Post Mortem Ultrasound and Computed Tomography Findings of an Extraluminal Urinary Bladder Leiomyoma in a Dog

Background: Neoplasia of the urinary bladder is common in dogs, accounting approximately 0.5 to 1.0 percent of all neoplasms. Most of the neoplasia of the urinary bladder is epithelial in origin and only 10% of urinary bladder neoplasms in dogs are from mesenchymal origin, of which the most frequent types are leiomyoma / leiomyosarcoma, and hemangioma / hemangiosarcoma. Virtual autopsy refers to the postmortem use of radiology, ultrasound and cross-sectional imaging prior to conventional necropsy. This paper reports the detection of a rare extra-luminal urinary bladder mass diagnosed as leiomyoma with a virtual autopsy techniques.Case: A 16-year-old male Schnauzer had previous history of seizure and no complains related to the urinary system. The animal was treated symptomatically to the neurological signs and responded to medical treatment. Nine weeks later from the first visit to the hospital the dog was found dead at home. Then postmortem ultrasound and computed tomography of the abdomen were performed. Postmortem ultrasound revealed a homogenously hypoechoic, rounded and slightly irregularly marginated mass located externally but adjacent to the left cranial wall of the urinary bladder and appears to extend from its serosal margins. Postmortem computed tomography was performed after postmortem ultrasound. A pedunculated homogenous soft tissue attenuating mass was located at the left lateral aspect of the urinary bladder and extended cranially. It had a stalk that connected to the left lateral wall of the urinary bladder. A partial necropsy of the abdomen was done just to examine the mass. A round extraluminal, pedunculated mass was observed at the left lateral aspect of the urinary bladder wall. It was pale pink on the outside and white inside, with a soft to firm consistency. The lumen and mucosal surface of the urinary bladder was smooth and regular. The histology of the mass revealed a densely cellular neoplastic proliferation, expansive, composed of spindle-shaped cells with moderate to large eosinophilic cytoplasm, sometimes wavy and with indistinct edges. The nuclei were large, oval to flattened, with dense chromatin and inconspicuous nucleoli. Anisocytosis and anisokariosis were discrete and no mitotic figures were observed. The arrangement consisted of dense, irregular and multidirectional bundles and the stroma was scarce. The mass was histologically confirmed as leiomyoma.Discussion: In this case, we performed postmortem ultrasound and computed tomography as part of a virtual necropsy study and in both modalities the urinary bladder mass was able to be identified, followed by a partial necropsy to further investigate the nature of the mass and to collect a sample to obtain the histological diagnosis. A few of the disadvantages of the postmortem ultrasound and computed tomography specially in this case were the lack of color Doppler investigation on ultrasound and the lack of evaluation of the patter of contrast enhancement on computed tomography. These techniques could have added important information related to the vascularity characteristics of the mass in a live patient. This is the first case report in veterinary medicine that describes an extra-luminal pedunculated urinary bladder leiomyoma in a canine patient, and it is emphasized the approach by postmortem ultrasound, postmortem computed tomography and conventional necropsy findings to reach the definitive diagnosis.