Preoperative factors associated with postoperative hypocalcemia in dogs with primary hyperparathyroidism that underwent parathyroidectomy: 62 cases (2004-2009).

OBJECTIVE: To identify preoperative variables associated with postoperative hypocalcemia in dogs with primary hyperparathyroidism undergoing parathyroidectomy.

DESIGN: Retrospective case series.

ANIMALS: 62 dogs.

PROCEDURES: Medical records of dogs undergoing parathyroidectomy for treatment of primary hyperparathyroidism between January 2004 and January 2009 at 4 institutions were reviewed; data regarding various preoperative variables and postoperative serum total and ionized calcium concentrations were recorded. Preoperative ultrasonographic and surgical findings were compared regarding laterality (right, left, or bilateral) of parathyroid gland lesions. Data were analyzed via ANOVA, simple linear regression, and multiple linear regression to identify associations between preoperative variables and postoperative serum total and ionized calcium nadir concentrations.

RESULTS: Preoperative variables significantly associated with low postoperative serum total calcium nadir concentrations included old age, history of weakness, lack of gastrointestinal tract signs, high serum parathyroid hormone concentration, and low serum calcium-phosphorus concentration product value. Preoperative variables significantly associated with low postoperative serum ionized calcium nadir concentrations included sexually intact status, low body weight, high serum urea nitrogen concentration, and lack of polyuria and polydipsia in the history. Age, body weight, serum calcium-phosphorus concentration product, and serum concentrations of parathyroid hormone and urea nitrogen were included in the final multiple linear regression model for prediction of postoperative serum calcium concentrations. Ultrasonography was performed in 58 dogs; results for 44 (75.9%) dogs agreed with surgical findings regarding laterality of parathyroid gland lesions.

CONCLUSIONS AND CLINICAL RELEVANCE: Prediction of postoperative hypocalcemia in dogs in this study with primary hyperparathyroidism that underwent parathyroidectomy was difficult and depended on multiple (history, physical examination, and clinicopathologic) factors.