GlcN-6-P) 3.7 x 10(-3) M and Km (AcCoA) 1.4 x 10(-3) M. The ions K+, Na+, NH4+, Mg2+, Mn2+, and CH3COO- do not stimulate the acetylase activity. The product of acetylase reaction (GlcNAc-6-P) inhibits this reaction according to the feedback process. The highly purified preparation of GlcN-6-P acetylase is unstable during storage and it is protected by ampholine or glycine from enzyme inactivation, but it is not protected by 2-mercaptoethanol.

Bonn Risk Index Based Micromethod for Assessing Risk of Urinary Calcium Oxalate Stone Formation

PURPOSE The Bonn Risk Index has been used to evaluate the risk of urinary calcium oxalate stone formation. According to the original method, risk should be determined based on a 200 ml urine sample taken from a 24-hour collection. We evaluated whether the Bonn Risk Index can also be effectively determined in small urine samples. MATERIALS AND METHODS We studied 190 children and adolescents with nocturia and calcium oxalate urolithiasis. Initially Bonn Risk Index was determined according to the original method of Laube. Subsequently Bonn Risk Index was calculated using a computer program controlling a specially designed system to define the time point of induced crystallization based on consecutive urine samples of 1.5, 2.0 and 3.0 ml. RESULTS No significant differences were found in Bonn Risk Index between values obtained from 200 ml samples and those based on the micromethod with urine samples of 2 and 3 ml. CONCLUSIONS Assessment of risk of urinary calcium oxalate stone formation with Bonn Risk Index in small urine volumes, based on prototype equipment controlled by specialized computer software, is comparable to the original method. This finding facilitates the procedure and improves Bonn Risk Index determination in children.

Assessment of Lithogenic Risk in Children Based on a Morning Spot Urine Sample

PURPOSE The Bonn Risk Index has been used to evaluate the risk of urinary calcium oxalate stone formation. According to the original method, risk should be determined based on 24-hour urine collection. We studied whether the Bonn Risk Index could be measured in spot urine samples and which part of the day is most suitable for this purpose. MATERIALS AND METHODS We collected total and fractionated 24-hour urine (in a 6-hour nocturnal portion and 9 consecutive 2-hour diurnal samples) in 42 children and adolescents with calcium oxalate urolithiasis and 46 controls. Bonn Risk Index values determined from each of the urine fractions were compared to those obtained from related 24-hour urine collections. RESULTS Both groups exhibited similar circadian patterns of Bonn Risk Index values. Median Bonn Risk Index for the nighttime portion of urine in the stone group was 1.4 times higher than that obtained from the total 24-hour urine. The morning hours between 08:00 and 10:00 showed the peak lithogenic risk, and this fraction had the highest sensitivity and selectivity regarding discrimination between stone formers and healthy subjects. The afternoon hours demonstrated lower and less fluctuating crystallization risk. Despite diurnal fluctuations in Bonn Risk Index, there was still a well-defined cutoff between the groups. CONCLUSIONS Bonn Risk Index determined from urine samples collected between 08:00 and 10:00 appears optimal in separating stone formers from healthy subjects, and appears as useful as the value determined from 24-hour urine collection. Investigation of this diurnal sample simplifies diagnosis in pediatric stone disease without loss of clinical information.

Urinary nerve growth factor level in children with neurogenic bladder due to myelomeningocele

Abstract Objective. Myelomeningocele is the most common physically disabling birth defect in humans. It is caused by the failure of the neural tube to close and is most common in the lumbosacral area. Because of associated neurogenic bladder dysfunction, children with myelomeningocele have an increased risk of urinary tract infections and, ultimately, of kidney damage. Nerve growth factor (NGF) is an important mediator inducing bladder overactivity in many pathological conditions. The aim of this study was to evaluate urinary NGF excretion in children with neurogenic bladder caused by myelomeningocele. Material and methods. The investigation was conducted into two groups. Group 1 comprised 28 children with neurogenic bladder, and group 2 comprised 20 healthy children with no abnormalities in the urinary and nervous systems. Urinary NGF levels were measured by enzyme-linked immunosorbent assay. Results. Median urinary NGF concentration in group 1 was higher when compared with healthy controls. Positive correlations between urinary NGF level and detrusor pressure at maximum bladder capacity, and negative correlations between NGF and bladder wall compliance were found. Conclusions. Urinary NGF levels were significantly elevated in patients with myelomeningocele. Future studies are needed to examine further the significance of urinary NGF levels in the pathogenesis of neurogenic bladder in this clinical condition.

Dyslipidaemia in overweight children and adolescents is associated with an increased risk of kidney stones.

There is conflicting evidence about the role of obesity in paediatric nephrolithiasis. This Polish study explored the influence of nutritional status and lipid disturbances on urinary lithogenic factors and the risk of kidney stone formation in children and adolescents from three to 18 years of age.

Induced urinary crystal formation as an analytical strategy for the prediction and monitoring of urolithiasis and other metabolism-related disorders

Crystal formation reflects the entire composition of the surrounding solution. In case of urolithiasis, induced crystal formation in native urine has led to the development of the Bonn-Risk-Index (BRI), a valuable tool to quantify an individuals risk of calcium oxalate urolithiasis. If the progression of a disease is associated with characteristic changes in the activities of urinary components, this leads to an altered urinary crystallisation capacity. Therefore, the results of induced urinary crystal formation can be used to detect and monitor any disease linked to the altered urinary composition. Since crystal formation inherently takes into account the entire urinary composition, the influence of the disease on individual urinary parameters does not have to be known in order to monitor the consequent pathologic alterations. In this paper, we review the background of urinary crystal formation analysis and describe its established application in urolithiasis monitoring as well as potential further fields of clinical application.

Urodynamic Findings and Renal Function in Children with Neurogenic Bladder after Myelomeningocele.

Introduction: Myelomeningocele (MMC) is a congenital central nervous system malformation caused by a failure of the neurulation process in early pregnancy. Patients with MMC present many abnormalities and the nervous, skeletal and urinary systems are the most affected. The aim of this study was to clinically evaluate patients with MMC, estimate renal and lower urinary tract (LUT) function and to ascertain whether urodynamic findings can predict the deterioration of urinary tract function. Materials and Methods: Medical records of 112 patients were gathered from a database and evaluated retrospectively. The data included age, sex, BMI Z-score WHO, physical activity, urodynamic parameters and diagnosis and renal function. Results: A total of 112 patients with MMC were enrolled in the study. There were no differences in age, sex, BMI Z-score WHO, physical activity, renal function and urodynamic findings (apart from cystometric capacity) between boys and girls. Detrusor overactivity was the most frequent urodynamic diagnosis in all groups of physical activity, level of lesion and in catheterized and non-catheterized children. The correlations between urodynamic findings and renal function tests were found. Conclusions: Patients with neurogenic bladder after MMC most often present detrusor overactivity. LUT function is disturbed in all MMC patients independent of lesion level and physical activity.