Kidney Cancer in Dogs: Types, Treatment, and Prognosis

Kidney cancer in dogs refers to abnormal cell growth within or around the kidney. Tumors can be primary (originating in the kidney itself) or secondary (spreading to the kidney from another site). Secondary tumors are more common than primary ones: the kidneys and the spleen receive a large share of the body's blood flow, which makes them two of the organs tumors most often spread to. While kidney tumors account for only about 0.5–1.5% of all canine tumors, they carry a high malignancy rate—approximately 90% of kidney tumors in dogs are malignant.

Key risk factors:

• Age: Dogs over 7 years old are at higher risk.
• Breed: German Shepherds appear to have a somewhat higher incidence.
• Sex: Some studies suggest a slightly higher occurrence in males.

Kidney tumors typically develop on one side (unilateral). Bilateral involvement is less common in dogs, though it does occur more frequently with certain tumor types in cats.

Which Primary and Secondary Tumors Affect the Kidneys?

Renal cell carcinoma is the most common primary malignant kidney tumor in dogs, accounting for nearly 70% of primary kidney tumors. It originates from the cells lining the kidney's tubules. Renal cell carcinoma tends to grow relatively slowly but is locally invasive. The metastatic rate is approximately 50%, with the lungs, liver, and regional lymph nodes being the most common sites of spread. In some cases, these tumors produce excess erythropoietin, leading to a paraneoplastic syndrome called polycythemia—an abnormal increase in red blood cells.

Nephroblastoma (Wilms tumor) is an embryonal tumor that usually appears in puppies or young dogs under one year of age. It develops from leftover embryonic kidney tissue and can grow quite large. When caught early and removed surgically, the prognosis is relatively favorable compared to other renal cancers.

Transitional cell carcinoma more commonly affects the bladder but can originate in the renal pelvis. It is seen most often in older dogs and may cause blood in the urine and difficulty urinating. This type shows some responsiveness to chemotherapy.

Lymphoma involving the kidneys is more common in cats than dogs and may be part of a systemic lymphoma diagnosis. In cats, renal lymphoma has been associated with Feline Leukemia Virus (FeLV) infection. It often involves both kidneys and can respond to chemotherapy, though outcomes depend on the extent of disease.

Metastatic tumors from other sites—such as hemangiosarcoma or other carcinomas—spread to the kidneys secondarily, and taken together they are more common in the kidney than tumors that start there.

Kidney tumor symptoms in dogs are often vague in the early stages, which is one reason these cancers are frequently diagnosed after they have progressed.

Common signs to watch for:

Most dogs with a kidney tumor show no urinary signs at first. The usual signs are those of general illness—poor appetite, weight loss, fever, vomiting—and some dogs limp because the tumor triggers a bone change called hypertrophic osteopathy.

• Blood in the urine (hematuria): Some dogs have blood in the urine. It may come and go, making it easy to dismiss, and a dog with no blood in the urine can still have a kidney tumor.
• Abdominal mass or enlargement: In some cases, an owner or veterinarian can feel an abnormal mass during a physical exam.
• Unexplained weight loss: Gradual wasting despite a normal or only slightly reduced appetite.
• Decreased appetite: A progressive decline in interest in food.
• Abdominal pain: Reluctance to have the belly touched, a hunched posture, or restlessness.
• Increased thirst and urination: Can indicate that kidney function is being affected.
• Lethargy and weakness: A general decline in energy and activity.

In cases of renal cell carcinoma that produce excess erythropoietin, you may notice unusually deep red gums—a sign of polycythemia that your vet can confirm with blood work.

Why Can Early Signs Be Easy to Miss?

Many of these symptoms—drinking more water, slowing down, losing a little weight—overlap with normal aging or other common senior dog conditions like kidney disease or arthritis. Blood in the urine may only appear intermittently and can be missed entirely if it is mild. This is why routine veterinary check-ups with blood work and urinalysis become increasingly important for dogs over seven.

