Kidneys are vital organs in cats, playing several critical roles to maintain their health. These include filtering waste products from the blood to form urine, regulating hydration by balancing fluids and electrolytes, producing hormones that stimulate red blood cell production, and helping to control blood pressure. Additionally, the kidneys are involved in activating vitamin D, making it usable for the body. Like humans, cats are born with two kidneys situated in their abdomen.
Unfortunately, kidney failure, also known as renal failure, occurs when these essential organs become too damaged to function effectively. This condition is frequently a consequence of chronic kidney disease (CKD). It’s important to note that kidney function can decline significantly—losing over 75% of its capacity—before routine blood work starts to show noticeable changes, such as elevated creatinine levels.
Kidney failure in cats is a severe, life-threatening condition. Once a cat reaches this advanced stage, treatment options become limited. If your cat is diagnosed with kidney failure, it’s crucial to have an open discussion with your veterinarian to understand their prognosis, closely monitor their quality of life, and consider the difficult but compassionate option of humane euthanasia when necessary.
Types of Kidney Failure in Cats
Kidney failure in cats can be categorized into two main types: acute and chronic, each with distinct characteristics and implications.
Acute Kidney Failure (ARF) in Cats
Acute kidney failure, also known as acute renal failure (ARF), is characterized by a sudden and rapid decline in kidney function, typically developing over a matter of hours or days. This abrupt kidney damage is often triggered by toxins or severe, fast-acting infections.
The prognosis for cats with ARF is variable. With prompt and intensive treatment, including supportive care, some cats may regain partial kidney function. The outcome largely depends on the underlying cause and the extent of kidney damage.
Despite treatment efforts, acute renal failure remains a grave condition, with approximately 50% of cases proving fatal. However, cats that survive the initial acute phase of ARF generally have a more favorable long-term outlook compared to those with chronic kidney disease (CKD).
Chronic Kidney Failure (CKD) in Cats
Chronic kidney failure, or chronic kidney disease (CKD), is a progressive condition where kidney function gradually deteriorates over months (defined as longer than 2 months) or even years. This slow decline is due to the gradual loss of kidney tissue and can be attributed to various factors, including genetic predispositions, persistent infections, aging, cancer, or other underlying health issues. End-stage renal failure (ESRF), representing stage 4 of CKD, is the ultimate progression of this chronic process.
Clinical signs of chronic kidney disease often don’t become apparent until a significant portion of kidney tissue—around two-thirds—has already been compromised. As CKD advances, the kidneys become increasingly unable to perform their essential functions, and medical management becomes less effective in supporting kidney function.
Symptoms of Kidney Failure in Cats
The clinical signs of kidney failure in cats can differ depending on whether the condition is acute or related to the final stages of chronic kidney disease. Recognizing these symptoms early is crucial for prompt veterinary intervention.
Symptoms of Acute Kidney Failure in Cats:
- Lethargy and weakness
- Loss of appetite or anorexia
- Vomiting
- Diarrhea
- Abdominal pain
- Dehydration
- Decreased urination or complete lack of urination
Symptoms of End-Stage Kidney Failure (Associated with Chronic Kidney Disease) in Cats:
- Anorexia or complete refusal to eat
- Vomiting
- Weight loss
- Lethargy and excessive sleepiness
- Dehydration
- Confusion, which may manifest as pacing or restlessness
- Behavioral changes, such as becoming withdrawn or irritable
- Uncontrolled urination or defecation
- Increased thirst and drinking more water than normal
- Breath with an ammonia-like odor
- Seizures
- Decreasing body temperature
- Unkempt, greasy, and thin hair coat
Stages of Kidney Failure in Cats
The staging of kidney failure in cats is determined by a combination of laboratory values and the clinical symptoms observed. These stages help veterinarians assess the severity of the condition and guide treatment strategies. The International Renal Interest Society (IRIS) guidelines are commonly used for staging CKD in cats.
Stage 1 Kidney Failure
In Stage 1, the kidneys are damaged, but there is no azotemia present. Azotemia refers to the buildup of waste products in the blood, indicated by elevated creatinine and blood urea nitrogen (BUN) levels.
Cats in Stage 1 typically show no outward clinical signs or symptoms.
This stage offers the best chance of successful management and slowing disease progression. However, diagnosis at Stage 1 is rare because there are no obvious signs or changes in routine lab work to alert pet owners or veterinarians.
