Objective—To determine the dimensions and volume of thyroid tissue in clinically normal cats by use of computed tomography.
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.
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.
Objectives—To quantify direction and velocity of
blood flow in hepatic veins in dogs under different
hemodynamic conditions by use of pulsed-wave
Animals—10 healthy dogs.
Procedure—Dogs were anesthetized, and venous
flow velocities in the quadrate lobe were measured.
Arterial blood pressure, right atrial pressure,
pulmonary artery pressure, and cardiac output
were measured simultaneously. The timing of each
waveform during the cardiac cycle was used to
identify velocity profiles. Peak waveform velocities
were measured during conditions of light anesthesia
with isoflurane (baseline; period 1), cardiovascular
depression following administration of highdose
isoflurane and esmolol IV (period 2), cardiovascular
depression with crystalloid volume expansion
(period 3), and high cardiac output induced
with dobutamine (period 4). Hemodynamic measurements
and maximum waveform velocities
were compared among the 4 periods by use of an
ANOVA and univariate and multivariate linear
Results—During each study period, 4 distinct, lowvelocity
waves were identified. Mean velocities
recorded during period 1 were as follows: retrograde
atrial contraction a-wave, 7.3 cm/s; antegrade systolic
S-wave, 15.0 cm/s; retrograde venous return v-wave,
2.7 cm/s; and antegrade diastolic D-wave, 11.4 cm/s.
Mean S:D ratio was 1.27. During periods 3 and 4, Swave
velocity increased; D-wave velocity was highest
during period 4.
Conclusions and Clinical Relevance—Consistent
hepatic venous velocity profiles were observed in
healthy dogs under different hemodynamic conditions.
These findings provide baseline values that may
be useful in evaluating clinical cases, but further study
involving healthy, awake dogs and dogs with cardiac
and hepatic diseases is required. (Am J Vet Res
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.
Objectives—To determine whether feed restriction
induces hepatic lipidosis (HL) in llamas and to evaluate
the metabolic changes that develop during feed
Animals—8 healthy adult female llamas.
Procedure—Llamas were fed grass hay at a rate of
0.25% of their body weight per day for 13 to 28 days.
Llamas were monitored by use of clinical observation,
serum biochemical analyses, and ultrasound-guided
Results—All 8 llamas lost weight and mobilized fat.
Five llamas developed HL, including 4 that were nursing
crias. During the period of feed restriction, mean
serum concentration of bile acids and activities of
aspartate aminotransferase (AST), sorbitol dehydrogenase
(SDH), and γ-glutamyl transferase (GGT) were
significantly higher in llamas that developed HL, compared
with llamas that did not. Mean insulin-to-cortisol
concentration ratios were lower in llamas with HL
before and up to 7 days of feed restriction, compared
with those that did not develop HL.
Conclusions and Clinical Relevance—HL in llamas
may be induced by severe feed restriction, particularly
in the face of increased energy demand. Llamas
with weight loss attributable to inadequate dietary
intake may develop biochemical evidence of
hepatopathy and HL. Increases in serum concentration
of bile acids and activities of GGT, AST, and SDH
may indicate the development of HL in llamas and
identify affected animals for aggressive therapeutic
intervention. (Am J Vet Res 2001;62:1081–1087)
Objective—To develop protocols for helical computed
tomography (CT) and axial high-resolution CT
(HRCT) of lungs and correlate densitometric CT values
with morphometric and histologic data for normal
pulmonary tissue in dogs.
Animals—8 healthy adult dogs.
Procedure—2 dogs were used to establish a protocol
for helical CT and HRCT of lungs. Six dogs were used
to acquire densitometric CT data regarding normal
lungs. After the dogs were euthanatized, their lungs
were fixed and sampled for morphometric and histologic
evaluation. Four CT acquisitions were compared
by means of paired t tests.
Results—For normal lung tissue of dogs, mean densitometric
CT value obtained during helical CT scans
reconstructed in a sharp algorithm was -846
Hounsfield units. Values obtained via helical CT or
HRCT acquisitions and reconstructed with sharp or
standard algorithms did not differ significantly.
Morphometric analysis was used to determine the
proportion of lung parenchymal (82%) and nonparenchymal
tissue (18%). Alveolar size, estimated by
mean linear intercept, was approximately 172 µm,
and alveolar surface area-to-volume ratio was 0.024 to
0.026 µm–1. Histologic evaluation confirmed the presence
of normal lung tissue.
Conclusions and Clinical Relevance—Correlation of
densitometric CT data with morphometric and histologic
findings and the establishment of helical CT and
HRCT protocols were attained; clinical use of this
information may facilitate investigation of pulmonary
disease in dogs. Sharp helical CT acquisitions were
preferred because of better lung parenchyma detail
and rapid image acquisitions, compared with HRCT.
