Ventricular empyema is a rare but severe complication of central nervous system (CNS) infections in dogs, with a poor prognosis due to limited treatment options. A 6-year-old intact female Pomeranian (1.9 kg) presented with acute-onset nonambulatory tetraparesis, spontaneous nystagmus, and head tilt. Hematological analysis revealed leukopenia with neutropenia and elevated C-reactive protein (CRP), suggesting systemic inflammation. MRI showed ventricular dilation with distinct stratified fluid-fluid levels. The dependent material was hypointense on T2-weighted (T2W) images and unsuppressed on T2W FLAIR (fluid-attenuated inversion recovery). It was hyperintense on diffusion-weighted imaging (DWI) and hypointense on apparent diffusion coefficient (ADC) maps, consistent with restricted diffusion. Its position changed with repositioning, suggesting a gravity-dependent nature. Cervical spinal cord MRI revealed a T2W hyperintense, contrast-enhancing intramedullary lesion from C3 to C7. Cerebrospinal fluid (CSF) analysis confirmed severe neutrophilic pleocytosis with numerous bacilli, later identified as Escherichia coli. Despite antibiotic therapy, the patient's condition deteriorated, leading to euthanasia. No extracranial infectious source was identified, supporting hematogenous dissemination as the most plausible route of infection. This is the first reported case of E. coli-induced ventricular empyema in veterinary medicine confirmed via advanced imaging. This report highlights the diagnostic role of DWI/ADC mapping and the novel use of patient repositioning to assess intraventricular material dynamics, underscoring the need for further research into advanced imaging and treatment strategies.

BACKGROUND:Doxorubicin (DOX) is a powerful chemotherapeutic agent, but its clinical use is restricted by cumulative and irreversible cardiotoxicity. Intestinal dysbiosis has been linked to DOX-induced cardiac injury, yet the underlying mechanisms and therapeutic targets remain elusive. This study aimed to investigate whether pterostilbene (PTE), a natural prebiotic plant extract, alleviates DOX cardiotoxicity by regulating gut microbiota and their metabolites. RESEARCH DESIGN AND METHODS:Eighteen beagles were randomized into control, DOX (30 mg/m² weekly for 7 weeks), and PTE (50 mg/kg daily for 9 weeks) + DOX groups. Fecal microbiota transplantation (FMT) from canine donors to microbiota-depleted rats, 16S rRNA sequencing, metabolome analysis, and in vitro H9C2 cell experiments were conducted. Main outcomes included survival rate, cardiac function parameters, cardiac injury biomarkers, microbial diversity, and oxidative stress-related indicators. RESULTS:In beagles receiving cumulative DOX (30 mg/m2 weekly for 7 weeks), PTE cotreatment (50 mg/kg daily for 9 weeks) significantly improved survival (83.3% vs. 50.0%, n = 6/group) and attenuated myocardial injury, evidenced by reduced plasma CK and LDH activities (both p < 0.01 vs. DOX). Echocardiography revealed PTE restored LVEF and LVFS while reducing EPSS and LVIDd (p < 0.05). 16S rRNA sequencing demonstrated PTE reversed DOX induced loss of α-diversity (ACE, Shannon, Chao indices, p < 0.05) and enriched beneficial Faecalibacterium while suppressing proinflammatory Corynebacterium and Allobaculum (q<0.05). Fecal microbiota transplantation confirmed microbiota dependent cardioprotection. Metabolomics identified 6-aminonicotinamide (6AN) as a key microbial metabolite inversely correlated with cardiac damage. In H9C2 cells, 6AN (1 µM) replicated PTE's protection by restoring antioxidant enzyme activities, reducing ROS and MDA, and attenuating apoptosis (all p < 0.01), effects abolished by NOX2 overexpression. CONCLUSIONS:PTE mitigates DOX cardiotoxicity via restructuring gut microbiota, increasing microbial metabolite 6AN, and suppressing NOX2-mediated oxidative stress. Targeting the microbiota-6AN-NOX2 axis represents a promising strategy to preserve cardiac function during anthracycline chemotherapy. These findings establish a mechanistic basis for PTE as a safe, natural adjunctive therapy in cancer patients receiving DOX. TRIAL REGISTRATION:Not applicable.

