The daily intake of 103 recurrent idiopathic calcium stone formers and 146 controls was assessed by means of a computer-assisted 24-h dietary record. Timed 24-h urine samples were collected over the same period to assess the relationship between dietary intake of nutrients and urinary risk factors for calcium stones. After standardisation for sex, age and social status a total of 128 subjects underwent final statistical analysis; 64 renal stone formers and 64 controls. Significant increases in the consumption of animal and vegetable protein and purine were identified as the nutritional factors that distinguished renal stone formers from controls. As expected, the daily urinary excretion of calcium and oxalate was higher and the daily urinary excretion of citrate was lower in stone formers than in controls. No difference with respect to daily urinary uric acid excretion was recorded. Daily urinary excretion of calcium was correlated to dietary protein intake while daily urinary oxalate was correlated to dietary vitamin C intake. It was concluded that renal stone formers could be predisposed to stones because of their dietary patterns. A link between the protein content of the diet and urinary calcium was confirmed, but dietary animal protein had a minimal effect on oxalate excretion.

The question of a familial predisposition towards stone formation in primary nephrolithiasis has not been explored completely. In a sample of 214 calcium stone patients, and 428 age and sex-matched controls we observed a higher frequency of stones among the first degree relatives of stone patients compared to the relatives of controls. A family history of renal stones was more common among the female (45 per cent) than among the male patients (31 per cent). There was no relationship between family history of renal stones, and abnormal calcium and oxalate excretion rates. A significant association between a family history and a higher urinary pH was observed among the female calcium stone patients. A genetic defect in urinary acidification with variable expressivity might be associated with a high frequency of stone formation. Moreover, uric acid excretion was higher in male stone patients with a family history of stones. Finally, the parents and siblings of the renal stone patients were affected more by calculi than were the corresponding relatives of their spouses.

One hundred and ninety-seven healthy subjects and 104 patients with idiopathic calcium stone disease had their urinary excretion of citrate, glycosaminoglycans, magnesium, and zinc measured and the results correlated with sex and age. In normal subjects the daily excretion of citrate, magnesium, and zinc increased with age to a maximum during the fifth decade and remained relatively constant until the eighth decade when they decreased. The daily excretion of magnesium and zinc were higher in men than in women, which was attributed to the higher body weights of the men. The urinary excretion of citrate, magnesium, and zinc related to creatinine remained relatively constant with age in adult life; analyses of magnesium and zinc excretion rates divided by urine creatinine did not distinguish men from women. There was no significant difference between men and women for citrate excretion in 24 hour urine, but the citrate:creatinine ratio was significantly higher in women than men. The higher citrate excretion in women may explain the lower incidence of calcium stones in women. The highest glycosaminoglycan excretion rates were seen during the first two decades which is why children and teenagers are less prone to develop calcium stones in spite of high urinary calcium concentrations. Urinary citrate and magnesium excretion were lower, and glycosaminoglycan and zinc excretion were higher, in stone formers than in controls. It seems that a decreased excretion of citrate and magnesium together with an increased excretion of calcium, may contribute to the formation of calcium stones. The role of urinary glycosaminoglycans and zinc in the formation of calcium stones remains uncertain.

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