The Role of Hyperoxaluria in the Formation of Calcium Oxalate Urinary Calculi, and its Association with other Biochemical Measurements

Abstract

The part played by hyperoxaluria in the formation of calcium oxalate urinary calculi was studied in 153 patients who had each been diagnosed as having calcium oxalate urinary calculi on one or more occasions. Seventy-seven of the patients excreted normal amounts of calcium (less than 6.2 mmol/d), and 76 had hypercalciuria (excretion greater than or equal to 6.2 mmol/d); each group was divided into a further two groups depending on whether the oxalate concentration was above or below 0.16 mmol/l. Pure calcium oxalate stones were more common in patients whose calcium excretion was normal, and mixed calcium oxalate and phosphate stones were more common among hypercalciuric patients. Urinary concentrations/day of magnesium, citrate, and phosphorus were significantly lower in the two groups in which the oxalate concentrations were below 0.16 mmol/l than in a normal control group, and magnesium and phosphorus were significantly lower in the two groups in which oxalate concentrations were less than 0.16 mmol/l than in the two in which they were above that value. The concentration of citrate was also lower, but not significantly so. In addition, the pH of the urine in patients with mixed stones was significantly higher in all groups than when the stones were composed of pure calcium oxalate.

Metabolic assessment in patients with urinary lithiasis

“…As for the association between hyperoxaluria and hypercalciuria, no positive correlation was observed. Studies with pure calcium oxalate stones concluded that they were more frequent in patients with normal calcium excretion and that mixed stones made of calcium phosphate and oxalate were more frequently found in patients with hypercalciuria (17). Other authors observed that small increases in urinary oxalate would be more critical than similar increases in calcium in the process of urinary supersaturation by calcium oxalate (18).…”