We describe a cystic duct neuroendocrine carcinoma in a dog evaluated with CEUS and multiphasic CT. The lesion was initially suspected to be hepatic but was reclassified as an intraluminal biliary mass on imaging. CEUS showed arterial hyperenhancement with early washout, and CT demonstrated a strongly enhancing intraluminal mass with progressive washout and biliary dilation. These findings enabled accurate localization and supported surgical management. Histopathology confirmed neuroendocrine carcinoma. Neoplasia of the canine gallbladder and biliary tract is uncommon, and tumors arising from the biliary ducts are rarely reported. Differentiating between hepatic and biliary origin can be challenging, particularly when intraductal lesions cause disproportionate biliary dilation relative to their size. Contrast-enhanced ultrasonography and multiphasic CT enable assessment of vascular characteristics and lesion localization, which may aid in distinguishing intraluminal biliary lesions from hepatic masses. This report describes a cystic duct neuroendocrine carcinoma characterized using CEUS, multiphasic CT, and histopathology, highlighting the role of multimodal imaging in accurate lesion localization.

Plasma cell neoplasia is uncommon in cats, and multicentric nodal-predominant involvement has not been well characterized. This report describes a multicentric round cell neoplasia with plasmacytic differentiation in a 14-year-old Domestic Shorthair cat, emphasizing multimodal imaging features and treatment response. Contrast-enhanced computed tomography and magnetic resonance imaging were performed for staging and longitudinal assessment. Cytomorphology supported plasmacytic differentiation, and flow cytometry did not demonstrate an immunophenotype consistent with conventional B- or T-cell lymphoma. Because histopathology, immunohistochemistry, bone marrow evaluation, and assessment for monoclonal gammopathy were not performed, definitive classification was not possible; however, cytomorphology supported plasmacytic differentiation, with plasma cell neoplasia remaining an important diagnostic consideration. A hypofractionated radiotherapy protocol (36 Gy in six fractions) combined with systemic chemotherapy was administered. Serial imaging demonstrated complete radiologic resolution of the irradiated mass, whereas non-irradiated presumed nodal lesions progressed and an extradural spinal lesion subsequently developed. These findings highlight the capacity of round cell neoplasia with plasmacytic differentiation to mimic lymphoma on imaging and illustrate the dissociation between effective local control and ongoing systemic progression.

A 12-year-old spayed female Maine Coon cat was diagnosed with cervical T-cell-rich B-cell lymphoma. During modified L-CHOP-based chemotherapy, the cat developed progressive upper airway obstruction associated with a laryngeal lesion. Initial CT suggested contiguous laryngeal involvement, and follow-up imaging revealed severe laryngeal narrowing. An emergency temporary tracheostomy was performed for airway stabilization, and subsequent punch biopsy of the laryngeal lesion was most consistent with diffuse large B-cell lymphoma. Hypofractionated palliative radiation therapy (6 Gy × 6 fractions; total dose 36 Gy) was initiated to address the obstructive mass. Progressive tumor shrinkage was observed during treatment, and by the fourth fraction the tracheostomy tube was successfully removed without recurrence of airway obstruction. Follow-up CT 17 days after radiation therapy initiation showed no visible laryngeal lesion, and no respiratory signs or airway obstruction recurred before the cat died on day 27 following clinically suspected systemic disease progression. This case suggests that hypofractionated radiation therapy, in combination with temporary tracheostomy, may provide rapid and effective relief of tumor-induced upper airway obstruction in cats with laryngeal B-cell lymphoma progressing during chemotherapy.

Advancements in radiotherapy, including intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), have reduced radiation-induced toxicities, enabling hypofractionated protocols to be feasible for treating intrapelvic tumours in dogs. This study aimed to determine the optimal planning technique for canine prostatic carcinoma using a radiotherapy protocol delivering 43 Gy in 10 fractions. Four techniques were compared-two full arcs (2FA), two partial arcs (2PA), 9-field IMRT (9F) and 7-field IMRT (7F). Computed tomography datasets from 22 dogs were analysed. While the conformity index did not differ significantly among techniques, IMRT demonstrated significantly lower homogeneity index than VMAT. IMRT yielded the lowest rectal normal tissue complication probabilities (NTCPs), maximum dose (Dmax) and V45, whereas 2PA achieved the lowest mean dose (Dmean) and V10, V15, V20, V25 and V30. Additionally, IMRT showed significantly lower NTCPs and V20, V25 and V30 for the colon; NTCPs and V20, V25, V30 and V35 for the small intestine; and Dmax, V20, V25 and V45 for the bladder. For the urethra, IMRT showed the lowest Dmax and V45, whereas 2PA demonstrated the lowest Dmean and V10, V15 and V20. The spinal cord (Dmean, V10, V15) and cauda equina (Dmean, Dmax, V10, V15 and V20) were best spared with 2PA. However, 2PA resulted in the highest femoral head NTCPs, Dmean, Dmax and V20, V25 and V30. IMRT showed significantly greater monitor units and beam-on time than VMAT, especially with 9F. In conclusion, under the predefined and unaltered planning objective and constraints used in this study, IMRT showed more favourable OAR sparing and improved dose homogeneity than VMAT. Among the IMRT techniques, 7F may be preferred over 9F due to reduced beam-on time and monitor units. However, these findings reflect the specific equipment, planning setting and optimisation approach applied in this study and different planner, systems or optimisation strategies may yield different results. Therefore, treatment planning should be individualised according to patient-specific dosimetric characteristics.

