Metabolic acidosis-induced hypercalcemia in an azotemic patient with primary hyperparathyroidism

A 58-year-old man with Stage 3b chronic kidney disease and primary hyperparathyroidism treated with cinacalcet was admitted for acute cholecystitis. A cholecystostomy tube was placed, estimated glomerular filtration rate decreased, metabolic acidosis developed and ionized calcium increased from 1.33 to 1.76 mM despite cinacalcet administration. A sodium bicarbonate infusion corrected the metabolic acidosis restoring ionized calcium to normal despite no improvement in renal function. The correlation between the increase in serum bicarbonate and decrease in ionized calcium was r = -0.93, P < 0.001. In summary, severe hypercalcemia was attributable to metabolic acidosis increasing calcium efflux from bone while renal failure decreased the capacity to excrete calcium.