Cat Kidney Cancer: Signs, Types, and What to Expect

The most common kidney cancer in cats is renal lymphoma, a cancer of white blood cells that grows in one or both kidneys (Penn Vet Ryan Hospital, 2017; Dias et al., 2024). Less often, cats develop renal carcinoma, a tumor that starts in the kidney tissue itself (Penn Vet Ryan Hospital, 2017).

The early signs are vague and easy to mistake for ordinary kidney disease: weight loss, poor appetite, vomiting or nausea, lethargy, and sometimes a swollen belly (Penn Vet Ryan Hospital, 2017; Clinical outcomes study, 2023). As the kidneys lose function, cats develop the signs of kidney failure (Dias et al., 2024). Enlarged kidneys found on an exam or ultrasound are often the first concrete clue.

The outlook depends on the type. Renal lymphoma responds to chemotherapy, but median survival is typically less than 7 months, and the cancer can spread to the brain and spinal cord (Taylor et al., 2019). Some cats with renal carcinoma that survive surgery to remove the affected kidney live for years (Clinical outcomes study, 2023).

Key points

• Lymphoma is the most common tumor of the kidneys in cats (Dias et al., 2024; Penn Vet Ryan Hospital, 2017).
• Feline renal lymphoma is usually B-cell and intermediate to high grade (Taylor et al., 2019).
• Up to 40% of cats with renal lymphoma may have involvement of the central nervous system (Taylor et al., 2019).
• Renal lymphoma is treated with chemotherapy because it's a body-wide cancer, not with surgery (Penn Vet Ryan Hospital, 2017).
• When both kidneys are affected, the prognosis is poor (Penn Vet Ryan Hospital, 2017).
• In a study of 36 cats with renal carcinoma treated by removing the kidney, cats that survived to go home had a median survival of 1,217 days (Clinical outcomes study, 2023).

Detailed explanation

Why kidney cancer is hard to spot

Cats with kidney cancer usually show nonspecific signs: nausea or vomiting, weight loss, lethargy, or a distended abdomen (Penn Vet Ryan Hospital, 2017). In cats with renal carcinoma, the most common reasons for the first visit were weight loss (36.1%) and reduced appetite (30.6%) (Clinical outcomes study, 2023). With renal lymphoma, signs often reflect failing kidney function (Dias et al., 2024).

Those signs overlap almost completely with chronic kidney disease, which is common in older cats. Signs of kidney problems often develop gradually and are easy to miss (Cornell Feline Health Center, 2024). What sets cancer apart is often found on examination or ultrasound: one or both kidneys may be enlarged or irregular. Enlarged kidneys can also come from inflammation, infection, cysts, or a blocked ureter, so they need further testing (Cornell Feline Health Center, 2024).

Any older cat with weight loss and kidney changes on bloodwork deserves a careful look at the kidneys themselves, not just the lab values.

Renal lymphoma

Lymphoma is the most frequently diagnosed cancer in cats overall (Cornell Feline Health Center, 2021). Renal lymphoma is the most common primary tumor of the cat's kidneys (Dias et al., 2024). It usually affects middle-aged to older cats (Dias et al., 2024), and a review of earlier studies describes it as mostly B-cell and intermediate to high grade (Taylor et al., 2019). Lymphoma in cats has a recognized connection with retroviral infections such as feline leukemia virus (Cornell Feline Health Center, 2021; Dias et al., 2024), so your veterinarian will likely test for FeLV and FIV.

Renal lymphoma can occur on its own or as part of lymphoma elsewhere in the body. Because it's a systemic cancer, it's treated with chemotherapy rather than surgery (Penn Vet Ryan Hospital, 2017). Cats do respond to chemotherapy, but the median survival is less than 7 months (Taylor et al., 2019). One case report cited a median survival of 50 days for cats with renal lymphoma (Dias et al., 2024).

A key concern is spread to the nervous system. Up to 40% of cats with renal lymphoma may develop central nervous system involvement (Taylor et al., 2019). Signs such as weakness in the back legs, wobbliness, seizures, or behavior changes in a cat being treated for renal lymphoma need prompt attention.

