Objective—To determine the effect of number of
blood samples and sampling times on plasma clearance
of technetium Tc 99m pentetate (Tc99mP) and
orthoiodohippurate sodium I 131(OIH).
Animals—20 dogs and 14 cats.
Procedure—Plasma clearances of OIH and Tc99mP
were calculated by use of a 2-compartment model, on
the basis of a 12-point curve as a reference method.
Plasma clearance was calculated by use of all possible
combinations of 4 to 11 samples. Time schedule yielding
the smallest difference from the reference method
was considered to be optimal. Regression analysis was
performed between the 12-point model and models
using a reduced number of samples.
Results—SD of the difference between the
12-point clearance and the models with reduced
numbers of samples increased when the number of
samples decreased. The SD of the difference
between 12-point clearance and 4-point clearance
was 4.17 ml/min for OIH and 0.94 ml/min for Tc99mP
in dogs and 0.45 ml/min for OIH and 0.11 ml/min for
Tc99mP in cats. Optimal schedules were distributed
logarithmically and included an early sample at 5 or
10 minutes, a late sample at 2.5, 3, 4, or 5 hours for
OIH, and a late sample at 4 or 5 hours for Tc99mP.
Conclusions and Clinical Relevance—Plasma clearances
of OIH and Tc99mP can be accurately calculated
in dogs and cats by use of a single-injection 2-compartment
pharmacologic model with a reduced number
of blood samples, resulting in an acceptable margin
of error. (Am J Vet Res 2000;61:280–285)
Objectives—To determine the effect of sedation and anesthesia on thyroid and salivary gland uptake of technetium Tc 99m pertechnetate (99mTcO4) in euthyroid cats.
Animals—6 euthyroid cats.
Procedures—Thyroid scintigraphy was performed by use of a high-resolution low-energy parallel-hole collimator after IV injection of 117 to 133 MBq (3.16 to 3.59 mCi) of 99mTcO4−. The procedure was performed 4 times on each cat during different sedative and anesthetic protocols in a rotating schedule as follows: propofol, ketamine-midazolam-atropine, ketaminemidazolam, and medetomidine. Regions of interest were drawn around thyroid and salivary glands and counts corrected for background and decay. Percentage of 99mTcO4− uptake in salivary and thyroid glands and thyroid-to-salivary gland 99mTcO4− uptake ratio were calculated at 20 and 40 minutes. Relative effects of anesthesia and sedation on salivary and thyroid gland 99mTcO4− uptake were compared.
Results—Significant differences among sedativeanesthetic protocols were found for thyroid gland 99mTcO4− uptake, salivary gland 99mTcO4− uptake, and thyroid-to-salivary gland 99mTcO4− uptake ratio. Thyroid gland 99mTcO4− uptake for the ketamine-midazolam protocol at 20 and 40 minutes after 99mTcO4− administration was significantly higher than for the propofol protocol. A significant difference in salivary gland99m TcO4− uptake was found between ketamine-midazolam and ketamine-midazolam-atropine protocols at 40 minutes. The thyroid-to-salivary gland 99mTcO4−uptake ratio for the ketamine-midazolam protocol was significantly higher at 40 minutes than for propofol or ketamine-midazolam-atropine protocols.
Conclusions and Clinical Relevance—Sedation and anesthesia have a significant effect on thyroid and salivary gland 99mTcO4 uptake in euthyroid cats that may interfere with thyroid scintigraphic image interpretation.
Objective—To describe clinical, ultrasonographic, and computed tomographic (CT) features of confirmed neoplastic and nonneoplastic disease in dogs with unilateral orbital diseases, determine criteria to differentiate between the 2 conditions, and assess the relative value of ultrasonography and CT for the differential diagnosis of these 2 conditions.
Animals—29 dogs with unilateral neoplastic orbital disease and 16 dogs with unilateral nonneoplastic orbital disease.
Procedures—Clinical history and results of physical and ophthalmologic examinations were recorded. Ultrasonographic and CT images were evaluated, and discriminating factors were identified to differentiate neoplastic from nonneoplastic diseases. Diagnostic value of ultrasonography and CT was assessed.
