Kidney stones: pathophysiology and medical management

DASH-style diet associates with reduced risk for kidney stones

The impact of the Dietary Approaches to Stop Hypertension (DASH) diet on kidney stone formation is unknown. We prospectively examined the relation between a DASH-style diet and incident kidney stones in the Health Professionals Follow-up Study (n = 45,821 men; 18 yr of follow-up), Nurses' Health Study I (n = 94,108 older women; 18 yr of follow-up), and Nurses' Health Study II (n = 101,837 younger women; 14 yr of follow-up). We constructed a DASH score based on eight components: high intake of fruits, vegetables, nuts and legumes, low-fat dairy products, and whole grains and low intake of sodium, sweetened beverages, and red and processed meats. We used Cox hazards regression to adjust for factors that included age, BMI, and fluid intake. Over a combined 50 yr of follow-up, we documented 5645 incident kidney stones. Participants with higher DASH scores had higher intakes of calcium, potassium, magnesium, oxalate, and vitamin C and had lower intakes of sodium. For participants in the highest compared with the lowest quintile of DASH score, the multivariate relative risks for kidney stones were 0.55 (95% CI, 0.46 to 0.65) for men, 0.58 (95% CI, 0.49 to 0.68) for older women, and 0.60 (95% CI, 0.52 to 0.70) for younger women. Higher DASH scores were associated with reduced risk even in participants with lower calcium intake. Exclusion of participants with hypertension did not change the results. In conclusion, consumption of a DASH-style diet is associated with a marked decrease in kidney stone risk.

Artificial neural networks for assessing the risk factors for urinary calcium stones according to gender and family history of stone

OBJECTIVE

In a previous work, we evidenced that artificial neural networks (ANNs) were more informative than classical statistical analyses for assessing the risk of idiopathic calcium nephrolithiasis in male stone-formers.

MATERIAL AND METHODS

We compared risk factors for idiopathic calcium nephrolithiasis (age, body mass index, calcemia, calcium oxalate supersaturation, and 24-h calciuria, oxaluria, uricosuria, citraturia, urea, and sodium) in four populations: men and women with and without a family history of stone (FHS). A total of 119 males (58 with an FHS, 61 without) and 59 females (30 with an FHS, 29 without) were compared to healthy controls. For each variable, receiver operating characteristic (ROC) curve indices were calculated by means of ANNs.

RESULTS

In men without an FHS, the most discriminant variables were 24-h urea (ROC curve index 0.76), supersaturation (ROC curve index 0.72), 24-h calciuria (ROC curve index 0.68), 24-h uricosuria (ROC curve index 0.64), 24-h oxaluria (ROC curve index 0.63), 24-h sodium (ROC curve index 0.62), and calcemia (ROC curve index 0.60). In men with an FHS, only supersaturation (ROC curve index 0.67) was discriminant. In women without FHS, calcemia (ROC curve index 0.67), 24-h calciuria (ROC curve index 0.64), and 24-h uricosuria (ROC curve index 0.62) were discriminant. In women with an FHS, supersaturation (ROC curve index 0.70), 24-h uricosuria (ROC curve index 0.69), 24-h urea (ROC curve index 0.68), and 24-h calciuria (ROC curve index 0.67) were discriminant.

CONCLUSIONS

Risk factors for idiopathic calcium nephrolithiasis were roughly the same in men with or without an FHS, and in women with an FHS. In these patients, calcium oxalate supersaturation and 24-h urea were the most discriminant factors. Conversely, in women without an FHS, calcium abnormalities (calcemia, 24-h calciuria) were discriminant and should prompt a search for infraclinical primary hyperparathyroidism or sarcoidosis.

Sequence variants in the CLDN14 gene associate with kidney stones and bone mineral density

Kidney stone disease is a common condition. To search for sequence variants conferring risk of kidney stones, we conducted a genome-wide association study in 3,773 cases and 42,510 controls from Iceland and The Netherlands. We discovered common, synonymous variants in the CLDN14 gene that associate with kidney stones (OR = 1.25 and P = 4.0 x 10(-12) for rs219780[C]). Approximately 62% of the general population is homozygous for rs219780[C] and is estimated to have 1.64 times greater risk of developing the disease compared to noncarriers. The CLDN14 gene is expressed in the kidney and regulates paracellular permeability at epithelial tight junctions. The same variants were also found to associate with reduced bone mineral density at the hip (P = 0.00039) and spine (P = 0.0077).

Metabolic abnormalities in patients with nephrolithiasis: comparison of first-episode with recurrent cases in Southern Iran

BACKGROUND

Metabolic disorders are one of the etiologic factors in renal stone formation. The aim of present study was to evaluate prevalence of metabolic disorders in patients with renal stone.

METHODS

From 572 patients referring to our urologic clinics, 376 patients participated in the study. Patients were divided to first time stone former (group A) and recurrent renal stone (group B). Twenty-four hour urine specimens were obtained for urinary calcium, oxalate, magnesium, citrate, uric acid, phosphor and 24-h urine volume. Venous blood samples were obtained evaluating serum phosphate, uric acid, and calcium. The prevalence of each metabolic disorder was detected, and two groups were compared regarding metabolic disorders.

RESULTS

The prevalence of renal stone in male patients was 63.04% versus 36.96% in female patients (P < 0.05). The most common abnormality observed in patients was low 24-h urine volume (58.24%) followed by hypercalciuria (17.18%) and hyperuricosuria (15.15%). Hyperuricemia was found in 6 first time stone former patients and 14 patients with recurrent renal stone (P = 0.04). There was no statistically significant difference between group A and B in other metabolic abnormalities (P > 0.05).

