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The aim of this paper is to present a protocol for the routine morphocompositional study of kidney stones in a clinical setting, and to demonstrate that it is a simple and useful approach that can reliably determine the etiology of all types of kidney stones. Our routine study of kidney stones consists of a combination of stereoscopic microscopy, scanning electron microscopy, and infrared spectroscopy. The usefulness of such a procedure is demonstrated by its application to several illustrating examples. The protocol applied here is reliable and fast, and does not require multiple infrared spectroscopic analyses for most non-homogeneous samples. It also provides the identification of components that are present in very small proportions, the characteristics of internal and external structures, and information about areas with biological structures, such as renal tubules. It should be noted that results are obtained in a relatively short time and with high reliability. The detailed morphocompositional study of a urinary calculus is essential for establishing the diagnosis and etiology and for initiating the treatment of a patient with renal lithiasis, because there is a relationship between the specific characteristics of a stone and the specific etiology of the disease. The increasing number of treatments available for patients with different types of renal calculi makes improvements in diagnosis and determination of stone etiology, such as the procedure described here, more important now than ever., (© 2023. The Author(s).)

The use of double J ureteral stents can lead to several adverse effects, as urinary infection. Bacteria tend to colonize the stent surface, leading to the formation of bacterial biofilms. The presence of urease-producing bacteria increase the urine pH leading to the incrustation and blockage of the stent. On the other hand, these large crystalline masses function as niduses, allowing the attachment of even more bacteria and decreasing its exposure to antibiotics. The aim of this in vitro study was to assess the effect of phytate on the attachment of bacteria to the catheter surface under conditions that favor crystallization. Catheter sections were incubated in a synthetic urine medium (pH 6.5) in the presence or absence of Pseudomonas aeruginosa and phytate. Amount of calcium deposits was measured using an Arsenazo III colorimetric method and the number of attached bacteria to the stent was determined. Differences were assessed using an ANOVA with a Bonferroni post hoc test. The formation of calcium phosphate deposits (brushite and hydroxyapatite) and oxalate crystals (COM), as were as the amount of bacteria decreased when phytate was present. Thus, phytate successfully decreased bacterial adhesion by inhibiting the formation of crystalline deposits., (© 2022. The Author(s).)

The objective is to evaluate the effect of phytate supplements on calciuria in patients with urinary stones and elevated bone resorption. The secondary objective is to analyze the therapeutic effect of phytate based on measurements of serum markers of bone resorption. This is a controlled randomized study included patients according to predefined inclusion and exclusion criteria, and randomized them into two groups. Patients in the phytate group received a 380 mg capsule of calcium-magnesium InsP6 (Salvat Laboratories ® ) every 24 h for 3 months and patients in the control group received no treatment. All included patients were male or female, 18-65 years old, had hypercalciuria (> 250 mg/24 h), had a ß-Crosslaps level greater than 0.4 ng/mL, and had bone densitometry results indicative of osteopenia or osteoporosis in the femur and/or spine. At study onset, calciuria was 321 ± 52 mg/24 h in the phytate group and 305 ± 57 mg/24 h in the control group (p > 0.05). At 3 months, calciuria was significantly lower in the phytate group than the control group (226 ± 45 mg/24 h vs. 304 ± 58 mg/24 h, p < 0.05). At study onset, the mean ß-CrossLaps level was 1.25 ± 0.72 ng/mL in the phytate group and 0.57 ± 0.13 ng/mL in the control group (p < 0.05). However, at 3 months, the ß-CrossLaps level was significantly lower in the phytate group than in the control group (0.57 ± 0.13 ng/mL vs. 0.77 ± 0.42 ng/mL, p < 0.05). Phytate reduced calciuria in patients with hypercalciuria secondary to bone resorption. The ß-CrossLaps assay was effective for evaluating the efficacy of phytate on hypercalciuria during follow-up., (© 2022. The Author(s).)

