The Mysterious Link Between Kidney Disease and Mouth Ulcers in Cats


Kidney disease is a common condition in cats, with studies estimating the prevalence at 2-20% of all cats and up to 30% in cats over 10 years old (Marino et al. 2014). As cats age, they are at increased risk of developing chronic kidney disease (CKD), which can lead to kidney failure if left untreated. Mouth ulcers, also known as stomatitis, are also frequently seen in cats. The ulcers can be painful and make it difficult for cats to eat. While kidney disease and mouth ulcers commonly occur in cats, it is unclear whether these two conditions are causally related. This article reviews the association between kidney disease and mouth ulcers in cats. It examines the evidence on whether kidney dysfunction can lead to or exacerbate ulcers in the mouth. The article also provides an overview of managing and preventing mouth ulcers in cats with kidney disease.

Kidney Disease in Cats

Kidney disease, also known as chronic kidney disease (CKD), refers to gradual kidney damage and reduced function over time. It is a common condition in older cats, with studies estimating the prevalence at 1-3% overall and up to 32% in cats 15 years and older (

The kidneys act as filters to remove waste and toxins from the blood. As kidney function declines, toxins build up and cause a range of clinical signs. CKD progresses through four stages based on levels of creatinine and urea in the blood. Symptoms include increased thirst and urination, weight loss, poor appetite, lethargy, and vomiting.

CKD is not curable but progression can be slowed with dietary changes, medications, intravenous fluids, and management of related issues. Causes include congenital disease, infections, toxins, dental disease, and high blood pressure. Older cats are at higher risk, along with breeds like Persians and Abyssinians. Preventive care like dental cleanings, blood pressure monitoring, and screening tests help detect early kidney changes.

Mouth Ulcers in Cats

Mouth ulcers, also known as stomatitis or gingivostomatitis, are painful sores that develop in a cat’s mouth and gums. They can range from small shallow lesions to severe widespread inflammation and ulceration that affects much of the mouth.

Studies show that the prevalence of oral lesions and stomatitis in cats ranges from 0.7% to 12% [1]. The most common oral problem identified is gingivitis, but ulcers, glossitis, and other issues also occur.

Symptoms of mouth ulcers in cats include drooling, foul breath, difficulty eating, weight loss, and behavioral changes due to oral pain and discomfort. The ulcers appear as circular red lesions on the gums, tongue, lips, or roof of the mouth.

Causes include bacterial, viral or fungal infections, trauma, foreign bodies, autoimmune disease, or metabolic issues. Certain breeds like Persians and Siamese may be at higher risk. The ulcers are often very painful and impact a cat’s quality of life.

The Association Between Kidney Disease and Mouth Ulcers

Research suggests there is an association between chronic kidney disease and mouth ulcers in cats. According to one source, “In the late stages, mouth ulcers are commonly present” in cats with chronic kidney disease ( Another notes that halitosis (bad breath) and mouth ulcers may be symptoms of chronic kidney disease in cats (

The exact mechanisms linking chronic kidney disease and mouth ulcers in cats are still being investigated. However, some possible connections have been proposed. Kidney disease can lead to uremic toxins building up in the blood, and these toxins may potentially damage the tissues in the mouth, making cats more prone to ulcers. The kidney helps regulate levels of calcium and phosphate, and imbalances in these minerals due to kidney dysfunction may also play a role in ulcer formation.

Additionally, reduced saliva production and alterations in saliva composition caused by kidney disease could make the mouth more susceptible to irritation and sores. More research is still needed to fully understand the association, but managing both conditions is an important part of caring for cats with chronic kidney disease.

Managing Mouth Ulcers in Cats with Kidney Disease

If your cat has mouth ulcers as a result of kidney disease, treatment will focus on managing both conditions. There are several options for treating painful mouth ulcers and soothing your cat’s symptoms while also addressing the underlying kidney problems.

Treatment options for mouth ulcers usually include:

  • Antibiotics to control secondary infections
  • Anti-inflammatory drugs like steroids to reduce inflammation and pain
  • Immunosuppressants like cyclosporine that modulate the immune system
  • Antiviral medications in cases of calicivirus

Your vet may prescribe a combination of medications to get the mouth ulcers under control. Severe ulcers may need to be surgically removed. Topical pain medications, rinses, or gels can provide relief as well. Always follow your vet’s instructions carefully when medicating your cat.

Diet and lifestyle changes are also important for cats with kidney issues and mouth ulcers. Your vet may recommend feeding wet food only to increase hydration. Canned foods with extra phosphorus and potassium can help maintain kidney health. Avoid dry kibble and foods with Added salts. Make water easily accessible to encourage drinking. Reduce stress and provide soft, comfortable bedding.

Treating the underlying kidney disease is crucial for preventing recurrence of mouth ulcers. Medications, dietary changes, IV fluids, and other therapies can support kidney function. Monitor lab work to ensure values stay in the normal range. Address any other conditions present like hyperthyroidism or high blood pressure. With diligent management of both the ulcers and kidney disease, many cats can enjoy a good quality of life.


