Three dogs that had a history of abdominal distension were referred to the hospital. All were female with unilateral involvement. History and clinical signs were nonspecific. Abdominal radiographs demonstrated that the abdomen of all cases was filled with large masses. At laparotomy, all masses were kidney tumors with invasion around tissue. The tumors were soft, irregular, creamish and confined within the capsule. One case had liver metastasis. Another case was found to have adrenal gland metastasis. One case had caudal vena cava invasion. A ureteronephrectomy was performed unilaterally in all cases. In the microscopic appearances, all the tumors had malignant features with nuclear pleomorphism and amount of necrosis. Three cases were diagnosed as renal carcinomas.