Hypercalcemia is best managed by treating the underlying cause. However, emergency measures to lower serum calcium concentrations
are indicated while diagnostic test results are pending if the calcium-phosphorus product is
> 60.13 Saline diuresis promotes renal excretion of calcium. The additional filtered sodium competes with calcium for renal tubular
reabsorption, so an increase in sodium results in enhanced calciuresis.14 After dehydration is corrected, furosemide is administered to inhibit calcium reabsorption in the thick ascending limb of
the loop of Henle, which enhances calcium excretion.14 Furosemide was not required in this case because the hypercalcemia and hyperphosphatemia resolved in a few days with rehydration
and treatment for Addison's disease. Glucocorticoids increase renal calcium excretion, decrease calcium resorption from bone,
and decrease absorption of calcium from the intestinal tract. However, premature glucocorticoid administration may confound
diagnostic test results for hypoadrenocorticism and lymphoma.14
Three forms of glucocorticoids were administered in this puppy. Prednisolone sodium succinate, a rapidly acting injectable
glucocorticoid with a short half-life, was initially used when the puppy was obtunded. The subsequent injectable dose was
with dexamethasone sodium phosphate, a slower-onset and longer-acting glucocorticoid. Once the puppy was eating, oral prednisone
was administered and injectable glucocorticoids were discontinued. Hydrocortisone, prednisone, and prednisolone cross-react
in the cortisol assay, so these glucocorticoid preparations must not be given before the ACTH stimulation test is completed.17
The prognosis for hypercalcemia tends to correlate with its cause, severity, and especially the solubility product of serum
calcium and phosphorus. If the underlying cause cannot be treated, the prognosis is poor. When the solubility product of serum
calcium and phosphorus is > 60 in dogs, soft tissue mineralization may occur, which can quickly result in renal and cardiac
In an Addisonian patient, hypercalcemia is not in itself remarkable. What is remarkable in the patient reported here is both
the severity of the hypercalcemia (26.8 mg/dl) and the calcium-phosphorus product (608) on presentation and the dramatic improvement
with treatment for hypoadrenocorticism.
Teresa L. Goodson, DVM, DACVIM
Susan C. Randell, BVSc, DACVIM
Affiliated Veterinary Specialists
9905 S. U.S. Highway 17-92
Maitland, FL 32751
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