OTOLITHIASIS IN THREE DOGS

Mineral opacities within the tympanic bullae, termed otoliths, were detected in three dogs by means of radiography and computed tomography. Radiographic signs of otitis externa were present in two dogs. One dog had clinical signs of vestibular disease, whereas the other two dogs had no clinical evidence of ear disease. Otolithiasis may represent mineralized necrotic material of a current or previous case of otitis media.     

RESULTS OF RADIATION THERAPY IN 19 DOGS WITH CUTANEOUS MAST CELL TUMOR AND REGIONAL LYMPH NODE METASTASIS

The records of 19 dogs with cutaneous mast cell tumor and regional lymph node metastasis (WHO Stage 2) were reviewed to determine the efficacy of radiation therapy in this population. Dogs with grade I (n = 1), grade II (n = 16), and grade III (n = 2) cutaneous mast cell tumor were included in this study. All dogs were treated with a combination of pre-irradiation surgical cytoreduction of the primary tumor, irradiation of the primary tumor and regional lymph node, and oral prednisone. Total radiation dose to the primary tumor and regional lymph node ranged from 48 to 57 Gray (Gy). The medial iliac and hypogastric lymph nodes were irradiated prophylactically in 11 dogs with primary tumor of the pelvic limb and positive ipsilateral popliteal lymph node. Total radiation dose to these lymph nodes ranged from 48 to 57 Gy. For all radiation fields, dose per fraction was 3 Gy, and therapy was administered on a Monday through Friday schedule. Acute and late radiation side effects observed in this study were considered acceptable. The median disease-free survival was 1,240 days (95% confidence interval 256 to 2,391 days). The disease-free survival in dogs with stage 2 mast cell tumor suggests that the combination of surgery, irradiation, and prednisone for the primary tumor along with irradiation of the positive lymph node is effective.     

SKELETAL LESIONS OF HISTIOCYTIC SARCOMA IN NINETEEN DOGS

The purpose of this study was to describe the clinical and radiographic findings in dogs with bone lesions secondary to histiocytic sarcoma. Nineteen dogs with radiographically identified bone lesions that were histologically diagnosed as histiocytic sarcoma were assessed. The medical records, all available radiographs and histologic sections were reviewed retrospectively. Dogs were subcategorized into localized or disseminated histiocytic sarcoma groups. Golden Retrievers or Rottweilers greater than 5 years of age, with a history of lameness or neurologic deficits localized to the spinal cord was the most common presentation. Fifteen of 19 dogs had a radiographically detectable soft tissue mass associated with bone destruction. The bone lesions had aggressive characteristics and the sites of involvement included periarticular bones (n = 11), vertebrae (n = 6), proximal humerus (n = 5), and rib (n = 2). Fifteen of 19 dogs had disseminated histiocytic sarcoma, and four had localized histiocytic sarcoma. All Rottweilers had disseminated histiocytic sarcoma. Histiocytic sarcoma should be considered as a differential diagnosis for aggressive periarticular, vertebral, or proximal humeral bone lesions identified on radiographs. The index of suspicion should be increased in greater than 5-year-old Golden Retrievers and Rottweilers when a soft tissue mass is associated with the bone lesion on radiographs or myelography. Bone involvement with histiocytic sarcoma, and the Rottweiler breed, was associated with the disseminated form of the disease.     

URINARY BLADDER MURAL HEMORRHAGE ASSOCIATED WITH SYSTEMIC BLEEDING DISORDERS IN THREE DOGS

The sonographic appearance of three dogs with diffuse bladder wall thickening due to mural hemorrhage is described. Two dogs were diagnosed with immune-mediated thrombocytopenia and the third dog with vitamin K antagonist toxicity. Urinary bladder wall thickening ranged from 5 to 12 mm on initial sonographic examination. In the two surviving dogs, the bladder wall returned to normal thickness. One dog, euthanatized for refractory hematuria, had submucosal hemorrhage in the urinary bladder at necropsy. Urinary wall thickening sonographically resolved at a rate of approximately 1 mm per day. Mural hemorrhage should be considered in patients with concurrent bleeding disorder and urinary bladder wall thickening.     

