title: Combined vitamin D and calcium supplementation in vitamin D inadequate patients with urolithiasis: Impact on hypercalciuria and de novo stone formation.
abstract: BACKGROUND
  We examined the effect of combined vitamin D and calcium supplementation (VDCS) on urinary calcium excretion and de novo stone formation in vitamin D inadequate (VDI) urolithiasis patients.
  
  
  METHODS
  We retrospectively reviewed the data of VDI patients (serum 25-hydroxyvitamin D <75 nmol/L) followed at a tertiary stone centre between September 2009 and December 2014. VDI patients with history of urolithiasis, who were placed on VDCS for abnormal bone mineral density or hyperoxaluria, were included. Hypercalciuric patients and patients on thiazide diuretics were excluded. Metabolic stone workup and two 24-hour urine collections were performed before and after VDCS.
  
  
  RESULTS
  In total, we included 34 patients, with a mean age of 54.8 years and a mean body mass index of 25.7 kg/m(2). After VDCS, there was a significant increase in the mean serum 25-hydroxyvitamin D (52.0 vs. 66.4 nmol/L, p < 0.001) and the mean urinary calcium excretion (3.80 vs. 5.64 mmol/d, p < 0.001). Eight (23.5%) patients developed de novo hypercalciuria. After a median follow-up of 39 (range: 7-60) months, 50% of hypercalciuric patients developed stones compared with 11.5% of non-hypercalciuric patients (p = 0.038).
  
  
  CONCLUSIONS
  This study showed a significant effect of combined VDCS on mean urinary calcium excretion, de novo hypercalciuria, and stone development in VDI patients with history of urolithiasis. Therefore, VDI urolithiasis patients receiving VDCS are advised to have monitoring with 24-hour urine collections and imaging studies. Although small, our sample size was good enough to validate the statistical outcomes. Prospective studies are needed to confirm these results.
authors.affiliation: Division of Urology, McGill University Health Centre, McGill University, Montreal, QC;
authors.forename: Charles
authors.initials: C
authors.lastname: Hesswani
authors.affiliation: Division of Urology, McGill University Health Centre, McGill University, Montreal, QC;; Department of Urology, Benha University Hospital, Benha University, Benha, Egypt;
authors.forename: Yasser A
authors.initials: YA
authors.lastname: Noureldin
authors.affiliation: Division of Urology, McGill University Health Centre, McGill University, Montreal, QC;; Department of Urology, Suez Canal University, Ismailia, Egypt.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Elkoushy
authors.affiliation: Division of Urology, McGill University Health Centre, McGill University, Montreal, QC;
authors.forename: Sero
authors.initials: S
authors.lastname: Andonian