Reversible defect in renal concentrating mechanism in patients with hypercalcemia

The effects of hypercalcemia on the renal concentrating mechanism were examined in eleven patients with hypercalcemia secondary to a variety of neoplasms and in one patient with milk-alkali syndrome. The results demonstrate that hypercalcemia leads to a potentially reversible defect in concentrating ability which, unlike chronic renal disease, is independent of concomitant changes in glomerular filtration rate. It is postulated that the defect in concentrating ability is primarily due to reduced back diffusion of water from the distal convoluted tubules and collecting ducts.