LITHORISK.COM: the novel version of a software for calculating and visualizing the risk of renal stone

Effects of thiazides and new findings on kidney stones and dysglycemic side effects

Thiazide and thiazide-like diuretics (thiazides) belong to the most frequently prescribed drugs worldwide. By virtue of their natriuretic and vasodilating properties, thiazides effectively lower blood pressure and prevent adverse cardiovascular outcomes. In addition, through their unique characteristic of reducing urine calcium, thiazides are also widely employed for the prevention of kidney stone recurrence and reduction of bone fracture risk. Since their introduction into clinical medicine in the early 1960s, thiazides have been recognized for their association with metabolic side effects, particularly impaired glucose tolerance, and new-onset diabetes mellitus. Numerous hypotheses have been advanced to explain thiazide-induced glucose intolerance, yet underlying mechanisms remain poorly defined. Regrettably, the lack of understanding and unpredictability of these side effects has prompted numerous physicians to refrain from prescribing these effective, inexpensive, and widely accessible drugs. In this review, we outline the pharmacology and mechanism of action of thiazides, highlight recent advances in the understanding of thiazide-induced glucose intolerance, and provide an up-to-date discussion on the role of thiazides in kidney stone prevention.

Comparison of two software programs used to determine the relative supersaturation of urine ions

Introduction

Relative supersaturation (RSS) values for urine crystals are a measure of the risk of urinary stone formation and have been shown to be lowered in foods shown to aid in the management of urolithiasis. In order to calculate RSS in pets, computer programs have been developed to calculate RSS and aid in the understanding of stone formation in veterinary medicine. However, some older programs have not been updated for use in animals, and the specific coefficients used are not publically available. One of the first RSS programs was developed in BASIC computer language and published in 1985 which was called EQUIL2. The EQUIL2 program was updated to a compiled version compatible with a PC platform. However, the formulas could not be read or altered.

Methods

This study evaluates a new program with known coefficients to the original EQUIL2 program. The RSS values of the two programs were compared through a t-test, calculating the r² from correlation analysis, Lin's concordance correlation coefficient, and by a Bland-Altman analysis of outputs from the two programs using urine samples from healthy dogs and cats.

Results and Discussion

Our results show that for both magnesium ammonium phosphate (struvite) and calcium oxalate, the RSS values of the original program could be calculated from the new programs RSS values. Although the actual RSS values were different (as might be expected through the use of the updated coefficients and different thermodynamic stability constants in the calculations) the results were highly correlated, finding elevations and reductions in RSS proportionally in the same urine samples. The current work creates a foundation for using the modernized program to calculate RSS and provides a shared method for understanding the risk of struvite and calcium oxalate stone formation.

Estimating 24-hour urinary excretion using spot urine measurements in kidney stone formers

BACKGROUND

One limitation of the use of 24-hour collection is impracticality. We analysed the performance of spot urine measurements to estimate 24-hour excretion in patients with kidney stones.

METHODS

A total of 74 adult patients from two centres performed a 24-hour urine collection. A sample of the last micturition was sent for spot urine analysis. Twenty patients were asked to collect two additional spot urine samples, one before dinner and the other after dinner. Urinary concentrations of creatinine, calcium, oxalate, uric acid, citrate and magnesium were measured in the 24-hour and each of the spot urine samples. Four approaches were used to estimate 24-hour urinary excretion, multiplying the ratio of the spot urinary analyte to creatinine concentration by (i) measured 24-hour urinary creatinine excretion (Prediction 1), (ii) estimated 24-hour urinary creatinine excretion (Prediction 2), (iii) assumed 1-g 24-hour urinary creatinine excretion (Prediction 3) or (iv) assumed 1.5-g 24-hour urinary creatinine excretion (Prediction 4). For each parameter we computed Lin's concordance correlation coefficients (CCCs), Bland-Altman plots and 95% limits of agreement.

RESULTS

The performance of estimates obtained with Prediction 1 and Prediction 2 was similar, except for citrate and uric acid, for which Prediction 2 performed worse. Both approaches performed moderately well: citrate CCC {0.82 [95% confidence interval (CI) 0.75-0.90]}, oxalate [0.66 (95% CI 0.55-0.78)], magnesium [0.66 (95% CI 0.54-0.77)], calcium [0.63 (95% CI 0.50-0.75)] and uric acid [0.52 (95% CI 0.36-0.68)]. The performance of Predictions 3 and 4 was worse.

CONCLUSIONS

Although spot urine samples may hold promise for clinical and population-based research, at present they have limited utility in clinical practice. Measuring or estimating 24-hour creatinine, rather than assuming a given creatinine excretion, will be necessary in future studies of spot urine samples.

