Atypical presentation of bladder urothelial carcinoma (inverted) with associated abdominal carcinomatosis in a dog

This case report describes an atypical presentation of a canine urothelial cell carcinoma and its outcome. An 11‐year‐old, male, entire Jack Russell dog was presented with a history of dysuria unresponsive to medical management. An abdominal ultrasound revealed an atypical mural mass‐like lesion, with no evidence of mucosal involvement and associated abdominal effusion. Cytology of the atypical bladder mass showed a necrotic population of epithelial cells, while abdominal fluid analysis confirmed the presence of urothelial cell carcinoma. Treatment with vinblastine chemotherapy was started, and an abdominal ultrasound was performed before the fifth dose, confirming complete resolution of the bladder mass with static abdominal effusion. After the sixth dose of vinblastine, the patient became anorexic and lethargic. Investigations revealed the presence of pleural effusion with cytological evidence of atypical urothelial cells. A rescue protocol was started with carboplatin; however, the patient was euthanased due to further clinical deterioration.