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in Journal of the American Veterinary Medical Association

Summary

Medical records of 176 animals that underwent transcolonic sodium pertechnetate Tc 99m scintigraphy between September 1988 and June 1992 were reviewed. The study included 162 dogs, 10 cats, and 4 potbellied pigs. Whenever possible, scan results were confirmed during exploratory surgery or necropsy. For animals that did not undergo surgery or necropsy, additional medical information, (ie, results of histologic examination of hepatic biopsy specimens, clinicopathologic testing, abdominal ultrasonography, and clinical outcome) was evaluated to estimate the likelihood that the scan interpretation was correct. Interpretations were classified as confirmed true, probable true, possible false, or unconfirmed results. Of the 97 scans interpreted as positive for portosystemic shunting, 85 were classified as confirmed true-positive results, 5 were classified as probable true-positive results, and 7 were classified as unconfirmed results. None were classified as confirmed or possible false-positive results. Of the 79 scans interpreted as negative for portosystemic shunting, 3 were classified as confirmed true-negative results, 54 were classified as probable true-negative results, 1 was classified as a possible false-negative result, and 21 were classified as unconfirmed results. Our results suggest that transcolonic pertechnetate scintigraphy has satisfactory performance as a diagnostic test for macrovascular portosystemic shunting.

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in Journal of the American Veterinary Medical Association

Summary

Transcolonic portal scintigraphy was used to evaluate immediate and long-term changes in shunt blood flow after partial ligation of single extrahepatic portosystemic shunts in 8 dogs. Scintigraphy was performed before surgery, within the first 7 days after surgery, and 3 to 9 months after surgery. Shunt fraction values for this group of dogs before surgery ranged from 67 to 87% (normal reference range, ≤ 15%). On the basis of postoperative scintigraphy, 4 dogs had immediate and lasting occlusion of shunt blood flow (shunt fraction, ≤ 15%). One dog had a shunt fraction value within the reference range immediately after surgery, had evidence of recurrent shunt blood flow (shunt fraction, 23%) at 3 months after surgery, and again had a shunt fraction value within the reference range 9 months after surgery. Persistent, though reduced, shunt blood flow (shunt fractions, 23 and 2 7%) was evident immediately after surgery in 2 dogs. One of these dogs had a shunt fraction within the reference range 3 months after surgery, whereas shunt blood flow in the other dog had increased to 41%. One dog had no appreciable change in shunt blood flow immediately after surgery (shunt fraction, 70%), but the shunt fraction value had decreased to 41% at the time of the final scintigraphic examination.

As assessed by transcolonic portal scintigraphy, partial single extrahepatic portosystemic ligation caused a significant decrease in mean shunt blood flow in this group of 8 dogs and resulted in eventual shunt occlusion in a majority of the dogs (6 of 8 dogs). Partial ligation with progressive attenuation of shunt blood flow may obviate the need to perform additional surgery.

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in Journal of the American Veterinary Medical Association

Abstract

Thyroid gland scintigraphy was performed in 29 dogs with histologically confirmed thyroid tumors. Twenty dogs were female, and 9 were male. Median age was 10 years. Of the 29 dogs, 21 were initially examined because of cervical swelling or a cervical mass. Of the 29 tumors, 24 were thyroid adenocarcinomas, 1 was a C-cell carcinoma, 3 were undifferentiated carcinomas, and 1 was a thyroid adenoma. Serum triiodothyronine and thyroxine concentrations were determined in 25 dogs. Sixteen dogs were euthyroid, 6 were hyperthyroid, and 3 were hypothyroid.

In all 29 dogs, results of scintigraphy were abnormal. The most common scintigraphic appearance (13 dogs) was a unilateral thyroid mass with increased radionuclide uptake, relative to that of the parotid salivary glands. There did not appear to be an association between distribution of radionuclide uptake and histologic diagnosis, although there appeared to be an association between distribution of uptake and histologic degree of capsular invasion. All 4 dogs with extensive capsular invasion and 11 of 17 dogs with limited capsular invasion had poorly circumscribed, heterogeneous uptake of pertechnetate by the tumor. All hyperthyroid dogs had intense uptake, and 5 of 6 hyperthyroid dogs had well-circumscribed, homogenous uptake. Scintigraphy did not appear to offer any additional benefit, compared with thoracic radiography, for detection of pulmonary metastases.