A 10-year-old spayed female Korean shorthair cat was presented with hematemesis and lethargy. Marked volume of free peritoneal gas was identified on abdominal radiographs. Bile pigment was identified in peritoneal fluid obtained by abdominocentesis, consistent with biliary peritonitis. Ultrasound examination was limited by pneumoperitoneum and severe peritonitis, making it difficult to differentiate gastrointestinal perforation from biliary system rupture. Two defects in the proximal duodenum near the major duodenal papilla (MDP) were identified with a non-anesthetic computed tomography (CT) scan. Exploratory laparotomy confirmed two perforations and revealed severe biliary peritonitis. Despite surgical repair and intensive treatment, the cat died 3 days later. This case highlights the importance of considering duodenal perforation near the MDP as a differential diagnosis when pneumoperitoneum and biliary peritonitis are present.

Myocardial calcification is an uncommon complication associated with end-stage chronic kidney disease (CKD) in feline patients. This report describes the clinical and multimodal imaging features of metastatic calcification in a 10-year-old castrated male mixed-breed cat. The patient presented with dyspnea and anorexia, and was diagnosed with IRIS Stage 4 CKD. Laboratory findings revealed severe hyperphosphatemia and an elevated calcium-phosphorus product (CPP) of 135 mg2/dL2, based on total calcium. This value significantly exceeds 70 mg2/dL2, a threshold associated with a high probability of inducing soft tissue mineralization. Echocardiography revealed extensive hyperechoic foci with posterior acoustic shadowing in the interventricular septum and left ventricular wall. Functional assessment demonstrated a restrictive diastolic filling pattern, suggesting increased myocardial stiffness and congestive heart failure. Computed tomography (CT) further visualized systemic involvement, showing diffuse, amorphous calcifications (400-900 HU) in the myocardium, multifocal aortic wall, and extracardiac tissues. Despite intensive treatment with diuretics and renal support, the patient was euthanized eight days later due to progressive renal failure. This case illustrates that the interaction between metastatic calcification and uremic cardiomyopathy (UC) can result in refractory heart failure, underscoring the value of combined echocardiography and CT in evaluating end-stage renal disease.

A 15-year-old castrated male Shih Tzu presented with anorexia and lethargy. Computed tomography (CT) revealed a hepatic mass with extensive central mineralization and an ill-defined hypoattenuating peripheral zone. The periportal halo sign extending to the lesser omentum was compatible with neoplastic infiltration of the periportal space, suggesting a potential metastatic pathway via this anatomical route. Whole-body CT excluded primary skeletal involvement, and histopathology confirmed extraskeletal osteosarcoma of hepatic origin. This case illustrates the value of CT in characterizing mineralized hepatic neoplasia and identifying potential routes of intra-abdominal dissemination.

Diaphragmatic tumors are uncommon in veterinary medicine. A 9-year-old neutered male Chihuahua was referred for evaluation of a suspected diaphragmatic hernia. Computed tomography revealed a soft tissue mass with a continuous border to the adjacent diaphragm, compressing the liver caudally. The tumor exhibited hypoattenuating lesions suspected of a mixture of fat and soft tissue. Histopathologic examination diagnosed a well-differentiated liposarcoma. A mass exhibiting a continuous border with the diaphragm and displacement of the adjacent liver may indicate a diaphragmatic tumor. Attenuation indicating a mixture of fat and soft tissue may be a feature of well-differentiated liposarcoma, but further studies on liposarcoma subtypes are needed.

