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.     

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.     

PAROSTEAL OSTEOSARCOMA OF THE CERVICAL VERTEBRA IN A DOG

A 12-year-old Maltese terrier was evaluated for progressive tetraparesis and neck pain. On radiographs, there was a periosteal reaction involving the fourth cervical vertebra. Myelographically, there was extradural compression of the spinal cord associated with the lesion. The dog was euthanized and necropsied. Histopathologic diagnosis was parosteal osteosarcoma of the vertebra.     

PALLIATIVE RADIOTHERAPY OF APPENDICULAR OSTEOSARCOMA IN 95 DOGS

Ninety-five dogs with either a presumptive (n = 24) or biopsy confirmed diagnosis (n = 71) of osteosarcoma received palliative radiotherapy using 60Co photons. Parallel opposed beams were used with each dog receiving either 10 Gy on days 0, 7 and 21 (n = 58) or 8 Gy on days 0 and 7 (n = 37). The 8 Gy fractionation scheme was given with the intent of retreating upon relapse from pain relief. Only 9 of 37 (24%) dogs in the 8 Gy group returned for retreatment. Forty-seven of the 95 dogs (49%) received concurrent or sequential chemotherapy. Seventy of the 95 dogs (74%) experienced pain relief following treatment. In dogs experiencing pain relief the median duration of response was 73 days. Numerous clinical variables were evaluated as predictors of response. The only variable significantly related to achieving a response was the use of chemotherapy. The following variables were significantly related to the duration of response: extent of bone lysis, chemotherapy use, length of bone involved and tumor site (humerus). In a multivariate analysis (n = 73 dogs), after adjusting for chemotherapy use, extent of bone involvement (p = 0.01) and tumor site (p = 0.02) retained statistical significance, while degree of bone lysis did not (p = 0.11). No difference in response incidence or duration was found between 3 fractions of 10 Gy vs. 2 fractions of 8 Gy. Administration of a low initial dose with the intent of retreatment was not a successful strategy.     

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.     

ACCURACY OF MAGNETIC RESONANCE IMAGING FOR ESTIMATING INTRAMEDULLARY OSTEOSARCOMA EXTENT IN PRE-OPERATIVE PLANNING OF CANINE LIMB-SALVAGE PROCEDURES

The objective of this work was to compare the accuracy of radiographs and magnetic resonance imaging (MRI) for estimating appendicular osteosarcoma margins. The accuracy of computed tomography (CT) and bone scintigraphy was also assessed when these studies were available. Eight dogs with appendicular osteosarcoma underwent radiographic and MRI of affected limbs. In addition, bone scintigraphy was performed in six dogs and CT examination was performed in five dogs. Two observers jointly measured tumor length on all imaging studies. Correlative gross and histologic evaluation of all affected limbs was performed to determine tumor extent as measured from the nearest articular surface. Results from imaging studies were compared to gross and microscopic morphometry findings to determine the accuracy of each modality for determining tumor boundaries. MRI images were accurate with a mean overestimation of actual tumor length of 3 +/- 13%. T1-weighted non-contrast images were superior in identifying intramedullary tumor margins in most instances whereas contrast-enhanced images provided supplemental information in two dogs. Lateromedial and craniocaudal radiographs overestimated tumor length by 17 +/- 28% and 4 +/- 26%, respectively. Scintigraphy and CT overestimated tumor margins by 14 +/- 28% and 27 +/- 36%, respectively. MRI appears to be an accurate diagnostic imaging modality in determining intramedullary osteosarcoma boundaries. MRI should be considered as part of a pre-operative assessment of appendicular osteosarcoma, particularly when a limb-sparing procedure is contemplated.     

PALLIATIVE RADIOTHERAPY FOR CANINE APPENDICULAR OSTEOSARCOMA

Fifteen dogs with appendicular osteosarcoma (presumptive diagnosis, n = 6 dogs; biopsy confirmed, n = 9 dogs) were treated with palliative radiotherapy. Treatment entailed a total of three 10 Gy fractions of ⁶⁰Co radiation delivered over a three week period on days 0, 7 and 21, for a total dose of 30 Gy. Twelve dogs experienced improvement in limb function 7–22 days after the start of treatment. Long term followup was available for nine of the twelve responders. The duration of response was 17–288 days (n = 9 dogs; median = 130 days; mean = 116 days). Response duration did not appear to be related to initial tumor size. Palliative radiotherapy can result in improved limb function in dogs with appendicular osteosarcoma.     

