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Factors Associated With the Lower Prevalence of Nephrolithiasis in Children Compared With Adults
Accepted Manuscript Factors associated with the lower prevalence of nephrolithiasis in children compared to adults Felix Grases, Adrian Rodriguez, Antonia Costa-Bauza, Concepcion Saez-Torres, Dolores Rodrigo, Cristina Gómez, Concepcion Mir-Perello, Guiem Frontera PII:
S0090-4295(15)00624-X
DOI:
10.1016/j.urology.2015.06.028
Reference:
URL 19286
To appear in:
Urology
Received Date: 21 April 2015 Revised Date:
15 June 2015
Accepted Date: 22 June 2015
Please cite this article as: Grases F, Rodriguez A, Costa-Bauza A, Saez-Torres C, Rodrigo D, Gómez C, Mir-Perello C, Frontera G, Factors associated with the lower prevalence of nephrolithiasis in children compared to adults, Urology (2015), doi: 10.1016/j.urology.2015.06.028. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Factors associated with the lower prevalence of nephrolithiasis in children compared to adults Authors: Felix Grases1, Adrian Rodriguez1, Antonia Costa-Bauza1, Concepcion SaezTorres1, Dolores Rodrigo1, 2, Cristina Gómez3, Concepcion Mir-Perello1, 2, Guiem
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Frontera4
Laboratory of Renal Lithiasis Research, University Institute of Health Sciences
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Research (IUNICS-IdISPa), University of Balearic Islands, Palma de Mallorca, Spain.
Department of Pediatric Nephrology, Son Espases University Hospital, Palma
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de Mallorca, Spain 3
Laboratory Department, Son Espases University Hospital, Palma de Mallorca,
Spain
Research Unit, Son Espases University Hospital, Palma de Mallorca, Spain
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Corresponding author: Felix Grases
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Laboratory of Renal Lithiasis Research, Faculty of Sciences, University Institute
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of Health Sciences Research (IUNICS), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain. Telephone number: +34 971 17 32 57
e-mail: [email protected]
Word Count: 2512 Abstract Word Count: 190 Key words: nephrolithiasis in children; urinary lithogenic parameters; calcium oxalate nephrolithiasis; urinary calcium; urinary magnesium
ACCEPTED MANUSCRIPT Funding Support This work was supported by grant PI 14/00853 from the Ministerio de Economia y Competitividad (Gobierno de España), and by FEDER funds (European Union).
Cultura i Universitats for the fellowship FPI/1570/2013.
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Financial Disclosure
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A.R. is grateful to the European Social Fund and the Conselleria d’Educació,
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The authors declare that they have no relevant financial interests.
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Abstract Objectives: to determine the reasons behind the lower prevalence of kidney stones in children by assessing urinary lithogenic parameters in healthy children, healthy adults, and three groups of stone former patients.
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Methods: The study subjects included 75 healthy adults, 105 healthy children, 62 patients with previous calcium oxalate monohydrate papillary stones, 120 patients with previous calcium oxalate monohydrate unattached stones, and
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248 patients with previous calcium oxalate dihydrate stones. Twenty-four hour
measured.
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urine samples were collected, and the urinary lithogenic parameters were
Results: Calcium, magnesium and phosphorous concentration differed significantly
between
healthy
children
and
adults.
Except
citrate,
all
solute/creatinine ratios differed between healthy children and adults. However,
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these differences were much more important in the cases of calcium and magnesium. The calcium/creatinine ratio was 2-fold lower, while the magnesium/creatinine ratio was 2-fold higher, in healthy children than in healthy
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adults (p<0.001 each). The calcium/creatinine ratio was higher and the
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citrate/creatinine ratio lower in calcium oxalate dihydrate stone formers than in healthy adults.
Conclusions: Ratios of calcium and magnesium to creatinine, as well as morphoanatomic factors and lifestyle habits, may explain the lower prevalence of nephrolithiasis in children than in adults.
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Introduction Formation of renal stones results from a combination of several factors. These include urine composition, as urinary pH, calcium, magnesium, oxalate, phosphate and uric acid concentrations; the presence of crystallization
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inhibitors; and the inclusion of solid micro particles that act as heterogeneous nucleants1, 2. Other factors are related to kidney morphoanatomy, including the presence of cavities of low urodynamic efficacy that can retain microparticles,
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and calcified injuries to the papillary tissue that can induce the formation of calcium oxalate monohydrate papillary renal calculi3. These factors have been
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associated with metabolic abnormalities and with inadequate lifestyle habits, including diet and chronic drug consumption1-3.
The prevalence of renal lithiasis in adults has increased in recent decades, with 10% of the population being affected in many countries4. Although the
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prevalence of calcium oxalate nephrolithiasis is increasing in children and tends to be recurrent, renal stones are still infrequent during the pediatric period5,
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and are often associated with an underlying metabolic disorder7, 8. Apart from
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congenital malformations of the urinary tract and urinary infection, recognized
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risk factors for kidney stone formation in children include hypercalciuria, hyperoxaluria, hypocitraturia, low urine volume and hyperuricosuria6, 9, 10. As in adults, hypertension and diabetes mellitus are also associated with renal stone formation in children7, 8. Furthermore, children in industrialized countries are subjected to the same environmental and lifestyle factors promoting stone formation as adults. Thus, although children and adults may present with similar metabolic profiles of factors that can induce renal stone development, renal lithiasis is much less frequent in children. To assess whether any urinary
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ACCEPTED MANUSCRIPT parameters are associated with the lower prevalence of nephrolithiasis in children, we compared the urinary lithogenic parameters in healthy children,
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healthy adults and three different groups of adult stone formers.
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Material and Methods Renal calculi studies Spontaneously passed renal stones were analyzed in less than a week after their collection. The procedure used to analyze and study the calculi requires an
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appropriate combination of observation by means of macroscopic and microscopic conventional techniques (stereoscopic microscope; Optomic, Madrid, Spain) with physical techniques such as infrared spectrometry (Infrared
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Spectroscope Brucker IFS 66; Bruker, Ettlingen, Germany) and scanning electron microscopy (Hitachi S-530; Hitachi, Tokyo, Japan) coupled to X-ray
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microanalysis (Oxford Link Isis; Oxford, UK)11.