The Consensus Group deliberated on a number of questions concerning urine and stone analysis over a period of months, and then met to develop consensus. The Group concluded that analyses of urine and stones should be routine in the diagnosis and treatment of urinary stone diseases. At present, the 24-h urine is the most useful type of urine collection, and accepted methods for analysis are described. Patient education is also important for obtaining a proper urine sample. Graphical methods for reporting urine analysis results can be helpful both for the physician and for educating the patient as to proper dietary changes that could be beneficial. Proper analysis of stones is also essential for diagnosis and management of patients. The Consensus Group also agreed that research has shown that evaluation of urinary crystals could be very valuable, but the Group also recognizes that existing methods for assessment of crystalluria do not allow this to be part of stone treatment in many places.

Currently an evidence-based approach to nephrolithiasis is hampered by a lack of randomized controlled trials. Thus, there is a need for common platforms for data sharing and recruitment of patients to interventional studies. A first step in achieving this objective would be to share practice methods and protocols for subsequent standardization in what is still a heterogeneous clinical field. Here, we present the results of a pilot survey performed across 24 European clinical kidney stone centers. The survey was distributed by a voluntary online questionnaire circulated between June 2017 and January 2018. About 46% of centers reported seeing on average 20 or more patients per month. Only 21% adopted any formal referral criteria. Centers were relatively heterogeneous in respect of the definition of an incident stone event. The majority (71%) adopted a formal follow-up scheme; of these, 65% included a follow-up visit at 3 and 12 months, and 41% more than 12 months. In 79% of centers some kind of imaging was performed systematically. 75% of all centers performed laboratory analyses on blood samples at baseline and during follow-up. All centers performed laboratory analyses on 24-h urine samples, the majority (96%) at baseline and during follow-up. There was good correspondence across centers for analyses performed on 24-h urine samples, although the methods of 24-h urine collection and analysis were relatively heterogeneous. Our survey among 24 European stone centers highlights areas of homogeneity and heterogeneity that will be investigated further. Our aim is the creation of a European network of stone centers sharing practice patterns and hosting a common database for research and guidance in clinical care.

Renal lithiasis is a complex multifactorial disease in which recurrence is common. Thus, simple and reliable procedures are needed to evaluate patients with previous kidney stones to determine the risk of recurrence. In this paper we review simple biochemical procedures that can be used to determine the risk for renal stone formation when the stone is available or unavailable for analysis. Our present knowledge of renal lithiasis indicates that renal stones form due to several well-defined factors. Analysis of the renal stone itself can provide important information about clinical factors that require further investigation. When the stone is unavailable, it is necessary to perform a general evaluation of main urinary risk factors associated to renal stone formation, but this study should be complemented considering information related to direct familial antecedents, recidivant degree, radiological images, medical history, and life style habits. Finally, tools for patient follow-up of stone-forming propensity during the preventive treatment are discussed .

Calcium oxalate monohydrate (COM) papillary calculi can be initiated by subepithelial calcification of the renal papillae. Hydroxyapatite disruption of the papillary epithelial layer can become the nidus of a COM papillary calculus. This study evaluated the causes of papillary tissue calcifications in 60 patients with calcium oxalate lithiasis, 30 with COM papillary and 30 with calcium oxalate dihydrate (COD) calculi. Urinary redox potential was higher in the COM than the COD group, suggesting that the former is more deficient in antioxidants due to increased oxidative stress. Urinary calcium was significantly higher in the COD group, whereas urinary oxalate was significantly higher in the COM group, suggesting a greater degree of oxidative injury of renal cells. Evaluations of their diets showed that both groups consumed low amounts of phytate-rich products. Of chronic diseases possibly associated with urolithiasis, only the prevalence of gastroduodenal ulcer differed significantly, being higher in the COM group and suggesting that epithelial lesions are common to gastroduodenal ulcers and COM papillary renal stones. Occupational exposure to cytotoxic products occurred in 47 % of the COM and 27 % of the COD group, but this difference was not statistically significant. These findings indicate that oxidative stress is associated with injury to papillary tissue and that this is the origin of intrapapillary calcifications. The continuation of this process is due to modulators and/or deficiencies in inhibitors of crystallization. Identifying and eliminating the causes of injury may prevent recurrent episodes in patients with papillary COM calculi.