Stage 2 Kidney Failure
Stage 2 is characterized by the kidneys beginning to lose their ability to effectively filter waste from the blood, and azotemia becomes evident in blood work. Urine starts to become more dilute as the kidneys struggle to concentrate it properly.
Urinalysis will reveal a decreased urine specific gravity (USG), indicating diluted urine.
Most cats in Stage 2 still do not show noticeable signs or symptoms. However, some may start exhibiting increased thirst and urination (polyuria and polydipsia, PU/PD).
Stage 3 Kidney Failure
In Stage 3, the kidneys’ filtering capacity continues to decline significantly. Azotemia worsens as more waste products accumulate in the bloodstream.
Cats in Stage 3 begin to display clinical signs of kidney disease, which may include lethargy, decreased appetite, and weight loss.
Stage 4 Kidney Failure
Stage 4 represents the final stage of kidney disease, where the kidneys’ ability to filter waste is severely compromised. The accumulation of toxins in the blood not only impacts the kidneys but also starts to affect other organs throughout the body.
Cats in Stage 4 are visibly and significantly ill.
A serious complication in this stage is renal secondary hyperparathyroidism, which can lead to weakened bones that break easily. In young cats, brittle jawbones can even cause teeth to fall out.
What Causes Kidney Failure in Cats?
The causes of kidney failure in cats can be broadly divided into those causing acute kidney failure and those leading to chronic kidney disease.
Causes of Acute Kidney Failure:
Acute kidney failure often results from exposure to toxins or underlying medical issues.
Toxin exposure can occur through ingestion of:
- Ethylene glycol antifreeze: Even small amounts are highly toxic to cats.
- Lilies: All parts of the lily plant are extremely poisonous to cats.
- Certain medications: Including NSAIDs (non-steroidal anti-inflammatory drugs) and some antibiotics if not dosed appropriately.
- Heavy metals: Such as lead or arsenic.
- Certain household cleaners and chemicals.
Underlying medical issues that can trigger acute kidney failure include:
- Urethral obstructions (blocking the flow of urine)
- Low blood pressure (hypotension)
- Clotting disorders
- Heart disease
- Pyelonephritis (kidney infection)
- Parasitic infections (like toxoplasmosis or kidney worms)
- Tick-borne diseases
- Feline infectious peritonitis (FIP)
- Trauma or severe allergic reactions leading to shock
Causes of Chronic Kidney Disease:
Chronic kidney disease is a progressive condition that eventually leads to end-stage renal failure. The progression rate varies, but it is commonly observed in older cats.
Genetic predisposition: Some breeds are at a higher risk of developing CKD, including:
- Abyssinians
- Persians
- Siamese
- Russian Blues
- Maine Coons
Other risk factors for CKD include:
- Tumors and cancer, such as lymphoma
- Viral infections specific to cats, like feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV)
- Chronic pyelonephritis (long-term kidney infection)
- Underlying genetic disorders such as polycystic kidney disease or amyloidosis
- Immune-mediated disorders
- Previous acute renal failure/acute kidney injuries that did not fully recover
- Underlying medical conditions like hyperthyroidism
- Use of certain medications over extended periods.
How Veterinarians Diagnose Kidney Failure in Cats
Diagnosing kidney failure in cats involves a comprehensive approach. For acute renal failure, immediate diagnostic steps are crucial.
Diagnostic Procedures:
- Blood work: To assess kidney function by measuring BUN, creatinine, and electrolytes, and to detect anemia.
- Urine samples (urinalysis): To evaluate urine concentration (specific gravity), check for protein, glucose, blood, and identify any signs of infection.
- Imaging (X-rays and ultrasound): To visualize the kidneys, assess their size and structure, and rule out obstructions or other abnormalities.
- Physical examination: A thorough examination by the veterinarian to assess hydration status, body weight, and overall health.
- Blood pressure measurement: To check for hypertension, which is common in cats with kidney disease.
Veterinary Assessment Will Look For Signs of:
- Anemia
- Elevated blood urea nitrogen (BUN) and creatinine levels
- Abnormal hydration levels, assessed through electrolyte concentrations (sodium, potassium, calcium, and phosphorus)
- Dilute urine or evidence of urinary tract infection
- High or low blood pressure
- Kidney size abnormalities (enlarged or shrunken kidneys)
Kidney Failure in Cats Treatment
Treatment options for end-stage kidney failure in cats are aimed at managing the disease and improving quality of life, rather than curing the condition.