CONCLUSION

Low 24-h urine volume was the most common abnormalities in patients with nephrolithiasis in our region. Metabolic evaluation must be performed in all patients with renal stone even those with first time stone formation.

Dissecting the genetic basis of kidney tubule response to hyperoxaluria using chromosome substitution strains

Whether genetics may play a role in the pathophysiologic response of kidney tubules to oxalate exposure remains unexplored despite that as many as 15% of the U.S. population annually will experience a kidney stone composed of calcium oxalate. To explore this issue, we utilized a panel of chromosome substitution strains in which one chromosome at a time was transferred from the Brown Norway (BN) rat onto the Dahl salt-sensitive (SS) genetic background. Hyperoxaluria was induced by adding hydroxyproline (HP) to the drinking water. A dose-response (0-2% HP) study found that both SS and BN exhibited the same level of oxalate excretion as HP concentration increased, but only the BN exhibited changes in urothelial pathology and demonstrated crystal deposition at sites of urothelial injury as a function of dose (at 1.5-2.0%). The consomic panel was treated with 2.0% HP and evaluated for hyperoxaluria, renal injury, and crystal deposition. Tubular injury (% Area) and crystal deposition (% Area) were similar between the resistant SS and SS-4, -6, -7, -8, -9, -11, -16, and -20(BN) consomic rats. However, tubular injury was significantly increased in SS-2(BN) compared with the SS parental (9.8 +/- 1.56 and 4.2 +/- 1.09%, respectively). Crystal deposition was observed in SS-2(BN) and SS-18(BN) (4.7 +/- 0.70 and 3.5 +/- 1.3%, respectively) to the same extent as seen in the susceptible BN (3.2 +/- 0.44%). The fact that crystal deposition was observed in SS-18(BN) without extensive overall tubule injury, compared with the more severe widespread tubular injury seen in SS-2(BN), suggests that the underlying mechanism of each locus is different. In conclusion, these studies establish that BN rats demonstrate oxalate-associated pathology and they retain calcium oxalate crystals coincident with urothelial injury but SS rats do not. These observations establish that BN rat chromosome 2 and 18 harbor genes that contribute to these processes.

Kidney stones: painful and common--but preventable

Kidney stones are among the more common and painful urological disorders, affecting approximately 10% of Americans. While most stones pass spontaneously, obstructions result in renal colic, often requiring aggressive management of pain. If obstructions persist, extracorporeal shockwave lithotripsy, ureteroscopy, or percutaneous nephrolithotomy may be required for a stone's removal. Recurrence rates are high, and prevention includes increased fluid intake, dietary restrictions, and the use of pharmacotherapy. Stone recurrence increases with age, underscoring the importance of prevention for those 60 years of age and older.

Loss of TIMP3 enhances interstitial nephritis and fibrosis

The balance of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) determines the integrity of the extracellular matrix. TIMP3 is the most highly expressed tissue inhibitor of metalloproteinase (TIMP) in the kidney, but its function in renal disease is incompletely understood. In this study, TIMP3-/- mice demonstrated an age-dependent chronic tubulointerstitial fibrosis. After unilateral ureteral obstruction (UUO), young TIMP3-/- mice exhibited increased renal injury (tubular atrophy, cortical and medullary thinning, and vascular damage) compared with wild-type mice. In addition, TIMP3-/- mice had greater interstitial fibrosis; increased synthesis and deposition of type I collagen; increased activation of fibroblasts; enhanced apoptosis; and greater activation of MMP2, but not MMP9, after UUO. TIMP3 deficiency also led to accelerated processing of TNFalpha, demonstrated by significantly higher TACE activity and greater soluble TNFalpha levels by 3 d after UUO. The additional deletion of TNFalpha markedly reduced inflammation, apoptosis, and induction of a number of MMPs. Moreover, inhibition of MMPs in TIMP3-/-/TNFalpha-/- mice further abrogated postobstructive injury and prevented tubulointerestitial fibrosis. In humans, TIMP3 expression increased in the renal arteries and proximal tubules of subjects with diabetic nephropathy or chronic allograft nephropathy. Taken together, these results provide evidence that TIMP3 is an important mediator of kidney injury, and regulating its activity may have therapeutic benefit for patients with kidney disease.

Effects of repeated extracorporeal shock wave on kidney apoptosis of normal and diabetic rat

OBJECTIVE

To assess the effect of repeated extracorporeal shock waves (ESW) on the apoptosis of renal parenchyma in normal and diabetic rats by the caspase-3 expression.

MATERIALS AND METHODS

80 rats were assigned for ESW (Direx Tripter X1(R) - 14 KVA) to one of three groups with 50% rats with diabetes (A) and 50% normal (B) in each: G1 (n = 40): no ESW; G2 (n = 20): one ESW; G3 (n = 20): two ESWin an interval of 14 days. The animals were sacrificed 3 days after the ESW and samples of the renal parenchyma were histologically prepared, stained by the caspase-3 cleavage immunohistochemical method, and the apoptotic index (ApIn) was calculated by computer program Image Pro-Plus V 4,5,1 Media Cybernetics ( ApIn = number of apoptotic cells in the microscopic section / total cells in the microscopic section).

RESULTS

There was no statistical difference in ApIn of normal rats with one ESW (8.4 +/- 0.2) or two ESW (9.1 +/- 0.3) and both were similar to the control group with no ESW (7.9 +/- 0.2). The ApIn of diabetic rats with one ESW (7.4 +/- 0.3) was similar to the normal rats with one or two ESW. On the other hand, the ApIn was statistically higher in diabetic rats with two ESW (11.9 +/- 0.4) than in diabetic rats with one ESW (7.4 +/- 0.3).