This analysis and study of calculi allows them to be classified into 11 main types, of which calcium oxalate renal calculi account for over 60% of all renal calculi11, 12.
distinguished:
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Three different types of calcium oxalate renal calculi can be clearly
a) Calcium oxalate monohydrate (COM) renal calculi developed on the
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renal papillary tissue. When these calculi are observed by a stereoscopic
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microscope or by scanning electron microscope, an attachment site to the papillae in clearly detectable, and their inner structure basically consists on a core near to the attachment site (concave zone), from which radially striated concentrically laminated layers originate13. They generally have a dark brown color. b) Unattached COM calculi consisting on a symmetrically round stone with a central core surrounded by columnar COM crystals emerging from the core. There calculi do not present attachment site to the renal papillae
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ACCEPTED MANUSCRIPT epithelium although their color is very similar to the papillary COM calculi13. c) Calcium oxalate dihydrate (COD) renal calculi, typically consisting on randomly distributed yellowish bipyramidal COD crystals, which form
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primary aggregates11, 12
The two different phases of calcium oxalate that can be found in renal calculi (COM and COD) present different crystal morphology and infrared spectra.
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COM is the thermodynamically stable phase and COD is the kinetically favorable but thermodynamically unstable phase, and for this reason COD
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crystals slowly transform into the stable COM14, 15.
In fact, most COD renal calculi present transformation although to varying degrees, in such a way that the infrared spectrum of a calculus may correspond to COM, even when the phase formed in urine was COD.
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Nevertheless, the morphology of COM and COD calculi is clearly different, even after COD transformation into COM, since an originally “pure” COD calculus still presents frames corresponding to the COD bipyramidal
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crystals, although containing some brown areas. In this study, we have included three groups of calcium oxalate stone forming
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patients: one group of papillary calcium oxalate monohydrate (papillary COM) stone-formers, whose calculi clearly present an attachment site to the papillae; one group of unattached calcium oxalate monohydrate (unattached COM) stone-formers, whose calculi do not present attachment site to the papillae; and one group of calcium oxalate dihydrate stone formers, also including in this group those patients with mixed COM/COD calculi in which COM comes from the transformation of COD.
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ACCEPTED MANUSCRIPT Study subjects The study subjects included 75 healthy adults and 105 healthy children and young teenagers aged 5-17 years with no history of nephrolithiasis; 62 patients with previous calcium oxalate monohydrate papillary stones (papillary COM
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group); 120 patients with previous calcium oxalate monohydrate unattached stones (unattached COM group); and 248 patients with previous calcium oxalate dihydrate stones (COD group). None of the healthy adults or children
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had chronic diseases or was being treated with any medications. They were asymptomatic at the time of the urine collection, and did never have, to their
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knowledge, any lithiasic episode such as sands, nephritic colic or positive radiological image. Children were recruited from different schools in Majorca, both state and private ones. Healthy adults were recruited from hospital and university workers. This healthy adult group presented similar age and
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distribution that the stone-former groups. All participants were asked not to change their usual patterns of food consumption, liquid intake and physical activity during the sampling period. Each participant, or his/her legal
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representative, provided written informed consent for their clinical samples to be used in scientific studies. This study was approved by the ethics committee of
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our institution.
Urine collection and analysis All subjects were on an unregulated diet at the time of urine collection and none of the previous stone-formers was receiving any pharmacological treatment. Twenty-four hour urine samples were collected from each subject into sterile flasks containing thymol as a preservative. Urinary volume was recorded and
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ACCEPTED MANUSCRIPT the samples were analyzed 3-4 h after collection was finished. Urine from patients in the papillary COM, unattached COM, and COD groups was collected 1-2 months after stone passage/removal. The main lithogenic biochemical parameters were measured on a Modular
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Autoanalyzer (Roche Diagnostics, Indianapolis, IN, USA). Urinary phosphorus (P) was measured by the ammonium molybdate reduction method; urinary magnesium (Mg) by colorimetric reaction with Xylidyl blue; calcium (Ca) by a
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colorimetric reaction with o-cresolphthalein; uric acid (Ur) by the uricase method; and creatinine (Cr) by the kinetic Jaffe method. Urinary citrate (Cit) was
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measured spectrophotometrically by an enzymatic assay (citrate lyase) using a test kit (R-Biopharm, Germany). Urinary oxalate (Ox) was determined enzymatically by the oxalate oxidase/peroxidase method (LTA, Milano, Italy). We also measured the AP Index according to Tisselius formula16: AP(index) .
were all the solutes were expressed in mmoles, and
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= 1.9
. . .
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the volume expressed in liters.
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ACCEPTED MANUSCRIPT Statistical Analysis The normality of the data was assessed using Shapiro-Wilk tests. As most of the data were not normally distributed, median and 25th and 75th percentiles were determined and presented graphically as box plots. Differences between
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the healthy adult group and each of the other groups were assessed using the Mann Whitney U test, followed by Bonferroni adjustment. Thus, a p-value <0.0125 was considered statistically significant. The differences in the AP index
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between the 5 groups was assessed by one way ANOVA followed by Tukey test. All statistical analyses were performed using SPSS for Windows version
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2.1 software.
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Results The 610 subjects were divided into five groups: 75 healthy adults, 105 healthy children, 62 patients with previous calcium oxalate monohydrate papillary stones, 120 patients with previous calcium oxalate monohydrate unattached
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stones and 248 patients with previous calcium oxalate dihydrate stones. The demographic, clinical, and anthropometric factors in these five groups are shown in Table 1 and their urinary biochemistry in Table 2. The Mg, Ca and P
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concentrations in healthy children and healthy adults differed significantly. However, as expected, diuresis values differed markedly in healthy children and
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healthy adults, as well as between healthy adults and the three groups of lithiasic patients. In most cases, increases in diuresis were associated with lower solute concentrations. However, despite diuresis being higher, Ca concentration was significantly higher in the COD than in the healthy adult
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group. Similarly, despite urinary output being lower, Ca concentration was lower in healthy children than in healthy adults. Table 3 shows solute/creatinine ratios in the five groups of subjects. Except
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citrate, all solutes/creatinine ratios differed significantly between healthy adults
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and healthy children. However, in the cases of Ur, Ox and P, the differences in the ratios are much lower than in the cases of Ca and Mg. Box plots showed that Mg/Cr was similar in the papillary COM, unattached COM, COD and healthy adult groups, but was about 2-fold higher in healthy children than in healthy adults (p<0.001, Fig. 1A). Ca/Cr ratios in the papillary COM and unattached COM groups were similar to that in healthy adults, but was significantly higher in the COD group (p<0.001) and significantly lower in healthy children (p<0.001) than in healthy adults (Fig. 1B).
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ACCEPTED MANUSCRIPT In addition, Cit/Cr ratios differed significantly between the COD and healthy adult groups (p<0.001). Regarding measures of urinary supersaturation, there were no statistical differences between the AP index in the papillary COM group, the unattached
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COM group and the healthy adult group (means: 1.00; 1.03 and 1.18 respectively). However, COD group has a mean AP index of 1.46 (p<0.001) and
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the healthy children group has a mean AP index of 0.60 (p<0.001).
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Comment Urinary composition is a key factor in kidney stone formation. To determine whether any urinary parameter could explain the lower prevalence of nephrolithiasis in childhood, we compared the main urinary biochemical
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parameters in healthy children and adults, as well as in adults with and without lithiasis.
As expected, we found that diuresis was lower in healthy children than in
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healthy adults, but was higher in all three groups of lithiasic patients than in healthy adults. Urine was collected from lithiasic patients 1-2 months after the
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lithiasic episode. Thus, the highest diuresis values in the stone former groups may have been due to higher fluid intake to prevent stone recurrence. In general, groups with higher diuresis had lower solute concentrations. However, Ca concentration was significantly higher in the COD than in the healthy adult
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group, despite the higher diuresis in the COD group. Similarly, Ca concentration was significantly lower in healthy children than in healthy adults, despite the lower urinary output of children. Although crystallization risk is calculated from
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solute concentrations, concentrations alone may be misleading, since
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differences between groups may be due to differences in diuresis values. Furthermore, we could not compare the absolute excretion of solutes in children and adults because of differences in their anthropometric measurements. Thus, all urinary solutes excretions were expressed as their ratio to creatinine. Ratios of Ox, P and Ur to creatinine were slightly different between healthy children and adults, probably due to a lower creatinine concentration in childhood17. The difference was much more important in the case of magnesium, since its median ratio was almost double in healthy children than in
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ACCEPTED MANUSCRIPT adults, difference that cannot be explained only by the lower creatinine concentration. Ca/Cr values not only did not increase in the children group as was expected but on the contrary we found much lower values than in adults, which can only be explained by low amounts of net calcium excretion.
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Mg/Cr ratios differed significantly between healthy children and healthy adults. In contrast, Mg/Cr ratios in the three stone former groups were similar to that in the healthy adult group. Mg concentrations and Mg/Cr ratios are higher in
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children and may be due to greater absorption of Mg17. Mg protects against calcium oxalate nephrolithiasis, since it competes with calcium in binding to
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oxalate. Since magnesium oxalate is 100 times more soluble than calcium oxalate, it does not crystallize in the kidneys18. The two-fold higher Mg/Cr ratio in children than in adults suggests that Mg may protect children against the formation of calcium oxalate kidney stones.
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Ca/Cr ratios also differed significantly between healthy children and healthy adults. Urinary Ca excretion is increased by intake of dairy products, sodium, animal protein and glucose, with many of these foods more frequently
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consumed by young people. However, urinary Ca/Cr ratio was significantly lower in children than in adults, perhaps due to the higher rates of bone
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turnover that occur during growth periods in childhood. The lower urinary Ca concentrations
in
children
may
protect
them
against
calcium
stone
development. As expected, however, the COD group had the highest urinary Ca concentration among the five subject groups, resulting in the formation of thermodynamically unstable COD stones11. Cit/Cr ratio was significantly lower in the COD than in the healthy adult group (p<0.001). Cit is an inhibitor of kidney stone formation that also forms
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ACCEPTED MANUSCRIPT complexes with Ca, reducing the free Ca concentration in urine. COD stone formation is usually due to a high Ca concentration in urine, suggesting that the lower Cit concentrations in this group contribute to a higher free Ca concentration.
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The AP index values indicate that there are no statistical difference in calcium oxalate urinary supersaturation between the papillary COM group, the unattached COM group and the healthy adult group. This can be explained
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since the papillary COM calculi start to develop as a result of an injury in the renal papillae tissue, and this is independent on urinary supersaturation.
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Unattached COM calculi are associated to normal supersaturation values and to the presence of retained heterogeneous nucleants (uric acid, hydroxyapatite, organic
matter,
etc)13.
However,
COD
group
has
a
higher
urinary
supersaturation (p<0.001) when compared with the healthy adult group. As
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expected, the higher calcium and lower citrate excretion increase urinary supersaturation in this group of patients. Precisely, this higher urinary supersaturation is the explanation of the kinetically favorable COD crystal Finally,
healthy
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development.
children
group
has
a
lower
urinary
supersaturation than the rest of the groups (p<0.001). In this case, the lower
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calcium and higher magnesium excretion result in a lower calcium oxalate supersaturation degree. This lower AP index may provide more evidence for the lower prevalence of nephrolithiasis in children. Morphoanatomic factors and lifestyle aspects, as well as urinary composition, may also be associated with the infrequency of kidney stones in children. Since their organs are smaller, so will the volume of liquid that remains in renal cavities, reducing the likelihood of undesirable crystallization processes.
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ACCEPTED MANUSCRIPT Moreover, the continuous growth and renewal of tissues in children reduce the likelihood of pathological tissue calcification processes; thus, papillary COM renal calculi are rarely found in children. Finally, the much greater physical activity of children provides unfavorable conditions for the development of
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undesirable solid concretions, since immobilization favors renal stone development19.
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Conclusion
This study showed that urinary Mg was much higher and urinary Ca much lower
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in healthy children than in healthy adults. These findings, as well as morphoanatomic factors and lifestyle habits, may explain why nephrolithiasis is
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much less prevalent in children than in adults.
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References 1.
Grases F, Costa-Bauza A, Gomila I, et al. Urinary pH and renal lithiasis. Urol Res. 2012;40:41-46.
2.
Parvin M, Shakhssalim N, Basiri A, et al. The most important metabolic
3.
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risk factors in recurrent urinary stone formers. J Urol. 2011;8:99-106.
Grases F, Costa-Bauza A, Bonarriba CR, et al. On the origin of calcium oxalate monohydrate papillary renal stones. Urolithiasis. 2015;43:S33-
4.
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S39.
Scales CD Jr., Smith AC, Hanley JM, et al. Prevalence of kidney stones
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in the United States. Eur Urol. 2012;62:160-165. 5.
Turney BW, Reynard JM, Noble JG, et al. Trends in urological stone disease. BJU Int. 2012;109:1082-1087.
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VanDervoort K, Wiesen J, Frank R, et al. Urolithiasis in Pediatric
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Patients: A Single Center Study of Incidence, Clinical Presentation and Outcome. J Urol. 2007;177:2300-2305. 7.
Schaeffer AJ, Feng Z, Trock BJ, et al. Medical comorbidities associated
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with pediatric kidney stone disease. Urology. 2011;77:195-199. Tiwari R, Campfield T, Wittcopp C, et al. Metabolic syndrome in obese
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adolescents is associated with risk for nephrolithiasis. J Pediatr.
2012;160:615-620.
9.
Worcester EM, Coe FL. Clinical practice. Calcium kidney stones. N Engl J Med. 2010;363:954-963.
10.
Porowski T, Konstantynowicz J, Zoch-Zwierz W, et al. Spontaneous urinary calcium oxalate crystallization in hypercalciuric children. Pediatr Nephrol. 2009;24:1705-1710.
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Grases F, Costa-Bauza A, Ramis M, et al. Simple classification of renal calculi closely related to their micromorphology and etiology. Clin Chim Acta. 2002;322:29-36.