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in Journal of the American Veterinary Medical Association

Summary

99mTechnetium-pertechnetate, when administered in high concentration into the colon, is rapidly absorbed across the colonic mucosa and results in a nuclear angiogram of the portal circulation. In normal dogs, a series of dynamic lateral scintigraphic images of the abdomen resulted in sequential visualization of the portal vein, liver, and several seconds later, the heart and lungs. In contrast, studies performed in 9 dogs with surgically confirmed portosystemic shunts demonstrated a different pattern of distribution, with heart and lung activity occurring before liver activity. In several cases, the aberrant shunt vessels could be identified. Studies were easy to perform, were well tolerated, and required no computer processing for interpretation.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine prevalence of pituitary tumors, detectable by means of computed tomography or magnetic resonance imaging, in cats with insulin resistance suspected to have acromegaly or hyperadrenocorticism versus cats with well-controlled diabetes mellitus.

Design—Case series.

Animals—16 cats with insulin resistance that were also suspected to have acromegaly (n = 12) or pituitary-dependent hyperadrenocorticism (4) and 8 cats with well-controlled diabetes mellitus.

Procedure—Computed tomography was performed on all 16 cats with insulin resistance and 2 cats in which diabetes mellitus was well-controlled. The remaining 6 cats in which diabetes mellitus was wellcontrolled underwent magnetic resonance imaging. Images were obtained before and immediately after IV administration of contrast medium.

Results—Computed tomography revealed a mass in the region of the pituitary gland in all 16 cats with insulin resistance. Maximum width of the masses ranged from 4.4 to 12.7 mm; maximum height ranged from 3.1 to 12.6 mm. Results of computed tomography performed on 2 cats with well-controlled diabetes and magnetic resonance imaging performed on the remaining 6 cats were considered normal.

Conclusions and Clinical Relevance—Results suggest that cats with insulin resistance suspected to have acromegaly or pituitary-dependent hyperadrenocorticism are likely to have a pituitary mass detectable by means of computed tomography or magnetic resonance imaging. (J Am Vet Med Assoc 2000;216: 1765–1768)

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in Journal of the American Veterinary Medical Association

SUMMARY

Objective

To determine plasma clearance kinetics and imaging biodistribution of indium 111-labeled transferrin (111In-TF) in dogs.

Animals

7 adult dogs.

Procedure

After 30 minutes’ incubation of 18.5 MBq (0.5 mCi) of 111InCl3 with 1 ml of serum (n = 3) or 1 ml of plasma (n = 4) at 37 C, dogs were given autologous 111In-TF IV, and serial blood samples and right lateral and dorsal scintigraphic images were obtained immediately and 1, 3, 5, 9, 22, and 48 hours later. Blood and plasma clearance kinetics were determined from a least-squares, nonlinear fit of the sample radioactivity data. Blood radioactivity was compared with plasma radioactivity to determine the extent of cellular labeling. Imaging biodistribution was characterized by subjective and objective assessment of blood pool, liver, gastrointestinal (abdomen) tract, kidney, and bone marrow activity.

Results

111In-TF plasma clearance was best described by a biexponential fit, with early and late clearance half-times of 6 and 49 hours, respectively. The 111In was not redistributed between transferrin (plasma proteins) and blood cells. Imaging studies documented progressive liver and bone marrow uptake of the 111In-TF over 48 hours. Some radioactivity was evident in the colon of 1 dog on 48-hour images. Decay-corrected count rates (counts/pixel/mCi/kg/min) within the abdominal region of interest increased over the 48-hour imaging period and exceeded the blood pool (cardiac) activity at 20 hours after injection.

Conclusion

111In-TF has a biexponential plasma clearance in clinically normal dogs, with early and late clearance half-time of 6 and 49 hours, respectively. Scintigraphically, 111In-TF localizes to sites of iron storage (bone marrow and liver) over time. Some loss of 111In-TF via the gastrointestinal tract may be seen on late 48-hour images.

Clinical Relevance

111In-TF appears to be a viable radiopharmaceutical for use in dogs, with specific application for identifying those with protein-losing enteropathy. (Am J Vet Res 1997;58:1188–1192)

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in American Journal of Veterinary Research

Objective

To determine efficacy of cobalt 60 radiotherapy in dogs with pituitary-dependent hyperadreno-corticism (PDH) that have detectable tumors but no neurologic abnormalities.

Design

Case series.

Animals

6 dogs with PDH that had a detectable pituitary mass on magnetic resonance images.