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.     

MECHANICAL ASPECTS OF SUBARACHNOID SPACE PUNCTURE IN THE DOG

Lumbar subarachnoid space puncture using two different techniques was performed repeatedly on a dog following injection of metrizamide into the subarachnoid space at the cervical cistern. The lumbar needle punctures were observed fluoroscopically and recorded on 100-mm spot films at a rate of 2/sec. The needle tip indented the dura, depressing it several millimeters before penetration. A hemilaminectomy was performed on a cadaver, to expose the cord and intact meninges for confirmation of this compression. Cord compression and penetration during subarachnoid space puncture may contribute to the exacerbation or aggravation of neurologic signs that sometimes follows myelography.     

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.     

IOHEXOL MYELOGRAPHY IN THE DOG

Myelography with iohexol (180 mg iodine/ml, 0.25 ml/kg), a new nonionic radiologic contrast medium, was performed in 100 dogs of 33 different breeds. In 96 of the dogs the iohexol mixed evenly with the cerebrospinal fluid, providing an homogeneous, continuous column of contrast medium within the subarachnoid space, and a radiologic diagnosis of a normal myelogram or disease involving the spinal cord was made. Pooling of iohexol in the dorsal part of the subarachnoid space occurred in four dogs; whether this was related to poor mixing of contrast medium with cerebrospinal fluid or disease of the spinal cord and meninges requires further study. Postmyelographic signs of central nervous system irritation (fasciculations of the temporal muscles and three episodes of seizure activity) were observed in only one dog and were controlled with diazepam. The presenting neurologic signs were aggravated after myelography in four other dogs, two of which were eventually killed. This study provided further evidence of the increased safety of iohexol compared with metrizamide, the first of the nonionic media, as a contrast medium for myelography in the dog.     

SCINTIGRAPHIC EVALUATION OF SOLID-PHASE GASTRIC EMPTYING IN THE DOG

A technique for scintigraphically quantitating solid-phase gastric emptying in the dog was developed in a Beagle model. The test meal was determined to empty in a linear fashion, indicating a solid-phase label. The evaluation was performed on a group of dogs presented for gastrointestinal signs that were judged to have normal liquid barium sulfate fluoroscopic and radiographic studies. The results of this study indicate that this technique is valuable for identifying those patients with surgically correctable pyloric obstruction that exhibit normal gastric emptying of liquid barium.     

HEMANGIOSARCOMA IN THE MAIN PULMONARY ARTERY OF A DOG

The clinical, radiological and necropsy findings in a five-year old dog with a hemangiosarcoma in the main pulmonary artery are described. Hemangiosarcoma in this location has not been previously described in the dog, the typical location in the heart being the right atrium and auricle. The tumor in this dog caused both a perfusion deficit to the right lung and obstruction of right ventricular outflow, which eventually caused right heart failure.     

SENSITIVITY OF RADIOGRAPHIC DETECTION OF LUNG METASTASES IN THE DOG

Thoracic radiographs were taken in right lateral recumbent (RLR), left lateral recumbent (LLR), and ventrodorsal (VD) projections in 80 dogs with known or suspected malignant tumors. Radiographs in each projection were interpreted, independently of those in the other two projections, by four veterinary radiologists, and classified as positive or negative for one or more lung metastases. The four radiologists then met, to agree on a diagnosis for each patient by simultaneously reviewing all three views. This panel diagnosis became the standard for subsequently classifying individual views as either true positive or true negative. As determined by a consensus of the panel, 25 dogs had at least one positive thoracic radiograph.
The three radiographic projections differed in sensitivity for the detection of lung metastases. In this study, the RLR view was the most sensitive, and the VD view the least sensitive. The sensitivity of detection improved significantly with multiple readers. From these data we recommend that, for detection of lung metastases in the dog, the RLR view be included in any diagnostic protocol; a minimum of two readers be used; and a three-view protocol be used if only one reader is available.     