Calcium Citrate Versus Calcium Carbonate in the Management of Chronic Hypoparathyroidism: A Randomized, Double-Blind, Crossover Clinical Trial

In hypoparathyroidism (HypoPT), calcium supplementation is virtually always required, although the disease is likely to be associated with an increased risk of nephrolithiasis. The use of calcium citrate (Ca-Cit) theoretically could have a positive impact on the nephrolithiasis risk because citrate salts are used to reduce this risk. Our objective was to evaluate the potential therapeutic advantage of Ca-Cit in comparison with calcium carbonate (CaCO₃ ) in HypoPT, on nephrolithiasis risk factors, as well as to their ability to maintain desirable serum calcium levels. We also evaluated these preparations on quality of life (QOL). This randomized, double-blind, crossover trial recruited 24 adults with postsurgical chronic hypoparathyroidism at Campus Bio-Medico University of Rome. Participants were randomized 1:1 to Ca-Cit or CaCO₃ for 1 month and then crossed over to the other treatment for another month. The primary outcomes were changes in albumin-adjusted serum calcium and in ion activity product of calcium oxalate levels (AP[CaOx] index). Secondary efficacy outcomes included changes in SF-36 survey score, fatigue score, constipation, and adverse events. No difference in terms of AP(CaOx) index was observed between the two groups. However, Ca-Cit was associated with a significant reduction in the oxalate/creatinine ratio compared with CaCO₃ (-2.46 mmol/mol [SD 11.93] versus 7.42 mmol/mol [SD 17.63], p = 0.029). Serum calcium and phosphorus concentration was not different between the two calcium preparations. Ca-Cit was associated with less constipation (p = 0.047). No difference was found in QOL scores. Although Ca-Cit did not modify the AP(CaOx) index when compared with CaCO_3, it was associated with a reduction in urinary oxalate excretion that could have a potential beneficial effect on nephrolithiasis risk. These results are likely to have clinical implications in HypoPT, particularly those who do not tolerate CaCO₃ and those affected by nephrolithiasis. A longer-term experience is needed to confirm these findings. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

LITHOSCREEN: a comprehensive screening program and database for the assessment and treatment management of patients with kidney stones

The aim of the LITHOSCREEN project was to construct a comprehensive screening program and database for recording and assessing the various risk factors for stone-formation in patients with urolithiasis. It is intended for use in Stone Clinics and is now being made available free of charge to researchers in the field who wish to maintain a comprehensive record of their patients' medical histories, demographic backgrounds, lifestyle activities, metabolic abnormalities, biochemical risk of forming stones of various types, diet histories, stone analysis and long-term treatment records. From the recorded data for each patient, the program automatically calculates numerous functions important in the understanding of the clinical and chemical risk factors for stone-formation, including the renal handling of the ions involved, various metabolic functions, the biochemical risk of forming kidney stones (P_SF), the Tiselius Indices of the supersaturation of urine with respect to calcium oxalate and calcium phosphate, the projected effects of changing the composition of each patient's urinary composition on the risk of stone recurrence, and a program for analysing the diet of patients. It automatically produces one-page Summaries of each patient's biochemical and dietary records with abnormal values highlighted according to a "traffic-light" colour-coding system and generates charts designed to improve patient compliance with treatment in the form of colour-coded "Target Diagrams" showing (a) the patient's 24-h urine composition, (b) the patient's biochemical risk of forming stones of different types and (c) the composition of the patient's diet. The Summary pages and "Target Diagrams" are suitable for inclusion in the patient's Case Notes. LITHOSCREEN also produces charts projecting the effect of changing the composition of urine on the patient's biochemical risk of forming further stones. These graphs provide clues as to which urinary risk factors to target to reduce the patient's risk of stone recurrence.

Critical Reappraisal of Methods for Measuring Urine Saturation with Calcium Salts

Background: Metabolic and physicochemical evaluation is recommended to manage the condition of patients with nephrolithiasis. The estimation of the saturation state (β values) is often included in the diagnostic work-up, and it is preferably performed through calculations. The free concentrations of constituent ions are estimated by considering the main ionic soluble complexes. It is contended that this approach is liable to an overestimation of β values because some complexes may be overlooked. A recent report found that β values could be significantly lowered upon the addition of new and so far neglected complexes, [Ca(PO₄)Cit]^4- and [Ca₂H₂(PO₄)₂]. The aim of this work was to assess whether these complexes can be relevant to explaining the chemistry of urine. Methods: The Ca-phosphate-citrate aqueous system was investigated by potentiometric titrations. The stability constants of the parent binary complexes [Cacit]^- and [CaPO₄]^-, and the coordination tendency of PO₄^3- toward [Ca(cit)]^- to form the ternary complex, were estimated. β_CaOx and β_CaHPO4 were then calculated on 5 natural urines by chemical models, including or not including the [CaPO₄]^- and [Ca(PO₄)cit]^4- species. Results: Species distribution diagrams show that the [Ca(PO₄)cit]^4- species was only noticeable at pH > 8.5 and below 10% of the total calcium. β values estimated on natural urine were slightly lowered by the formation of [CaPO₄]^- species, whereas [Ca(PO₄)cit]^4- results were irrelevant. Conclusions: While [CaPO₄]^- species have an impact on saturation levels at higher pHs, the existence of ternary complex and of the dimer is rejected.