Paradoxic hypercalcemia and hypophosphatemia associated with chronic renal failure in horses.

Chronic renal failure associated with hypercalcemia and hypophosphatemia was diagnosed in 6 horses. The renal lesions in 5 of the horses were classified as chronic glomerulonephritis and in the sixth, as chronic interstitial nephritis/pyelonephritis. There was no evidence of primary hyperparathyroidism or pseudohyperparathyroidism, thus suggesting that hypercalcemia associated with advanced renal failure in horses is related to a unique role of the equine kidney in calcium homeostasis.