Estudio de factores litogénicos en pacientes con fractura osteoporótica

Resumen

INTRODUCTION Several studies in the literature have shown a relationship between osteopenia/osteoporosis and calcium nephrolithiasis. Apart from this clinical relationship, patients with recurrent calcium nephrolithiasis show altered markers of bone remodeling (bone formation and mainly resorption) and urinary lithogenic activity markers such as calciuria, citraturia, calcium/creatinine ratio and calcium/citrate ratio. Although the relationship and causality link between these two conditions is not well known, genetic, immunologic, inflammatory and dietetic factors could be facilitating the appearance and maintenance of the osteoporosis-renal lithiasis pairing. It seems that the presence of recurrent calcium nephrolithiasis is a risk factor in the development of bone fractures in patients with osteoporosis due to an increase of its accumulated incidence as time passes. The aim of this doctoral dissertation is to study the lithogenic factors in patients with osteoporotic fractures in order to determine if they are altered as compared to the general population. METHODS AND MATERIALS Sixty-seven patients (55 women and 12 men) were selected with osteoporotic fracture determined by radiologic imaging or bone densitometry using dual energy X-ray absorptiometry. An additional group of 32 patients without osteoporosis or lithiasis was studied. Exclusion criteria included patients with a previous or current diagnosis of renal lithiasis based on abdominal X-rays and ultrasound, lithogenic treatment and bone or known endocrine and metabolic disorders. + Analyzed variables: • Blood analysis of creatinine, calcium, phosphorus, uric acid, sodium, potassium, chloride, PTH, 25-OH-vitamin D. • Urine analysis of 24h calcium, 24h uric acid, 24h citrate and 24h oxalate. • Fasting urine calcium/creatinine ratio. + Statistic analysis: SPSS software for Windows was used. Different statistical tests were used depending on the characteristics of the variables used. Statistical significance was set at p<0.05. + Ethical considerations: All patients read and signed the consent form to take part in this research and this study was approved by the Ethical Committee of Rafael Méndez Hospital of Lorca (Spain). RESULTS In the first study, among the 67 patients with osteoporotic fracture, we found 42% with hypercalciuria and up to 34% with hypocitraturia and hyperoxaluria. Patients with hypercalciuria had a calcium/creatinine ratio statistically higher than patients with normal calciuria. The second study confirmed these results among 55 women with osteoporotic fracture showing fasting calcium/creatinine ratio to be statistically higher in those with hypercalciuria. The third study compared women with osteoporotic fracture with women without osteoporosis and showed that the former group had a higher percentage of hypercalciuria (40% vs. 18.8%) and a decrease in the excretion of citrate in the urine (303 mg/24h vs. 1047mc/24h) and an increase in the fasting calcium/creatinine ratio (0.12 vs. 0.08). CONCLUSIONS Patients with osteoporotic fracture show a high percentage of hypercalciuria, fasting calcium/creatinine >0.11, a decrease in the excretion of citrate and a significant percentage of hyperoxaluria and hypocitraturia. These factors could contribute to the development of lithiasis and have implications for the medical treatment of osteoporosis. Therefore, their measurement could be recommended in these patients, although further prospective studies with larger number of patients are needed to confirm our findings.