12.
Daudon M, Bader CA, Jungers P. Urinary calculi: review of classification
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methods and correlations with etiology. Scanning Microsc. 1993;7:10811104. 13.
Pieras E, Costa-Bauza A, Ramis M, et al. Papillary and nonpapillary
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calcium oxalate monohydrate renal calculi: comparative study of etiologic factors. ScientificWorldJournal. 2006;6:2411-2419.
Conti C, Brambilla L, Colombo C, et al. Stability and transformation
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14.
mechanism of weddellite nanocrystals studied by X-ray diffraction and infrared spectroscopy. Phys Chem Chem Phys. 2010;12:14560-14566. 15.
Conti C, Casati M, Colombo C, et al. Phase transformation of calcium
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oxalate dihydrate-monohydrate: Effects of relative humidity and new spectroscopic data. Spectrochim Acta. 2014;128:413-419. 16.
Tiselius HG. Aspects on estimation of the risk of calcium oxalate
17.
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crystallization in urine. Urol Int. 1991;47:255-259. Simeckova A, Zamrazil V, Cerovska J. Calciuria, magnesiuria and
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creatininuria--relation to age. Physiol Res. 1998;47:35-40.
18.
Massey L. Magnesium therapy for nephrolithiasis. Magnes Res.
2005;18:123-126.
19.
Hwang TI, Hill K, Schneider V, Pak CY. Effect of prolonged bedrest on the propensity for renal stone formation. J Clin Endocrinol Metab. 1988;66:109-112.
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ACCEPTED MANUSCRIPT Figure captions
Figure 1. Magnesium and calcium levels in the five groups of subjects. (A)
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*p<0.001 compared with the healthy adult group
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Magnesium/creatinine ratios (mg/mg) (B) Calcium/creatinine ratios (mg/mg).
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Tables Table 1 Mains anthropometrics measures in the five groups of subjects Sex
Group
Age (years)
Weight (Kg)
Height (cm)
Women
Mean (SD)
Mean (SD)
Mean (SD)
Healthy adults
42 (56%)
33 (44%)
38 (13)
66 (12)
167 (7)
Papillary COM
35 (56%)
27 (44%)
48 (14)
65 (12)
163 (7)
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Male
Unattached COM
70 (58%)
50 (42%)
54 (12)
71 (13)
164 (8)
COD
167 (67%)
81 (33%)
47 (13)
72 (12)
165 (8)
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Healthy Children 64 (61%) 41 (39%) 12 (3) 45 (14) 151 (18) COM calcium oxalate monohydrate, COD calcium oxalate dihydrate, SD standard deviation
ACCEPTED MANUSCRIPT Table 2 Diuresis and calcium, magnesium, phosphorus, oxalate, citrate and uric acid concentrations in 24-h urine samples from the five groups of subjects Group
P25
median
P75
Healthy adults
950
1200
1500
1175
1600
2025
Mg (mg/L)
1250
1600
2300
COD
1200
1500
Healthy children
638
810
Healthy adults
108
159
Papillary COM
82
120
Unattached COM
78
112
COD
142
195
Healthy children
43
73
Healthy adults
56
62
Papillary COM
45
58
38
0.02
165
<0.001
242
<0.001
127
<0.001
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178
75
63
<0.001
50
60
72
0.105
79
113
144
<0.001
490
648
904
367
497
694
0.001
314
505
751
<0.001
444
582
814
0.051
Healthy children
609
840
1062
0.001
Healthy adults
15
20
29
Papillary COM
12
17
24
0.006
Unattached COM
11
16
24
0.003
COD
13
18
24
0.045
Healthy children
17
22
29
0.132
Healthy adults
366
504
748
Papillary COM
239
377
586
Papillary COM Unattached COM
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COD
0.002
Unattached COM
232
369
527
<0.001
COD
267
393
539
<0.001
Healthy children
375
517
679
0.695
Healthy adults
367
465
605
Papillary COM
289
383
494
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Ur (mg/L)
<0.001
50
Unattached COM
Healthy adults
Cit (mg/L)
1128
0.087
Healthy children
Ox (mg/L)
<0.001
72
COD
P (mg/L)
<0.001
1850
204
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Ca (mg/L)
<0.001
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Papillary COM Diuresis (mL) Unattached COM
p-value
0.004
Unattached COM
262
375
492
<0.001
COD
291
417
550
0.023
Healthy children
394
546
690
0.022
Ca calcium, Mg magnesium, P phosphorous, Ox oxalate, Cit citrate, Ur uric acid, COM calcium oxalate monohydrate, COD calcium oxalate dihydrate. P-values correspond to the comparison of results of each group with the healthy adult group
ACCEPTED MANUSCRIPT Table 3 Ratios of calcium, magnesium, phosphorus, oxalate, citrate and uric acid to creatinine in 24-h urine samples from the five groups of subjects P75
Healthy adults
0,1
0,14
0,2
Papillary COM
0.09
0.14
0.20
0.615
Unattached COM
0.10
0.14
0.19
0.612
COD
0.15
0.19
Healthy children
0.05
0.08
Healthy adults
0,049
0.061
Papillary COM
0.049
0.063
Unattached COM
0.049
0.062
0.081
0.313
COD
0.048
0.062
0.081
0.267
Healthy children
0.087
0.109
0.125
<0.001
Healthy adults
0.51
0,61
0,79
Papillary COM
0.46
0.58
0.70
0.080
Unattached COM
0.11
<0.001
0,072 0.079
0.298
0.74
0.136
0.49
0.61
0.72
0.251
0.65
0.78
0.96
<0.001
19
25
32
18
22
30
0.330
20
26
36
0.242
18
25
33
0.993
Healthy children
23
30
37
0.001
Healthy adults
371
532
711
Papillary COM
254
438
749
0.108
Unattached COM
313
467
632
0.084
COD
252
401
594
<0.001
Healthy children
360
536
705
0.872
Healthy adults
0,41
0,45
0.52
Papillary COM
0.30
0.40
0.52
0.029
Unattached COM
0.35
0.41
0.51
0.045
COD
0.33
0.43
0.52
0.060
Healthy children
0.45
0.51
0.61
<0.001
Healthy adults Papillary COM Unattached COM
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COD
Ur/Cr (mg/mg)
<0.001
0.59
Healthy children
Cit/Cr (mg/g)
0.25
0.46
COD
Ox/Cr (mmol/mol)
p-value
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P/Cr (mg/mg)
median
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Mg/Cr (mg/mg)
P25
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Ca/Cr (mg/mg)
Group
Ca calcium, Mg magnesium, P phosphorous, Ox oxalate, Cit citrate, Ur uric acid, Cr creatinine, COM calcium oxalate monohydrate, COD calcium oxalate dihydrate. P-values correspond to the comparison of results of each group with the healthy adult group
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ACCEPTED MANUSCRIPT
S0090-4295(15)00624-X
DOI:
10.1016/j.urology.2015.06.028
Reference:
URL 19286
To appear in:
Urology
Received Date: 21 April 2015 Revised Date:
15 June 2015
Accepted Date: 22 June 2015
Please cite this article as: Grases F, Rodriguez A, Costa-Bauza A, Saez-Torres C, Rodrigo D, Gómez C, Mir-Perello C, Frontera G, Factors associated with the lower prevalence of nephrolithiasis in children compared to adults, Urology (2015), doi: 10.1016/j.urology.2015.06.028. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Factors associated with the lower prevalence of nephrolithiasis in children compared to adults Authors: Felix Grases1, Adrian Rodriguez1, Antonia Costa-Bauza1, Concepcion SaezTorres1, Dolores Rodrigo1, 2, Cristina Gómez3, Concepcion Mir-Perello1, 2, Guiem
1
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Frontera4
Laboratory of Renal Lithiasis Research, University Institute of Health Sciences
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Research (IUNICS-IdISPa), University of Balearic Islands, Palma de Mallorca, Spain.