Soft tissue sarcomas (STSs) constitute a heterogeneous group of tumors that originate from mesenchymal cells. Imaging plays an important role in the assessment of the oncological stage of STSs. Computed tomography findings facilitate the identification of the tumor location and margins in relation to the surrounding anatomic boundaries and thereby enable preoperative planning of tumor management. The histological grade is among the most important parameters that affect tumor recurrence and metastasis rates. However, the prediction of STS histological grades using CT characteristics has not yet been elucidated. This study retrospectively investigated CT findings of patients with different STS grades for differentiation. Thirty dogs with STSs (12 Grade 1, 10 Grade 2, and 8 Grade 3) were included from three animal hospitals. The investigated CT features included tumor delineation, dysmorphic intratumoral or peritumoral vessels, contrast enhancement patterns, peripheral rim enhancement, intratumoral calcification, degree of intratumoral cystic lesions, peritumoral fat stranding, metastatic regional lymphadenopathy, and lung metastasis. Quantitative findings included tumor size and pre- and postcontrast attenuation. Tumor size, dysmorphic intratumoral or peritumoral vessels, peritumoral fat stranding, and metastatic regional lymphadenopathy significantly differed among tumor grades. On post hoc analysis, Grade 3 tumors were significantly larger, had a higher prevalence of dysmorphic vessels than Grade 1 tumors, and had a significantly higher rate of adjacent metastatic lymphadenopathy than Grade 2 tumors. Predicting STS grades before the histopathological examination could potentially aid in the planning of the STS resection margins.

This retrospective, multicenter study aimed to identify key computed tomography (CT) features that differentiate renal cell carcinoma (RCC) from lymphoma, the two most common feline renal neoplasms. CT images from 25 cats with renal tumors (15 RCC and 10 lymphoma) were evaluated. Of the RCC cases, 10 were diagnosed through histopathology and 5 through FNA. Among the lymphoma cases, two were extranodal lymphoma, including one case of primary renal lymphoma, and eight were gastrointestinal (GI) lymphoma with renal involvement. Qualitative features (tumor distribution, growth pattern, and enhancement characteristics) and quantitative parameters (tumor size and attenuation values) from triphasic or single post-contrast-enhanced CT scans were analyzed and compared. RCC typically presented as unilateral (93.3%) masses with expansile growth (73.3%) and heterogeneous enhancement among contrast-enhancing tumors (100%). Lymphoma more often showed bilateral involvement (60%), infiltrative growth (50%), and homogeneous enhancement (90%) (p < 0.001). Tumor vessel enhancement was observed exclusively in RCC. Compared with lymphoma, RCC demonstrated significantly higher attenuation values in the late nephrographic/early excretory phase. While histopathology remains the gold standard, this study provides a detailed CT analysis of these tumors, specifically within a feline population.

This report describes the case of a 5-year-old spayed female munchkin cat that was presented with respiratory distress. Thoracic radiography revealed pleural effusion with a diffuse interstitial lung pattern. Echocardiography identified a mass compressing the left atrium, accompanied by a turbulent jet-like flow from the pulmonary veins, with a velocity of 1.6 m/s. Computed tomography revealed a diffuse, homogenous mediastinal mass compressing the dorsal border of the left atrium and surrounding the ascending aorta and the pulmonary arteries and veins. The distal caudal pulmonary veins were dilated, indicating pulmonary vein stenosis secondary to the mediastinal mass. The caudodorsal ostium was stenotic due to the mediastinal mass compression. In addition, bilateral adrenomegaly and multifocal masses were evident in the kidneys, stomach, and cecum. Lymphoma was diagnosed in the cecal mass using cytology and PCR for antigen receptor rearrangements (PARR). This case describes clinically significant acquired pulmonary vein stenosis secondary to a mediastinal mass, which was likely responsible for the respiratory distress and pleural effusion. Key clinical message: To our knowledge, this is the first report of acquired pulmonary vein stenosis secondary to a mediastinal mass in a cat. Computed tomography could be helpful in confirming pulmonary vein stenosis and identifying its etiology.