CONCLUSIONS

The ApIn of normal rats with a single (2,000 SW) or repeated ESW (4,000 SW) was similar to the control animals without any ESW. In diabetic rats, the repeated ESW (4,000 SW) may result in an additional risk of tissue damage expressed by the higher ApIn.

The role of polymer nanosurface roughness and submicron pores in improving bladder urothelial cell density and inhibiting calcium oxalate stone formation

Synthetic polymers have been proposed for replacing resected cancerous bladder tissue. However, conventional (or nanosmooth) polymers used in such applications (such as poly(ether) urethane (PU) and poly-lactic-co-glycolic acid (PLGA)) often fail clinically due to poor bladder tissue regeneration, low cytocompatibility properties, and excessive calcium stone formation. For the successful reconstruction of bladder tissue, polymer surfaces should be modified to combat these common problems. Along these lines, implementing nanoscale surface features that mimic the natural roughness of bladder tissue on polymer surfaces can promote appropriate cell growth, accelerate bladder tissue regeneration and inhibit bladder calcium stone formation. To test this hypothesis, in this study, the cytocompatibility properties of both a non-biodegradable polymer (PU) and a biodegradable polymer (PLGA) were investigated after etching in chemicals (HNO(3) and NaOH, respectively) to create nanoscale surface features. After chemical etching, PU possessed submicron sized pores and numerous nanometer surface features while PLGA possessed few pores and large amounts of nanometer surface roughness. Results from this study strongly supported the assertion that nanometer scale surface roughness produced on PU and PLGA promoted the density of urothelial cells (cells that line the interior of the bladder), with the greatest urothelial cell densities observed on nanorough PLGA. In addition, compared to respective conventional polymers, the results provided evidence that nanorough PU and PLGA inhibited calcium oxalate stone formation; submicron pored nanorough PU inhibited calcium oxalate stone formation the most. Thus, results from the present study suggest the importance of nanometer topographical cues for designing better materials for bladder tissue engineering applications.

Antiurolithic effect of Bergenia ligulata rhizome: an explanation of the underlying mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Bergenia ligulata is widely used plant in South Asia, mainly India and Pakistan, as a traditional medicine for treatment of urolithiasis.

AIM OF THE STUDY

To rationalize the Bergenia ligulata use in kidney stones and to explain the underlying mechanisms.

MATERIALS AND METHODS

The crude aqueous-methanolic extract of Bergenia ligulata rhizome (BLR) was studied using in vitro and in vivo methods.

RESULTS

BLR inhibited calcium oxalate (CaC(2)O(4)) crystal aggregation as well as crystal formation in the metastable solutions and exhibited antioxidant effect against 1,1-diphenyl-2-picrylhydrazyl free radical and lipid peroxidation in the in vitro. BLR caused diuresis in rats accompanied by a saluretic effect. In an animal model of urolithiasis, developed in male Wistar rats by adding 0.75% ethylene glycol (EG) in drinking water, BLR (5-10 mg/kg) prevented CaC(2)O(4) crystal deposition in the renal tubules. The lithogenic treatment caused polyuria, weight loss, impairment of renal function and oxidative stress, manifested as increased malondialdehyde and protein carbonyl contents, depleted reduced glutathione and decreased antioxidant enzyme activities of the kidneys, which were prevented by BLR. Unlike the untreated animals, EG intake did not cause excessive hyperoxaluria and hypocalciuria in BLR treated groups and there was a significant increase in the urinary Mg(2+), instead of a slight decrease.

CONCLUSIONS

These data indicate the antiurolithic activity in Bergenia ligulata mediated possibly through CaC(2)O(4) crystal inhibition, diuretic, hypermagneseuric and antioxidant effects and this study rationalizes its medicinal use in urolithiasis.

Diet to reduce mild hyperoxaluria in patients with idiopathic calcium oxalate stone formation: a pilot study

OBJECTIVES

To assess whether a normal-calcium, low-animal protein, low-salt diet is effective in reducing hyperoxaluria in idiopathic calcium oxalate nephrolithiasis compared with a traditional low-oxalate diet, routinely recommended by clinicians

METHODS

We treated 56 patients with idiopathic calcium oxalate stone formation who presented with mild hyperoxaluria (>40 mg/d) while consuming a free diet with a normal-calcium, low-animal protein, low-salt diet for a 3-month period. We compared the results obtained with this diet with those of a historical control group of 20 hyperoxaluric patients treated in the traditional way with a low-oxalate diet

RESULTS

After 3 months of therapy, the mean oxaluria level had decreased from 50.2 to 35.5 mg/d with the normal-calcium, low-animal protein, low-salt diet and from 45.9 to 40.2 mg/d with the traditional diet (adjusted difference between post-treatment mean value -7.3 mg/d, 95% confidence interval -12.3 to -2.2, P = .005)

CONCLUSIONS

The results suggest that a normal-calcium, low-animal protein, low-salt diet can reduce oxalate excretion in hyperoxaluric patients. This should encourage the undertaking of a randomized-control study to confer more solid evidence in support of our findings.

Differences in quantitative urine composition in stone-forming versus unaffected mate kidneys

Objectives

Many patients present with bilateral stones. There is a unique group of patients, however, that presents with stones exclusively on one side. We hypothesize that in such situations, 24-hour urine collections may not reveal specific defects on the affected stone-bearing kidney. We therefore evaluated selective 12-hour urine collections after percutaneous nephrolithotomy (PNL) to help determine if there is differential renal excretion.