PROOF OF PRINCIPLE OF OCULAR SPARING IN DOGS WITH SINONASAL TUMORS TREATED WITH INTENSITY‐MODULATED RADIATION THERAPY

Intensity‐modulated radiation therapy (IMRT) allows optimization of radiation dose delivery to complex tumor volumes with rapid dose drop‐off to surrounding normal tissues. A prospective study was performed to evaluate the concept of conformal avoidance using IMRT in canine sinonasal cancer. The potential of IMRT to improve clinical outcome with respect to acute and late ocular toxicity was evaluated. Thirty‐one dogs with sinonasal cancer were treated definitively with IMRT using helical tomotherapy and/or dynamic multileaf collimator (DMLC) delivery. Ocular toxicity was evaluated prospectively and compared with a comparable group of historical controls treated with conventional two‐dimensional radiotherapy (2D‐RT) techniques. Treatment plans were devised for each dog using helical tomotherapy and DMLC that achieved the target dose to the planning treatment volume and limited critical normal tissues to the prescribed dose–volume constraints. Overall acute and late toxicities were limited and minor, detectable by an experienced observer. This was in contrast to the profound ocular morbidity observed in the historical control group treated with 2D‐RT. Overall median survival for IMRT‐treated and 2D‐treated dogs was 420 and 411 days, respectively. Compared with conventional techniques, IMRT reduced dose delivered to eyes and resulted in bilateral ocular sparing in the dogs reported herein. These data provide proof‐of‐principle that conformal avoidance radiotherapy can be delivered through high conformity IMRT, resulting in decreased normal tissue toxicity as compared with historical controls treated with 2D‐RT.     

DEFINITIVE RADIATION THERAPY FOR INFILTRATIVE THYROID CARCINOMA IN DOGS

The medical records of eight dogs with histopathologically confirmed infiltrative thyroid carcinoma treated with external beam radiation were reviewed and a retrospective analysis of survival and local tumor control were performed. The dogs received a definitive radiotherapy protocol of 46.8-48 Gray. All dogs had a reduction in tumor size to a clinically undetectable level on follow up examinations. Kaplan-Meier analysis indicated a median survival time of 24.5 months. Pulmonary metastasis was detected in three dogs and one of these dogs had concurrent bone metastasis. One dog had bone metastasis alone. Two dogs were alive at the censor. This study suggests that fractionated, definitive radiation therapy using multiple, moderate doses of radiation is an effective treatment for local control of invasive thyroid carcinoma in dogs.     

OSTEORADIONECROSIS AND RADIATION INDUCED BONE TUMORS FOLLOWING ORTHOVOLTAGE RADIATION THERAPY IN DOGS

Osteoradionecrosis and radiation-induced bone tumors are rare complications of radiation therapy. Little information regarding these complications is available in veterinary medicine. We characterized these complications and investigated risk factors in 119 dogs (122 sites) that received definitive orthovoltage radiation therapy to appendicular sites. Long-term survival was expected in all dogs. The complications of interest were osteoradionecrosis and secondary bone tumor, evaluated radiographically, histopathologically, or both. Complication rates were estimated using the Kaplan–Meier product-limit method, and Fisher's exact test or chi-square test was used to compare the complication rate. The median survival time was 1405 days, with median follow-up duration of 657 days. There were 10 radiation-induced bone tumors and five radiation-induced fractures, with two dogs developing both, for an overall complication rate of 11%. The latent period ranged from 1.2 to 6.4 years for osteoradionecrosis and from 2.6 to 8.7 years for radiation-induced bone tumor. Complications were significantly higher in the humerus ( P <0.0001), and in dogs younger than 7 years ( P =0.014). Similar assessment of complications in dogs irradiated with megavoltage photons or electrons are needed.     

CARDIAC MAGNETIC RESONANCE IMAGING OF PATENT DUCTUS ARTERIOSUS IN THREE DOGS

Patent ductus arteriosus (PDA) is the most common congenital cardiovascular disorder in dogs and requires an accurate diagnosis for an appropriate treatment. Cardiac MRI (cMRI) has been reported as a method for characterization of canine thoracic vasculature. However, to the authors’ knowledge, no published studies describe evaluation of canine PDA through cMRI. Three dogs were selected for this exploratory study. Electrocardiogram gating and breath‐hold techniques were performed using a 3T MR scanner. Both black blood imaging and bright blood cine acquisitions were performed. Quantification of stroke volume (SV) and shunting volume were calculated using a stack of short‐axis cine images. Additional 4D (three‐spatial dimensions plus time)‐TRAK (time‐resolved MR angiography with keyhole) sequences were conducted in patient 2 to verify other vasculature abnormality. Black blood images clearly depicted the course of the ductus from the descending aorta to the pulmonary artery in all three dogs. Morphological evaluation of PDA classified patients 1 and 2 as Type 2a and patient 3 as Type 1. Patient 2 was confirmed to have a concurrent persistent left cranial vena cava. Left ventricular SV, right ventricular SV, and left‐to‐right SV ratio were 12.4 ml, 3.36 ml, and 3.704, respectively, in patient 1; 6.85 ml, 1.22 ml, and 5.60 in the patient 2; and 3.67 ml, 2.14 ml, and 1.702 in patient 3. Findings indicated that cMRI is a feasible method for characterizing the morphology of PDA and extracardiac vasculature anomalies in dogs.     

