Modified in vitro method to label equine red blood cells with technetium 99m in concentrated whole blood

An in vitro method to label equine RBC with technetium 99m was modified to achieve quantitative labeling of cells in concentrated whole blood. After a blood sample was incubated with a reducing agent (stannous citrate), an oxidizing reagent (NaOCl) and a chelating agent (EDTA) were added to inactivate residual Sn2+ in the plasma. This step prevented premature reduction of pertechnetate in plasma. Labeling of RBC from 9 healthy horses, using a standard whole blood protocol, resulted in only moderate labeling efficiency (44 to 85%) and indicated a linear relationship between labeling efficiency and PCV. Effects of increased incubation time, increased incubation temperature, prelabeling sedimentation, and double addition of NaOCl/EDTA were investigated in whole blood from 10 healthy horses. Labeling efficiency was improved by each independent factor and by combination of factors. Highest labeling efficiencies (96 to 97%) were achieved when blood samples were sedimented for 20 minutes before being labeled, regardless of incubation time or incubation temperature. Morphologic features of RBC were unaffected by labeling procedures. In vivo whole blood clearance time for labeled cells was determined in 5 healthy horses. Sedimented blood samples were labeled, using a standard 15-minute incubation time at 20 to 22 C. Mean clearance half-time for 5 horses was approximately 20 hours. More than 95% of 99mTc activity was associated with the cells during the 24 hours after reinjection.     

SCINTIGRAPHIC EVALUATION OF SKELETAL DISEASE AND ITS APPLICATION TO THE HORSE

Bone scintigraphy is a valuable aid in the evaluation of lameness in horses. This review describes the principles of bone radiolabeling, scanning, and scan interpretation. Examples are used to illustrate how bone imaging can contribute significantly to a diagnosis after equivocal physical examination or radiographic findings.     

Incomplete palmar fracture of the proximal extremity of the third metacarpal bone in horses: ten cases (1981-1986)

In 4 adult horses, simple, nondisplaced, incomplete fracture of the proximal extremity of the third metacarpal bone (MC3) was identified radiographically only on the dorsopalmar projection. Lameness was slight to moderate. Although nerve blocks of the foot and fetlock did not alter the lameness, high palmar regional nerve block improved the gait in 1 of the 2 horses on which it was performed. Pain on palpation or swollen distal accessory (inferior check) ligament, flexor tendons, and suspensory ligament were not found in any horse. The fracture was localized to the palmar surface of the proximal extremity of the MC3 on the basis of the intense uptake of radiopharmaceutical (99MTc-labeled sodium medronate) observed in that area during the soft tissue and delayed bone phases of a nuclear scintigraphic examination (nuclear scan) performed concurrently with radiography. Of 4 horses evaluated 6 months after the initial diagnosis, 3 had medullary sclerosis without radiographic evidence of fracture; results of follow-up nuclear scintigraphy performed in one of these horses at the same time were normal. Incomplete fracture also was suspected in another 6 adult horses with clinical lameness referable to the proximal extremity of the MC3. Although a fracture line could not be seen radiographically, trabecular hypertrophy and/or medullary sclerosis of the proximal extremity of the MC3 were detected on the dorsopalmar projection. Further, during nuclear scintigraphy, an intense uptake of the radiopharmaceutical was observed on the palmar aspect of the proximal extremity of the MC3 in all 6 horses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of transcolonic 99mtechnetium-pertechnetate as a screening test for portosystemic shunts in dogs

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.     

Technetium 99m Sulfur Colloid Scintigraphy to Evaluate Reticuloendothelial System Function in Dogs With Portasystemic Shunts

In a retrospective study, technetium 99m sulfur colloid scintigraphy was used to evaluate reticuloendothelial system function in 61 dogs with single congenital and 40 dogs with multiple acquired portasystemic shunts. Whole body reticuloendothelial function was measured by calculating the plasma clearance rate constant from a dynamic study of liver uptake of ^99mTc sulfur colloid. Relative liver, spleen, and lung uptake, and a ratio of hepatic:extrahepatic uptake were measured on static equilibrium images. Results were compared with those of a group of 26 normal dogs. Compared with values for the group of normal dogs, the plasma clearance rate constant, relative liver uptake, and hepaticiextrahepatic uptake ratio were significantly decreased, and relative spleen and lung uptake were significantly increased in dogs with portasystemic shunts ( P <.0001). The only significant difference between dogs with single congenital versus multiple acquired shunts was that the relative splenic uptake was higher in the former group ( P <.0002). Based on these results, we concluded that dogs with portasystemic shunts have significantly impaired reticuloendothelial function. The primary cause of this dysfunction is likely a reduction in effective liver blood flow. Increases in spleen and lung reticuloendothelial activity did occur, but only partially compensated for the reduction of liver reticuloendothelial activity. Possible mechanisms for the increased spleen and lung uptake are discussed.     

