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Objective—To determine the dimensions and volume of thyroid tissue in clinically normal cats by use of computed tomography.

Animals—8 cats.

Procedure—Helical computed tomography images (2-mm collimation) were acquired from the cranial aspect of the second cervical vertebra through the caudal aspect of the fourth cervical vertebra. Data were acquired before contrast medium administration (n = 7 cats) and immediately after contrast medium enhancement (1 cat). Length, width, and height measurements of each thyroid lobe were made by use of transverse, dorsal, and sagittal plane images. Thyroid lobe volume was estimated by use of 3 methods.

Results—All thyroid lobes were histologically normal. Mean dimensions for a thyroid lobe were 16.5 × 2.00 × 4.31 mm (length × width × height) using only data from transverse images. Mean thyroid lobar volume was 113.75 mm3 using the sum of areas method. Mean total volume of thyroid tissue was 215.25 mm3 using the sum of areas method.

Conclusions and Clinical Relevance—Results may be useful for computed tomography evaluation of abnormal thyroid glands in cats, which warrants investigation.

Full access
in American Journal of Veterinary Research


Objective—To quantitatively and qualitatively assess the radiographic appearance of the thorax of clinically normal alpaca crias.

Animals—21 clinically normal alpaca crias.

Procedures—Left-right lateral (LR), right-left lateral (RL), dorsoventral (DV), and ventrodorsal (VD) projections of the thorax were acquired. To account for differences in cria size, measurements of thoracic structures were compared with other anatomic landmarks.

Results—Mean ± SD vertebral heart scale was 9.36 ± 0.65 for LR projections, 9.36 ± 0.59 for RL projections, 8.21 ± 0.51 for DV projections, and 8.65 ± 0.57 for VD projections. Dimensions of the heart were compared with the length of the T3 through T5 vertebral bodies, third to fifth rib distance, and thoracic height and width, which provided additional methods of cardiac evaluation. For RL projections, mean ratio of the right cranial pulmonary artery diameter to the third rib width was 0.41 ± 0.10 and mean ratio of the right cranial pulmonary vein to the third rib width was 0.44 ± 0.10. Caudal lobar pulmonary vessels and the caudal vena cava were difficult to quantitatively assess on DV or VD projections. On lateral projections, the trachea was increased in diameter at the origin of the right cranial lobar bronchus. No qualitative differences were found between LR and RL radiographs. The lungs were generally better inflated on VD projections, with more separation of the heart and diaphragm.

Conclusions and Clinical Relevance—Establishment of radiographic values for alpaca crias should prove useful in assessment of thoracic disease in this species.

Full access
in American Journal of Veterinary Research


Objective—To determine whether the reported drug-drug interaction between the flea medication spinosad and ivermectin is attributable to inhibition of P-glycoprotein by spinosad.

Animals—6 healthy adult dogs with the ABCB1 wildtype genotype.

Procedures—The study was conducted as a prospective, masked, randomized crossover design. Six dogs were allocated to 2 groups; each dog served as its own control animal. Dogs in one of the groups received spinosad at the manufacturer's recommended dose; the other group received no treatment. Forty-eight hours later, scintigraphic imaging of the head and abdomen were performed with the radiolabeled P-glycoprotein substrate methoxy-isobutyl-isonitrile (sestamibi) in both groups of dogs. After a washout period of 60 days, the dogs in each group received the alternate treatment, and scintigraphic imaging again was performed 48 hours later. Gallbladder-to-liver and brain-to-neck musculature ratios of technetium Tc 99m sestamibi were calculated for each dog and compared between treatments.

Results—No significant differences in gallbladder-to-liver or brain-to-neck musculature ratios were found between treatments.

Conclusions and Clinical Relevance—Results provided evidence that spinosad did not inhibit P-glycoprotein function 48 hours after spinosad was administered at the manufacturer's recommended dose. Further investigations will be necessary to elucidate the mechanism of the reported toxic interaction between spinosad and ivermectin.

Full access
in American Journal of Veterinary Research