Methods

We collected urine specimens from patients with nephrolithiasis who underwent unilateral PNL. Urine samples were collected and analyzed from nephrostomy tubes, representing the affected kidneys, and from Foley bladder catheters, representing the contralateral mate kidney.

Results

Thirty-one patients were studied (14 with unilateral nephrolithiasis and 17 with bilateral). Treated kidneys from patients with unilateral nephrolithiasis displayed lowered urine excretion of uric acid, sodium, chloride, calcium, and total osmoles when compared to patients with bilateral nephrolithiasis. Stone size and length of procedure were not predictive of urine composition after PNL.

Conclusions

Treated kidneys from patients with a history of unilateral stone disease revealed marked differences in urine excretion compared to those with bilateral nephrolithiasis after unilateral PNL. These findings could be secondary to the surgical insult, urinary stone disease, or could be a responsible factor for stone pathogenesis.

Comparison of effect of high intake of magnesium with high intake of phosphorus and potassium on urolithiasis in goats fed with cottonseed meal diet

The effect of high intake of Mg on urolithiasis was compared with high intake of P and K in goats being fed with a cottonseed meal and rice straw diet. Eighteen wether goats were randomly allocated into group A, B and C evenly and fed with cottonseed meal and rice straw diet for three months. From day 60 onwards, KH(2)PO(4) and K(2)HPO(4) were provided via drinking water to goats in group B to increase the intake of P, K, and MgO to goats in group C to increase the intake of Mg. Blood and urine samples were collected to analyze the concentration of P, K, Mg and Ca, and the activity product (AP) of potassium magnesium phosphate (MKP) in urine was also calculated. The composition of calculi and urinary sedimentary crystals were examined by chemical qualitative analysis, X-ray diffraction, X-ray energy dispersive spectrometry and Fourier transform infrared spectroscopy. The results showed that the incidence of urolithiasis in group C (6/6) was higher than that in group A (1/6) and B (1/6) (P<0.05). The calculi were mainly composed of magnesium ammonium phosphate (MAP) and partly composed of MKP. MKP presented in crystals of different phases in this experiment. The high intake of Mg contributed to a significant increase of plasma Mg, but additional P, K did not cause a further increase of plasma P, K. Urine P, K, Mg and Ca and AP of MKP in group C decreased significantly after the onset of urolithiasis. In conclusion, high intake of Mg was more important in inducing struvite calculi compared with high intake of K and P in goats under these feeding conditions. Cottonseed meal and rice straw with additional Mg is a good dietary model for inducing struvite calculi in castrated goats.

Diagnostic performance of low-dose CT for the detection of urolithiasis: a meta-analysis

OBJECTIVE

The objective of our study was to perform a meta-analysis to evaluate the diagnostic performance of low-dose CT for the diagnosis of urolithiasis (seven studies, 1,061 patients).

MATERIALS AND METHODS

The medical literature from 1995 to 2007 was searched using PubMed, Medline, and Cochrane Library databases for articles on studies that used low-dose CT (< 3 mSv dose applied for the entire CT examination) as a diagnostic test for the detection of urolithiasis. Prospective and retrospective studies were included if they separately reported the rate of true-positive, true-negative, false-positive, and false-negative diagnoses of urolithiasis from low-dose CT compared with the positive and negative rates of normal-dose CT or a combination of diagnostic tests. Two readers assessed the quality of the studies.

RESULTS

The pooled sensitivity and specificity of low-dose CT for the diagnosis of urolithiasis were 0.966 (95% CI, 0.950-0.978) and 0.949 (95% CI, 0.920-0.970), respectively.

CONCLUSION

The results of this meta-analysis suggest that a low-dose CT protocol can be used as the initial imaging technique in the workup of patients with suspected urolithiasis.

Proteomic analysis of renal calculi indicates an important role for inflammatory processes in calcium stone formation

Even though renal stones/calculi occur in approximately 10% of individuals, they are an enormous economic burden to the entire US health system. While the relative metabolic composition of renal calculi is generally known, there is no clear understanding of the genetics of renal stone formation, nor are there clear prognostic indicators of renal stone formation. The application of proteomics to the analysis of renal calculi axiomatically holds that insight into renal stone pathobiology can be gained by a more comprehensive understanding of renal calculus protein composition. We analyzed isolated renal stone matrix proteins with mass spectrometric and immunohistochemical methods identifying 158 proteins with high confidence, including 28 common proteins. The abundant proteins included those identified previously in stones and proteins identified here for the first time, such as myeloid lineage-specific, integral membrane and lipid regulatory proteins. Pathway analyses of all proteins identified suggested that a significant fraction of the most abundant matrix proteins participate in inflammatory processes. These proteomic results support the hypothesis that stone formation induces a cellular inflammatory response and the protein components of this response contribute to the abundant stone matrix proteome.

Impact of a proprietary concentrate of Sambucus nigra L. on urinary pH

A proprietary concentrate from Sambucus nigra L.--in its diluted preparation as part of a hypocaloric diet available in Switzerland--had no impact on urinary pH, urinary hydrogen ion concentrations or 24 h excretion and thus did not influence the solubility of stone-inducing ions.

Dual energy CT: preliminary observations and potential clinical applications in the abdomen

Dual energy CT (DECT) is a new technique that allows differentiation of materials and tissues based on CT density values derived from two synchronous CT acquisitions at different tube potentials. With the introduction of a new dual source CT system, this technique can now be used routinely in abdominal imaging. Potential clinical applications include evaluation of renal masses, liver lesions, urinary calculi, small bowel, pancreas, and adrenal glands. In CT angiography of abdominal aortic aneurysms, dual energy CT techniques can be used to remove bones from the datasets, and virtual unenhanced images allow differentiation of contrast agent from calcifying thrombus in patients with endovascular stents. This review describes potential applications, practical guidelines, and limitations of dual energy CT in the abdomen.

