Objective—To evaluate the usefulness of serum biochemical
variables and scintigraphic study results for
differentiating between dogs and cats with complete
extrahepatic biliary obstruction (EHO) and those with
partial EHO or patent bile ducts.
Study Design—Retrospective case series.
Animals—17 dogs and 1 cat.
Procedure—Animals that underwent hepatobiliary
scintigraphy and had either surgical or postmortem
confirmation of the degree of bile duct patency were
included. Scintigraphic images were evaluated and biliary
tracts were classified as patent, partially obstructed
but patent, or obstructed. Surgery or postmortem
examination was considered the gold standard for
diagnosis, and compared with those findings, sensitivity
and specificity of scintigraphy were calculated.
Results—With absence of radioactivity in the intestinal
tract as the diagnostic criterion for EHO, the sensitivity
and specificity of scintigraphic diagnosis were
both 83% when final images were acquired at 19 to
24 hours, compared with 100% and 33%, respectively,
when 180 minutes was used as the cutoff time.
Animals with partial biliary obstruction had less
intestinal radioactivity that arrived later than that
observed in animals with patent biliary tracts.
Conclusions and Clinical Relevance—Animals in
which intestinal radioactivity has not been observed after
the standard 3 to 4 hours should undergo additional
scintigraphic imaging. Findings in animals with partial biliary
obstruction include delayed arrival of radioactivity
and less radioactivity in the intestine. Distinguishing
between complete and partial biliary tract obstruction is
important because animals with partial obstruction may
respond favorably to medical management and should
not be given an erroneous diagnosis of complete
obstruction. (J Am Vet Med Assoc 2005;227:1618–1624)
Objective—To standardize techniques for renal
scintigraphy in birds, to use scintigraphy to assess
gentamicin nephrotoxicosis in birds, to compare
nuclear medicine assessments with histologic assessment
of gentamicin nephrotoxicosis and serum uric
acid concentrations, and to determine the radiopharmaceutical
that best quantifies avian renal function.
Procedure—Serum uric acid concentrations were
determined for all birds. Renal scintigraphy techniques
that used technetium-m99 (99mTc)-dimercaptosuccinic
acid (DMSA; 4 hours after injection) and
99mTc-diethylenetriamine pentaacetic acid (DTPA; 15-
minute dynamic study) were evaluated in all birds.
Renal biopsy specimens were collected following
baseline scans. Number and size of renal tubule granules
positive for periodic acid-Schiff stain were scored
for severity (scale of 0 to 4). Nephrotoxicosis was
induced by administration of gentamicin. Serum uric
acid concentrations were measured, and 99mTc-DMSA
and99mTc-DTPA scans were repeated after gentamicin
administration. Birds were euthanatized, and complete
necropsies were performed.
Results—Standard avian renal scintigraphy techniques
were developed for 99mTc-DMSA and 99mTc-
DTPA. Decreased renal radiopharmaceutical uptake
for 99mTc-DMSA and 99mTc-DTPA indicated nephrotoxicosis.
Cloacal accumulation of 99mTc-DTPA was significantly
decreased after administration of gentamicin.
Histologic grading of renal tissue before and after
gentamicin administration confirmed nephrotoxicosis.
Inconsistent serum uric acid concentrations could not
be used to assess nephrotoxicosis.
Conclusions and Clinical Relevance—Renal nuclear
scintigraphy is a useful, noninvasive means to determine
renal function in birds. Although 99mTc-DMSA may
prove useful in the evaluation of renal morphology,
99mTc-DTPA is the radiopharmaceutical agent of choice
for the assessment of renal function in avian species.
(Am J Vet Res 2003;64:453–462)
Objective—To evaluate the use of scintigraphy involving
technetium Tc 99m diethylenetriamine pentaacetic
acid (99mTc-DTPA) or technetium Tc 99m
dimercaptosuccinic acid (99mTc-DMSA) for the determination
of kidney morphology and function in green
iguanas ( Iguana iguana ).
Animals—10 healthy iguanas weighing > 1.6 kg.
