Table of Contents and Abstracts

Objective
Thymoma and mediastinal lymphoma (ML) are the most common cranial mediastinal masses in cats. Considering differences in treatment and prognosis, accurate antemortem diagnosis is essential. However, fine-needle aspiration can be inconclusive. Computed tomography (CT) is often used as a diagnostic tool, though apparently no previous studies have directly compared CT findings for thymoma and ML. This pilot study was a preliminary investigation of using CT to differentiate thymoma from ML in cats.

Animals and procedure
Six cats diagnosed with either thymoma or ML underwent triple-phase contrast-enhanced CT. Parameters assessed included changes in CT attenuation across contrast phases and enhancement patterns.

Results
Thymomas exhibited peak enhancement during the equilibrium phase with heterogeneous contrast patterns, whereas MLs enhanced rapidly in the arterial phase and peaked in the venous phase with homogeneous contrast distribution.

Conclusion and clinical relevance
We suggest that the contrast-enhancement patterns and variations in CT values in triple-phase contrast-enhanced CT scans may be key to differential diagnosis of thymoma versus ML in cats. However, this pilot study had a small sample size and the objective of proposing hypotheses. Large-scale studies are needed to test this hypothesis.

Two domestic shorthair cats from the same household developed acute liver injury with exposure to human transdermal diclofenac cream. A 7-year-old spayed female cat (Cat 1) was brought to the Western College of Veterinary Medicine (Saskatoon, Saskatchewan) with anorexia, lethargy, and fever. The cat had markedly elevated ALT (10 549 U/L) and glutamate dehydrogenase (1456 U/L), and hyperbilirubinemia (total bilirubin: 16.7 µmol/L). Cat 1 improved with supportive care and was discharged. The following day, a 6-year-old spayed female cat (Cat 2) was presented with anorexia and lethargy. Laboratory tests also showed severe hepatocellular injury (ALT: 20 838 U/L, glutamate dehydrogenase: 2054 U/L) and hyperbilirubinemia (total bilirubin: 26.7 µmol/L). A blood smear revealed green to dark-blue cytoplasmic material in neutrophils, consistent with “critical green inclusions” in humans. Cat 2 developed progressive clinical deterioration and was euthanized. The caregiver reported having used 10% diclofenac cream for 3 mo. Drug screening via liquid chromatography-mass spectrometry detected diclofenac in both cats (30 µg/mL in Cat 1, 42 µg/mL in Cat 2). The toxic threshold of diclofenac in cats is currently unknown. Although direct evidence linking acute liver injury to diclofenac exposure was lacking in this case, the report does highlight the potential risk to pet cats whose owners use topical diclofenac.

Key clinical message:
Topical NSAID formulations such as diclofenac are commonly used by pet owners to treat human pain. The risk to pets, particularly smaller animals exposed to human skin upon which transdermal medication has been applied, remains unknown. Pet owners should be made aware of the potential risks these products pose to animals. Also, to the authors’ knowledge, this is the first case report to describe “critical green inclusions” in a cat with severe liver disease.

Bradycardia-induced cardiomyopathy is a reversible form of myocardial dysfunction caused by prolonged bradyarrhythmia, most commonly due to high-grade atrioventricular block or sinus node dysfunction. Although bradycardia-induced cardiomyopathy is well recognized in human medicine, it remains underreported in veterinary literature. This case series describes 3 dogs diagnosed with 3rd-degree atrioventricular block that presented with clinical signs including exercise intolerance, syncope, and cardiomegaly. Each dog underwent comprehensive diagnostic evaluation, including physical examination, thoracic radiography, echocardiography, and electrocardiography. Bradycardia-induced transient myocardial dysfunction was suspected, based on the presence of bradyarrhythmia in conjunction with cardiac enlargement and preserved systolic function. All dogs were treated with permanent pacemaker implantation. Postoperative follow-ups documented marked clinical improvement, with resolution of exercise intolerance or syncope. Radiographic and echocardiographic reassessments demonstrated reductions in atrial and ventricular internal dimensions, supporting the reversibility of myocardial remodeling once normal heart rate was restored. No major complications were observed during follow-up periods that ranged from several months to > 4 y.

Key clinical message:
These findings supported the presence of bradycardia-induced transient myocardial dysfunction in dogs and underscored the importance of recognizing bradyarrhythmia as a potentially reversible cause of cardiomyopathy. Early diagnosis and timely pacemaker implantation can result in substantial clinical and structural cardiac recovery.