Citraturic, alkalinizing and antioxidative effects of limeade-based regimen in nephrolithiasis patients

Potassium citrate has long been used as a prophylactic remedy for nephrolithiasis recurrence. Lemonade consumption is also suggested as an option. We compared the efficacy of consumption of solution containing manufactured lime powder with that of potassium citrate, on the improvement of metabolic risk factors, oxidative stress and renal tubular damage in nephrolithiasis patients. Patients with kidney stone were enrolled and randomly assigned to three treatment programs for 3 month period consisting of consumption of solution containing lime powder (Group 1, n=13), potassium citrate (Group 2, n=11) and lactose as placebo regimen (Group 3, n=7). Lime powder and potassium citrate contained equal amounts of potassium (21 mEq) and citrate (63 mEq). After treatment, there was an increase in urinary pH, potassium and citrate in Group 1 and 2. Increased plasma potassium and red blood cell glutathione (R-GSH) and decreased urinary malondialdehyde were found in Group 1, but not observed in Group 2. R-GSH was decreased in Group 2. Urinary N-acetyl-beta-glucosaminidase activity and fractional excretion of magnesium, as renal tubular damage indicators, were decreased only in Group 1. In Group 3, all measured parameters were unaltered except for an increased urinary chloride. In conclusion, consumption of our in-house lime powder exerted citraturic and alkalinizing actions as efficient as consumption of potassium citrate. In addition, it provided an antioxidative effect and was able to attenuate renal tubular damage. These pharmacological properties may be clinically useful to diminish the stone-forming potential in kidney stone patients and hence for preventing recurrent calculi.

[PDE5 inhibitors. A new option in the treatment of ureteral colic?]

BACKGROUND

PDE5 inhibitors represent the gold standard in the medical therapy of erectile dysfunction (ED). Promising results have been published regarding further urological indications such as treatment of ureteral colic. The aim of the present study was to evaluate the functional effects of the PDE5 inhibitors sildenafil (SIL), vardenafil (VAR), and tadalafil (TAD) on tissue tension and cyclic nucleotide levels of human ureteral smooth muscle segments in vitro.

METHODS

Relaxant responses of human ureteral smooth muscle were investigated in vitro using the organ bath technique. Cyclic nucleotides cAMP and cGMP were determined by specific radioimmunoassays.

RESULTS

Relaxing effects of ureteral muscle tension were observed in the rank order VAR>SIL>TAD. While only VAR significantly elevated cGMP levels 3.3-fold over control, no increase for cAMP levels was observed.

CONCLUSIONS

Our data provide evidence that cGMP is involved in the control of the normal function of the smooth musculature of the human ureter. Our findings suggest the potential of using selective inhibitors of PDE isoenzymes in the treatment of ureteral colic.

A CMOS active pixel sensor system for laboratory- based x-ray diffraction studies of biological tissue

X-ray diffraction studies give material-specific information about biological tissue. Ideally, a large area, low noise, wide dynamic range digital x-ray detector is required for laboratory-based x-ray diffraction studies. The goal of this work is to introduce a novel imaging technology, the CMOS active pixel sensor (APS) that has the potential to fulfil all these requirements, and demonstrate its feasibility for coherent scatter imaging. A prototype CMOS APS has been included in an x-ray diffraction demonstration system. An industrial x-ray source with appropriate beam filtration is used to perform angle dispersive x-ray diffraction (ADXRD). Optimization of the experimental set-up is detailed including collimator options and detector operating parameters. Scatter signatures are measured for 11 different materials, covering three medical applications: breast cancer diagnosis, kidney stone identification and bone mineral density calculations. Scatter signatures are also recorded for three mixed samples of known composition. Results are verified using two independent models for predicting the APS scatter signature: (1) a linear systems model of the APS and (2) a linear superposition integral combining known monochromatic scatter signatures with the input polychromatic spectrum used in this case. Cross validation of experimental, modelled and literature results proves that APS are able to record biologically relevant scatter signatures. Coherent scatter signatures are sensitive to multiple materials present in a sample and provide a means to quantify composition. In the future, production of a bespoke APS imager for x-ray diffraction studies could enable simultaneous collection of the transmitted beam and scattered radiation in a laboratory-based coherent scatter system, making clinical transfer of the technique attainable.

Renal calcinosis and stone formation in mice lacking osteopontin, Tamm-Horsfall protein, or both

Although often supersaturated with mineral salts such as calcium phosphate and calcium oxalate, normal urine possesses an innate ability to keep them from forming harmful crystals. This inhibitory activity has been attributed to the presence of urinary macromolecules, although controversies abound regarding their role, or lack thereof, in preventing renal mineralization. Here, we show that 10% of the mice lacking osteopontin (OPN) and 14.3% of the mice lacking Tamm-Horsfall protein (THP) spontaneously form interstitial deposits of calcium phosphate within the renal papillae, events never seen in wild-type mice. Lack of both proteins causes renal crystallization in 39.3% of the double-null mice. Urinalysis revealed elevated concentrations of urine phosphorus and brushite (calcium phosphate) supersaturation in THP-null and OPN/THP-double null mice, suggesting that impaired phosphorus handling may be linked to interstitial papillary calcinosis in THP- but not in OPN-null mice. In contrast, experimentally induced hyperoxaluria provokes widespread intratubular calcium oxalate crystallization and stone formation in OPN/THP-double null mice, while completely sparing the wild-type controls. Whole urine from OPN-, THP-, or double-null mice all possessed a dramatically reduced ability to inhibit the adhesion of calcium oxalate monohydrate crystals to renal epithelial cells. These data establish OPN and THP as powerful and functionally synergistic inhibitors of calcium phosphate and calcium oxalate crystallization in vivo and suggest that defects in either molecule may contribute to renal calcinosis and stone formation, an exceedingly common condition that afflicts up to 12% males and 5% females.