ULTRASONOGRAPHY OF GASTRIC ULCERATION IN THE DOG

The clinical, ultrasonographic and, when available, histopathologic findings of gastric ulceration in 7 dogs were reviewed. The most common clinical signs were vomiting, hematemesis, melena, weight loss and anemia. Ultrasonographic features of gastric ulcer included local thickening of the gastric wall, possible loss of the 5-layer structure, the presence of a wall defect or "crater", fluid accumulation in the stomach and diminished gastric motility.The localized gastric thickening varied from 9 to 16 mm. The ulcer crater was often located in the center of the thickened site and appeared as a mucosal defect associated with persistent accumulation of small echoes, most likely representing microbubbles. In this preliminary study, there was no definitive ultrasonographic distinction between benign and malignant ulcers.     

TWO-DIMENSIONAL REAL-TIME OCULAR ULTRASONOGRAPHY IN THE DOG

Two-dimensional real-time ultrasonography was performed with three different methods to determine the optimal technique for scanning canine orbital soft tissues. The three techniques included positioning the transducer on the clipped closed eyelid (eyelid contact method), directly on the cornea (corneal contact method), or on a small waterfilled balloon in direct contact with the cornea (water bath offset method). Horizontal and vertical images from the three techniques were compared and graded for diagnostic quality. The corneal contact method provided superior anatomic definition of the posterior globe and extraorbital tissues, whereas the water bath method gave higher-quality images of the anterior chamber and lens. Use of the eyelid contact method to image the eye and periorbital structures was not recommended because of multiple artifacts that severely degrade the image.     

CYSTIC UTERUS MASCULINUS IN THE DOG

Radiographic, historical, clinical signs, and surgical and histopathologic findings of six dogs with diagnosed cystic uterus masculinus are given. The condition was seen in aged dogs between 4 and 15 years (mean of 8.8 years). There was no breed predisposition, although the larger breeds were involved in this study. The predominant clinical signs were constipation, dysuria and anuria. Lateral survey recumbent abdominal radiographs coupled with negative-or positive-contrast cystography were useful in delineating the bladder and the urethra, thus revealing the smooth-contoured, asymmetrical fluid-filled viscus in the caudal abdomen. The bi-horned cysts were connected to the dorsal urethra through a short blind-ending pedicle. The nonseptic, aspermic, cystic fluid averaged 146.7 ml (range of 100–200 ml). The predominant epithelial lining cells seen were simple columnar to pseudostratified columnar.     

TESTICULAR ULTRASOUND IN THE NORMAL DOG

The testicles of ten dogs presented for routine castration were imaged with real time ultrasound. A scanning technique using multiple imaging planes (sagittal, transverse, and dorsal planes) was developed to image the testicles and epididymi. The testes were characterized by a coarse medium echo pattern. The mediastinum testis was consistently seen as a 0.2 cm wide linear hyperechoic structure in the central long axis of the testis. The ability to identify and the appearance of the epididymis was variable. The tail was consistently seen as an anechoic to hypoechoic structure. Ultrasound images were compared for anatomical structure with frozen gross sections. Ultrasonic and gross measurements were made and analyzed. Individual gross and ultrasonic measurements compared favorably. Linear regression coefficients between body surface area versus testicular length and diameter were 0.73 and 0.58 respectively. A Wilcoxin signed rank test for similarity p = 0.33 value was found when comparing the right to the left testicle.     

THE SUPINATED MEDIOLATERAL RADIOGRAPH FOR DETECTION OF HUMERAL HEAD OSTEOCHONDROSIS IN THE DOG

Mediolateral and supinated mediolateral radiographs of the shoulder joint were compared in 19 dogs. Twenty shoulders, representing 15 dogs (5 had bilateral lesions), had osteochondrosis of the humeral head. The flattened humeral head and subchondral defect were detectable in both views in all affected shoulders. The lesions were slightly more easily detected in the supinated view. The supinated view more consistently demonstrated the presence of a calcified cartilage flap and therefore, could be useful in determining a course of therapy. In four dogs (8 shoulders) without osteochondrosis and six normal shoulders from affected dogs, there were no instances in which a shoulder appeared normal on one view, but demonstrated a lesion on the other. The supinated view should be obtained in addition to the mediolateral view in dogs with osteochondrosis of the humeral head.     

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.