Results—Dogs with neoplastic disease were significantly older; had clinical signs for a longer time before initial examination; had more progressive onset of clinical signs; and more frequently had protrusion of the nictitating membrane, fever, and anorexia. The most discriminating factor for both imaging modalities was delineation of the margins (odds ratio was 41.7 for ultrasonography and 45 for CT), with neoplastic lesions clearly delineated more often. Ultrasonographically, neoplastic lesions were more frequently hypoechoic and homogeneous, with indentation of the globe and bone involvement evident more frequently than for nonneoplastic lesions. Mineralization was detected only with neoplasia. Fluctuant fluid was seen more frequently in dogs with nonneoplastic disease. Computed tomography more frequently revealed extraorbital involvement. Diagnostic value was similar for both imaging modalities.
Conclusions and Clinical Relevance—Ultrasonography and CT are valuable imaging modalities to assist in differentiating neoplastic from nonneoplastic unilateral orbital disease in dogs.
Objective—To compare the results of computed tomography (CT) and magnetic resonance imaging (MRI) of the pituitary gland in dogs with pituitary-dependent hyperadrenocorticism (PDH) caused by histologically confirmed pituitary adenoma.
Design—Retrospective case series.
Animals—11 dogs with PDH that underwent transsphenoidal hypophysectomy.
Procedures—Medical records of dogs examined between January 2001 and March 2003 were reviewed. Dogs were included in this study if they had clinical signs of hypercortisolism at the time of admission (for which PDH was diagnosed) and underwent transsphenoidal hypophysectomy. Pre- and postcontrast CT and low-field MRI (0.2-Tesla magnet) were performed on the same day as surgery for each dog.
Results—An abnormal pituitary gland was found in 7 dogs by use of MRI and in the same 7 dogs by use of CT. Significant differences were found between postcontrast CT and MR images for height, width, and length of the pituitary gland; brain area; and thickness of the sphenoid bone. However, the pituitary gland height-to-brain area ratio determined from postcontrast CT and MR images was not significantly different. The signal-to-noise ratio and contrast-to-noise ratio of pre- and postcontrast MR images were significantly higher than those of the CT images.
Conclusions and Clinical Relevance—Low-field MRI and dynamic CT imaging of the pituitary gland provided comparable information on the presence of pituitary adenomas in dogs with PDH.
Objective—To determine maximum extrarenal plasma
clearance of technetium-99m-mercaptoacetyltriglycine
(99mTc–MAG3) and maximum extrarenal
hepatic uptake of 99mTc–MAG3 in cats.
Animals—6 clinically normal adult cats.
Procedure—Simultaneously, baseline plasma clearance
and camera-based uptake of 99mTc–MAG3 were
determined in anesthetized cats. Double exponential
curves were fitted to plasma clearance data. Injected
dose was divided by area under the curve and body
weight to determine 99mTc–MAG3 clearance. Regions
of interest were drawn around kidneys and liver, and
percentage dose uptake was determined 1 to 3 minutes
after injection. After bilateral nephrectomy,
simultaneous extrarenal plasma clearance and camera-
based hepatic uptake of 99mTc–MAG3 were evaluated
in each cat.
Results—Mean ± SD baseline plasma clearance and
extrarenal clearance were 5.29 ± 0.77 and 0.84 ± 0.47
mL/min/kg, respectively. Mean extrarenal clearance
(as a percentage of baseline plasma clearance) was
16.06 ± 7.64%. For right, left, and both kidneys, mean
percentage dose uptake was 9.42 ± 2.58, 9.37 ± 0.86,
and 18.79 ± 2.47%, respectively. Mean hepatic percentage
dose uptake before and after nephrectomy
was 12.95 ± 0.93 and 21.47 ± 2.00%, respectively.
Mean percentage change of hepatic uptake after
nephrectomy was 166.89 ± 23.19%.
Conclusions and Clinical Relevance—In cats,
extrarenal clearance of 99mTc–MAG3 is higher than that
of other species; therefore, 99mTc–MAG3 is not useful
for estimation of renal function in felids. Evaluation of
renal function in cats may be more accurate via camera-
based versus plasma clearance-based methods
because camera-based studies can discriminate specific
organs. (Am J Vet Res 2003;64:1076–1080)