[The lithiasis in the upper urinary tract in children: endourological treatment]

INTRODUCTION

Urolithiasis in the pediatric age is a growing problem. In the developed world they are of calcium oxalate and in the upper urinary tract. It is very similar to the presentation of lithiasis in adults, so we have to make an effort to apply the experience in this age to the children. The shock wave lithotripsy is admitted as the first treatment for this pathology in the pediatric population already. The endourological approach must be use as a common approach in this group. We present our technique and experience.

MATERIAL AND METHODS

A retrospective, descriptive study of the children diagnosed of lithiasis in the upper urinary tract that were treated by an endourological technique in our centre between January 1992 and January 2005. We gathered data on: 1.) Preoperative: age, sex, clinical manifestations, size (mm) and position of the lithiasis (we divided the upper urinary tract in: renal, proximal third, medial third and distal third) 2.) Operative variable: endourological technique: percutaneus neprolithotomy or ureteroscopy. Reconversion to open surgery. 3.) Postoperative variables: time since surgery, complications and the current state of the patient (ultrasonography and renal function).

RESULTS

Seven children, 4 boys and 2 girls with an age range of 2,5 to 14 years, underwent operation using an endourological technique. Lumboabdominal pain was the main clinical manifestation (4/7). The lithiasis size was 4-7mm, with the exception of a staghorn calculis. The calculis were: 5 ureteral proximal, 1 ureteral distal and one in the kidney (staghound stone). We performed one percutaneus neprolithotomy for the staghorn calculi. We removed completly the stone and had no complications. The 6 other procedures were ureteroscopies. In 3 of them we removed the calculi (4/7 success rate of 57%). The rest procedures we needed to transform in open surgery. With a following time of 1-13 years all of them are asymptomatic, and with ultrasonography and renal function in the normal limits. We did see no complications.

CONCLUSION

The endourological treatment for urolithiasis in pediatric patients is possible but must be individualized in each case. With the development of new endourological material and more surgical experience this technique will be to the reach of the most of the urologists.

Epidemiology and risk factors in urolithiasis

Stone formation in the urinary tract affects about 5-10% of the population in industrialized countries, although it is very rare in other countries such as Greenland or Japan. The high incidence and recurrence rate contribute to making the urolithiasis a serious social problem. Nowadays, urolithiasis must be considered a 'disease in evolution' for several reasons, such as epidemiological changes, evolution of the methods used for diagnosis, and the treatment and prophylaxis of the population considered 'at risk' of stone disease. Some features of stone disease have changed over the last few years due to many social, economical and cultural factors that are described here. The increased prevalence of small urinary calculi has brought about a change in clinical symptoms, with frequent episodes of renal-ureteral colic, persistent pain and hydronephrosis. Similarly, the presence of residual fragments after extracorporeal shock wave lithotripsy has induced a radical change in the management of small calculi through the use of mini-invasive surgical techniques.

Zonisamide and renal calculi in patients with epilepsy: how big an issue?

OBJECTIVES

To determine the prevalence of renal calculi in patients treated with zonisamide during randomized, controlled and open-label clinical trials, and from post-marketing surveillance data.

METHODS

Reports of renal calculi from four placebo-controlled double-blind trials of zonisamide, their long-term open-label treatment extension phases, and the US/European zonisamide clinical trial programme were reviewed. One double-blind study and its extension included routine ultrasound screening to identify asymptomatic calculi. Post-marketing surveillance data were also investigated, as was concomitant treatment with topiramate.

RESULTS

No symptomatic renal calculi were reported during four randomized double-blind, placebo-controlled trials involving 848 subjects (including 498 zonisamide recipients) treated for up to 3 months. In long-term extension studies with treatment for up to 24 months, symptomatic renal calculi were reported in 9/626 (1.4%) patients. Pooled safety data from all US/European clinical trials identified 15/1296 (1.2%) patients with symptomatic renal calculi during treatment for up to 8.7 years. Post-marketing surveillance revealed nine cases from 59 667 patient-years of exposure in the USA, and 14 from 709 294 patient-years of exposure in Japan; only one case occurred during concomitant topiramate and zonisamide treatment. No imbalance in electrolyte levels was found from 35 patients receiving such co-treatment in clinical trials.

CONCLUSIONS

The available data suggest that the risk of developing renal calculi during zonisamide treatment is low. Data are insufficient to determine whether concomitant treatment with topiramate increases the risk of renal stones.

Ethnic differences in relative risk of idiopathic calcium nephrolithiasis in North America

PURPOSE

Data on susceptibility to kidney stone disease are sparse in individuals of nonEuropean ancestry residing in North America. We determined the relative risk of calcium nephrolithiasis among people of different ethnic backgrounds living in the same geographic region.

MATERIALS AND METHODS

Using a cross-sectional design 1,128 consecutive patients with idiopathic calcium nephrolithiasis 18 to 50 years old were recruited from a population based Kidney Stone Center in Toronto. Age and gender adjusted odds ratios and 95% confidence intervals were calculated by logistic regression using the 2001 Canada Census population data.

