title: Vascular calcification and bone mineral density in recurrent kidney stone formers.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
authors: Centre for Nephrology, Royal Free Campus and Hospital, University College London Medical School, London, United Kingdom; Adult Nephrology Unit, Shaare Zedek Medical Center, Jerusalem, Israel; lshavit@szmc.org.il.
authors: Linda
authors: L
authors: Shavit
authors: Centre for Nephrology, Royal Free Campus and Hospital, University College London Medical School, London, United Kingdom;
authors: Daniela
authors: D
authors: Girfoglio
authors: Centre for Nephrology, Royal Free Campus and Hospital, University College London Medical School, London, United Kingdom;
authors: Vivek
authors: V
authors: Vijay
authors: Nephrology and Transplantation, King's Health Partners Academic Health Sciences Centre, Guy's Hospital Campus, London, United Kingdom; and.
authors: David
authors: D
authors: Goldsmith
authors: Division of Nephrology, Catholic University of the Sacred Heart, Rome, Italy.
authors: Pietro Manuel
authors: PM
authors: Ferraro
authors: Centre for Nephrology, Royal Free Campus and Hospital, University College London Medical School, London, United Kingdom;
authors: Shabbir H
authors: SH
authors: Moochhala
authors: Centre for Nephrology, Royal Free Campus and Hospital, University College London Medical School, London, United Kingdom;
authors: Robert
authors: R
authors: Unwin
mesh_terms: D000328:Adult; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging; D001018:Aortic Diseases / Q000175:diagnosis / Q000453:epidemiology*; D001027:Aortography / Q000379:methods; D015519:Bone Density; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D053565:Hypercalciuria / Q000175:diagnosis / Q000453:epidemiology; D007669:Kidney Calculi / Q000175:diagnosis / Q000453:epidemiology*; D016014:Linear Models; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010024:Osteoporosis / Q000175:diagnosis / Q000453:epidemiology*; D010044:Outpatient Clinics, Hospital; D015995:Prevalence; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013131:Spine / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D061205:Vascular Calcification / Q000175:diagnosis / Q000453:epidemiology*
keywords: cardiovascular; kidney stones; vascular calcification
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