[Differential diagnosis of hypercalcemia--a retrospective study of 46 dogs]

The case records of 46 dogs with hypercalcemia were studied retrospectively. The most common cause of hypercalcemia was malignancy, of which the majority were diagnosed as having lymphosarcoma (LSA, n = 23). Interestingly only 15 had palpable lymphadenopathy. Other neoplasia were apocrine adenocarcinoma of the anal sac (n = 4), mammary adenocarcinoma (n = 2), anaplastic carcinoma (n = 1), and malignant histiocytosis (n = 1). Non-neoplastic reasons for hypercalcemia were hypoadrenocorticism (n = 5), acute renal failure (n = 2), chronic renal failure (n = 2), hypervitaminosis D (n = 1), and primary hyperparathyroidism (n = 1). In 4 cases no definitive diagnosis could be obtained. Moderate to marked hyperphosphatemia and azotemia was found in all dogs with primary renal failure and in 4 of 5 dogs with hypoadrenocorticism. In contrast only 4 of 31 dogs with neoplasia showed (mild) hyperphosphatemia and 20 showed mild to moderate azotemia. Elevated PTH levels were found in dogs with primary chronic renal failure and with primary hyperparathyroidism, but also in one dog with neoplasia. Low PTH concentrations were measured in the dog with hypervitaminosis D and in 8 cases with neoplasia. Additional three cases with neoplasia had values in the reference range.

1. The most common cause of hypercalcemia is LSA. Absence of palpable lymphadenopathy does not exclude LSA and further diagnostic steps may be necessary 2. The combination of moderate to marked hyperphosphatemia suggests primary renal failure or hypoadrenocorticism. 3. An elevated PTH level is consistent with primary hyperparathyroidism, but does not exclude other causes of hypercalcemia.