(Am J Vet Res 2003;64:935–944)
Objective—To measure the effects of lowmolecular-weight inhibitors on the activity of bovine neutrophil matrix metalloproteinase 9 (MMP-9).
Sample Population—Bovine MMP-9 purified from bovine neutrophilconditioned medium.
Procedures—Neutrophils were degranulated by stimulation with phorbol ester. Enzyme purification was performed by use of gelatin affinity and gel-filtration chromatography. Activated enzyme was incubated with inhibitors prior to addition of substrate (gelatin fluorescein conjugate or fluorogenic peptide). Rates of enzymatic cleavage were determined by monitoring fluorescence as the reactions progressed. Values of IC50 (molar concentration of compound that inhibits specific activity by 50%) and KI (in vitro inhibition constant) were determined.
Results—Rates of enzymatic activity of monomeric and dimeric bovine MMP-9 measured by use of gelatin and peptide substrates were linear with respect to time and concentrations of enzyme and substrate. The MMP-9 was potently inhibited by hydroxamic acids (IC50 for gelatin, 29.2 to 55.7nM; IC50 for peptide, 4.8 to 24.6nM; KI, 0.2 to 0.5nM), whereas tetracyclines (IC50 for gelatin, 30.1 to 112.7MM; IC50 for peptide, 48.0 to 123.8MM; KI, 25.2 to 61.4µM) and chlorhexidine (IC50 for gelatin, 139.1MM; IC50 for peptide, 672.5MM to 1.7mM; KI, 495.0 to 663.0MM) had limited inhibition. Gelatinase-specific inhibitor SB-3CT had intermediate potency (IC50 for peptide, 185.0 to 290.0nM; KI, 66.5 to 86.0nM).
Conclusions and Clinical Relevance—Bovine MMP-9 was potently inhibited by hydroxamic acids and gelatinase inhibitor. These compounds may be useful as modulators of neutrophil-mediated protease activity in cattle.
Objective—To describe the signalment, clinical features, and most common MRI characteristics in dogs with diskospondylitis and investigate whether a correlation exists between the degree of spinal cord compression and neurologic status of the patient.
Design—Retrospective case series.
Procedures—The medical records and imaging database of the Veterinary Teaching Hospital at Washington State University were retrospectively cross-referenced for cases of diskospondylitis in dogs from 1997 through 2010. Signalment, clinical signs, MRI characteristics, and results of bacteriologic cultures of urine, blood, CSF, or intervertebral disk material were reviewed.
Results—On T2-weighted sequences, vertebral endplates were most often of mixed signal intensity, whereas the vertebral body was hypointense. The intervertebral disk space was most often hyperintense on T2-weighted and short tau inversion recovery sequences and of mixed signal intensity on T1-weighted sequences. Paravertebral soft tissue hyperintensities were noted commonly on T2-weighted and short tau inversion recovery sequences. Heterogenous contrast enhancement of endplates and intervertebral disk spaces also occurred commonly, whereas contrast enhancement of vertebral bodies and paravertebral soft tissues was uncommon. Intramedullary spinal cord intensity was noted at 10 of 27 sites on T2-weighted sequences. Static spinal cord compression occurred in 17 of 23 dogs, and a significant direct correlation was found between the percentage of spinal cord compression and the patient neurologic score.
Conclusions and Clinical Relevance—Results suggested that diskospondylitis in dogs has a characteristic MRI appearance, and in some patients, MRI may aid in the identification of severe spinal cord compression, which could warrant surgical intervention.
To describe the use of non–contrast-enhanced CT to identify deep digital flexor (DDF) tendinopathy in horses with lameness attributed to pain in regions distal to the metatarsophalangeal or metacarpophalangeal joints.
Retrospective case series.
28 client-owned horses.
Medical records were searched to identify horses that underwent non–contrast-enhanced CT with or without high-field MRI as part of an evaluation for lameness localized to areas distal to the metacarpophalangeal or metatarsophalangeal joint in ≥ 1 limb. Horses were included in the study if they had ≥ 1 DDF tendon lesion (DDF tendinopathy) identified. Signalment, lameness examination findings and response to perineural anesthesia, imaging modality, anesthetic agents and duration of anesthesia, and imaging findings were recorded. Data were summarized descriptively.
Bilateral imaging was performed for all horses, irrespective of unilateral or bilateral lameness. Nine of 28 horses underwent both CT and MRI, and all DDF tendon lesions identified by one modality were identified by the other. Of 48 limbs with DDF tendinopathy, 46 (96%) had core lesions and 35 (73%) had dorsal border irregularities. Median anesthesia time for CT and CT followed by MRI was 15 and 110 minutes, respectively.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that non–contrast-enhanced CT was useful for identifying DDF tendinopathy in horses with lameness localized to the phalangeal regions, and this was supported by consistency of findings in a subset of horses that underwent MRI. Further research is needed to confirm these results.