Synthetic calcium phosphate (CaP) concretions in the form of hemispheres formed under carefully controlled conditions (pH 7.4, 37 °C, no evaporation) from stagnant simulated body fluid on anionic polymeric substrate (laminin) were observed by scanning and transmission electron microscopy and atomic force microscopy. The hemispheres with diameter between approximately 50 and 200 μm were composed of closely connected round spherical and elliptical objects of diameter varying from 70 to 120 nm with surface layer composed of tightly packed spherical objects of diameter 25-30 nm. The phase composition of concretions consisting of amorphous material was uniform. The concretions were formed by aggregation of CaP clusters (Posner's clusters Ca9(PO4)3 or [Ca3(PO4)2] n ) generated in the solution by perikinetic coagulation, their settling onto a substrate and subsequent accumulation through surface migration (surface nucleation) followed by accretion of nanoparticles arriving from surrounding solution. The similarity of ultrafine structures of these synthetic CaP concretions and the compact phosphatic phase appearing in some phosphate calculi indicates that analogous mechanisms could be active at the formation of the latter in the kidneys.

Background: Understanding the mechanism of calcium deposition in soft tissues is of great importance in a variety of pathological conditions such as chronic kidney disease. The present study examined the role of phytate and osteopontin during the development of soft tissue calcification in an animal model., Methods: Male Wistar rats (16 rats per treatment) were fed with a diet (AIN-76A) in which phytate is undetectable (non-phytate-treated group), or with a phytin-enriched AIN-76A diet (phytate-treated group). After 21 days on the respective diets, all rats were subjected to calcinosis induction by subcutaneous injection with KMnO4 at 2 sites on either side of the interscapular region. At 2, 5, 8 and 10 days after the calcinosis induction, 4 rats of each group were sacrificed, and the injured tissues were removed for histological analysis and for calcium determination., Results: Calcification was notably and significantly reduced in phytate-treated rats compared with non-phytate-treated rats. Calcified deposits appeared as soon as 2 days after calcinosis induction, but inflammation with the presence of macrophages, lymphocytes and eosinophils was not typically observed until 5 days postinduction. Osteopontin was only detected 8 days postinduction, and was clearly associated with calcified areas., Conclusions: The results suggest an important role for crystallization inhibitors such as phytate in reducing hydroxyapatite crystal formation in the first steps of soft tissue calcification. Histological analysis indicated that osteopontin was not involved during initiation of soft tissue calcification. Osteopontin appears be involved in the control of calcification rather than its genesis.

Ureterocele calculi are developed in cavities with urinary retention but far from the upper renal cavities. The structural features of three ureterocele calcium oxalate stones were observed by scanning electron microscope coupled with X ray microanalysis. The urinary parameters of the three patients were also determined. The stone A consisted of loose structure of large calcium oxalate dihydrate crystals and small spheres of hydroxyapatite. The interior contains disorganized plate-like calcium oxalate monohydrate crystals. The stone B was formed by a compact outer layer of calcium oxalate monohydrate columnar crystals. The structure of stone interior was similar to the stone A. The stone C was formed by concentric layers composed of either calcium oxalate monohydrate columnar crystals or hydroxyapatite. The core consisted of agglomerated calcium oxalate monohydrate crystals, hydroxyapatite and organic matter. From the urinary biochemical data it was deduced that two ureterocele patients (who formed A and B stones) were hypercalciuric (calcium > 300 mg/24 h), being 6.5 the urinary pH value of the patient that formed the A stone, and 7.0 the urinary pH of the patient that formed the C stone. The rest of urinary parameters for the three patients were normal. Thus, one of the requisite conditions for unattached stone development is the existence of a place inside the urinary tract where the solid particles that act as calculus initiator of the stone can be retained enough time to exert this action.

Two flow methods for the enzymatic determination of pyrophosphate are described that are used to diminish the consumption of reagents. One method is based on the use of an open-close circuit with manual injection using a syringe. The other is a sequential injection method. The analytical features of both methods are: a linear range of 0.4 - 20 mg L(-1), an LOD of 0.38 mg L(-1), and a CV of 2.0% for the sequential injection method, and a linear range of 0.3 - 15 mg L(-1), an LOD of 0.29 mg L(-1), and CV of 2.2% for the open-close circuit method. The methods were applied to the determination of pyrophosphate in urine. The pyrophosphate concentration determined in urine samples varied from 1.26 to 6.67 mg L(-1).