Preventing Mouth Ulcers in Cats with Kidney Disease

There are several ways cat owners can help prevent painful mouth ulcers from developing in cats with kidney disease.

Proactive dental care is important for supporting kidney health and preventing ulcers. Daily tooth brushing, dental wipes, antiseptic rinses or gels, water additives, and dental diets can all help reduce plaque buildup and fight infection in a cat’s mouth (

Ensuring proper diet and hydration is also key. Cats with kidney disease often have reduced appetites, but getting adequate calories and fluids can help prevent ulcers. Feeding wet food, adding water to dry food, and providing fresh water fountain sources can encourage hydration. Consulting a vet about the best renal diet is advised.

Regular vet checkups allow monitoring of kidney values and early detection of mouth ulcers or other problems. Cats over age 10 should have bloodwork done at least annually, and twice yearly for senior cats. This allows vets to make any needed dietary or medication adjustments to support kidney and mouth health.

With proactive dental care, optimal nutrition and hydration, and consistent vet monitoring, cat owners can help prevent painful mouth sores and promote better quality of life for felines with kidney issues.

Outlook for Cats with Both Conditions

The prognosis for cats with both chronic kidney disease and mouth ulcers depends on the stage and progression of the kidney disease. According to the International Renal Interest Society, cats with IRIS stage 1-2 kidney disease have a good prognosis and life expectancy if managed appropriately. However, cats with IRIS stage 3-4 kidney disease have a guarded to grave prognosis, with stage 4 being terminal[1].

Maintaining quality of life is crucial when managing cats with advanced kidney disease. This includes providing an appropriate diet, medications, intravenous or subcutaneous fluids, and regular veterinary monitoring[2]. Preventing dehydration and managing electrolyte imbalances can help reduce the frequency and severity of mouth ulcers. Oral pain medication may provide relief from ulcer discomfort.

For cats reaching end-stage kidney failure, palliative care focuses on comfort and pain management. Fluid therapy, medications, and nutritional support aim to maintain hydration and slow further deterioration. Euthanasia may eventually become the most humane option to prevent prolonged suffering[3].


Kidney disease and mouth ulcers in cats may be linked. Mouth ulcers are common in cats with chronic kidney disease due to toxins building up in the body. Inflammation from disease itself can also cause ulcers. Managing kidney disease is key to reducing ulcers. Steps owners can take include:

  • Getting regular vet checkups to monitor kidney function
  • Feeding a kidney-friendly diet lower in phosphorus and protein
  • Encouraging water intake to flush toxins
  • Using medications and supplements that support kidney health
  • Providing soft foods to reduce irritation of mouth ulcers
  • Practicing good dental hygiene to prevent infection
  • Watching for refusal to eat which may indicate mouth pain

While chronic kidney disease cannot be cured, proper management can improve quality of life and reduce complications like mouth ulcers in cats.


[1] Johnson, C. A. (2020). Kidney disease and oral health in cats and dogs. Veterinary Clinics of North America: Small Animal Practice, 50(4), 789-807.

[2] Lulich, J. P., Osborne, C. A., O’Brien, T. D., & Polzin, D. J. (1992). Feline renal failure: questions, answers, questions. The Compendium on continuing education for the practicing veterinarian (USA).

[3] Elliott, J., Rawlings, J. M., Markwell, P. J., & Barber, P. J. (2000). Survival of cats with naturally occurring chronic renal failure: effect of dietary management. Journal of small animal practice, 41(6), 235-242.

[4] Paepe, D., Verjans, G., & Duchateau, L. (2013). Routine health screening: findings in apparently healthy middle-aged and old cats. Journal of feline medicine and surgery, 15(1), 8-19.

[5] Quimby, J. M., & Lappin, M. R. (2020). Feline focus: diagnosis and management of chronic kidney disease in cats. Today’s Veterinary Practice, 10(4), 46-52.


Kidney disease is a common consequence of aging in cats. As kidney function deteriorates, the risk of secondary diseases and conditions increases. Mouth ulcers are one such potential complication of chronic kidney disease in cats.

The evidence suggests that kidney disease can in fact contribute to the development of mouth ulcers in cats. This is primarily due to the buildup of toxins in the blood that occurs with kidney failure. These toxins can cause inflammation and ulcers in the mouth. Additionally, medications used to manage kidney disease, such as calcium supplements, may also irritate the lining of the mouth.

Therefore, cat owners should monitor their pet’s mouth closely if they have been diagnosed with kidney disease. Any signs of mouth ulcers should be reported to the veterinarian. Treatment options are available to reduce discomfort and promote healing. With proper management, mouth ulcers do not have to be an inevitable consequence of feline kidney disease.

In summary, kidney disease appears capable of causing mouth ulcers in cats. But owners have options available to treat the ulcers and improve their pet’s quality of life. Staying alert and working closely with the veterinarian is key to mitigating complications from kidney disease in cats.

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