RESULTS

Compared to Europeans the relative risk of calcium nephrolithiasis was significantly higher in individuals of Arabic (OR 3.8, 2.7-5.2), West Indian (OR 2.5, 1.8-3.4), West Asian (OR 2.4, 1.7-3.4) and Latin American (OR 1.7, 1.2-2.4) origin, and significantly lower in those of East Asian (OR 0.4, 0.3-0.5) and African (OR 0.7, 0.5-0.9) background. Several ethnic groups had kidney stone risk factors that were significantly different from those of the European group including higher urinary uric acid, urea excretion and estimated protein intake, and lower urinary citrate, potassium, magnesium and phosphate excretion. However, none was consistent with the variation in relative risk of stone disease overall.

CONCLUSIONS

The propensity for the development of calcium nephrolithiasis differed markedly among ethnic groups in North America. While environmental factors could not be completely ruled out, this variability may reflect the influence of genetic susceptibility because there was no dominant environmental factor to account for the differences in relative risk of stone disease.

Renal stone disease: Causes, evaluation and medical treatment

The purpose of the present review is to provide an update about the most common risk factors or medical conditions associated with renal stone formation, the current methods available for metabolic investigation, dietary recommendations and medical treatment. Laboratory investigation of hypercalciuria, hyperuricosuria, hyperoxaluria, cystinuria, hypocitraturia, renal tubular acidosis, urinary tract infection and reduction of urinary volume is based on the results of 24-hr urine collection and a spot urine for urinary sediment, culture and pH. Blood analysis for creatinine, calcium and uric acid must be obtained. Bone mineral density has to be determined mainly among hypercalciurics and primary hyperparathyroidism has to be ruled out. Current knowledge does not support calcium restriction recommendation because it can lead to secondary hyperoxaluria and bone demineralization. Reduction of animal protein and salt intake, higher fluid intake and potassium consumption should be implemented. Medical treatments involve the use of thiazides, allopurinol, potassium citrate or other drugs according to the metabolic disturbances. The correction of those metabolic abnormalities is the basic tool for prevention or reduction of recurrent stone formation.

Nephrolithiasis in patients with duchenne muscular dystrophy

OBJECTIVES

To present the first series of patients with Duchenne muscular dystrophy (DMD) and nephrolithiasis.

METHODS

A retrospective chart review was done to identify patients with DMD who were referred for urologic consultation because of nephrolithiasis from June 2004 to April 2006.

RESULTS

Four patients were identified with DMD and nephrolithiasis. Of the 4 patients, 2 underwent treatment, and their stones were obtained for analysis. The other 2 patients had stones diagnosed by computed tomography. Their stones were passed but not retrieved. Stone analysis for the available patients revealed a mixed calcareous composition. All 4 patients had had a relatively small stone burden. The patients ranged in age from 18 to 31 years.

CONCLUSIONS

Stone disease appears to have many of the same characteristics in patients with DMD as it does in the general population. Risk factors, including immobilization and corticosteroid use, are present. Additional studies are needed before conclusions can be made regarding the associations between DMD and nephrolithiasis.

The repeated extracorporeal shock waves and the renal parenchyma injury on normal and diabetic rats

PURPOSE

To assess the effect of repeated extracorporeal shock waves (ESW) on renal parenchyma of normal and diabetic rats.

METHODS

40 normal rats (A) and 40 diabetic rats (B) were assigned for ESW (Direx Tripter X1 - 14 KVA) as follow: A1/B1 and A3/B3 no ESW; A2/B2 one ESW (2,000 SW); A4/B4 two ESW (4,000 SW) in an elapsed 14 days. All the animals were sacrificed 3 days after the ESW and samples of renal parenchyma were histological prepared, stained by H&E. For each animal the frequency of hemorrhage focus (HF) in the subcapsular, interstitial and glomerulus area was calculated (percentage) on 20 randomly histological sections.

RESULTS

No one HF was identified in all normal or diabetic animals without ESW (A1, A3 and B1, B3). In the normal rats the HF frequency was similar to one ESW (subcapsular =15%; interstitial =20% and glomerular =10%) or repeated ESW (subcapsular =25%; interstitial =20%; glomerular=10%). In diabetic rats the occurrence of HF with repeated ESW was more frequent (subcapsular =40%; interstitial =30% and glomerular =10%) than with a single ESW (subcapsular =25%; interstitial =15% and glomerular =15%).

CONCLUSION

A single ESW or a repeated ESW caused a mild and similar damage on renal cortex of normal rats. In diabetic rats the repeated ESW may result in an accumulated damage, especially with focus of hemorrhage in subcapsular and interstitial tissue and glomerulus edema.

Inhibitors of calcification in blood and urine

In bone and teeth formation, coordinated calcification is a highly desirable biological process. However, heterotopic calcification at unwanted tissue sites leads to dysfunction, disease and, potentially, to death and therefore requires prevention and treatment. With the recent discovery of calcification inhibitors we now know that biological calcification is not passive but a complex, active and highly regulated process. Calcification at vascular sites is the most threatening localization and manifests as part of atherosclerosis or arteriosclerosis. Atherosclerosis is often accompanied by intimal plaque calcification, whereas arteriosclerosis is characterized by calcification of the media. The severity of calcification of cerebral or coronary atherosclerotic plaques is associated with an increased incidence of events such as stroke or myocardial infarction. Medial calcification is the major cause of arterial stiffness, which contributes to left ventricular dysfunction and heart failure. Patients with chronic kidney disease are at especially increased risk for both intimal and medial calcification. In this context, it is currently thought that calcium-regulatory factors including fetuin-A, matrix Gla protein, osteoprotegerin, and pyrophosphates act in a local or systemic manner to prevent calcifications of the vasculature, and that dys-regulations of such calcification inhibitors may contribute to progressive calcifications. Nephrolithiasis represents another process of unwanted calcification responsible for significant morbidity. More than 80% of renal stones contain calcium. Urinary factors inhibiting calcification are citrate, glycosaminoglycans, Tamm-Horsfall protein, and osteopontin. This review summarizes current experimental and clinical data underlining the biological importance of these calcification inhibitors.