Department of Pediatric Nephrology, Son Espases University Hospital, Palma
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2
de Mallorca, Spain 3
Laboratory Department, Son Espases University Hospital, Palma de Mallorca,
Spain
Research Unit, Son Espases University Hospital, Palma de Mallorca, Spain
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4
Corresponding author: Felix Grases
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Laboratory of Renal Lithiasis Research, Faculty of Sciences, University Institute
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of Health Sciences Research (IUNICS), University of Balearic Islands, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca, Spain. Telephone number: +34 971 17 32 57
e-mail: [email protected]
Word Count: 2512 Abstract Word Count: 190 Key words: nephrolithiasis in children; urinary lithogenic parameters; calcium oxalate nephrolithiasis; urinary calcium; urinary magnesium
ACCEPTED MANUSCRIPT Funding Support This work was supported by grant PI 14/00853 from the Ministerio de Economia y Competitividad (Gobierno de España), and by FEDER funds (European Union).
Cultura i Universitats for the fellowship FPI/1570/2013.
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Financial Disclosure
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A.R. is grateful to the European Social Fund and the Conselleria d’Educació,
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The authors declare that they have no relevant financial interests.
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Abstract Objectives: to determine the reasons behind the lower prevalence of kidney stones in children by assessing urinary lithogenic parameters in healthy children, healthy adults, and three groups of stone former patients.
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Methods: The study subjects included 75 healthy adults, 105 healthy children, 62 patients with previous calcium oxalate monohydrate papillary stones, 120 patients with previous calcium oxalate monohydrate unattached stones, and
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248 patients with previous calcium oxalate dihydrate stones. Twenty-four hour
measured.
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urine samples were collected, and the urinary lithogenic parameters were
Results: Calcium, magnesium and phosphorous concentration differed significantly
between
healthy
children
and
adults.
Except
citrate,
all
solute/creatinine ratios differed between healthy children and adults. However,
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these differences were much more important in the cases of calcium and magnesium. The calcium/creatinine ratio was 2-fold lower, while the magnesium/creatinine ratio was 2-fold higher, in healthy children than in healthy
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adults (p<0.001 each). The calcium/creatinine ratio was higher and the
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citrate/creatinine ratio lower in calcium oxalate dihydrate stone formers than in healthy adults.
Conclusions: Ratios of calcium and magnesium to creatinine, as well as morphoanatomic factors and lifestyle habits, may explain the lower prevalence of nephrolithiasis in children than in adults.
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Introduction Formation of renal stones results from a combination of several factors. These include urine composition, as urinary pH, calcium, magnesium, oxalate, phosphate and uric acid concentrations; the presence of crystallization
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inhibitors; and the inclusion of solid micro particles that act as heterogeneous nucleants1, 2. Other factors are related to kidney morphoanatomy, including the presence of cavities of low urodynamic efficacy that can retain microparticles,
SC
and calcified injuries to the papillary tissue that can induce the formation of calcium oxalate monohydrate papillary renal calculi3. These factors have been
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associated with metabolic abnormalities and with inadequate lifestyle habits, including diet and chronic drug consumption1-3.
The prevalence of renal lithiasis in adults has increased in recent decades, with 10% of the population being affected in many countries4. Although the
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prevalence of calcium oxalate nephrolithiasis is increasing in children and tends to be recurrent, renal stones are still infrequent during the pediatric period5,
6
and are often associated with an underlying metabolic disorder7, 8. Apart from
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congenital malformations of the urinary tract and urinary infection, recognized
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risk factors for kidney stone formation in children include hypercalciuria, hyperoxaluria, hypocitraturia, low urine volume and hyperuricosuria6, 9, 10. As in adults, hypertension and diabetes mellitus are also associated with renal stone formation in children7, 8. Furthermore, children in industrialized countries are subjected to the same environmental and lifestyle factors promoting stone formation as adults. Thus, although children and adults may present with similar metabolic profiles of factors that can induce renal stone development, renal lithiasis is much less frequent in children. To assess whether any urinary
1
ACCEPTED MANUSCRIPT parameters are associated with the lower prevalence of nephrolithiasis in children, we compared the urinary lithogenic parameters in healthy children,
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healthy adults and three different groups of adult stone formers.
2
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Material and Methods Renal calculi studies Spontaneously passed renal stones were analyzed in less than a week after their collection. The procedure used to analyze and study the calculi requires an
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appropriate combination of observation by means of macroscopic and microscopic conventional techniques (stereoscopic microscope; Optomic, Madrid, Spain) with physical techniques such as infrared spectrometry (Infrared
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Spectroscope Brucker IFS 66; Bruker, Ettlingen, Germany) and scanning electron microscopy (Hitachi S-530; Hitachi, Tokyo, Japan) coupled to X-ray
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microanalysis (Oxford Link Isis; Oxford, UK)11.
This analysis and study of calculi allows them to be classified into 11 main types, of which calcium oxalate renal calculi account for over 60% of all renal calculi11, 12.
distinguished:
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Three different types of calcium oxalate renal calculi can be clearly
a) Calcium oxalate monohydrate (COM) renal calculi developed on the
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renal papillary tissue. When these calculi are observed by a stereoscopic
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microscope or by scanning electron microscope, an attachment site to the papillae in clearly detectable, and their inner structure basically consists on a core near to the attachment site (concave zone), from which radially striated concentrically laminated layers originate13. They generally have a dark brown color. b) Unattached COM calculi consisting on a symmetrically round stone with a central core surrounded by columnar COM crystals emerging from the core. There calculi do not present attachment site to the renal papillae
3
ACCEPTED MANUSCRIPT epithelium although their color is very similar to the papillary COM calculi13. c) Calcium oxalate dihydrate (COD) renal calculi, typically consisting on randomly distributed yellowish bipyramidal COD crystals, which form
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primary aggregates11, 12
The two different phases of calcium oxalate that can be found in renal calculi (COM and COD) present different crystal morphology and infrared spectra.