Objective:To identify the most reliable method for assessing renal function in dogs with chronic kidney disease (CKD) by comparing renal cortical thickness (RCT) evaluated using B-mode ultrasonography, conventional color Doppler imaging (CDI), and superb microvascular imaging (SMI). Methods:This observational study included dogs with at least 2 stable serum creatinine measurements within 30 days. Dogs were classified into CKD stages 1 to 4 based on International Renal Interest Society (IRIS) guidelines. Dogs without renal abnormalities were included in the control group. Ultrasonographic measurements of renal dimensions and RCT normalized to aortic diameter (RCT:Ao ratio) were obtained in sagittal, transverse, and dorsal planes. Results:85 dogs were analyzed including 36 control dogs and 49 dogs with CKD, consisting of 19 at stage 1, 19 at stage 2, 6 at stage 3, and 5 at stage 4. The RCT:Ao ratio in SMI showed the strongest correlation with IRIS stages, followed by CDI. Color Doppler imaging and SMI demonstrated superior diagnostic performance over B-mode according to receiver operating characteristic curve analysis. The optimal cutoff values for the RCT:Ao ratio in CDI and SMI were 0.58, 0.56, 0.51, and 0.44 for IRIS stages 1 to 4 in the sagittal plane and 0.62, 0.57, 0.53, and 0.45 in the transverse and dorsal planes. Conclusions:The RCT:Ao ratio measured using CDI and SMI correlated more strongly with IRIS stages than B-mode ultrasound and showed superior diagnostic performance, suggesting improved diagnostic utility. Clinical Relevance:Color Doppler imaging may improve the clinical assessment of RCT in dogs with CKD, enhancing its utility as a reliable indicator for diagnosing and staging CKD.

Splenic metastasis of hepatocellular carcinoma (HCC) is rare. An 11-year-old neutered male Maltese dog was presented for HCC recurrence surveillance. The dog had a history of transarterial chemoembolization and resection of HCC in the left medial liver lobe and papillary process of the caudate liver lobe. Computed tomography (CT) revealed a splenic mass with characteristics similar to those of the previous hepatic mass, including arterial tumor hypervascularity and heterogeneous enhancement in the portal venous and delayed venous phases. Splenic metastasis of HCC was confirmed via histopathological examination after splenectomy. Key clinical message: To our knowledge, this is the first report describing the CT findings of splenic metastasis of HCC in a dog. Splenic metastasis of HCC exhibited attenuation characteristics similar to those of the primary hepatic tumor in triple-phase CT. Therefore, comparing CT findings of previously diagnosed HCC to those of splenic masses may aid in diagnosing splenic metastasis of HCC.

This report describes the case of a 13-year-old castrated male poodle with respiratory distress and coughing. The dog had had its right thyroid gland and ipsilateral lymph node resected because of thyroid follicular carcinoma originating in the right thyroid gland and metastasis to the ipsilateral medial retropharyngeal lymph node. The dog was initially treated for chronic bronchitis but showed no resolution of the clinical signs. Ultrasonography revealed an enlarged hypoechoic left medial retropharyngeal mass. Computed tomography further revealed an enlarged, heterogeneously enhanced left medial retropharyngeal mass with irregular margins. The mass compressed the laryngeal borders and was considered responsible for the coughing and respiratory distress. Based on the dog's history of thyroid carcinoma, metastatic lymphadenopathy of the left medial retropharyngeal lymph node was suspected, and the mass was surgically removed. Histopathologic examination revealed mild adenomatous salivary hyperplasia with duct ectasia. No evidence of neoplasm or severe inflammation was observed. The final diagnosis was salivary adenomatous hyperplasia in the retropharyngeal region. Salivary adenomatous hyperplasia can be responsible for clinical signs, depending on size and location. Differentiating salivary adenomatous hyperplasia from malignancies based on imaging findings alone can be difficult. This case demonstrated how salivary adenomatous hyperplasia may mimic malignant tumors, particularly in animals with a history of adjacent tumor malignancy. Key clinical message: To the best of our knowledge, this is the first report in a dog of salivary adenomatous hyperplasia that mimicked tumor metastasis. Differentiating between malignant and salivary adenomatous hyperplasia can be difficult using imaging findings alone. Despite being histologically benign, salivary adenomatous hyperplasia may cause clinical signs.

