Category: Clinical Stones: Medical Management
Introduction & Objective :
There is a high prevalence of vitamin D [25(OH)D] deficiency in temperate regions of the world and among stone formers. Our study aimed to estimate the prevalence of vitamin D deficiency in a metabolic stone clinic patient population in southern Ontario, Canada. We also wished to determine the presence of concomitant metabolic risk factors and the potential impact on stone recurrence.
A retrospective analysis of a metabolic stone clinic database from September 2001 to February 2017 was performed including patient demographics, clinical data and metabolic evaluations. Patients were excluded if they had incomplete evaluations or inappropriately collected 24-hour urine collections (24-HUC) based on urine creatinine levels. Patients identified to have low 25(OH)D levels were individually counselled by a registered dietician on dietary and medical supplementation. A multivariate regression analysis was used to determine the correlation between 24-HUC abnormalities and 25(OH)D and parathyroid hormone (PTH) levels. The effect of normalizing 25(OH)D and PTH levels on 24-HUC findings and stone recurrence was evaluated with a Pearson’s chi-squared coefficient.
Our cohort of 608 patients had a mean age of 52 ± 14 years, were 54.1% male, and had a mean body mass index of 29.8 ± 7. Stone composition was most predominantly calcium oxalate (71.3%). 25(OH)D deficiency and secondary hyperparathyroidism (SHPT) was identified in 404 (66.40%) and 56 (9.2%) patients respectively. SHPT was correlated with an increased rate of 24-HUC abnormalities (p<0.0001). Follow-up in 277 (45.6%) patients showed improvement or normalization in 25(OH)D levels in 68 (45.6%) and 39 (26.2%) patients respectively. 38 (67.0%) patients had resolution of their SHPT with increase of their 25(OH)D levels; which was associated with significant improvement in urinary calcium (p<0.0001), sodium (p=0.004), phosphate (p<0.0001), and citrate (p=0.036) levels. 40 (26.8%) patients developed recurrent stones within a median follow-up of 17.9 ± 34 months. There was no correlation between 25(OH)D or PTH level correction and recurrent stones.
25(OH)D inadequacy is highly prevalent among high risk stone formers; especially in Northern climates. 25(OH)D and PTH should be included in metabolic stone evaluations to allow for the identification of SHPT. Correction of SHPT through individualized dietary counseling and with 25(OH)D supplementation may improve 24-HUC parameters.
Jennifer Bjazevic– Endourology Fellow, Western University, London, Ontario, Canada
Linda Nott– London, Ontario, Canada
Patti Hoddinott– London, Ontario, Canada
Nabil Sultan– London, Ontario, Canada
Hassan Razvi– Professor and Chairman, Division of Urology, Western University, London, ON Canada, London, Ontario, Canada