Procedure

Radiation was delivered in 11 fractions during a 3.5-week period for a total dose of 44 Gy. Clinical signs were evaluated, a urinalysis and ACTH stimulation test were performed, and urine cortisol-to-creatinine ratio and plasma endogenous ACTH concentration were measured before, immediately after, and 1, 3, 6, 9, and 12 months after radiotherapy. Magnetic resonance imaging was repeated 1 year after radiotherapy.

Results

Clinical signs of hyperadrenocorticism resolved in 3 dogs but recurred in 2 of the 3. Clinical condition of 2 dogs improved but did not return to normal. One dog did not improve. Results of ACTH stimulation tests and urine cortisol-to-creatinine ratios correlated with clinical signs. Plasma endogenous ACTH concentration transiently decreased in all 6 dogs. One year after radiotherapy, size of tumors was decreased by 25% in 2 dogs; in the other 4 dogs, tumors could no longer be detected. None of the dogs developed neurologic abnormalities. Adverse effects of radiotherapy were mild.

Clinical Implications

Radiotherapy did not result in adequate control of clinical signs of hyperadrenocorticism in 5 of 6 dogs, but size of pituitary tumors was dramatically reduced. Thus, it may be reasonable to recommend radiotherapy in dogs with PDH that have pituitary tumors for which greatest vertical height is 8 mm or more. (J Am Vet Med Assoc 1998; 212:374-376)

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in Journal of the American Veterinary Medical Association

SUMMARY

Technetium-99m sulfur colloid scintigraphy was used to study alterations of reticuloendothelial function in 7 dogs with experimentally induced biliary cirrhosis and portosystemic shunting. Scintigraphic studies were performed before and 6 weeks after common bile duct ligation. Radiocolloid plasma clearance rate was determined by measuring activity in plasma samples and by analyzing the rate of liver uptake on dynamic scintigraphic image sequences. Percentage of uptake in the liver, spleen, and lungs, as well as the ratio of hepatic-to-extrahepatic uptake, was determined from static equilibrium images. Relative to preoperative values, there were significant decreases in plasma clearance rate, percentage of fiver uptake, and ratio of hepatic-to-extrahepatic uptake and significant increases in percentage of spleen and lung uptake on postoperative studies.

The mechanism of technetium-99m-labeled sulfur colloid extraction by the liver is different from that of other radiocolloids; it does not require active phagocytosis or pinocytosis. Thus, fiver uptake of this tracer principally reflects effective liver blood flow. Portosystemic shunting was documented in these dogs at the time of the postoperative radiocolloid scans, and we believed was responsible for the decrease in liver reticuloendothelial activity. Possible mechanisms for the increased splenic and pulmonary reticuloendothelial activities are discussed.

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in American Journal of Veterinary Research

SUMMARY

The source of a previously described radiolucent crescent in the flexor cortex of the distal sesamoid (navicular) bone on the palmaro45°proximal-palmarodistal oblique (Pa45°Pr-PaDio) clinical radiographic projection was investigated in 48 forelimb navicular bones from 24 Thoroughbreds by use of high-detail radiography and x-ray computed tomography (ct). Twenty-five of these bones also were evaluated, using microradiography and histologic examinations. Of these 25 bones, 5 had been labeled in vivo with fluorochrome markers. Tetrachrome-stained 100-µm-thick nondecalcified sections of these 5 bones were examined, using epifluorescence microscopy.

A reinforcement line of compacted cancellous bone, parallel and several millimeters deep to the flexor cortex in the region of the flexor central eminence, was visualized by ct in 42 of 48 navicular bones and by microradiography in 23 of 25 navicular bones investigated. Variable degrees of compaction were observed in the cancellous bone between the flexor cortex and the reinforcement line. High-detail skyline radiographic projections and reconstructed ct images indicated a crescent-shaped lucency within the flexor central eminence of the flexor cortex in the bones in which the reinforcement line was identified, but the cancellous bone between the reinforcement line and the flexor cortex had not been compacted. The radiolucent crescent seen in the flexor central eminence of the navicular bone on the Pa45°Pr-PaDiO projection was not caused by the concave defect or synovial fossa of the flexor central eminence overlying the flexor cortex, as was described. The crescent-shaped lucency within the navicular bone flexor central eminence identified on clinical radiographs was associated with remodeling of cancellous bone within the medullary cavity of the navicular bone. It is hypothesized that remodeling of the cancellous bone is secondary to biomechanical stresses and strains placed on the navicular bone, although the clinical relevance of this finding was not determined during the study.

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in American Journal of Veterinary Research