A 14-year-old spayed female papillon dog was presented with hematuria and a right renal mass. Contrast-enhanced computed tomography revealed a tumor thrombus extending about 1.5 cm cranially from the right renal vein into the caudal vena cava (CVC), consistent with renal cell carcinoma and caval thrombus, with no signs of distant metastasis. The dog underwent open right-sided nephrectomy and CVC thrombectomy, using 2 tourniquets, with a total occlusion time of 12 min 13 s. Transient hypotension during surgery was successfully managed, and there were no major intra- or postoperative complications. Histopathology confirmed a highly malignant renal cell carcinoma with vascular invasion. Adjuvant toceranib therapy was initiated to address potential microscopic residual disease. Pulmonary metastasis was detected on Day 553 after surgery, and the dog remained alive on Day 722. This case demonstrates that renal cell carcinoma with caval thrombus in dogs can be surgically managed without severe complications. Moreover, adjuvant toceranib therapy can be used safely. Together, these findings offer valuable insights into the feasibility and safety of surgical strategies for CVC-invasive renal tumors in dogs.

Key clinical message:
Renal cell carcinoma with caval thrombus in dogs can be safely managed with surgery, highlighting the feasibility of aggressive surgical intervention for this rare condition.

A 3-year-old castrated male German shepherd dog was presented with a 48-hour history of lethargy and anorexia. On presentation, the dog was laterally recumbent, hyperthermic, tachycardic, severely dehydrated, and exhibiting abdominal pain. Abdominal radiographs raised suspicion for splenic torsion. An exploratory laparotomy revealed a suspected splenic vein thrombosis, prompting a splenectomy and an incisional gastropexy. Computed tomography revealed multifocal osseous pneumatosis, rib abscesses, costochondral luxation, renal infarcts, suspected intramuscular thrombosis, aspiration pneumonia, and lymphadenopathy. Despite negative blood culture and peri-costal abscess cultures, Clostridium botulinum was isolated from bone marrow obtained via costochondral rib aspiration. During hospitalization, persistent non-regenerative anemia and thrombocytopenia were observed; the dog was also nonambulatory tetraparetic, worse on the right, indicating a predominantly right-sided myelopathy. After some improvement, the dog was discharged from the hospital; however, his condition progressively worsened despite treatment, leading to humane euthanasia 1 mo later. Necropsy revealed disseminated round cell tumor consistent with lymphoma.

Key clinical message:
Visceral organ gas accumulation or intraosseous gas in the absence of previous trauma or surgery should prompt suspicion for an anaerobic infection. To the authors’ knowledge, this is the first reported case of rib pneumatosis secondary to disseminated C. botulinum in a dog.

An 11-year-old neutered male domestic shorthair cat was incidentally diagnosed with hypercalcemia during routine wellness screening. Subsequent workup revealed elevated ionized calcium, increased parathyroid hormone concentrations, and undetectable parathyroid hormone-related peptide, consistent with a diagnosis of primary hyperparathyroidism. Cervical ultrasound revealed a left parathyroid nodule, and the cat underwent a left cranial parathyroidectomy without intraoperative or postoperative complications. Histopathology was consistent with parathyroid hyperplasia. At the time of writing (> 1100 d after diagnosis), the cat was clinically well, with normal total and ionized calcium, and had not required calcium supplementation.|

Key clinical message:
Only a few cases of feline primary hyperparathyroidism are described in the literature. Most previously published case reports described cats evaluated for clinical signs attributable to hypercalcemia. In contrast, this case was identified during a routine wellness examination in an asymptomatic cat. This emphasizes the importance of preventive care and demonstrates that routine wellness screening can facilitate early detection of subclinical disease, enabling timely intervention and contributing to improved long-term outcomes.

Animal welfare benefits associated with international pet rescue and adoption are somewhat offset by increased potential for introduction and spread of foreign pathogens. This report describes clinical and parasitological findings in an adopted stray cat imported from Thailand. The cat was presented to a veterinary clinic for veterinary care 5 d after arrival in Canada. The cat was dewormed and passed a large mass of tapeworms on the following day. Fecal and blood samples were submitted to Diagnostic Services at the Atlantic Veterinary College (Charlottetown, Prince Edward Island). Eggs of Mammomonogamus spp. and Spirometra spp., oocysts of Cystoisospora spp., and a metastrongyloid 1st-stage nematode larva (L₁) were seen on microscopic examination of fecal flotation. Additional L₁ recovered using the Baermann technique were molecularly characterized using small subunit rRNA-PCR, and DNA sequencing identified the larvae as Oslerus rostratus. The cat was treated with a 2-day course of milbemycin oxime (10.7 mg/kg) and praziquantel (26.8 mg/kg), followed 5 d later by a 5-day course of fenbendazole (50 mg/kg). Posttreatment fecal examinations showed no evidence of parasitic infection. The cat resumed shedding Spirometra spp. eggs 40 d later and was given a second 2-day course of milbemycin oxime and praziquantel. Fecal examinations conducted at 7 and 35 d after treatment did not reveal any parasitic eggs or cysts. The occurrences of O. rostratus and Mammomonogamus spp. are reported and diagnosed for the first time in Canada. The risk of foreign pathogen spread into a new geographical region was minimized by timely diagnoses, appropriate veterinary care, and the cooperation of conscientious owners via biocontainment by isolation of the cat and proper feces disposal.