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COM is the thermodynamically stable phase and COD is the kinetically favorable but thermodynamically unstable phase, and for this reason COD
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crystals slowly transform into the stable COM14, 15.
In fact, most COD renal calculi present transformation although to varying degrees, in such a way that the infrared spectrum of a calculus may correspond to COM, even when the phase formed in urine was COD.
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Nevertheless, the morphology of COM and COD calculi is clearly different, even after COD transformation into COM, since an originally “pure” COD calculus still presents frames corresponding to the COD bipyramidal
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crystals, although containing some brown areas. In this study, we have included three groups of calcium oxalate stone forming
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patients: one group of papillary calcium oxalate monohydrate (papillary COM) stone-formers, whose calculi clearly present an attachment site to the papillae; one group of unattached calcium oxalate monohydrate (unattached COM) stone-formers, whose calculi do not present attachment site to the papillae; and one group of calcium oxalate dihydrate stone formers, also including in this group those patients with mixed COM/COD calculi in which COM comes from the transformation of COD.
4
ACCEPTED MANUSCRIPT Study subjects The study subjects included 75 healthy adults and 105 healthy children and young teenagers aged 5-17 years with no history of nephrolithiasis; 62 patients with previous calcium oxalate monohydrate papillary stones (papillary COM
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group); 120 patients with previous calcium oxalate monohydrate unattached stones (unattached COM group); and 248 patients with previous calcium oxalate dihydrate stones (COD group). None of the healthy adults or children
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had chronic diseases or was being treated with any medications. They were asymptomatic at the time of the urine collection, and did never have, to their
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knowledge, any lithiasic episode such as sands, nephritic colic or positive radiological image. Children were recruited from different schools in Majorca, both state and private ones. Healthy adults were recruited from hospital and university workers. This healthy adult group presented similar age and
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distribution that the stone-former groups. All participants were asked not to change their usual patterns of food consumption, liquid intake and physical activity during the sampling period. Each participant, or his/her legal
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representative, provided written informed consent for their clinical samples to be used in scientific studies. This study was approved by the ethics committee of
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our institution.
Urine collection and analysis All subjects were on an unregulated diet at the time of urine collection and none of the previous stone-formers was receiving any pharmacological treatment. Twenty-four hour urine samples were collected from each subject into sterile flasks containing thymol as a preservative. Urinary volume was recorded and
5
ACCEPTED MANUSCRIPT the samples were analyzed 3-4 h after collection was finished. Urine from patients in the papillary COM, unattached COM, and COD groups was collected 1-2 months after stone passage/removal. The main lithogenic biochemical parameters were measured on a Modular
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Autoanalyzer (Roche Diagnostics, Indianapolis, IN, USA). Urinary phosphorus (P) was measured by the ammonium molybdate reduction method; urinary magnesium (Mg) by colorimetric reaction with Xylidyl blue; calcium (Ca) by a
SC
colorimetric reaction with o-cresolphthalein; uric acid (Ur) by the uricase method; and creatinine (Cr) by the kinetic Jaffe method. Urinary citrate (Cit) was
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measured spectrophotometrically by an enzymatic assay (citrate lyase) using a test kit (R-Biopharm, Germany). Urinary oxalate (Ox) was determined enzymatically by the oxalate oxidase/peroxidase method (LTA, Milano, Italy). We also measured the AP Index according to Tisselius formula16: AP(index) .
were all the solutes were expressed in mmoles, and
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= 1.9
. . .
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the volume expressed in liters.
6
ACCEPTED MANUSCRIPT Statistical Analysis The normality of the data was assessed using Shapiro-Wilk tests. As most of the data were not normally distributed, median and 25th and 75th percentiles were determined and presented graphically as box plots. Differences between
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the healthy adult group and each of the other groups were assessed using the Mann Whitney U test, followed by Bonferroni adjustment. Thus, a p-value <0.0125 was considered statistically significant. The differences in the AP index
SC
between the 5 groups was assessed by one way ANOVA followed by Tukey test. All statistical analyses were performed using SPSS for Windows version
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2.1 software.
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Results The 610 subjects were divided into five groups: 75 healthy adults, 105 healthy children, 62 patients with previous calcium oxalate monohydrate papillary stones, 120 patients with previous calcium oxalate monohydrate unattached
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stones and 248 patients with previous calcium oxalate dihydrate stones. The demographic, clinical, and anthropometric factors in these five groups are shown in Table 1 and their urinary biochemistry in Table 2. The Mg, Ca and P
SC
concentrations in healthy children and healthy adults differed significantly. However, as expected, diuresis values differed markedly in healthy children and
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healthy adults, as well as between healthy adults and the three groups of lithiasic patients. In most cases, increases in diuresis were associated with lower solute concentrations. However, despite diuresis being higher, Ca concentration was significantly higher in the COD than in the healthy adult
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group. Similarly, despite urinary output being lower, Ca concentration was lower in healthy children than in healthy adults. Table 3 shows solute/creatinine ratios in the five groups of subjects. Except
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citrate, all solutes/creatinine ratios differed significantly between healthy adults
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and healthy children. However, in the cases of Ur, Ox and P, the differences in the ratios are much lower than in the cases of Ca and Mg. Box plots showed that Mg/Cr was similar in the papillary COM, unattached COM, COD and healthy adult groups, but was about 2-fold higher in healthy children than in healthy adults (p<0.001, Fig. 1A). Ca/Cr ratios in the papillary COM and unattached COM groups were similar to that in healthy adults, but was significantly higher in the COD group (p<0.001) and significantly lower in healthy children (p<0.001) than in healthy adults (Fig. 1B).
8
ACCEPTED MANUSCRIPT In addition, Cit/Cr ratios differed significantly between the COD and healthy adult groups (p<0.001). Regarding measures of urinary supersaturation, there were no statistical differences between the AP index in the papillary COM group, the unattached
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COM group and the healthy adult group (means: 1.00; 1.03 and 1.18 respectively). However, COD group has a mean AP index of 1.46 (p<0.001) and
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the healthy children group has a mean AP index of 0.60 (p<0.001).
9
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Comment Urinary composition is a key factor in kidney stone formation. To determine whether any urinary parameter could explain the lower prevalence of nephrolithiasis in childhood, we compared the main urinary biochemical
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parameters in healthy children and adults, as well as in adults with and without lithiasis.