The aim of this paper is to study possible synergic effects between crystallization-inhibitor molecules of low molecular weight on the hydroxyapatite and brushite crystal nucleation. Kinetic-turbidimetric measurements were performed to follow the nucleation process in synthetic urine at 37 degrees C. Only pyrophosphate + phytate mixture manifested synergic effects on the brushite nucleation, whereas the mixture pyrophosphate + citrate exhibited synergic effects only on the hydroxyapatite nucleation. It seems clear that synergic effects between the crystallization inhibitory capacity of some substances in urine can take place and as a consequence, the high crystallization inhibitory capacity of healthy urine could be assigned not only to the individual inhibitory capacity of each product but also to the synergic effects between different products.

Calcium renal lithiasis formation depends on the balance between thermodynamic (supersaturation) and kinetic (inhibitors, nucleants) factors. In this paper, the importance of both groups was evaluated using (a) the complete urine analysis data obtained from 32 healthy volunteers and 141 active stone-formers, and (b) a comprehensive computer model to calculate the supersaturation values of calcium oxalate monohydrate, hydroxyapatite and brushite in each urine sample. The results of this evaluation were used to assess the possible effectiveness of a given pharmacological treatment.

The crystallization of indinavir in synthetic urine at different pH values and indinavir concentrations was kinetically studied. It was found that precipitation time notably decreases at urinary pH values above 6.0. The effects of some products as potential crystallization inhibitors were studied. Some natural saponins such as escin and glycyrrhizic acid provoked a notable increase in the precipitation time of indinavir, this pointing out their possible use to prevent renal tubular solid deposition.

A concise account of formation mechanisms of attached (papillary) and unattached renal stones is presented. Urinary conditions prevailing at least during the stone forming period are indicated. Ten main categories of renal stones, covering over 95% of all conceivable calculi, are distinguished based on their composition and structure. Aetiologic factors leading to stone formation of every category are specified and general outlines of recommended treatment procedures indicated.

The changes in some nocturnal urine urolithogenic parameters in response to the extradietary ingestion of 2.16 g potassium citrate (20 meq) after dinner have been determined. The study included 15 patients (hypocitraturic calcium oxalate stone formers). On the basis of the different pH changes three groups have been differentiated. Different kinetics of citrate metabolism can justify the existence of these three groups. In general, a beneficial effect on urolithogenic parameters was confirmed, and a pH control of patients under treatment was recommended.

The effect of minimum doses of extradietary potassium citrate ingestion on urolithogenic parameters has been studied. Separate urine fractions were collected in 24-hour periods. Five calcium oxalate stone formers have participated in the study. pH, calcium, citric acid, and the crystallization inhibitory capacity levels in fractional urine samples were determined before and during treatment. The most beneficial effect (increase in citraturia and crystallization inhibitory capacity) was produced by potassium citrate tablets ingested after dinner.

A procedure to evaluate the global inhibitory capacity of heterogeneous nucleation for a given urine without any modification of its composition was developed. The procedure is based on the use of flat solid substrates that are submerged in urine. The quantification of the amount of formed crystals on the substrate permits to evaluate the crystallization inhibitory capacity for a whole urine. The proposed method was applied to study the inhibitory capacity of urines belonging to stone-formers and healthy people, before and after the ingestion of a dietary complement containing phytate in order to prove its reliability. A clear increase of the inhibitory capacity of the urine was detected in most cases when the dietary complement was consumed. Moreover, lack of crystallization inhibitory capacity was more frequent in stone-formers than in healthy people.

The effects of seven plants with suspected application to prevent and treat stone kidney formation (Verbena officinalis, Lithospermum officinale, Taraxacum officinale, Equisetum arvense, Arctostaphylos uva-ursi, Arctium lappa and Silene saxifraga) have been studied using female Wistar rats. Variations of the main urolithiasis risk factors (citraturia, calciuria, phosphaturia, pH and diuresis) have been evaluated. It can be concluded that beneficial effects caused by these herb infusions on urolithiasis can be attributed to some disinfectant action, and tentatively to the presence of saponins. Specifically, some solvent action can be postulated with respect to uric stones or heterogeneous uric nucleus, due to the basifying capacity of some herb infusions. Nevertheless, for all the mentioned beneficial effects, more effective and equally innocuous substances are well known.

