OSTEOSARCOMA WITH A PATHOLOGIC FRACTURE IN A SIX-MONTH-OLD DOG

This case history report describes the clinical, radiographic, and histopathologic features of an osteosarcoma with an associated pathologic fracture in a 6-month-old dog. A 6-month-old intact male Bloodhound was presented with a primary complaint of a right forelimb lameness of one month's duration. In radiographs, a minimally displaced transverse fracture of the proximal humeral metaphysis was seen. There was extensive cortical bone destruction at the fracture site and minimal periosteal new bone suggestive of a primary bone tumor with a pathologic fracture. Biopsy specimens demonstrated neoplastic mesenchymal cells producing osteoid compatible with a diagnosis of osteosarcoma. This case history report constitutes the youngest reported canine osteosarcoma.     

OSTEOSARCOMA OF THE PATELLA WITH PULMONARY METASTASES IN A DOG

A 6-year-old neutered male Rottweiler was examined for a progressive right pelvic limb lameness. In radiographs of the right stifle, there was an osteolytic lesion with irregular new bone formation along the cranial aspect of the patella consistent with an aggressive bone lesion. In thoracic radiographs, there were multiple soft tissue nodular opacities throughout the lung fields, consistent with pulmonary metastases. Microscopically, fine needle aspirate samples from the right patella contained pleomorphic spindle cells with cytologic features of osteosarcoma. The presence of pulmonary metastases at the time of initial diagnosis in the dog described herein suggests that osteosarcoma of the patella has the potential for similar aggressive biologic behavior as that seen in dogs with appendicular osteosarcoma.     

OSTEOSARCOMA IN THE MIDDIAPHYSIS OF THE RADIUS IN THE DOG

This case report describes the radiographic/clinical progression of a lesion in the middiaphysis of the radius in a dog. The lesion initially looked benign but progressed and eventually was diagnosed as an anaplastic osteosarcoma.     

ULTRASONOGRAPHIC EXAMINATION OF CERVICAL MASSES IN THE DOG AND CAT

The ultrasonographic appearance of clinically undifferentiated neck masses for which a definitive diagnosis was eventually obtained in nineteen dogs and one cat is presented in this report. Multiple lesions were seen ultrasonographically in 4 dogs and no cervical abnormalities were seen in 2 dogs resulting in 22 lesions in 20 annuals. Of 7 benign lesions, there were 2 patients with reactive lymph nodes from a regional inflammatory process, and 1 patient each with primary pyogranulomatous lymphadenitis, arteriovenous malformation, foreign body granuloma, cellulitis, and hematoma. Of 15 malignant lesions, 7 were thyroid carcinomas, 3 were lymphomas with submandibular and cervical lymph node enlargement, 3 were lymph node enlargements associated with regional metastasis of malignant tumors, one was a leiomyosarcoma and one was a carotid body tumor. One dog with a diffuse soft tissue swelling of the ventral cervical region had only slight asymmetry of the thyroid lobes on ultrasound examination and no abnormalities of the neck at post mortem. A second dog examined with ultrasound 4 months after surgical removal of a carotid body tumor had no evidence of tumor recurrence. Ultrasonographic examination provided information regarding the character of the lesions, the tissue or organ of origin, and invasion into other anatomic structures. Ultrasound examination in conjunction with fine needle or tissue biopsy provided a definitive diagnosis in those animals in which biopsies were performed.     