Procedure—Renal scintigraphy was performed by
use of 99mTc-DTPA in 6 of the iguanas and by use of
99mTc-DMSA in all 10 iguanas. After the injection of
99mTc-DMSA, scans were performed for each iguana at
intervals during a 20-hour period. Renal biopsies were
performed in all 10 iguanas after the final scintigraphic
Results—In iguanas, the use of 99mTc-DTPA for renal
scintigraphy was nondiagnostic because of serum
protein binding and poor renal uptake of the isotope;
mean ± SD 99mTc-DTPA bound to serum proteins was
48.9 ± 9.9%. Renal uptake of 99mTc-DMSA produced
distinct visualization of both kidneys. Renal uptake
and soft tissue clearance of 99mTc-DMSA increased
over the 20-hour imaging period; mean ± SD renal
uptake of 99mTc-DMSA was 11.31 ± 3.06% at 20 hours.
In each of the 10 iguanas, ultrasonographic and histologic
examinations of biopsy specimens from both
kidneys revealed no abnormalities.
Conclusions and Clinical Relevance—Results indicate
that the kidneys of iguanas can be evaluated
scintigraphically by use of 99mTc-DMSA; this technique
may be potentially useful for the diagnosis of renal
failure in iguanas. (Am J Vet Res 2005;66:87–92)
CASE DESCRIPTION A 7-year-old castrated male Havanese was evaluated at a veterinary teaching hospital because of a 12-week history of hyperactivity, aggression, and progressive weight loss despite a healthy appetite.
CLINICAL FINDINGS Tachycardia was the only remarkable finding during physical examination. Serum 3,5,3′-triiodothyronine (T3) and free T3 concentrations were markedly increased, and thyroxine (T4), free T4, and thyroid-stimulating hormone concentrations were at or decreased from the respective reference ranges. Thyroid scintigraphy revealed suppressed uptake of sodium pertechnetate Tc 99m by the thyroid gland but no ectopic thyroid tissue, which was indicative of thyrotoxicosis induced by an exogenous source of T3.
TREATMENT AND OUTCOME The dog was hospitalized for 24 hours, and its diet was changed, after which the clinical signs rapidly resolved and serum T3 and free T3 concentrations returned to within the respective reference ranges. This raised suspicion of an exogenous source of T3 in the dog's home environment. Analysis of the commercial beef-based canned food the dog was being fed revealed a high concentration of T3 (1.39 μg/g) and an iodine (82.44 μg/g) concentration that exceeded industry recommendations. No other source of T3 was identified in the dog's environment.
CLINICAL RELEVANCE To our knowledge, this is the first report of clinical thyrotoxicosis in a dog induced by exogenous T3, although the source of exogenous T3 was not identified. This case highlights the importance of measuring serum T3 and thyroid-stimulating hormone concentrations in addition to T4 and free T4 concentrations when there is incongruity between clinical findings and thyroid function test results.
Objective—To identify ventilatory protocols that yielded good image quality for thoracic CT and hemodynamic stability in cats.
Animals—7 healthy cats.
Procedures—Cats were anesthetized and ventilated via 4 randomized protocols (hyperventilation, 20 seconds [protocol 1]; single deep inspiration, positive inspiratory pressure of 15 cm H2O [protocol 2]; recruitment maneuver [protocol 3]; and hyperventilation, 20 seconds with a positive end-expiratory pressure of 5 cm H2O [protocol 4]). Thoracic CT was performed for each protocol; images were acquired during apnea for protocols 1 and 3 and during positive airway pressure for protocols 2 and 4. Heart rate; systolic, mean, and diastolic arterial blood pressures; blood gas values; end-tidal isoflurane concentration; rectal temperature; and measures of atelectasis, total lung volume (TLV), and lung density were determined before and after each protocol.
Results—None of the protocols eliminated atelectasis; the number of lung lobes with atelectasis was significantly greater during protocol 1 than during the other protocols. Lung density and TLV differed significantly among protocols, except between protocols 1 and 3. Protocol 2 TLV exceeded reference values. Arterial blood pressure after each protocol was lower than before the protocols. Mean and diastolic arterial blood pressure were higher after protocol 3 and diastolic arterial blood pressure was higher after protocol 4 than after protocol 2.
Conclusions and Clinical Relevance—Standardization of ventilatory protocols may minimize effects on thoracic CT images and hemodynamic variables. Although atelectasis was still present, ventilatory protocols 3 and 4 provided the best compromise between image quality and hemodynamic stability.