As expected, we found that diuresis was lower in healthy children than in
SC
healthy adults, but was higher in all three groups of lithiasic patients than in healthy adults. Urine was collected from lithiasic patients 1-2 months after the
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lithiasic episode. Thus, the highest diuresis values in the stone former groups may have been due to higher fluid intake to prevent stone recurrence. In general, groups with higher diuresis had lower solute concentrations. However, Ca concentration was significantly higher in the COD than in the healthy adult
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group, despite the higher diuresis in the COD group. Similarly, Ca concentration was significantly lower in healthy children than in healthy adults, despite the lower urinary output of children. Although crystallization risk is calculated from
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solute concentrations, concentrations alone may be misleading, since
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differences between groups may be due to differences in diuresis values. Furthermore, we could not compare the absolute excretion of solutes in children and adults because of differences in their anthropometric measurements. Thus, all urinary solutes excretions were expressed as their ratio to creatinine. Ratios of Ox, P and Ur to creatinine were slightly different between healthy children and adults, probably due to a lower creatinine concentration in childhood17. The difference was much more important in the case of magnesium, since its median ratio was almost double in healthy children than in
10
ACCEPTED MANUSCRIPT adults, difference that cannot be explained only by the lower creatinine concentration. Ca/Cr values not only did not increase in the children group as was expected but on the contrary we found much lower values than in adults, which can only be explained by low amounts of net calcium excretion.
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Mg/Cr ratios differed significantly between healthy children and healthy adults. In contrast, Mg/Cr ratios in the three stone former groups were similar to that in the healthy adult group. Mg concentrations and Mg/Cr ratios are higher in
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children and may be due to greater absorption of Mg17. Mg protects against calcium oxalate nephrolithiasis, since it competes with calcium in binding to
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oxalate. Since magnesium oxalate is 100 times more soluble than calcium oxalate, it does not crystallize in the kidneys18. The two-fold higher Mg/Cr ratio in children than in adults suggests that Mg may protect children against the formation of calcium oxalate kidney stones.
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Ca/Cr ratios also differed significantly between healthy children and healthy adults. Urinary Ca excretion is increased by intake of dairy products, sodium, animal protein and glucose, with many of these foods more frequently
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consumed by young people. However, urinary Ca/Cr ratio was significantly lower in children than in adults, perhaps due to the higher rates of bone
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turnover that occur during growth periods in childhood. The lower urinary Ca concentrations
in
children
may
protect
them
against
calcium
stone
development. As expected, however, the COD group had the highest urinary Ca concentration among the five subject groups, resulting in the formation of thermodynamically unstable COD stones11. Cit/Cr ratio was significantly lower in the COD than in the healthy adult group (p<0.001). Cit is an inhibitor of kidney stone formation that also forms
11
ACCEPTED MANUSCRIPT complexes with Ca, reducing the free Ca concentration in urine. COD stone formation is usually due to a high Ca concentration in urine, suggesting that the lower Cit concentrations in this group contribute to a higher free Ca concentration.
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The AP index values indicate that there are no statistical difference in calcium oxalate urinary supersaturation between the papillary COM group, the unattached COM group and the healthy adult group. This can be explained
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since the papillary COM calculi start to develop as a result of an injury in the renal papillae tissue, and this is independent on urinary supersaturation.
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Unattached COM calculi are associated to normal supersaturation values and to the presence of retained heterogeneous nucleants (uric acid, hydroxyapatite, organic
matter,
etc)13.
However,
COD
group
has
a
higher
urinary
supersaturation (p<0.001) when compared with the healthy adult group. As
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expected, the higher calcium and lower citrate excretion increase urinary supersaturation in this group of patients. Precisely, this higher urinary supersaturation is the explanation of the kinetically favorable COD crystal Finally,
healthy
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development.
children
group
has
a
lower
urinary
supersaturation than the rest of the groups (p<0.001). In this case, the lower
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calcium and higher magnesium excretion result in a lower calcium oxalate supersaturation degree. This lower AP index may provide more evidence for the lower prevalence of nephrolithiasis in children. Morphoanatomic factors and lifestyle aspects, as well as urinary composition, may also be associated with the infrequency of kidney stones in children. Since their organs are smaller, so will the volume of liquid that remains in renal cavities, reducing the likelihood of undesirable crystallization processes.
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ACCEPTED MANUSCRIPT Moreover, the continuous growth and renewal of tissues in children reduce the likelihood of pathological tissue calcification processes; thus, papillary COM renal calculi are rarely found in children. Finally, the much greater physical activity of children provides unfavorable conditions for the development of
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undesirable solid concretions, since immobilization favors renal stone development19.
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Conclusion
This study showed that urinary Mg was much higher and urinary Ca much lower
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in healthy children than in healthy adults. These findings, as well as morphoanatomic factors and lifestyle habits, may explain why nephrolithiasis is
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much less prevalent in children than in adults.
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References 1.
Grases F, Costa-Bauza A, Gomila I, et al. Urinary pH and renal lithiasis. Urol Res. 2012;40:41-46.
2.
Parvin M, Shakhssalim N, Basiri A, et al. The most important metabolic
3.
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risk factors in recurrent urinary stone formers. J Urol. 2011;8:99-106.
Grases F, Costa-Bauza A, Bonarriba CR, et al. On the origin of calcium oxalate monohydrate papillary renal stones. Urolithiasis. 2015;43:S33-
4.
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S39.
Scales CD Jr., Smith AC, Hanley JM, et al. Prevalence of kidney stones
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in the United States. Eur Urol. 2012;62:160-165. 5.
Turney BW, Reynard JM, Noble JG, et al. Trends in urological stone disease. BJU Int. 2012;109:1082-1087.
6.
VanDervoort K, Wiesen J, Frank R, et al. Urolithiasis in Pediatric
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Patients: A Single Center Study of Incidence, Clinical Presentation and Outcome. J Urol. 2007;177:2300-2305. 7.
Schaeffer AJ, Feng Z, Trock BJ, et al. Medical comorbidities associated
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with pediatric kidney stone disease. Urology. 2011;77:195-199. Tiwari R, Campfield T, Wittcopp C, et al. Metabolic syndrome in obese
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adolescents is associated with risk for nephrolithiasis. J Pediatr.
2012;160:615-620.
9.
Worcester EM, Coe FL. Clinical practice. Calcium kidney stones. N Engl J Med. 2010;363:954-963.
10.
Porowski T, Konstantynowicz J, Zoch-Zwierz W, et al. Spontaneous urinary calcium oxalate crystallization in hypercalciuric children. Pediatr Nephrol. 2009;24:1705-1710.
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Grases F, Costa-Bauza A, Ramis M, et al. Simple classification of renal calculi closely related to their micromorphology and etiology. Clin Chim Acta. 2002;322:29-36.
12.
Daudon M, Bader CA, Jungers P. Urinary calculi: review of classification
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methods and correlations with etiology. Scanning Microsc. 1993;7:10811104. 13.