Key clinical message:
Knowing the clinical and travel history of an animal is critical for making an accurate diagnosis. Molecular confirmatory testing is valuable when diagnosing parasitic infections with similar morphologies.

A 3-year-old intact female American Guinea hog that was presented for an elective ovariohysterectomy appeared systemically healthy, with no overt medical conditions. Premedication with clonazepam, tiletamine-zolazepam, and xylazine; anesthetic induction with propofol and maintenance with isoflurane with oxygen on spontaneous ventilation; a ketamine infusion; and morphine for analgesia were provided. Approximately 95 min after isoflurane was initiated, the pig acutely became hyperthermic and severely hypercapnic, with hyperkalemia, hyperlactatemia, and severe metabolic and respiratory acidosis. With high suspicion of malignant hyperthermia syndrome (MHS), isoflurane was discontinued, and active cooling, ventilatory support, dantrolene, aggressive fluid therapy, lidocaine, insulin, and dextrose were administered. The pig developed ventricular tachycardia with subsequent cardiopulmonary arrest. Cardiopulmonary resuscitation was attempted without success. Necropsy findings were suggestive of MHS and genetic testing confirmed a dimutant RYR1 gene.

Key clinical message:
This is the first report of MHS in a subject from a porcine companion breed and of an atypical, delayed onset. As MHS is life-threatening, preanesthetic genetic testing and/or preemptive treatment with oral dantrolene should be considered for pigs undergoing inhalant-based anesthesia.

Objective, animals, and procedure
Handheld ultrasound devices (HUDs), a cost-effective alternative to cart-based ultrasound in humans, are not well studied in veterinary medicine. Twelve healthy dogs underwent point-of-care ultrasound (POCUS) examinations [abdomen, pleural space and lung (PLUS), cardiovascular] using 3 HUDs. Twelve views were recorded (6 abdominal, 2 PLUS, and 4 cardiovascular) and retrospectively assessed by 2 expert reviewers (1 for thoracic and 1 for abdominal) who were blinded to the HUD used. Reviewers assessed overall image quality (Likert scale) and ability to answer clinically relevant POCUS binary choice questions.

Results
Image quality varied among HUDs for lung sliding (P = 0.001), curtain signs (P = 0.032), cardiac subxiphoid (P = 0.002), stomach (P < 0.001), short- and long-axis kidney views, gallbladder (P = 0.003), and caudal vena cava (P = 0.002). There were no differences among devices in answering key POCUS questions: subxiphoid heart (P = 0.332), stomach (P = 0.294), short-axis kidney (P = 0.308), caudal vena cava (P = 0.037 for group comparison; IQ versus VScan: P = 0.214, IQ versus Clarius: P = 0.03, VScan versus Clarius: P = 0.584), 4-chamber heart (P = 0.092), 5-chamber heart, long-axis kidney, mushroom, gallbladder, PLUS, and left atrium to aortic ratio (P > 0.999).

Conclusion and clinical relevance
Results of the current study suggest that, although image quality varied among HUDs, all 3 HUDs answered key abdominal, PLUS, and cardiac POCUS questions.

Objective
Pretreatment inflammatory indices are established negative prognostic factors for survival in human osteosarcoma (OSA). However, studies investigating these values in canine malignancies, specifically canine appendicular OSA, are limited. The prognostic significance of pretreatment inflammatory indices in canine appendicular OSA was investigated in this retrospective study.

Animals and procedure
Medical records for dogs with appendicular OSA treated with amputation and adjuvant carboplatin were retrospectively reviewed. The following pretreatment values were evaluated for prognostic significance for progression-free survival (PFS) and disease-specific survival (DSS): serum alkaline phosphatase, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, and albumin-to-globulin ratio. Effects of proximal humeral location, presence of metastasis at diagnosis, and use of rescue chemotherapy on prognosis were also analyzed.

Results
Elevated albumin-to-globulin ratio was prognostic for PFS and DSS on univariate analysis but did not retain significance on multivariate analysis. On multivariate analysis, metastasis at diagnosis, elevated serum alkaline phosphatase, and administration of rescue chemotherapy were significantly associated with shorter PFS; whereas metastasis at diagnosis was significantly associated with DSS.

Conclusion and clinical relevance
Despite pretreatment inflammatory indices being independently associated with prognosis in human OSA, these values were not associated with either PFS or DSS in this study. Prospective investigation with a larger, standardized cohort is needed to further evaluate the prognostic role of pretreatment inflammatory indices in canine OSA.