Figure 3. A right lateral thoracic radiograph of a 10-year-old spayed female dalmatian with urethral transitional cell carcinoma and pulmonary metastasis in the form of soft tissue nodules evident at initial diagnosis.

On abdominal ultrasonographic examination, iliac (regional) and other abdominal (distant) lymph nodes are evaluated for lymphadenopathy or abnormal appearance. Although less common, metastasis can occasionally be identified in visceral organs, such as the liver or spleen. In addition, seeding from previous transabdominal needle-tract or transmural invasion of the bladder tumor can occasionally result in metastatic dissemination in the abdomen or carcinomatosis and is identified as free fluid, serosal thickening, or nodular lesions. Ultrasound-guided aspirates can be obtained for cytologic examination to confirm metastasis as needed.

Figure 4. A plain ventrodorsal thoracic radiograph of the left ninth, 10th, and 11th ribs of an 8-year-old female spayed Basset hound with bladder transitional cell carcinoma. A destructive, mixed lytic and proliferative lesion is visible in the 10th rib that was palpable on the chest wall. The results of a cytologic examination were compatible with carcinoma, and bone metastasis was confirmed. This dog also had widespread pulmonary metastasis.

The typical location of transitional cell carcinomas in dogs, the trigone, precludes complete surgical excision in nearly all cases. Additionally, multiple microscopic lesions are often present in the bladder. In people, this field carcinogenesis effect is well-documented, whereby multiple sites of the bladder mucosa undergo malignant transformation simultaneously or sequentially, subsequent to years of carcinogen exposure.²⁴ As a result, therapy for transitional cell carcinoma can be frustrating.