Importance of citrate and the calcium : citrate ratio in patients with calcium renal lithiasis and severe lithogenesis

Objective To analyse the importance of urinary citrate and the urinary calcium : citrate ratio in patients with calcium renal lithiasis and severe lithogenesis compared with a control group of patients without lithiasis. Material and Methods A cross-sectional study of 115 patients in eastern Andalusia, Spain was conducted. The patients were divided into two groups: Group A: 56 patients aged 25-60 years without calcium renal lithiasis; Group B: 59 patients aged 25-60 years, presenting with calcium renal lithiasis and severe lithogenesis. The citrate levels and the calcium : citrate ratio in the patients' urine and the relationship of these two factors to lithiasic activity were analysed and compared. Results In Group B, 32.2% of the patients presented with hypocitraturia, compared with 14.3% of the patients in Group A (P = 0.02). The urinary citrate levels were lower in Group B than in Group A (P = 0.001) and the calcium : citrate ratio was higher in Group B than in Group A (P = 0.005). The results suggest that a patient urinary calcium : citrate ratio > 0.25 indicates severe lithogenesis (with a sensitivity of 89% and a specificity of 57%). After linear regression analysis, we found that the urinary citrate level is an independent factor associated with the changes in bone densitometry T-score values of patients. Conclusions The patients with severe lithogenesis presented with hypocitraturia, which was associated with lower bone mineral density. The calcium : citrate ratio, which is linearly related to the bone resorption marker beta-crosslaps, could be useful in evaluating the risk of severe lithogenesis when this ratio is > 0.25.