RADIOGRAPHIC DEFINITION OF THE ANTICLINAL VERTEBRA IN THE DOG

The anticlinal vertebra is a point in the caudal thoracic vertebral column at which vertebral anatomic features change. It may be used as a point of reference in diagnostic imaging studies. However, its exact definition and anatomic location are not consistent between anatomic texts. The position of the anticlinal vertebra was evaluated radiographically in 100 dogs, using three different definitions of the anticlinal vertebra. Definition P referred to perpendicularity of the spinous proceses, definition V referred to verticality of the spinous processes, and definition J referred to the orientation of the intervertebral joints. The anticlinal vertebra was assessed to be T11 in 85%, 75%, and 89% of dogs for definitions P, V, and J, respectively. Combining definitions improved the likelihood that the vertebra assessed to be the anticlinal vertebra was T11, if the combination included definition J, but at the expense of loss of sensitivity. The degree of agreement between the definitions ranged from fair to poor. The level of agreement between definitions P and J was improved for small and large dogs and the level of agreement between definitions V and J was improved for medium and large dogs. Compared with large breed dogs, small breed dogs were more likely to have T10 described as the anticlinal vertebra. The presence of transitional vertebra did not affect the position of the anticlinal vertebra. It should not be assumed that the anticlinal vertebra is T11 in all dogs. Care should be taken to define this anatomic feature accurately when using it as an anatomic landmark.     

FEMORAL OSTEOMYELITIS AND OSTEOSARCOMA IN A DOG

An eight-year-old, female, spayed Golden Retriever was referred to the University of Missouri Veterinary Teaching Hospital for a persistent lameness of 9 days duration. The initial diagnosis made by cytology and culture was Clostridium spp osteomyelitis of the right femoral head and neck. After approximately 1 month of treatment with ampicillin, it was noted radiographically that the lesion was progressing. An excision arthroplasty was done. Histological examination of the surgical specimen revealed osteogenic sarcoma. This case documents the importance of bone biopsy in differentiating osteomyelitis from a primary bone tumor.     

IMAGING DIAGNOSIS: CRANIAL CERVICAL INTRASPINAL SCHWANNOMA IN A DOG

A 3‐year‐old, intact female Golden Retriever was presented with acute tetraplegia. Neurologic examination was consistent with a C1–C5 myelopathy. On magnetic resonance (MR) imaging a well‐defined, extradural mass was detected within the spinal canal at the level of C1–C2. The mass was isointense to normal spinal cord gray matter on T1‐weighted (T1W) images, hyperintense on T2‐weighted (T2W), and gradient‐echo (GE) images, and enhanced homogeneously after intravenous contrast administration. MR imaging features were mainly consistent with a meningioma. Surgical treatment was refused by the owners, and the dog was euthanized. Postmortem examination demonstrated that the intraspinal mass was a schwannoma.     

SCINTIGRAPHIC DETECTION OF SUBCUTANEOUS METASTASIS IN A DOG WITH APPENDICULAR OSTEOSARCOMA

This report describes the detection of subclinical soft tissue metastasis of an appendicular osteosarcoma in a dog using bone scintigraphy. A 7-year-old spayed female Rottweiler was presented with a biopsy confirmed diagnosis of osteosarcoma. Initial radiographs revealed an aggressive bone lesion of the left distal radius. At presentation, there was no clinical or radiographic evidence of metastasis; however, a nuclear bone scan showed the primary bone lesion of the distal left radius and numerous soft tissue lesions consistent with diffuse soft tissue metastases. A left foreleg amputation was performed and cisplatin chemotherapy was given post-operatively. A second bone scan performed one month following initial presentation showed progression in size and number of soft tissue masses. Many of the lesions had become apparent on physical exam and survey radiographs. Excisional biopsy was performed on one of the soft tissue masses and a diagnosis of metastatic osteosarcoma was made. The dog was euthanized 2 months after initial presentation at the owners request due to deterioration of the animals physical condition.     

DIPHOSPHONATE TREATMENT OF A PRIMARY OSTEOSARCOMA IN A DOG: A CASE REPORT

The following sequence of treatments was administered to a Saint Bernard dog with a primary distal right radius osteosarcoma: 54 days of daily disodium 1-hydroxyethylidenediphosphonate (HEDP) subcutaneous injections; 53 days of HEDP per os ; one ³²P-HEDP intravenous injection. During the pretreatment period, there was an extensive increase in calcific tumor growth and osteoblastic proliferation. After the subcutaneous HEDP treatment, almost complete tumor necrosis was seen. After the oral HEDP treatment, only the deepest tumor portion contained active osteoblasts, calcific growth of the tumor was completely blocked, and uptake of ^99mTc-Sn-HEDP was reduced to one fourth of the pretreatment uptake. After a single ³²P-HEDP dose, large areas of tumor necrosis were evident histopathologically. However, subsequent resumption of cellular activity occurred in the tumor, and the uptake of ^99mTc-Sn-HEDP increased to pretreatment values. These data suggest that systemically administered HEDP should be studied further for its possible therapeutic potential in the treatment of osteosarcoma and indicate a need for further study of ³²P-HEDP or possibly ³³P-HEDP.     