Physiology of epithelial Ca2+ and Mg2+ transport

Ca2+ and Mg2+ are essential ions in a wide variety of cellular processes and form a major constituent of bone. It is, therefore, essential that the balance of these ions is strictly maintained. In the last decade, major breakthrough discoveries have vastly expanded our knowledge of the mechanisms underlying epithelial Ca2+ and Mg2+ transport. The genetic defects underlying various disorders with altered Ca2+ and/or Mg2+ handling have been determined. Recently, this yielded the molecular identification of TRPM6 as the gatekeeper of epithelial Mg2+ transport. Furthermore, expression cloning strategies have elucidated two novel members of the transient receptor potential family, TRPV5 and TRPV6, as pivotal ion channels determining transcellular Ca2+ transport. These two channels are regulated by a variety of factors, some historically strongly linked to Ca2+ homeostasis, others identified in a more serendipitous manner. Herein we review the processes of epithelial Ca2+ and Mg2+ transport, the molecular mechanisms involved, and the various forms of regulation.

In vitro effects of PDE5 inhibitors sildenafil, vardenafil and tadalafil on isolated human ureteral smooth muscle: a basic research approach

Cyclic nucleotide phosphodiesterase (PDE) isoenzymes are key proteins regulating intracellular cyclic nucleotide turnover and thus smooth muscle tension. Several in vitro studies have indicated that the cyclic GMP and cyclic AMP-mediated signaling may play a role in the control of human ureteral muscle. The aim of the present study was to evaluate the functional effects of PDE5 inhibitors sildenafil (Sil), vardenafil (Var) and tadalafil (Tad), as well as nitric oxide (NO)-donating agent sodium nitroprusside (SNP) and non-selective muscarinic antagonist butylscopolamine (BSC) on the tension induced by KCl and the turnover of cyclic nucleotides in isolated human ureteral smooth muscle. In vitro relaxant responses of human ureteral smooth muscle to the PDE5 inhibitors mentioned above were investigated using the organ bath technique. Cyclic nucleotides cAMP and cGMP were determined by means of specific radioimmunoassay following incubation of the tissue with Sil, Var, Tad and SNP. The tension induced by KCl of the ureteral tissue was dose dependently reversed by the drugs with the following rank order of efficacy: SNP > Var >or= Sil > Tad > BSC. R(max) values ranged from 25 +/- 9% (SNP) to 5 +/- 3% (BSC). Relaxant responses were paralleled by threefold to fourfold increase in tissue levels of cGMP. Our results indicate that PDE5 inhibitors can reverse the tension of isolated human ureteral smooth muscle via cGMP-mediated pathways. Nevertheless, further studies are indicated in order to evaluate as to whether there might be a use for PDE5 inhibitors in the treatment of ureteral stone disease.

Maternal kidney stones during pregnancy and adverse birth outcomes, particularly congenital abnormalities in the offspring

OBJECTIVE

The possible adverse birth outcomes, particularly congenital abnormalities (CAs) in pregnant women with kidney stones (KS) previously have not been evaluated; therefore, we decided to study this possible association.

METHODS

The population-based data set of the Hungarian Case-Control Surveillance of CAs, 1980-1996, was used for this analysis.

RESULTS

Of 22,843 newborns or fetuses with CAs, 69 (0.30%) had mothers with KS during pregnancy. Of 38,151 matched control newborns without any abnormalities, 147 (0.39%) had KS during pregnancy. KS were associated with an adjusted prevalence odds ratio (POR) with 95% CI of 0.8, 0.6-1.0 for CAs. A higher prevalence of maternal KS during the first trimester of pregnancy was not found in any CA group. There was no higher rate of preterm birth and low birthweight in the newborns of pregnant women with KS.

CONCLUSIONS

There is no higher risk for adverse birth outcomes particularly CAs in the offspring of mothers with KS and related drug treatments during pregnancy.

Medical Therapy of Urolithiasis

Nephrolithiasis treatment has become easier and less invasive with the development of extracorporeal shockwave lithotripsy (SWL) and endourologic techniques. However, medical therapy represents a well-established and complementary approach that can improve the efficacy of SWL and endourology. During recent decades, pharmacologic intervention has become more effective in stone disease: drugs can control the pain of renal colic, interfere at various levels in lithogenesis, and contribute to the expulsion of stones. It is well known that lithogenesis is a multifactorial process influenced by environmental-nutritional factors (low urinary volume, diet rich in animal protein, etc) and metabolic alterations; i.e., hypercalciuria, hyperuricosuria, and deficiency of stone-inhibiting factors (citrate, magnesium, glycosaminoglycans [GAGs]). Specific drugs such as citrate, allopurinol, and thiazide represent highly effective treatments for the promoting factors. Furthermore, recent findings suggest an interesting role for a phytotherapeutic agent, Phillantus niruri, and its inhibitory action on calcium oxalate crystallization related to the higher incorporation of GAGs into the calculi. Another step forward in medical management of stone disease is expulsive therapy. Many studies have proven the efficacy of medical expulsive therapy with nifedipine and alpha-blockers: their specific action on ureteral smooth muscle in association with anti-edema drugs accounts for their efficacy in expelling ureteral stones. In this paper, we provide an update on the medical treatment of stone disease, focusing our attention on what is known and what is new in renal colic and litholithic and expulsive medical therapy.