(1) Background: This study evaluated the quality of medical imaging acquired using radiography, ultrasonography, and computed tomography (CT) in canine cadavers prepared with formalin solution, Thiel solution (TS), and saturated salt solution (SS). Additionally, the duration whereby image quality could be properly reproduced was investigated. (2) Methods: Nine dog cadavers, divided into three groups per embalming solution, were imaged pre- and post-embalming at 6 and 12 weeks using three different imaging modalities. Image quality was qualitatively scored based on human medicine guidelines criteria. The score was assigned as follows: “0 = not invisible, 1 = poorly invisible, 2 = adequately reproduced, 3 = very well reproduced”. (3) Results: On plain radiography, most scores were > 1.34, although the quality of all embalming solutions in thoracic and abdominal images decreased over time. Using ultrasound to image the liver, spleen, and kidney, the SS group was evaluated as poorly visible and scored < 0.82 at 6 and 12 weeks. CT images showed a tendency to degrade over time, but all solution groups had properly implemented images and scored > 1.62. (4) Conclusions: Regarding image quality and ease of application, TS is considered the most suitable embalming solution for medical imaging acquisition and is usable over time in all imaging modalities.

Stereotactic body radiotherapy (SBRT) has been increasingly used in dogs for mediastinal tumors and is generally considered a precise and relatively safe treatment, with clinically significant complications reported only rarely. A cranial mediastinal mass was incidentally identified in a 10-year-old Pomeranian dog and cytologically diagnosed as a carcinoma. SBRT was performed using volumetric-modulated arc therapy, with a total dose of 27 Gy delivered in three fractions on alternate days. One day after completing treatment, the dog developed acute dyspnea and anemia. Thoracic radiography revealed mediastinal widening and pleural effusion. Subsequent imaging and hematological assessments suggested intra-tumoral hemorrhage and hematoma formation. The patient was managed conservatively with supportive therapy, resulting in gradual clinical improvement. Follow-up computed tomography (CT) demonstrated a 25% reduction in contrast-enhancing tumor volume, accompanied by a large non-enhancing region presumed to represent hematoma. Despite these changes, the patient remained clinically stable during follow-up. This case represents the first documented report of an acute hemorrhagic complication following SBRT in a veterinary patient, emphasizing the importance of awareness of this rare adverse event during treatment planning and client communication.

This study investigated breed-specific variations in vertebral right heart index (VRHi) values and their diagnostic accuracy in detecting right heart enlargement (RHE) in dogs. A total of 359 dogs from various breeds, including brachycephalic and non-brachycephalic groups, were evaluated using radiographic and echocardiographic methods. The VRHi was measured from lateral (RL) and ventrodorsal (VD) thoracic radiographs. Certain breeds, such as brachycephalic dogs, Schnauzers, Dachshunds, Pomeranians, Yorkshire Terriers, and Miniature Pinschers, demonstrated significantly higher VRHi values than non-brachycephalic breeds, even without true RHE. The RL VRHi showed stronger clinical relevance than the VD VRHi, correlating better with the echocardiographic findings. Breed-specific diagnostic cutoff values were established: RL VRHi ≥ 3.45 vertebral units (v) (sensitivity: 75%, specificity: 75%) and VD VRHi ≥ 2.75 v (sensitivity: 72%, specificity: 72%) for brachycephalic breeds and RL VRHi ≥ 3.25 v (sensitivity: 78%, specificity: 80%), VD VRHi ≥ 2.4 v (sensitivity: 61%, specificity: 61%) for non-brachycephalic breeds not belonging to the aforementioned categories. Body weight and chest conformation showed no significant association with VRHi values. These findings highlight the necessity of considering breed-specific factors in radiographic cardiac evaluations, as some breeds may present radiographic signs of RHE despite a normal cardiac anatomy and function.

IMPORTANCE:Cystic masses in the abdominal cavity near the vaginal area can have a range of origins, including urothelial cysts, which have never been reported in dogs. This paper reports the first known occurrence of a urothelial cyst in a dog. CASE PRESENTATION:An 18-year-old, 2.05 kg intact female Maltese dog presented with a mammary nodule with no systemic clinical signs. The radiographs and ultrasound revealed a large cystic mass in the abdominal cavity. Computed tomography imaging showed that the mass was in contact with the bladder, urethra, and vagina but had no direct connections to these organs. Surgical removal was performed. Histopathology analysis confirmed a urothelial cyst lined with transitional and stratified squamous epithelium. CONCLUSIONS AND RELEVANCE:This case highlights the need to include urothelial cysts in a differential diagnosis of cystic masses near the vaginal region in dogs. Early imaging-based detection is crucial to preventing misdiagnoses and ensuring appropriate surgical intervention. Veterinarians must carefully differentiate this condition from other reproductive disorders, including pyometra and uterine tumors, to avoid complications and ensure appropriate management.