Unilateral Ureteral Obstruction Caused by Transitional Cell Papilloma in a Dog

Abstract

A 10-year-old mixed breed dog presented with hematuria and lethargy. Clinical examination confirmed a mass in the proximal lumen of the left ureter causing unilateral ureteral obstruction and hydronephrosis. Intrarenal pressure was reduced through placement of a nephrostomy tube. After stabilization of the patient, a biopsy was taken via laparotomy. Tissue samples were obtained via traumatic catheterization of the left ureter via the left kidney, without a ureterotomy. The traumatic catheterization technique successfully removed enough of the intraluminal mass that the ureteral obstruction was resolved. Histopathological examination suggested a possible tumor of transitional cell origin. However, a definitive diagnosis was not made from the histopathology. Piroxicam was administered orally for 659 days, and the patient remained clinically stable during this period. Serial ultrasonographic examinations revealed no signs of recurrence of the obstruction in the left ureter, therefore, piroxicam was discontinued. After 965 days, the patient presented with hematuria and lethargy. Ultrasonographic examination revealed re-obstruction of the left ureter from the intraluminal mass. Because the tumor progressed slowly, we speculated that it was most likely benign. Surgical debulking was performed via left ureterotomy under laparotomy. Histopathological examination confirmed transitional cell papilloma. The dog remained clinically stable without recurrence of the ureteral mass one year after surgery. Because some ureteral tumors in dogs have been reported as benign lesions, not only nephrouretectomy on the affected side but also debulking surgery could be a diagnostic and therapeutic option.