Malignant tumors of the lower urinary tract include transitional cell carcinoma, squamous-cell carcinoma, adenocarcinoma,
leiomyosarcoma, fibrosarcoma, hemangiosarcoma and rhabdomyosarcoma.
Transitional-cell carcinoma (TCC) is the most common of these malignancies and involves the bladder and/or the urethra. Affected
dogs tend to be older and smaller in size (<10 kg). There may be a gender predilection, with females being more commonly affected,
although this finding has not been consistent in all studies. Scottish Terriers, Shetland Sheepdogs, Collies, Airedales and
Beagles are at a higher risk for developing these tumors.
Photo 1: Typical ultrasound appearance of TCC in the bladder.
There appear to be both genetic and environmental risk factors for the development of TCC in dogs. In humans, cigarette smoking,
exposure to chemicals, use of select medications and chronic inflammatory conditions of the bladder have been associated with
an increased risk of bladder tumors.
Previous studies have found that dogs exposed to insecticidal dips, live near marshes or are overweight are at higher risk
for the development of bladder tumors. Prior use of Cytoxan has been suggested as a risk factor. Two recent studies evaluated
exposure to herbicides and topical flea and tick pesticides as possible risk factors in Scotties (Glickman 2004, Raghaven
2004). The conclusions were that the use of the topical flea and tick medications currently available did not increase the
risk of TCC, but exposure to phenoxy herbicides did.
Although cause and effect can be proven, it still is prudent to recommend minimizing exposure to phenoxy herbicides. Interestingly,
another study showed a decreased risk in development of bladder tumors in Scottish Terriers that consumed vegetables at least
three times weekly; they had a 70 percent reduction in the risk of developing TCC (Raghaven 2005).
Photo 2: Typical ultrasound appearance of TCC in the bladder. This dog has a more diffuse thickening of the bladder than the
dog in Photo 1.