For more on lymphoma in cats generally, including the more common intestinal form, see our overview of cat cancer.

Renal carcinoma

Renal carcinomas start in the kidney's own tissue. They're less common than lymphoma in cats, but surgery can offer meaningful time when the tumor is confined to one kidney.

In a multi-institution study of 36 cats with renal carcinoma that had the affected kidney removed (nephrectomy), 77.8% survived to discharge. Median survival was 203 days for all cats and 1,217 days for those that went home after surgery. The one-, two-, and three-year survival rates were each 40.4%. About 22% of cats had suspected spread at the time of surgery, and about 19% developed it later (Clinical outcomes study, 2023). Preoperative findings such as anemia or blood in the urine didn't predict survival.

Removing a kidney is only an option if the other kidney works well enough to support the cat. Cats can do quite well with just one healthy kidney (Cornell Feline Health Center, 2024), but your veterinarian will want to check the remaining kidney's function carefully before surgery.

How kidney cancer is diagnosed

Diagnosis usually involves bloodwork and urinalysis to assess kidney function, abdominal ultrasound to look at the kidneys' size and structure, and a needle aspirate or biopsy of the affected tissue. Chest X-rays and sometimes CT check for spread (Penn Vet Ryan Hospital, 2017).

Quality of life and support

Because many cats with kidney cancer are diagnosed when the kidneys are already struggling, supportive care matters alongside cancer treatment. Your veterinarian can tailor that care to your cat. A veterinary oncologist can help you weigh chemotherapy or surgery against your cat's overall condition. When the time comes to think about the end of life, our resources on anticipatory grief and grieving a pet apply to any family.

When to contact a veterinarian

Book an appointment soon if your cat:

• Is losing weight or eating less
• Is vomiting more often than usual
• Seems lethargic or is hiding more
• Has a belly that looks swollen
• Has been diagnosed with kidney disease and is declining faster than expected

Call the same day if your cat stops eating for more than a day, can't use their back legs normally, has a seizure, or seems suddenly much weaker.

Questions to ask your veterinarian

• Are my cat's kidneys enlarged, small, or irregular on exam or ultrasound?
• Could this be kidney cancer rather than chronic kidney disease?
• Can we do a needle aspirate of the kidney?
• Should my cat be tested for FeLV and FIV?
• If it's lymphoma, what chemotherapy options exist, and what side effects should I expect?
• If it's a carcinoma in one kidney, is the other kidney healthy enough for surgery?
• What signs would suggest the cancer has spread to the nervous system?
• How can we keep my cat comfortable and eating during treatment?

Sources

Clinical outcomes study. (2023). Clinical outcomes in cats with renal carcinoma undergoing nephrectomy: A retrospective study. Veterinary and Comparative Oncology. PMID: 37464904. 

Cornell Feline Health Center. (2021). Lymphoma. Cornell University College of Veterinary Medicine. Retrieved November 5, 2026, from https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/lymphoma

Cornell Feline Health Center. (2024, March 20). Enlarged kidneys in cats. Cornell CatWatch. https://www.catwatchnewsletter.com/?p=60520

Dias, C. G. F., Coimbra, B. dos S., Bins, I. O. G., Christ, R. H., Vinter, L. B., Andrade, E. P., Cota, J. M., & Pereira, C. M. (2024). Primary renal lymphoma in a cat. Acta Scientiae Veterinariae, 51. https://seer.ufrgs.br/index.php/ActaScientiaeVeterinariae/article/view/132233

Penn Vet Ryan Hospital. (2017). Renal tumors in dogs and cats [Client information sheet]. Comprehensive Cancer Care Service, University of Pennsylvania School of Veterinary Medicine. https://www.vet.upenn.edu/wp-content/uploads/2025/05/renal-tumors-in-dogs-and-cats.pdf

Taylor, A., Finotello, R., Vilar-Saavedra, P., Couto, C. G., Benigni, L., & Lara-Garcia, A. (2019). Clinical characteristics and outcome of dogs with presumed primary renal lymphoma. Journal of Small Animal Practice.