Urinoma (para-ureteral pseudocyst) as a consequence of trauma in a cat.

A two-year-old cat was involved in a road traffic accident. Survey abdominal radiographs and urinary function were considered unremarkable. Six weeks later the cat presented with a palpable dorsal abdominal mass. Radiography revealed a soft tissue opacity mass caudal to the right kidney. Ultrasonography revealed a cyst-like structure with moderately echogenic contents, and right-sided hydronephrosis. There was no excretion of contrast medium from the right kidney after intravenous urography. Surgery revealed a disrupted right ureter adherent to the retroperitoneal mass. The mass contained serosanguineous fluid consistent with extravasated urine. Ureteronephrectomy was performed. The majority of the mass was excised and the cavity ablated. Histopathology of the excised tissue revealed a thick fibrous wall with no epithelial lining, consistent with a urinoma, which is thought to have developed as a consequence of ureteral trauma. The cat was clinically well three months postoperatively.