Management Strategies Include:
- Prescription kidney diets: These diets, such as Hills® k/d or Royal Canin® Renal Support, are formulated to be lower in protein and phosphorus to reduce the workload on the kidneys and minimize toxin buildup. They are also often low in sodium to help manage hydration and enriched with omega-3 fatty acids and amino acids to support kidney health and muscle mass.
- Fluid therapy: Maintaining hydration is critical. This can be achieved through increased water intake, subcutaneous fluids administered at home, or intravenous (IV) fluids in a hospital setting. Purina® Hydracare™ is a supplement designed to encourage cats to drink more.
- Medications:
- Anti-nausea medications: Like Cerenia® or antacids like famotidine to control nausea and vomiting associated with kidney disease.
- Appetite stimulants: Such as mirtazapine to encourage eating.
- Blood pressure medication: To manage hypertension.
- Phosphate binders: To reduce phosphorus levels in the blood.
- Supplements: Certain supplements like AminAvast® and VetriScience Renal Essentials® may help support kidney function and reduce azotemia. Always consult with your veterinarian before starting any supplements.
- Hospitalization and intensive care: In severe cases, hospitalization with IV fluids and nutritional support via a feeding tube may be necessary to stabilize the cat.
- Hemodialysis: This advanced treatment filters waste from the blood, offering temporary improvement in quality of life but is costly and not widely available. It requires specialized veterinary centers and consultation with specialists from the American Society of Veterinary Nephrology and Urology.
- Kidney transplant: An experimental procedure, rarely performed in cats due to its complexity and need for specialized centers.
Recovery and Management of Kidney Failure in Cats
The prognosis for cats with kidney failure is generally guarded to poor, especially in advanced stages. While treatment can help manage symptoms and slow disease progression, kidney failure is not curable.
End-of-Life Considerations:
As kidney failure progresses, there will come a point when medical management can no longer maintain an acceptable quality of life for the cat. Discussing end-of-life planning and humane euthanasia with your veterinarian is a compassionate step to consider when your cat’s comfort and well-being can no longer be assured. Your vet can provide guidance on assessing your cat’s quality of life and help you make these difficult decisions.
How to Prevent Kidney Failure in Cats
While chronic kidney disease is often related to age or genetics and not preventable, certain causes of acute kidney failure can be avoided.
Preventive Measures:
- Prevent toxin exposure:
- Keep lilies out of your home: These plants are extremely toxic to cats.
- Secure medications and cleaners: Store all medications and household chemicals in closed cabinets, out of reach of cats.
- Limit garage access: Antifreeze is highly toxic and often found in garages. Clean up any spills immediately and store antifreeze safely.
- Responsible breeding: Avoid breeding cats with known genetic predispositions to kidney disease to reduce the incidence of inherited forms of CKD.
Kidney Failure in Cats FAQs
Is kidney failure in cats painful?
The discomfort associated with kidney failure can vary. Acute kidney failure can cause pain due to kidney swelling and abdominal discomfort. Urinary tract issues that can lead to kidney disease, such as obstructions or infections, are also painful. Chronic kidney disease, with its gradual progression, is typically less associated with pain directly from the kidneys themselves, but the systemic effects and complications can cause discomfort and illness.
What is the life expectancy of cats with kidney failure?
Life expectancy varies greatly depending on the stage of kidney failure and the cat’s response to treatment. Cats diagnosed in early stages (1 and 2) of CKD, with appropriate management including diet and medications, can live for many years. Cats in later stages (3 and 4) have a more guarded prognosis, and life expectancy is significantly shorter, ranging from months to potentially a year, depending on their response to aggressive treatment and overall health. Humane euthanasia is often considered in these advanced stages to prevent suffering.
What are the early signs of kidney failure in cats?
The earliest and most common signs of kidney disease in cats are polyuria and polydipsia (PU/PD). Polyuria is increased urination, which may be noticeable as larger urine clumps in the litter box or accidents outside the litter box. Polydipsia is increased thirst, characterized by cats drinking more water than usual, often seeking water from unusual sources like toilets or sinks. Observing these signs warrants a prompt veterinary check-up.
WRITTEN BY
Jamie Case, DVM
Veterinarian
Dr. Jamie Case graduated from the University of Missouri College of Veterinary Medicine in 2017, after receiving a Bachelor of Science…
