Urinary tract tumors are uncommon in dogs. They can be benign (not cancerous) or malignant (cancerous).
Kidney Tumors in Dogs
Kidney tumors are rare in dogs. Cancers can also start in the kidney or spread there from other organs, especially the lymph nodes.
Benign tumors are usually found by accident and often don't require any treatment. Malignant kidney tumors, when they occur, are more common in middle-aged and older dogs. German Shepherd Dogs can inherit a tendency to develop a specific kidney-related cancer called renal cystadenocarcinoma.
The most common malignant kidney tumor in dogs is a carcinoma originating in the kidney tubules (hollow tubes inside the kidneys through which urine flows and from which water and other substances are reabsorbed back into the body). This type of tumor usually affects one kidney and often spreads quickly.
Nephroblastoma, a type of kidney cancer, is linked to abnormal kidney tissue that develops before birth. Nephroblastomas occur mostly in dogs less than 1 year old and can grow very large.
Kidney tumors in dogs might cause no signs, particularly when they are small or benign. When kidney tumors cause illness, signs in dogs are often vague. Affected dogs might be unusually tired, less active, or less interested in normal activities. Other signs can include weight loss, poor appetite, fever, belly enlargement, and bloody urine.
To diagnose kidney tumors, a veterinarian will do a physical exam and might also use ultrasound, x-rays, urine testing, and a biopsy (sampling a piece of the dog's urinary tract to analyze it under a microscope).
Depending on the type of kidney tumor and whether it has spread, as well as the health of the opposite kidney, treatment can include surgically removing the affected kidney. Some dogs might need chemotherapy.
Lower Urinary Tract Tumors in Dogs
"Lower urinary tract" refers to the parts of the urinary tract below the kidneys—namely, the ureters, bladder, and urethra (see diagrams in The Urinary System of Dogs). Tumors in these organs are uncommon in dogs and mainly happen in older dogs. Benign tumors can develop in the lower urinary tract, but cancerous ones are more common. The most common one is called a transitional cell carcinoma.
Tumors in the lower urinary tract can block urine flow and often occur with urinary infections that don't improve with antibiotics. Signs that your dog might have one of these tumors include bloody urine, painful or difficult urination, frequent urination, and abdominal pain. If a tumor blocks the flow of urine, waste products can build up in the blood, causing signs such as vomiting, weakness, loss of appetite, and dehydration.
A veterinarian will test your dog's urine to look for blood and possibly infection. Imaging tests and biopsies (samples of parts of the urinary tract that are analyzed under a microscope) are usually needed to confirm the diagnosis and identify the tumor type.
Surgery might be possible, but lower urinary tract tumors are often in hard-to-access areas and can return or spread. Chemotherapy or radiation might help but can have serious side effects. You and your vet should discuss treatment options and quality of life for your dog both during and after treatment.
For More Information
Also see professional content regarding tumors (neoplasia) of the urinary system in dogs.