Diagnostic workup:

When a kidney tumor is suspected, your vet will typically recommend:

• Blood work: A complete blood count may reveal anemia or, less commonly, polycythemia. A biochemistry panel assesses overall kidney function.
• Urinalysis: Looks for blood, protein, or abnormal cells in the urine.
• Abdominal ultrasound: Usually the first imaging study. It can evaluate the size, location, and blood flow of a kidney mass and check the opposite kidney.
• Abdominal X-rays: May show an enlarged kidney silhouette.
• CT scan: Provides detailed information about tumor extent and possible metastasis to nearby structures.
• Chest X-rays: Essential for checking whether the cancer has spread to the lungs.
• Biopsy/histopathology: A definitive diagnosis usually requires tissue from surgical excision. Ultrasound-guided needle aspiration can sometimes provide useful information, but carries a small risk of tumor cell dissemination and may not yield enough tissue for a complete diagnosis.

The right treatment plan depends on the tumor type, whether it has spread, the function of the remaining kidney, and the dog's overall health.

Surgical removal (nephrectomy)

Surgery is the primary treatment for most localized kidney tumors. Removing the affected kidney is considered when:

• The tumor is confined to one kidney with no evidence of distant metastasis.
• The opposite kidney is functioning well enough to sustain the dog on its own.
• The dog's overall condition allows safe anesthesia and recovery.

For non-metastatic renal cell carcinoma, reported median survival times after nephrectomy range from roughly one to two years. Nephroblastoma in young dogs tends to carry a better surgical prognosis when caught early.

Chemotherapy

Chemotherapy plays a role primarily in:

• Lymphoma: Multi-drug protocols (such as CHOP) are standard.
• Transitional cell carcinoma: Agents like mitoxantrone or carboplatin may be used.
• Renal cell carcinoma: Generally shows poor sensitivity to chemotherapy, so it is not a primary treatment for this type.

Targeted therapy

Tyrosine kinase inhibitors such as toceranib (Palladia) have shown some effect in certain kidney tumors, though evidence remains limited. Your veterinary oncologist can discuss whether this option is appropriate.

When May Surgery or Oncology Care Be Considered?

Surgery is most beneficial when imaging shows a tumor confined to one kidney without metastasis. If the cancer has already spread—detected via chest X-rays or CT—surgery may still be discussed for palliative purposes (to reduce the tumor burden and improve comfort), but the expected outcomes change significantly. Oncology referral is recommended whenever a malignant kidney tumor is confirmed, even if surgery has already been performed, to discuss whether adjuvant treatment could help.

Palliative care

When a tumor cannot be surgically removed or has spread widely, the focus shifts to maintaining quality of life:

• Pain management tailored to the individual dog.
• Nutritional support to maintain body weight and energy.
• Anti-nausea medications and fluid therapy as needed.
• Regular quality of life assessments to guide ongoing decisions.

Prognosis for kidney cancer in dogs varies widely depending on several factors.

Which Factors Influence Outlook?

• Tumor type and grade: Renal cell carcinoma without metastasis has a more favorable outlook than high-grade or widely metastatic tumors.
• Stage at diagnosis: Dogs diagnosed before metastasis generally do better.
• Completeness of surgical removal: Clean surgical margins improve outcomes.
• Response to treatment: For tumors treated with chemotherapy (particularly lymphoma), the degree of response significantly affects survival.

Post-treatment monitoring schedule:

After surgery, your vet will typically recommend:

Monitoring aims to catch any recurrence or metastasis early, when intervention may still be possible. It also tracks the remaining kidney's function, since the dog now relies on a single kidney.

Quality of life throughout treatment:

Throughout diagnosis, treatment, and monitoring, regularly assess your dog's comfort, appetite, activity level, and engagement with your family. Share these observations with your veterinary team. If you notice a sustained decline despite treatment, it may be time to discuss adjusting the care plan—including whether continued aggressive treatment is in your dog's best interest.

Medical Disclaimer: This article is for informational purposes only and does not constitute professional veterinary or diagnostic advice. If your dog shows any signs that could indicate a kidney tumor, consult a licensed veterinarian promptly.

1. Neoplasia of the Urinary System in Dogs and Cats — Merck Veterinary Manual
2. Noninfectious Diseases of the Urinary System in Dogs — Merck Veterinary Manual
3. Chronic Kidney Disease in Dogs — VCA Animal Hospitals