COMPUTED TOMOGRAPHIC EVALUATION OF HEAD TRAUMA IN A FOAL

This case report describes computed tomographic findings of a three-month-old, 180 kg female Arabian foal that had suffered head trauma. Computed tomography proved valuable in antemortem diagnosis of skull base fracture and extradural hematoma, which were confirmed by postmortem examination.     

AZYGOS CONTINUATION OF THE CAUDAL VENA CAVA IN A DOG: RADIOGRAPHIC AND ULTRASONOGRAPHIC DIAGNOSIS

Azygos continuation of the caudal vena cava was identified via ultrasonography and angiography in a 7 month old female boxer. Azygos continuation of the caudal vena cava is a rare vascular anomaly that results from failure of anastomosis between the caudal cardinal system and the right vitelline vein during embryogenesis. This anomaly has also been described in association with portoazygos shunt.     

Pulmonary Lymphomatoid Granulomatosis in Seven Dogs (1976–1987)

Seven dogs with pulmonary lymphomatoid granulomatosis were reviewed. The disease occurred in six large-breed and one small-breed dogs. The dogs were five to 14 years old (mean, 8.4; median, 7), and four of seven dogs were males. Three dogs had been previously treated with adulticide therapy for canine dirofilariasis. Clinical histories included a progressive respiratory disease characterized by varying degrees of cough, dyspnea, exercise intolerance, and weight loss. Thoracic radiographic features included hilar lymphadenopathy, pulmonary masses of varying sizes, and mixed pulmonary patterns of lobar consolidation with ill-defined interstitial and alveolar pulmonary infiltrates. Cardiovascular changes compatible with chronic dirofilariasis were present in three dogs. The clinical course was usually progressive and fatal. The survival time ranged from six days to four years (mean, 12.5 mos; median, 3 mos). Gross and histologic features included mass lesions with areas of necrosis that replaced normal pulmonary architecture. Cytologically, these lesions were characterized by infiltration with pleomorphic, angioinvasive mononuclear cells that often resulted in vascular obliteration. The infiltrating cells resembled large lymphoid cells that possessed large hyperchromatic nuclei and small amounts of cytoplasm. Systemic lymphoid neoplasia with peripheral lymphadenopathy was diagnosed in two dogs. In both cases, lymph-node cytology was similar to the cellular infiltrates found in the lungs and consistent with a diagnosis of lymphomatoid granulomatosis. These features are compared with previously reported cases of canine lymphomatoid granulomatosis and those features identified in a similar disease described in man.     

QUANTITATIVE SURVEY RADIOGRAPHIC EVALUATION OF THE LUMBOSACRAL SPINE OF NORMAL DOGS AND DOGS WITH DEGENERATIVE LUMBOSACRAL STENOSIS

Survey radiographic studies of the lumbosacral region for 93 normal dogs and for 26 dogs with confirmed degenerative lumbosacral stenosis were reviewed. Normal dogs were divided into 9 groups based on age and body weight. For normal dogs, increasing age and body weight were associated with a decreased ability to extend the lumbosacral joint and with increased incidence and severity of spondylosis. Transitional lumbosacral vertebrae and evidence of lumbosacral disc space collapse were very infrequent findings, and the pivot point for lumbosacral motion was consistently centered over the lumbosacral disc space. Relative to an age/weight matched sub-population of normal dogs, dogs with degenerative lumbosacral stenosis had similar mean normalized lumbosacral vertebral canal height, larger mean neutral lumbosacral angle, decreased extension of the lumbosacral joint, increased flexion of the lumbosacral joint, reduced lumbosacral range of motion, increased lumbosacral dynamic malalignment, higher incidence and severity of spondylosis, higher incidence of transitional vertebrae, and higher incidence of lumbosacral disc space collapse. A logistic model based strictly on radiographic parameters was able to discriminate normal from affected dogs with an overall accuracy rate of 86%.