INCOMPLETE OSSIFICATION OF THE ATLAS IN DOGS WITH CERVICAL SIGNS

Osseous defects affecting the atlas were identified in computed tomography and magnetic resonance images of five dogs with cervical signs including pain, ataxia, tetraparesis, or tetraplegia. Osseous defects corresponded to normal positions of sutures between the halves of the neural arch and the intercentrum, and were compatible with incomplete ossification. Alignment between the portions of the atlas appeared relatively normal in four dogs. In these dogs the bone edges were smooth and rounded with a superficial layer of relatively compact cortical bone. Displacement compatible with unstable fracture was evident in one dog. Concurrent atlantoaxial subluxation, with dorsal displacement of the axis relative to the atlas, was evident in four dogs. Three dogs received surgical treatment and two dogs were treated conservatively. All dogs improved clinically. Incomplete ossification of the atlas, which may be associated with atlantoaxial subluxation, should be considered in the differential diagnosis of dogs with clinical signs localized to the cranial cervical region.     

A LUMBOSACRAL TRANSITIONAL VERTEBRA IN THE DOG PREDISPOSES TO CAUDA EQUINA SYNDROME

The association between the occurrence of a lumbosacral transitional vertebra (LTV) and the cauda equina syndrome (CES) in dogs was investigated. In 4000 control dogs without signs of CES, 3.5% had an LTV, while in 92 dogs with CES, 16.3% had an LTV. The lesion causing CES always occurred between the last true lumbar vertebra and the LTV. Dogs with an LTV were eight times more likely to develop CES than dogs without an LTV. German Shepherd dogs were eight times more likely to develop CES compared with other breeds. Male dogs were twice as likely to develop CES than females. Dogs with an LTV develop CES 1-2 years earlier than dogs without an LTV.     

A COMPARISON OF IOPAMIDOL AND METRIZAMIDE FOR CERVICAL MYELOGRAPHY IN THE DOG

Cervical myelography using iopamidol, a new nonionic contrast medium, was studied in nine dogs. Postmyelographic seizure activity, motor evoked potentials, and rectal temperatures were monitored, and myelographic quality was subjectively evaluated. The results were compared with data from eight dogs that had metrizamide myelography. The iopamidol group had fewer seizures ( p < 0.01) but exhibited no difference in motor evoked potential or rectal temperature recordings. Myelographic quality was similar for iopamidol and metrizamide. The study suggests that iopamidol was less neurotoxic than metrizamide for canine cervical myelography.     

EVALUATION OF TRADITIONAL AND NOVEL RADIOGRAPHIC VERTEBRAL RATIOS IN GREAT DANES WITH VERSUS WITHOUT CERVICAL SPONDYLOMYELOPATHY