RESULTS OF IRRADIATION OF INFILTRATIVE LIPOMA IN 13 DOGS

Thirteen dogs with infiltrative lipomas were treated with cobalt 60 radiation. Four of the thirteen dogs also received either whole body (n = 2) or combination local/whole body (n = 2) hyperthermia in conjunction with radiation therapy. Cytoreductive surgery was performed prior to radiation in 10 dogs, although only 3 dogs had microscopic disease at the time of radiation therapy. Dogs received a total dose of 45.6 Gy-63 Gy in 2.5-4 Gy/fraction on either a Monday/Wednesday/Friday schedule or on a daily Monday through Friday schedule. Twelve of the 13 dogs had computed tomography (CT) images acquired prior to irradiation. Survival time was determined from the time of completion of radiation therapy. Survival ranged from 6 months to 94 months, with a median (95% confidence interval) of 40 (18.5-77) months and a mean of 46.4 months. Only one dog was euthanized due to persistent signs related to the infiltrative lipoma at 6 months after the end of radiation therapy. There was no apparent difference in response based on whether or not the dogs received hyperthermia in conjunction with irradiation, although the numbers were too small to make any significant conclusions. It appears that dogs with infiltrative lipomas can benefit from external beam irradiation alone or in combination with surgery to effect long-term local tumor control.     

Soft tissue sarcoma in dogs: A treatment review and a novel approach using electrochemotherapy in a case series

Canine soft tissue sarcomas (STSs) are locally invasive mesenchymal neoplasms. Electrochemotherapy (ECT) is an antitumour local ablative treatment that uses electric pulses to enhance the intracellular delivery of cytotoxic drugs. The aim of this retrospective study was to review the current treatment for STSs and to evaluate the efficacy and safety of ECT with bleomycin in canine STSs. Fifty‐two dogs with 54 STSs were included. Three groups were arranged: (a) ECT alone, (b) intra‐operative ECT and (c) adjuvant ECT. Signalment, tumour size, location, histological grade and margins and ECT parameters were collected. Recurrence rate (RR) and disease‐free interval (DFI) were calculated. Treatment toxicity was assessed using a 6‐point scale. STSs were mostly located on limbs (77.8%). Median tumour size was 4.3 cm (range 0.4‐17.0 cm). Most STSs were grade I (47.7%) and II (50.0%), and histological margins were incomplete in 94.5% of cases. Two complete remissions, one partial remission and one stable disease were recorded in group 1. Group 2 and 3 were similar for tumour location, size and grade, histological margins, treatment toxicity, pulse frequency and voltage. Moreover, RR and DFI were similar between group 2 and 3 (23% and 25%, 81.5 and 243 days, respectively). Local toxicity post ECT was mild (score ≤ 2) in 66.7% of cases. Higher toxicity score was associated with higher pulse voltage (1200 vs 1000 V/cm) (P = 0.0473). ECT coupled with bleomycin resulted safe and efficient in tumour local control and should be considered as an option for treatment of canine STSs.     

USE OF A PETROLEUM-BASED BOLUS FOR PHOTON RADIATION THERAPY OF DISTAL EXTREMITIES IN DOGS

While skin sparing is an advantage of megavoltage beams, in certain clinical situations the planning target volume includes the skin surface and a skin sparing effect is not desirable. A tissue equivalent material, termed build up bolus, is used in these situations to provide adequate absorbed dose at the surface of the skin. However, an irregular patient contour can lead to air gaps between the build up bolus and the skin surface, which may result in variability in radiation dose across the target volume. The shape of the canine distal hind extremity is irregular, and commercially available bolus materials do not conform well to this region. The purpose of this study was to assess the dose homogeneity achieved using a petroleum-based bolus material, in combination with a commercially available sheet bolus, for radiation treatment of the canine tarsus. Repeated setups were performed to mimic daily treatment setups in the clinic setting, and computed tomographic scans were performed after each setup. Dose distribution achieved with a cobalt therapy machine and a 6 MV linear accelerator was assessed using three-dimensional treatment planning software. The dose to the clinical target volume fell within 95% and 107% of the prescribed dose for both treatment machines, which is considered clinically acceptable by the authors. This petroleum-based bolus is equivalent to water in its photon attenuation, conforms well to an irregular patient contour, and retains its shape after positioning. Applications to other anatomical sites could be considered.     

VACUUM PHENOMENON IN TWELVE DOGS

The clinical and imaging features of twelve dogs with vacuum phenomena are reviewed. Gas accumulations were identified as radiolucent areas within the intervertebral discs of the cervical, thoracic, and lumber spine, the joint spaces in the sternum, and the shoulder joint. The intervertebral and sternal gas accumulations were associated with other radiographic features of degeneration such as endplate sclerosis and spondylosis. Gas attributable to vacuum phenomenon has not been previously described in the sternum of animals. Abnormal radiographic positioning stresses or instability were through to be responsible for the focal gas accumulations.     

