Bone Abstracts

Background: Bone fragility and vascular calcifications are to the two main morbidities of the mineral and bone disorders associated with chronic kidney disease (CKD), resulting from a combination of abnormalities such as impaired GH axis, vitamin D deficiency, hyperparathyroidism, increased FGF23 levels, hypogonadism, denutrition and drug toxicity.

Methods: In a single-centre ancillary study of the longitudinal prospective European 4C study (Cardiovascular Comorbidities in Children with CKD), we evaluated bone and cardiovascular status in 22 teenagers with pre-dialysis CKD. We used the tridimensional non-invasive high resolution peripheral quantitative computed tomography (HR-pQCT, SCANCO), as well as pulse wave velocity (PWV), carotid intima-media thickness (IMT) and ambulatory blood pressure (BP) monitoring (ABPM). Statistical analyses were performed with non-parametric tests (SPSS).

Results: At a mean age of 14.1±2.7 years (skeletal age 12.8±2.5 years, 16 boys), average height and BMI were 152±15 cm and 18.9±2.5 kg/m² corresponding to SDS of −0.8±1.2 and 0.0±1.0 respectively. Median serum phosphorus was 1.41 (0.90–2.58) mmol/l for an average GFR of 32±10 ml/min per 1.73 m². PTH and 25OH-vitamin D levels were 107 (29–359) pg/ml and 66±18 nmol/l respectively. Bivariate analyses between bone and cardiovascular data showed strong positive associations between trabecular densities/thickness and BP (24-h and daytime ABPM results for systolic, diastolic and mean BP), the Spearman correlation coefficient ranging from 0.46 to 0.65 (P<0.05). Trabecular thickness was also strongly associated with PWV (r=0.598, P=0.003). In contrast, IMT results were not associated with any bone parameter.

Conclusion: For the first time, these results suggest a significant interplay between trabecular bone and BP in teenagers with pre-dialysis CKD: the greater the trabecular thickness, the greater the PWV and ABPM parameters, and thus the greater the arterial stiffness. These data seem conflicting with previously published studies in adults showing increased vascular calcifications with decreased bone densities as assessed by DXA. In pediatric CKD however, one may hypothesize that the use of calcium therapies may be efficient for improving bone quality while deleterious for vessels.