Great Danes are predisposed to osseous‐associated cervical spondylomyelopathy (Wobbler syndrome). The first aim of this prospective study was to compare values measured using previously published intravertebral and intervertebral ratio methods and a novel ventrodorsal ratio method in radiographs of clinically normal and affected Great Danes. The second aim was to determine whether these ratios could be used as predictors of sites of spinal cord compression based on magnetic resonance imaging (MRI). Thirty dogs (15 normal, 15 affected) were prospectively enrolled. Lateral and ventrodorsal radiographs were obtained and six measurements were recorded from C3‐T1. For each vertebral location, intravertebral ratios and intervertebral ratios were calculated from lateral views, and the ratio of the distance between the articular process joints vs. vertebral body width (novel ventrodorsal ratio) was calculated from ventrodorsal views. Values for these three ratios were compared, by vertebral location and dog group. Intravertebral and intervertebral ratios did not differ between dog groups. The ventrodorsal ratio was significantly smaller in affected Great Danes at C5–6 (P = 0.005) and C6–7 (P < 0.001). The ventrodorsal ratio was significantly associated with MRI presence of spinal cord compression. For each 0.1 unit increase in this ratio value, there was a 65% decrease in the odds of spinal cord compression being present at that site, independent of vertebral location (P = 0.002). Findings from this study supported use of the novel ventrodorsal ratio as an initial radiographic screening method for Great Danes with suspected cervical spondylomyelopathy.     

MAGNETIC RESONANCE IMAGING OF THE CERVICAL SPINE IN 27 DOGS

The cervical spine of 27 dogs with cervical pain or cervical myelopathy was evaluated using magnetic resonance imaging (MRI). Spin echo T1, T2, and post-contrast T1 weighted imaging sequences were obtained with a 0.5 Tesla magnet in 5 dogs and a 1.5 Tesla magnet in the remaining 22 dogs. MRI provided for visualization of the entire cervical spine including the vertebral bodies, intervertebral discs, vertebral canal, and spinal cord. Disorders noted included intervertebral disc degeneration and/or protrusion (12 dogs), intradural extramedullary mass lesions (3 dogs), intradural and extradural nerve root tumors (3 dogs), hydromyelia/syringomyelia (1 dog), intramedullary ring enhancing lesions (1 dog), extradural synovial cysts (1 dog), and extradural compressive lesions (3 dogs). The MRI findings were consistent with surgical findings in 18 dogs that underwent surgery. Magnetic resonance imaging provided a safe, useful non-invasive method of evaluating the cervical spinal cord.     

PRIMARY OSTEOSARCOMA OF THE STERNUM OF A DOG

Primary osteosarcoma of the fifth sternebra is reported in a 6-year-old male Great Dane. Presenting signs were suggestive of myocarditis and pulmonary congestion. Electrocardiography revealed R waves of low and variable amplitude and the plasma alpha-hydroxibutyrate dehydrogenase level was elevated. Radiography revealed neoplasia of the fifth sternebra with extensive bilaterial pulmonary metastases. Histologically the neoplasm showed typical osteosarcoma with plentiful osteoid production.     

RELATIONSHIP OF CERVICAL SPINAL CORD DIAMETER TO VERTEBRAL DIMENSIONS: A RADIOGRAPHIC STUDY OF NORMAL DOGS

Cervical spinal cord abnormalities are often unapparent on myelographic studies, because no normal values for cervical spinal cord diameter are currently available. The purpose of this study was to establish, myelographically, the normal sagittal diameter of the cervical spinal cord in large and small breed dogs and its relationship to the sagittal diameter of the vertebral canal and sagittal height/length of the corresponding vertebral bodies. Forty-one adult dogs underwent cervical radiography and myelography. Spinal cord and vertebral canal sagittal diameter, vertebral body height at C2 to 5, body length at C3 to 5, and dorsal spine length of C2 were measured on lateral views. Ratios of spinal cord:vertebral canal diameter, spinal cord:body height, and spinal cord:body length/spine were calculated, and a normal range was determined for small and large breed dogs. The spinal cord:vertebral canal ratios showed that small breeds have a higher cervical cord-to-canal ratio than large breeds. The mean values and ranges of 14 ratios are reported. The ratios of spinal cord:body length at C2 to 4 in small breeds and spinal cord:body height at C3 to 5 in large breeds were found to be the most accurate for assessing spinal cord sagittal diameter. These normal ranges would allow quantitative and objective evaluation of the cervical spinal cord by myelography and early identification of dogs with altered spinal cord diameter, which could be further evaluated by means of alternative imaging techniques.     