Subcutaneous Soft Tissue Sarcoma with Rhabdoid Features in a Dog

A nine-year-old male beagle dog had a white spherical mass in the subcutis of the left lumbar region. Microscopically, spindle to oval cells diffusely proliferated in the fibrous and myxoid stroma. Many neoplastic cells showed rhabdoid features or vacuolated cytoplasm. Immunohistochemically, the neoplastic cells were positive for vimentin and S100 and partly positive for neuron-specific enolase and glial fibrillary acidic protein but were negative for von Willebrand factor, desmin and α-smooth muscle actin. Ultrastructurally, the neoplastic cells had abundant cytoplasmic processes and desmosome-like structures. Cytoplasmic inclusions of rhabdoid-featured cells in HE sections were composed of aggregates of intermediate filaments, and cytoplasmic vacuoles were identified as an invagination of cytoplasm. Although malignant peripheral nerve sheath tumor was suggested according to these results, the present case was diagnosed as a soft tissue sarcoma with rhabdoid features due to a lack of identification of the basal lamina under electron microscopy.     

SYSTOLIC AORTIC VALVE FLUTTER IN 6 DOGS

Systolic aortic valve flutter was identified by M-mode echocardiography in 6 large-breed dogs without evidence of structural cardiac disease. It ranged in amplitude, timing, and frequency. Systolic aortic valve flutter is considered an incidental and normal finding in some dogs, similar to the situation in humans.     

Efficacy and toxicity of carboplatin in the treatment of macroscopic mesenchymal neoplasia in dogs

Palliative chemotherapy options for dogs with macroscopic non-osseous mesenchymal tumours are limited. The purpose of this study was to assess the response rate of these tumours to carboplatin chemotherapy. Medical records of 28 dogs treated with carboplatin for macroscopic mesenchymal neoplasia between 1990 and 2022 were retrospectively reviewed. Sixteen dogs with soft tissue sarcoma and 12 dogs with haemangiosarcoma were included. Responses observed included one complete response and three partial responses, for an overall response rate of 14.2% (4/28) and median time to progression of 42 days (range 21–259 days). Responses were only seen in patients with haemangiosarcoma, for a response rate of 33.3% (4/12) and median time to progression for responders of 103 days (range 39–252 days). Median time to progression for dogs with metastatic disease was similar to those with only local disease (distant median: 44 days; local median: 23 days, p = 0.56). Dogs with chemotherapy-naïve disease were compared to dogs having received previous chemotherapy treatment and had a median time to progression of 75 days and 40.5 days respectively (p = 0.13). Twenty-two dogs experienced 48 adverse events, with most being grade 1 or 2 (79%). Carboplatin was well tolerated, with variable macroscopic anti-tumour activity and short response duration. Carboplatin may be an acceptable rescue option for dogs with macroscopic haemangiosarcoma, especially those patients that cannot receive doxorubicin.     

CONTRAST‐ENHANCED ULTRASONOGRAPHY OF THE PANCREAS IN HEALTHY DOGS AND IN DOGS WITH ACUTE PANCREATITIS

Pancreatitis is the most frequent disease affecting the exocrine pancreas in dogs and reliable diagnostic techniques for predicting fatal complications are lacking. Contrast‐enhanced ultrasound (CEUS) improves detection of tissue perfusion as well as organ lesion vascular pattern. Objectives of this prospective case control study were to compare perfusion characteristics and enhancement patterns of the pancreas in healthy dogs and dogs with pancreatitis using CEUS. Ten healthy dogs and eight dogs with pancreatitis were selected based on physical examination, abdominal ultrasound, and blood analysis findings. A CEUS study of the pancreas was performed for each dog and two observers who were aware of clinical status used advanced ultrasound quantification software to analyze time‐intensity curves. Perfusion patterns were compared between healthy and affected dogs. In dogs with acute pancreatitis, mean pixel and peak intensity of the pancreatic parenchyma was significantly higher than that of normal dogs (P = 0.05) in between 6 and 60 s (P = <0.0001–0.046). This corresponds to a 311% increase in mean pixel intensity in dogs with acute pancreatitis compared to healthy dogs. Wash‐in rates were greater and had a consistently steeper slope to peak in dogs with pancreatitis as opposed to healthy dogs. All dogs with pancreatitis showed a decrease in pixel intensity 10–15 days after the initial examination (P = 0.011) and their times to peak values were prolonged compared to the initial exam. Findings from the current study supported the use of CEUS for diagnosing pancreatitis, pancreatic necrosis, and disease monitoring following therapy in dogs.