Investigation and treatment of renal calculi

Kidney stones as a manifestation of hypercalcemic disorders. Hyperparathyroidism and sarcoidosis

When hypercalcemia is detected in a kidney stone formation, an intact parathyroid hormone measurement should be made. Detection of hyperparathyroidism (HPT) is important to prevent further stone episodes and to avoid the complications of high serum calcium in other organ systems. Stones in patients with HPT often contain apatite salts in addition to calcium oxalate because parathyroid excess may create a renal tubular acidosis. The calculi seen in patients with sarcoidosis, another hypercalcemic state that may cause stone formation, however, are usually pure calcium oxalate. Excess generation of 1,25-dihydroxyvitamin D results in intestinal hyperabsorption of calcium and secondary hyperoxaluria.

The effect of low-dose cyclical etidronate and calcium on bone mass in early postmenopausal women

This 2-year study was carried out in 36 healthy women of mean age 53.9 +/- 3.8 (SD) years and 3.4 +/- 2.3 years postmenopausal. Bone mineral density (BMD) in the spine, measured by single-energy quantitative computed tomographic scanning, gave a mean initial value of 110 +/- 26 mg/ml. The women were divided randomly into group 1 (n = 11), calcium 600 mg/day; group 2 (n = 15), calcium plus etidronate sodium 400 mg/day for 14 days every 3 months; and group 3 (n = 10), calcium plus etidronate plus phosphate, the 14-day etidronate course being preceded by phosphate 1 g twice daily for 3 days. During the first year of the study BMD decreased by 6.0 +/- 5.8% (p < 0.005) in group 1 subjects and increased by 4.5 +/- 7.8% (p < 0.005) in the combined etidronate-treated groups (difference between control and treated p < 0.001). Inclusion of phosphate in the regimen did not affect the response to etidronate. In the second year there was no significant mean change in BMD in any of the three groups. However, whilst there was little change in BMD values for most of the group 1 subjects, there was considerable variation in individual response within the etidronate-treated groups, with some subjects gaining and some losing bone. The change in BMD during the second year in the subjects as a whole was highly correlated with the change in plasma calcium after 3 months of treatment (r = 0.60, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The variability and dietary dependence of urinary oxalate excretion in recurrent calcium stone formers

Twenty-two recurrent calcium stone formers had 24-h urinary oxalate excretions on their home diets which were significantly greater than those of 30 normal subjects (0.48 +/- 0.23 mmol/d; mean +/- SD compared with 0.31 +/- 0.11; P less than 0.01). The stone formers also demonstrated marked day to day variability in oxalate excretion indicating that a single normal urinary oxalate measurement did not exclude significant hyperoxaluria at other times. On a hospital diet containing 1000 mg calcium per day, urinary oxalate excretion fell significantly from 0.48 +/- 0.23 mmol/d to 0.32 +/- 0.12; P less than 0.01. As the urinary calcium excretion in and out of hospital was similar, it seems unlikely that low calcium intake at home was responsible for the hyperoxaluria. All patients had recurrent symptomatic stone disease and had been advised to avoid foods rich in oxalate. Whilst poor compliance is a possible explanation for the variability in oxalate excretion, we believe it is more likely that there is an inadvertent intake of oxalogenic precursors in their diet. As normal subjects do not demonstrate hyperoxaluria on similar home diets, stone formers may have a metabolic defect in the handling of these precursors.