RADIATION INDUCED VERTEBRAL OSTEOSARCOMA FOLLOWING TREATMENT OF AN INTRADURAL EXTRAMEDULLARY SPINAL CORD TUMOR IN A DOG

A 2-year-old neutered female Rottweiler diagnosed with an intradural extramedullary spinal cord tumor at T12-T13 was successfully treated with cytoreductive surgery followed by Cobalt 60 teletherapy. The dog was euthanised 5-and-a-half years later following diagnosis of an osteosarcoma involving the L1 and L2 vertebrae. Evidence of the initial tumor was not present at necropsy. The vertebral neoplasm fulfilled all of the accepted criteria for a radiation induced tumor. It was concluded that adjunctive irradiation should be considered for treatment of intradural extramedullary tumors of young dogs when total surgical resection is not possible. Although tumor induction is a rare late effect of radiation therapy, the risk of this occurrence should be considered when irradiating young animals. Radiation induced tumors in dogs have been associated with coarse fractionation schemes, or when large intraoperative doses have been administered. A lower dose per fraction, e.g., 3 Gy/fraction or less, is advisable when irradiating young dogs or any dog in which the life expectancy is 3-5 or more years after irradiation.     

PREVALENCE OF ANATOMICAL VARIATION OF THE SIXTH CERVICAL VERTEBRA AND ASSOCIATION WITH VERTEBRAL CANAL STENOSIS AND ARTICULAR PROCESS OSTEOARTHRITIS IN THE HORSE

The sixth cervical vertebra (C6) has unique morphology due to a ventral extension from the transverse process known as the ventral lamina. Little information was found regarding the prevalence and clinical relevance of morphologic variations. Aims of this observational, retrospective study were to characterize C6 morphologic variations in a large sample of horses. Cervical radiographic studies of 100 horses were retrieved. Data recorded were signalment, clinical history, morphology of the C6 ventral lamina, presence of articular process osteoarthritis, and presence of static vertebral canal stenosis. Morphologic variations were found in C6 vertebrae for 24/100 horses, with symmetric absence of the ventral lamina in nine horses and asymmetric absence in 15. Anomalous C6 vertebrae were more common in Warmbloods, with 19/55 Warmbloods in the population being affected (P = 0.006). No association was found with sex. There was no significant difference in the mean of the intravertebral sagittal ratios between horses with normal or anomalous C6 vertebrae; however there was a significantly greater proportion of horses with anomalous C6 vertebrae that had an intravertebral sagittal ratio of less than 0.5 at C6 (P = 0.047). There was no association between the morphology of C6 and articular process osteoarthritis. Anomalous C6 vertebrae in our population were associated with a higher likelihood of cervical pain (P = 0.013). Authors propose that morphologic variations in the C6 ventral laminae could be linked to other developmental abnormalities such as vertebral canal stenosis, might affect regional biomechanics and should therefore be considered clinically relevant in horses. Future, controlled prospective studies are needed to test this theory.     

CORCTATION OF THE AORTA IN A DOG

This paper describes coarctation of the aorta with a large fusiform post-stenotic aneurysm in a 6 year old Great Dane. No clinical signs were attributable to the lesion, which was an incidental finding. The radiological and pathological features of aortic coarctation are described.     

ENDOSCOPIC ULTRASONOGRAPHY OF THE PANCREAS IN THE DOG

Endoscopic ultrasonography was done in 12 normal adult dogs to investigate its efficacy in visualization of the pancreas. The endoscopic ultrasonographic device used in the present study had a curved-array ultrasound transducer mounted in front of the objective lens. The tip of the ultrasonic endoscope was inserted into the stomach, and all examinations of the pancreas were performed from within the stomach. Endoscopic ultrasonography provided good images of most parts of the pancreas except for the ends of each lobe. Useful information about the pancreatic parenchyma, including pancreatic lobular structure, pancreatic duct, and vessels of the pancreas was obtained by endoscopic ultrasonography. Blood flow within vessels was detected using color Doppler and pulsed-wave Doppler examination. These results suggest that endoscopic ultrasonography is available as an effective diagnostic modality in small animal practice.