Approach to the diagnosis of bilateral ureteral transitional cell carcinoma in a cat

A cat with bilateral ureteral obstruction and long-term urolithiasis that had been medically managed for a year was presented to the emergency department of our hospital. Severe azotemia and metabolic acidosis were identified. Ultrasonography and computed tomography supported a diagnosis of ureteral calculi, with no evidence of other underlying abnormalities. During exploratory laparotomy, irreversible renal failure secondary to bilateral ureteral obstruction was suspected, and euthanasia was elected. Histopathological and immunohistochemical examination of the ureters revealed tubulopapillary urothelial carcinoma (transitional cell carcinoma). This case is noteworthy because it represents only the second reported case of feline ureteral transitional cell carcinoma associated with ureteral calculi causing bilateral ureteral obstruction. It also highlights that ureteral calculi may coexist with ureteral transitional cell carcinoma in cats, potentially masking the underlying neoplasm and delaying its diagnosis.