Simple test to evaluate the risk of urinary calcium stone formation
Introduction
The formation of renal calculi in practically all cases, must be attributed to a combination of diverse factors. These factors may be classified into two main groups: (1) factors related to urine composition and (2) factors related to renal morphoanatomy.
Urine is a metastable system in which several substances capable of crystallizing and generating renal calculi coexist. Normally, these substances are in supersaturated conditions and the ease of crystallization depends on the degree of supersaturation, the presence of promoter substances (heterogeneous nucleants) and the level of inhibitors of crystallization. On the other hand, the presence of cavities with low urodynamic efficacy that, as a consequence, retain the urine for a long time, and alterations of the epithelium that covers the renal papillae (damaged anti-adherent glycosaminoglycan layer, necrosis, etc.), are the main factors linked to the renal structure that favour the calculi formation. Usually, to develop renal calculi, the coexistence of factors from both main groups is necessary.
Several procedures have been previously established to evaluate the crystallization properties of a urine 1, 2, 3, 4. Here a very simple test to evaluate the capacity of a urine to crystallize calcium salts is presented. The test is based on the fact that urines which tend to form renal calculi have a higher capacity to generate calcium salts than non-lithogenic urines. Thus, a healthy urine does not produce crystals in the proposed test whereas a lithiasic one does.
Section snippets
Materials and methods
The test is based on the fact that if a non-protected non-renewed surface remains in contact with a urine, sooner or later the contained supersaturated substances crystallize on it. The ease of crystallization depends on the balance of the forces that drive it (supersaturation and heterogeneous nucleants) and those that appose it (crystallization inhibitors). Thus, by using an adequate surface, it is possible to derive a period within which a normal urine does not crystallize whereas a
Results
A total of 32 healthy people and 92 patients with oxalocalcic urolithiasis were selected to evaluate the suitability of the proposed test. Results are shown in Table 2, Table 3, where biochemical measurements are also included.
Between 75% (urine 1) and 83% (urine 2) of the healthy group gave negative results (Table 2), 100% of healthy people with normal urine gave a negative result when the test was applied, whereas between 50% (urine 2) and 100% (urine 1) of healthy people with hypercalciuric
Discussion
The test is based on the fact that when a non-renewed, non-protected surface remains in contact with urine, sooner or later the contained supersaturated substances crystallize on it 6, 7. Several substances (different calcium phosphate salts and paraffin) were tested as substrates to induce the crystallization of salts when in contact with urine and showed similar results. Paraffin was selected as the optimum substrate because it permits an easier evaluation of the calcium crystallized on it by
Acknowledgements
Financial support by the D.G.I.C.Y.T. (grant PB 92-0249) is gratefully acknowledged.
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Validation of a novel diagnostic test for assessing the risk of urinary uric acid crystallization
2021, Clinica Chimica ActaCitation Excerpt :Thus, we evaluated the effect of theobromine administration on UA crystallization using a procedure that assessed the joint effect of all compounds present in urine [17]. During the 1990 s, the Renal Lithiasis Research Group developed a procedure to determine the lithogenic risk for calcium salts [18–19]. In this study, we present a new test that assesses the risk for UA stones and then applied this test to compare UA stone formers and healthy volunteers to demonstrate and validate its utility for UA stone-formers follow-up.
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2002, Journal of Trace Elements in Medicine and BiologyThe idiopathic hypercalciuria reviewed. Metabolic abnormality or disease?
2019, NefrologiaCitation Excerpt :However, to confirm that a hypercalciuria is an IH, levels of calcemia, intact PTH, ions (including chloride) and acid base balance must be normal. In the follow-up, and to simplify the management of patients with IH, it has been postulated to determine calcium, citrate and creatinine in isolated urine samples at two different times of the day, namely before dinner and in the first morning urine, so it would not be necessary to collect urine from 24 h.105 If calcium / citrate ratio in either urine exceeds 0.33 mg/mg there is a risk of urinary crystallization.106,107 With this method, it has been shown that urinary concentrations of calcium and the calcium/citrate ratio are modified throughout the day so that the urine formed during the night is the most lithogenic.105
Quantification of the risk of urinary calcium stone formation in the urine collected at 2 times of the day in a group of children studied to rule out prelithiasis
2018, NefrologiaCitation Excerpt :There were considered calculi if the size was greater than 3 mm with a sonic shadow, and the microcalculi were particles in the renal calyces less than 3 mm in diameter and in general without shadow cones.9 The results were evaluated according to the criteria of Grases et al., which establish that a urine is potentially lithogenic if the calcium concentration is greater than 27 mg/dl, the citrate is less than 230 mg/l or the calcium/citrate ratio is greater than 0.33 ng/mg.7,10 The Kolmogorov–Smirnov test was used to examine the distribution of the simple, then a basic statistic test was performed.