Vascular calcification and bone mineral density in recurrent kidney stone formers - PubMed (original) (raw)

Vascular calcification and bone mineral density in recurrent kidney stone formers

Linda Shavit et al. Clin J Am Soc Nephrol. 2015.

Abstract

Background and objectives: Recent epidemiologic studies have provided evidence for an association between nephrolithiasis and cardiovascular disease, although the underlying mechanism is still unclear. Vascular calcification (VC) is a strong predictor of cardiovascular morbidity and the hypothesis explored in this study is that VC is more prevalent in calcium kidney stone formers (KSFs). The aims of this study were to determine (1) whether recurrent calcium KSFs have more VC and osteoporosis compared with controls and (2) whether hypercalciuria is related to VC in KSFs.

Design, setting, participants, & measurements: This is a retrospective, matched case-control study that included KSFs attending an outpatient nephrology clinic of the Royal Free Hospital (London, UK) from 2011 to 2014. Age- and sex-matched non-stone formers were drawn from a list of potential living kidney donors from the same hospital. A total of 111 patients were investigated, of which 57 were KSFs and 54 were healthy controls. Abdominal aortic calcification (AAC) and vertebral bone mineral density (BMD) were assessed using available computed tomography (CT) imaging. The prevalence, severity, and associations of AAC and CT BMD between KSFs and non-stone formers were compared.

Results: Mean age was 47±14 years in KSFs and 47±13 in non-stone formers. Men represented 56% and 57% of KSFs and non-stone formers, respectively. The prevalence of AAC was similar in both groups (38% in KSFs versus 35% in controls, P=0.69). However, the AAC severity score (median [25th percentile, 75th percentile]) was significantly higher in KSFs compared with the control group (0 [0, 43] versus 0 [0, 10], P<0.001). In addition, the average CT BMD was significantly lower in KSFs (159±53 versus 194 ±48 Hounsfield units, P<0.001). A multivariate model adjusted for age, sex, high BP, diabetes, smoking status, and eGFR confirmed that KSFs have higher AAC scores and lower CT BMD compared with non-stone formers (P<0.001 for both). Among stone formers, the association between AAC score and hypercalciuria was not statistically significant (P=0.86).

Conclusions: This study demonstrates that patients with calcium kidney stones suffer from significantly higher degrees of aortic calcification than age- and sex-matched non-stone formers, suggesting that VC may be an underlying mechanism explaining reported associations between nephrolithiasis and cardiovascular disease. Moreover, bone demineralization is more prominent in KSFs. However, more data are needed to confirm the possibility of potentially common underlying mechanisms leading to extraosseous calcium deposition and osteoporosis in KSFs.

Keywords: cardiovascular; kidney stones; vascular calcification.

Copyright © 2015 by the American Society of Nephrology.

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Figures

Figure 1.

Figure 1.

Distribution of AAC score in KSFs and healthy controls. The plot shows the distribution of AAC score in participants with and without stones. In the multivariate model adjusted for age, sex, high BP, diabetes, smoking status, and eGFR, the relationship between AAC severity score and kidney stone disease remained significant (P<0.001). The bottom and top of the box represent the first and third quartiles, the line represents the second quartile (median), the whiskers represent 1.5 times the interquartile range of the first and third quartiles, and the circles represent any values lying outside the whiskers. AAC, aortic calcification; KSF, kidney stone former.

Figure 2.

Figure 2.

Distribution of CT BMD in KSFs and healthy controls. The plot shows the distribution of CT BMD in participants with and without stones. In the multivariate model adjusted for age, sex, high BP, diabetes, smoking status and eGFR, the relationship between osteoporosis and kidney stone disease remained significant (P<0.001). The bottom and the top of the box represent the first and third quartiles, the line represents the second quartile (median), the whiskers represent 1.5 times the interquartile range of the first and third quartiles, and the circles represent any values lying outside the whiskers. BMD, bone mineral density; CT, computed tomography.

Figure 3.

Figure 3.

Distribution of urinary excretion of calcium among KSFs with and without vascular calcification. Urinary excretion of calcium was roughly similar among patients with and without an AAC score >0 (median 280 mg/d [120, 400] versus 288 mg/d [140, 360], _P_=0.86).The bottom and the top of the box represent the first and third quartiles, the line represents the second quartile (median), and the whiskers represent 1.5 times the interquartile range of the first and third quartiles.

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