Double-phase parathyroid scintigraphy in dogs using technetium-99M-sestamibi.

The purpose of this study was to evaluate the utility of double-phase parathyroid scintigraphy using 99mTc-sestamibi for detecting and localizing hyperfunctioning parathyroid glands in hypercalcemic dogs. Fifteen hypercalcemic dogs that underwent parathyroid scintigraphy were included in this study: 3 dogs with hypercalcemia of malignancy, and 12 dogs with hyperfunctioning parathyroid tissue (parathyroid adenoma or parathyroid hyperplasia). The presence of parathyroid adenoma or parathyroid hyperplasia was documented by histopathologic examination. In 3 dogs with hypercalcemia of malignancy, parathyroid scintigraphy was negative for hyperfunctioning parathyroid tissue and the scans were classified as true negative. Parathyroid scintigraphy correctly identified the presence and location of hyperfunctioning parathyroid tissue in only 1 of 6 dogs with a parathyroid adenoma. False positive and false negative results occurred in dogs with parathyroid adenomas. Parathyroid scintigraphy failed to detect hyperfunctioning parathyroid tissue in 5 of 6 dogs with parathyroid hyperplasia and were classified as false negative. False positive results were obtained in the remaining dog with parathyroid hyperplasia. Sensitivity of parathyroid scintigraphy for detecting and localizing hyperfunctioning parathyroid tissue was 11%, specificity was 50%, and overall accuracy was 27%. Positive and negative predictive value were 25% and 27%, respectively. Sensitivity for detection of parathyroid adenomas was 25%, and sensitivity for detection of hyperplastic glands was 0 %. Results of this study indicate that double-phase parathyroid scintigraphy does not appear to have acceptable accuracy in detecting hyperfunctioning parathyroid glands in dogs. Due to the poor sensitivity and specificity of the technique in dogs, parathyroid scintigraphy is not recommended for definitive identification of abnormal parathyroid glands as the cause of hypercalcemia in dogs.

Evaluation of plasma time-activity curves of technetium-99m-mebrofenin for measurement of hepatic function in dogs.

In this study, plasma time-activity curves of 99mTc-mebrofenin were used to quantify hepatic function in dogs before and after induction of hepatic damage using a hepatotoxic agent. Nine dogs were determined to be healthy on the basis of physical examination, laboratory data and hepatic imaging. Plasma samples were collected 1, 3, 5, 7, 9, 15, 20, 30, 40, 50, and 60 minutes following a peripheral venous injection of 111-222 MBq (3-6 mCi) of 99mTc-mebrofenin. The area under the plasma time-activity curve (AUC) was calculated using two different methods and compared to direct measurement of the hepatic extraction efficiency. First pass hepatic extraction efficiency of 99mTc-mebrofenin was calculated from differential equation analysis of a two-compartment model following mesenteric venous injection of the radiopharmaceutical. In 7 of the original 9 dogs and 2 additional healthy dogs, plasma clearance and hepatic extraction efficiency determination were repeated following induction of hepatic injury by thiacetarsamide (3 mg/kg IV twice daily for 1 day). In one additional dog, hepatic injury was induced using carbon tetrachloride (0.3 ml/kg IP). Plasma time-activity curves of 99mTc-mebrofenin had kinetics of a two compartment model. Area under the curve was highly correlated with hepatic extraction efficiency. The AUC integrated from 1-60 minutes (AUC60) had the best correlation with hepatic extraction efficiency (r2 = 0.978, p < 0.001). A formula for calculation of hepatic extraction efficiency was derived using linear regression analysis: hepatic extraction efficiency = 105.583 - 3.099 x 10(5) x AUC60. Plasma clearance of a peripheral venous injection of 99mTc-mebrofenin is a simple, non-invasive, convenient method to quantify hepatic function which can be performed without a gamma camera.

Profound postanesthetic hypoglycemia attributable to glucocorticoid deficiency in 2 dogs.

Glucocorticoid deficiency was diagnosed as the cause of severe postanesthetic hypoglycemia in 2 dogs. Prior signs of systemic illness were not described in either dog; however, preoperative hematologic findings were consistent with glucocorticoid deficiency. Fasting hypoglycemia is a possible complication of chronic adrenal insufficiency primarily because of impaired gluconeogenesis.

Changes in rectal temperature and hematologic, biochemical, blood gas, and acid-base values in healthy Labrador Retrievers before and after strenuous exercise.

OBJECTIVE: To measure changes in rectal temperature and hematologic, biochemical, blood gas, and acid-base values before and after exercise. ANIMALS: 14 healthy adult Labrador Retrievers. PROCEDURE: Dogs exercised continuously for 10 minutes by repeatedly retrieving a dummy thrown approximately 40 to 50 yards on land. The ambient temperature during each exercise period was recorded. Rectal temperature, pulse, and respiratory rate were measured; CBC and serum biochemical profile were determined; and arterial blood gas tensions, acid-base status, and plasma lactate and pyruvate concentrations were measured at rest and immediately after exercise. Rectal temperature, pulse, respiratory rate, and lactate and pyruvate concentrations were evaluated at intervals up to 120 minutes after exercise. RESULTS: Immediately after exercise, rectal temperature increased markedly; ambient temperature did not affect rectal temperature. Arterial blood pH and PaO2 were significantly increased after exercise, and PaCO2 and bicarbonate concentration were significantly decreased after exercise. Also, statistically, but not clinically, significant increases were observed in RBC, WBC, and segmented neutrophil counts; hemoglobin, total protein, and serum sodium and potassium concentrations; PCV; anion gap; and creatine kinase activity. Plasma lactate and pyruvate concentrations increased significantly after exercise, but there was no change in the lactate-to-pyruvate ratio. CONCLUSION AND CLINICAL RELEVANCE: Reference values for healthy Laborador Retrievers during a standardized exercise protocol were established to compare data obtained from Laborador Retrievers with exercise intolerance and collapse. Important characteristics of lactate and pyruvate metabolism were documented that will enable more precise evaluation of exercise intolerance in this breed.

Use of technetium Tc 99m sestamibi for detection of a parathyroid adenoma in a dog with primary hyperparathyroidism.

Double-phase parathyroid gland scintigraphy, using technetium Tc 99m sestamibi, correctly identified the existence and location of a parathyroid adenoma in a dog with primary hyperparathyroidism. The parathyroid adenoma was removed surgically 2 days after scintigraphy. An area of focal radionuclide uptake persisted in the region corresponding to the left external parathyroid gland in the delayed-phase image. Delayed-phase images from 3 healthy dogs and a dog with hypercalcemia of malignancy caused by lymphoma did not reveal an area of persistent radiotracer uptake. Double-phase parathyroid gland scintigraphy, using 99mTc-sestamibi, is a simple, rapid, noninvasive test, which can be used for detection and localization of parathyroid adenomas in hypercalcemic dogs. It also can help to differentiate these dogs from dogs with hypercalcemia of malignancy.