Pieras E, Costa-Bauza A, Ramis M, et al. Papillary and nonpapillary
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calcium oxalate monohydrate renal calculi: comparative study of etiologic factors. ScientificWorldJournal. 2006;6:2411-2419.
Conti C, Brambilla L, Colombo C, et al. Stability and transformation
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14.
mechanism of weddellite nanocrystals studied by X-ray diffraction and infrared spectroscopy. Phys Chem Chem Phys. 2010;12:14560-14566. 15.
Conti C, Casati M, Colombo C, et al. Phase transformation of calcium
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oxalate dihydrate-monohydrate: Effects of relative humidity and new spectroscopic data. Spectrochim Acta. 2014;128:413-419. 16.
Tiselius HG. Aspects on estimation of the risk of calcium oxalate
17.
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crystallization in urine. Urol Int. 1991;47:255-259. Simeckova A, Zamrazil V, Cerovska J. Calciuria, magnesiuria and
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creatininuria--relation to age. Physiol Res. 1998;47:35-40.
18.
Massey L. Magnesium therapy for nephrolithiasis. Magnes Res.
2005;18:123-126.
19.
Hwang TI, Hill K, Schneider V, Pak CY. Effect of prolonged bedrest on the propensity for renal stone formation. J Clin Endocrinol Metab. 1988;66:109-112.
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ACCEPTED MANUSCRIPT Figure captions
Figure 1. Magnesium and calcium levels in the five groups of subjects. (A)
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*p<0.001 compared with the healthy adult group
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Magnesium/creatinine ratios (mg/mg) (B) Calcium/creatinine ratios (mg/mg).
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Tables Table 1 Mains anthropometrics measures in the five groups of subjects Sex
Group
Age (years)
Weight (Kg)
Height (cm)
Women
Mean (SD)
Mean (SD)
Mean (SD)
Healthy adults
42 (56%)
33 (44%)
38 (13)
66 (12)
167 (7)
Papillary COM
35 (56%)
27 (44%)
48 (14)
65 (12)
163 (7)
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Male
Unattached COM
70 (58%)
50 (42%)
54 (12)
71 (13)
164 (8)
COD
167 (67%)
81 (33%)
47 (13)
72 (12)
165 (8)
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Healthy Children 64 (61%) 41 (39%) 12 (3) 45 (14) 151 (18) COM calcium oxalate monohydrate, COD calcium oxalate dihydrate, SD standard deviation
ACCEPTED MANUSCRIPT Table 2 Diuresis and calcium, magnesium, phosphorus, oxalate, citrate and uric acid concentrations in 24-h urine samples from the five groups of subjects Group
P25
median
P75
Healthy adults
950
1200
1500
1175
1600
2025
Mg (mg/L)
1250
1600
2300
COD
1200
1500
Healthy children
638
810
Healthy adults
108
159
Papillary COM
82
120
Unattached COM
78
112
COD
142
195
Healthy children
43
73
Healthy adults
56
62
Papillary COM
45
58
38
0.02
165
<0.001
242
<0.001
127
<0.001
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178
75
63
<0.001
50
60
72
0.105
79
113
144
<0.001
490
648
904
367
497
694
0.001
314
505
751
<0.001
444
582
814
0.051
Healthy children
609
840
1062
0.001
Healthy adults
15
20
29
Papillary COM
12
17
24
0.006
Unattached COM
11
16
24
0.003
COD
13
18
24
0.045
Healthy children
17
22
29
0.132
Healthy adults
366
504
748
Papillary COM
239
377
586
Papillary COM Unattached COM
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COD
0.002
Unattached COM
232
369
527
<0.001
COD
267
393
539
<0.001
Healthy children
375
517
679
0.695
Healthy adults
367
465
605
Papillary COM
289
383
494
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Ur (mg/L)
<0.001
50
Unattached COM
Healthy adults
Cit (mg/L)
1128
0.087
Healthy children
Ox (mg/L)
<0.001
72
COD
P (mg/L)
<0.001
1850
204
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Ca (mg/L)
<0.001
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Papillary COM Diuresis (mL) Unattached COM
p-value
0.004
Unattached COM
262
375
492
<0.001
COD
291
417
550
0.023
Healthy children
394
546
690
0.022
Ca calcium, Mg magnesium, P phosphorous, Ox oxalate, Cit citrate, Ur uric acid, COM calcium oxalate monohydrate, COD calcium oxalate dihydrate. P-values correspond to the comparison of results of each group with the healthy adult group
ACCEPTED MANUSCRIPT Table 3 Ratios of calcium, magnesium, phosphorus, oxalate, citrate and uric acid to creatinine in 24-h urine samples from the five groups of subjects P75
Healthy adults
0,1
0,14
0,2
Papillary COM
0.09
0.14
0.20
0.615
Unattached COM
0.10
0.14
0.19
0.612
COD
0.15
0.19
Healthy children
0.05
0.08
Healthy adults
0,049
0.061
Papillary COM
0.049
0.063
Unattached COM
0.049
0.062
0.081
0.313
COD
0.048
0.062
0.081
0.267
Healthy children
0.087
0.109
0.125
<0.001
Healthy adults
0.51
0,61
0,79
Papillary COM
0.46
0.58
0.70
0.080
Unattached COM
0.11
<0.001
0,072 0.079
0.298
0.74
0.136
0.49
0.61
0.72
0.251
0.65
0.78
0.96
<0.001
19
25
32
18
22
30
0.330
20
26
36
0.242
18
25
33
0.993
Healthy children
23
30
37
0.001
Healthy adults
371
532
711
Papillary COM
254
438
749
0.108
Unattached COM
313
467
632
0.084
COD
252
401
594
<0.001
Healthy children
360
536
705
0.872
Healthy adults
0,41
0,45
0.52
Papillary COM
0.30
0.40
0.52
0.029
Unattached COM
0.35
0.41
0.51
0.045
COD
0.33
0.43
0.52
0.060
Healthy children
0.45
0.51
0.61
<0.001
Healthy adults Papillary COM Unattached COM
AC C
EP
TE D
COD
Ur/Cr (mg/mg)
<0.001
0.59
Healthy children
Cit/Cr (mg/g)
0.25
0.46
COD
Ox/Cr (mmol/mol)
p-value
RI PT
P/Cr (mg/mg)
median
SC
Mg/Cr (mg/mg)
P25
M AN U
Ca/Cr (mg/mg)
Group
Ca calcium, Mg magnesium, P phosphorous, Ox oxalate, Cit citrate, Ur uric acid, Cr creatinine, COM calcium oxalate monohydrate, COD calcium oxalate dihydrate. P-values correspond to the comparison of results of each group with the healthy adult group
AC C
EP
TE D
M AN U
SC
RI PT
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