Hypercalciuria and hyperuricosuria in patients with calcium nephrolithiasis

Studies of glucose turnover and renal function in an unusual case of hereditary fructose intolerance

Examination of glucose kinetics, pancreatic alpha and beta cell function, plasma lipids, urinary acidification and calcium excretion has been undertaken in a patient with hereditary fructose intolerance. This case was unusual as it was associated with insulin-requiring diabetes, type IV hyperlipemia, hypercalciuria and renal calculi. He also demonstrated the previously described fructose-induced defect of urine acidification. Glucagon and C-peptide assays showed that the pancreatic alpha cells were stimulated by fructose and that the beta cells did not respond to fructose. It is not known whether the latter was due to his diabetes or to the lack of a beta cell response to this sugar. Primed 14C-glucose infusions were used for the first time to study nonsteady state glucose kinetics in man. They showed that, 24 hours after the last insulin injection and under basal conditions, the glucose concentrations increased because glucose production exceeded glucose utilization. However, after the administration of sorbitol the plasma glucose concentration decreased because glucose production decreased. After the administration of sorbitol there was no change in the metabolic clearance of glucose. This reflects the lack of a peripheral insulin effect and is consistent with the lack of any measurable C-peptide. Glucose utilization also decreased, but this decrease was less than the decrease in glucose production. Because the metabolic clearance of glucose remained unchanged, it was concluded that the change in glucose utilization was solely due to the decrease in glucose concentration. The absence of C-peptide in the plasma indicated that changes in glucose turnover were not related to any changes in endogenous plasma insulin. Furthermore, the plasma glucagon concentration increased and, hence, changes in this hormone could not account for the decrease in glucose production. Therefore, it was concluded that the sorbitol-induced decline in glucose production was due to a direct effect on hepatic metabolism.

The management of the patient with calcium stones

Results of investigation of 800 patients with renal calculi are presented. The high incidence of medullary sponge kidneys (tubular ectasia) in patients of either sex is stressed as is the low incidence of idiopathic hypercalciuria in the female. Hydrochlorothiazide has been found to be highly effective in preventing recurrence of calcium stones in our personal experience with over 300 patients who have been treated for as long as 14 years with this agent. The efficacy and mode of action of other measures advocated for stone prevention is reviewed.

Recurrent nephrolithiasis: natural history and effect of phosphate therapy. A double-blind controlled study

In a double-blind controlled clinical study, 71 patients with recurrent calcium oxalate stones were divided into three treatment groups: those who received potassium acid phosphate, those who received an inert placebo, and those who received a low calcium diet only. Follow-up periods averaged 2.9 years. Although the mean urinary calcium level of the patients who received phosphate was reduced 33 per cent, their renal stone disease did not diminish. Mean urinary phosphorus increased 88 per cent with phosphate treatment but did not correlate with the decrease in urinary calcium, or with treatment success. The data did not suggest that phosphorus and its metabolites retard calcium oxalate crystallization in urine. No evidence appeared for an association of hypercalciuria with severe stone disease, or with a specific clinical or chemical response to phosphate therapy. Patients whose urinary calcium level fell more than 25 percent when dietary calcium was reduced may have excessive gastrointestinal calcium absorption, which appears to be associated with improved chemical response to phosphate therapy.

Uric acid disorders in patients with calcium stones

Plasma and uric acid levels were measured in 132 men with calcium-containing renal stones and in 24 healthy men of similar ages. Fasting resulted in a significant fall in the mean plasma uric acid level of normal subjects. Intermittent hyperuricaemia was observed in 7% of fasting patients. Intermittent hyperuricosuria was found in 17% of non-fasting patients but in only 2 to 6% of fasting subjects. Most of the uric acid abnormalities in patients with calcium stones therefore appear to be due to diet and may be prevented by reducing the consumption of purine-rich foods. A direct relationship was observed between uric acid excretion and urine flow at normal flow rates. It is suggested that the apparent increase in stone incidence, which occurs with rising living standards, may be due partly to increased consumption of purine-rich foods.