A challenging case: Severe hypercalcemia in a puppy with hypoadrenocorticism - Veterinary Medicine
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A challenging case: Severe hypercalcemia in a puppy with hypoadrenocorticism
The point of interest in this case was not the disease, but the degree to which it caused an elevated calcium concentration.


VETERINARY MEDICINE


Treating hypercalcemia

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

Prognosis

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 damage.13

CONCLUSION

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

REFERENCES

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17. Kemppainen RJ, Behrend EN. CVT Update: interpretation of endocrine diagnostic test results for adrenal and thyroid disease. In: Bonagura JD, ed. Kirk's current veterinary therapy XIII small animal practice. Philadelphia, Pa: WB Saunders Co, 2000;321-324.


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