Vitamin D is not seen anymore only as a phosphocalcic and bone hormone, but also as having an effect on global health (anti-infective, anti-inflammatory, anti-tumour roles and cardiovascular protection).

Until recently, vitamin D repletion was defined as the minimal concentration that enables the prevention of rickets in children and osteomalacia in adults, i.e, approximately 8 ng/mL (20 nmol/L). However, most of the international experts agree to set minimal threshold of 25 OH vitamin D serum concentration, higher than the one previously admitted, with a limit of 20 ng/mL (50 nmol/L) to define a vitamin D deficiency and a limit of 30 ng/mL (75 nmol/L) to define vitamin D insufficiency.

Recommendations for Vit D supplementation in healthy children were updated in France in 2012. The invariable supplementation of infants and toddlers is efficient since deficiency-related rickets have almost disappeared; however there is very few information in ill children populations.

Vit D supplementation tolerance is usually considered as good and over-dosage risks are low, however these studies were conducted more than 30 years ago, and as far as we know, there is no study about calcium urinary excretion kinetics after intake of a 100 000 IU vial of cholecalciferol (Uvedose®). When 25 OH vitamin D serum concentrations exceeds 200 ng/mL, which is very rare in daily practice, toxic effects of Vit D may theoretically be observed, particularly hypercalcemia and hypercalciuria.

Vitamin D deficit is very common in children with chronic kidney disease (CKD) with a 50 to 92% prevalence depending on the studies; it it is a risk factor for secondary hyperparathyroidism.

Although international guidelines regarding the care of CKD children recommend 25 OH vitamin D serum concentrations over 75 nmol/L, there are no practical recommendations in terms of dose and frequency of native Vit D treatment.

Therefore, the objectives of the present study has are the following:

• to validate prospectively the efficacy of our service usual care for Vit D supplementation of children and adolescents seen in the paediatric nephrology department.
• and to study the effect of Vit D supplementation (100 000 IU vial of cholecalciferol) on calciuria in these patients.

Inclusion Criteria:

• Age : between [18 mo et 18 yo[

• Patients seen in the paediatric nephrology service and having :

  • Chronic kidney disease
  • Renal transplant
  • Stable nephrotic syndrome (i.e., normal protidemia at inclusion)

• Initial 25 OH vitamin D concentration < 75nmol/l

• Patient agree to participate (if old enough to give his agreement) and written informed consent signed by parents

• Patients affiliated within the French universal healthcare system

Exclusion Criteria:

- Contraindication to 100 000 IU Uvedose® treatment (according to the Summary of Product Characteristics: known hypersensitivity to vitamin D or hypercalcemia, hypercalciuria or nephrolithiasis).](streamdown:incomplete-link)