Hypercalcemia after nephrectomy in the dog: role of the kidneys and parathyroid glands

Abstract

To examine the role of the kidneys and parathyroid glands in the development of hypercalcemia after bilateral nephrectomy, changes in serum calcium and iPTH were measured in dogs after bilateral nephrectomy, bilateral ureteral ligation, bilateral nephrectomy of thyroparathyroidectomized animals, or sham operation. Total calcium increased at 24 hr after nephrectomy, remained unchanged after bilateral ureteral ligation or sham surgery, and decreased after nephrectomy of thyroparathyroidectomized dogs. Ionized calcium decreased significantly at 12 hr after nephrectomy or ureteral ligation but returned to normal after 24 to 48 hr. At 72 hr ionized calcium remained normal in the nephrectomized animals but fell significantly in the ureteral ligation animals. At 12 and 24 hr, PTH was significantly higher (4.3- and 2.0-fold, respectively) in the nephrectomized group than in the ureteral ligation group.

Conclusions: (1) the increase in total serum calcium after bilateral nephrectomy in the dog is not accompanied by an increase in ionized calcium; (2) intact parathyroid function is necessary for the increase in total calcium and for the maintenance of ionized calcium after nephrectomy; (3) the presence of the kidneys in the ureteral ligation model prevents the rise in total serum calcium and allows a fall in ionized calcium.