In a survey conducted on 1500 individuals, an overall prevalence of 14.3% for the year 1990 was found for urinary stone disease in the Balearic Islands. The prevalence showed higher figures for people living in rural areas than for those living in cities, and this could be correlated with traditional living habits such as traditional Balearic diet. Finally, a surprising fact is that only 54% had consulted a urologist as outpatients and the rare occasion at which the calculi were analyzed (15.1%).

Based on reconsideration of the contemporary knowledge on calcium oxalate urolithiasis a feasible mechanism of calculi generation is suggested. Experimental findings and clinical aspects supporting the suggested mechanism are presented. The ways of urolithiasis treatment and areas of future research are indicated.

An animal model involving rats fed with different diets (high protein, high carbohydrate, high lipid, high fiber and control balanced diet) was used to evaluate the dietary effects on the main oxalocalcic urolithogenic parameters. It was found that the inhibitory factors that prevent calcium oxalate stone formation (citrate and magnesium) were clearly more favorable in the group of rats fed with a balanced diet. However, factors favouring the heterogeneous calcium phosphate nucleation were also found in the balanced diet. On the other hand, factors facilitating the heterogeneous uric acid nucleation were found in rats treated with high protein, high lipid, high carbohydrate and high fiber diets. In conclusion it seems that the balanced diet appears to be the less lithogenic one.

The aim of this paper is to evaluate the possible causes of the origin of "infection stones". The main differences between the ordinary biochemical parameters of a group of patients with this type of stones was analyzed and compared with a group of oxalocalcic stone-formers and with a group of healthy subjects. The importance of persistent basic urinary pH values is pointed out as possible origin of "infection stones" in some instances. The main urinary citrate concentration in patients with "infection stones" was significantly lower than in healthy subjects, this being an important factor that favours this kind of stone formation.

Different mathematical expressions have been proposed in the literature with the aim to reflect the risk of calcium oxalate urolithiasis. Such expressions, as well as a number of new relationships proposed by us, have been evaluated in 76 patients and 34 normal subjects. Stone-formers were divided into two groups: patients with normal calcium and oxalate excretion and patients with hypercalciuria and/or hyperoxaluria. The results obtained were comparatively evaluated. Several formulae gave some acceptable results, but none of them were excellent. This can be explained by the fact that these discrimination indexes more or less reflect supersaturation and/or inhibition deficit, but none of them reflect promoting factors such as heterogeneous nucleation and/or aggregation capacity.

The aim of this work is to evaluate citrate in a group of patients with calcium oxalate urolithiasis and in a control group for detecting possible differences between the two groups. The mean urinary concentration in the stone-formers was found significantly lower than in the controls. Particularly interesting was the correlation study between citrate and calcium. It was found that patients with hypocitraturia have hypercalciuria. Thus, it is particularly interesting to point out the importance of citrate in preventing the risk of lithiasis in the group of stone-formers studied by us.

The aim of this work is to evaluate citrate in a group of patients with calcium oxalate urolithiasis and in a control group for detecting possible differences between the two groups. The mean urinary concentration in groups of stone-formers was found significantly lower than in the control group. Particularly interesting was the correlation study between citrate and calcium. It was found that patients with hypocitraturia have hypercalciuria. Thus, it is particularly interesting to point out the importance of citrate in preventing the risk of lithiasis in stone-formers studied by us.

The role of urinary glycosaminoglycans (GAGS) in calcium oxalate lithiasis is of great interest in urologic research. It has been claimed that GAGS are important inhibitors of calcium oxalate crystal growth and aggregation. The aim of this paper is to evaluate GAGS excretion and concentration in two groups of patients, calcium stone formers (with or without metabolic alteration) and a control group, to detect possible differences. The findings of this study show that significant differences exist not only in the 24-hour average excretion between stone formers without alteration and healthy subjects but also in the mean concentration values between the stone former and control groups. The same results are obtained from the 2-hour urine analysis. It is concluded that 2-h urine analyses of GAGS have the same or more practical value than a 24-h urine analysis and that the results must be expressed in terms of concentration.