Ambidirectional cohort study on the agreement of ultrasonography and surgery in the identification of parathyroid pathology, and predictors of postoperative hypocalcemia in 47 dogs undergoing parathyroidectomy due to primary hyperparathyroidism.

OBJECTIVE: To investigate (1a) agreement of ultrasonographic, surgical, and histopathologic findings in the diagnosis of a neoplastic etiology underlying primary hyperparathyroidism (PHPT), (1b) the ability of ultrasonographically determined parathyroid gland size to distinguish between malignant (carcinoma) and non-malignant (hyperplasia, adenoma) pathology, and (2) variables associated with postoperative hypocalcemia in dogs undergoing surgical treatment of PHPT. STUDY DESIGN: Ambidirectional cohort study. ANIMALS: Forty-seven client owned dogs with PHPT (34 retrospective; 13 prospective). METHODS: Data were extracted from medical records. Method agreements were explored using Cohen's Kappa statistic. A receiver operating characteristic curve (ROC) was used to determine a cut-off separating parathyroid pathologies. Univariable and multivariable models assessed associations between postoperative hypocalcemia and potential risk factors. RESULTS: Agreement of ultrasound and surgery for number and side of affected glands was 31/47 (65.9%) and 34/47 (72.3%), respectively. In 37/47 (78.7%) cases, parathyroid tissue was correctly assessed as pathologic by the surgeon. An ultrasonographic cut-off of ≥8.0 mm (ROC AUC = 0.82) best distinguished malignant from benign pathologies. Dogs with a preoperative serum ionized calcium (iCa) concentration ≥1.75 mEq/L had 7.5 times greater odds of becoming hypocalcemic postoperatively. CONCLUSION: A fair agreement existed between ultrasonographic and surgical findings in dogs with PHPT. A parathyroid mass ≥8.0 mm on ultrasonographic examination was suggestive of malignancy, while dogs with a preoperative serum iCa concentration ≥1.75 mEq/L were at increased risk for postoperative hypocalcemia in this study. CLINICAL SIGNIFICANCE: This study supports the use of bilateral cervical surgical exploration to identify abnormal parathyroid glands for the treatment of PHPT.

Rare diagnosis of intraosseous lipoma in the scapula of a 15-year-old domestic shorthair cat.

Case summary: A 15-year-old male castrated domestic shorthair cat originally presented to its primary care veterinarian with a chief complaint of a multi-month history of decreased appetite, weight loss and mild weight-bearing lameness. On physical examination, over the right scapula there was mild-to-moderate muscle wasting and a palpable firm, bony mass measuring approximately 3.5 cm × 3 cm. A complete blood count, chemistry panel, urinalysis, urine culture and baseline thyroxine were clinically unremarkable. Further diagnostics included CT, which revealed a large, expansile, irregularly mineralized mass centered over the caudoventral scapula at the site of attachment of the infraspinatus muscle. Following wide surgical excision by means of complete scapulectomy the patient regained function of the limb and has been free of disease since. The clinical institution's pathology service examined the resected scapula with associated mass and diagnosed an intraosseous lipoma. Relevance and novel information: Intraosseous lipoma is a rare form of bone neoplasia that has only been reported once in the small animal veterinary literature. Histopathology, clinical signs and radiographic changes were consistent with what is described in human literature. It is hypothesized that these tumors occur because of invasively growing adipose tissue within the medullary canal following trauma. Considering the rarity of primary bone tumors in cats, intraosseous lipomas should be considered as a differential diagnosis in future cases with similar signs and history.