INTRODUCTION: A kidney stone is a common urologic complaint. The association between hypercalciuria and bone mineral density (BMD) is well known. However, BMD reduction is also recognized among normocalciuric patients.
OBJECTIVE: Bone density in patients with stones was analyzed for the variables of age, sex, and stone configuration. Data were compared with a control group.
METHODS: Participants were 340 randomly chosen patients with upper urinary calcium stones. The control group included 340 healthy participants who were age and sex matched with the patient group. The quantitative variables included age, body mass index, T-score of bone densitometry in the lumbar vertebrae (L2-L4) and femoral neck, and the serum levels of uric acid, calcium, potassium, sodium, phosphor, alkaline phosphatase and parathyroid hormone. Furthermore, each patientâ€™s 24-hour urine was studied for levels of creatinine, oxalate citrate, uric acid calcium, urea, and total volume.
RESULTS: The mean age of the patients was 43.22 years (SD =12.62); mean body mass index (BMI) was 27.44 kg/m2 (SD = 6.16). Lumbar vertebral bone densitometry bone mineral density (BMD) was normal in 144 patients (42.4%) and low normal in an additional 20 patients. One hundred forty patients (41.2%) had osteopenia and 56 (16.5%) were osteoporetic. Femoral neck BMD was normal in 188 patients (55.3%) and low normal in 28 patients. In comparison with the control group, lumbar and femoral BMD were significantly lower in patients with renal stones (P < .05). There were no significant differences among groups in quantitative variables, with the exception of serum uric acid level. There was a significant correlation between both lumbar T-score and femoral neck T-score with 24 hour urine uric acid. Lumbar T-scores increased in inverse relationship with age (P = .03).
CONCLUSION: The authors established that patients who form renal stones have a reduction in bone density. There was no significant difference in bone loss between hypercalciuric and normocalciuric patients, which indicates the existence of some interfering factors other than increased calcium loss. A low-calcium diet does not decrease stone formation, and it also leads to calcium imbalance and bone loss. Considering that the role of hypercalciuria in bone loss was not proven in this study and considering that a low-calcium diet has no proven role in renal stone prevention, the authors do not suggest low-calcium diets for renal stone formers.
KEYWORDS: Bone mineral density; Urolithiasis; Low-calcium diet; Hypercalciuria
CORRESPONDENCE: Dr. Mahmood Molaei, Department of Urology, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran (