Kidney Failure in Cats: Symptoms, Stages and Causes

What Is Kidney Failure in Cats?

Kidneys serve many vital roles in the body, including filtering and removing waste in the form of urine.

Kidneys maintain proper hydration by balancing water and electrolytes, creating the hormones responsible for red blood cell production, and regulating blood pressure. In addition, the kidneys help modify vitamin D so it can be used by the body.

Like people, cats have two kidneys, one on each side of the abdomen.

Unfortunately, kidney failure can occur when these organs become too damaged to work properly.

Kidney failure usually develops because of chronic kidney disease. It takes a kidney losing more than 75% of its function before you start to see changes in routine blood work (such as in creatinine levels).

Kidney failure in cats is a life-threatening situation, and there are few treatment options when a cat reaches this stage.

Pet parents are advised to discuss their cat’s prognosis with their veterinarian, monitor their cat’s quality of life, and discuss humane euthanasia.

Types of Kidney Failure in Cats

Kidney failure in cats can be described as acute or chronic.

Acute Kidney Failure in Cats

Also called acute renal failure (ARF), acute kidney failure in cats occurs when the kidneys are suddenly damaged, usually within hours or days. This may be due to poison or from a fast-acting infection.

Cats with ARF may regain some kidney function with treatment, supportive care, and time, depending on the cause.

Even with treatment, ARF is terminal in about 50% of cases.

However, cats that do survive the initial cause usually have a better outcome compared to cats with chronic kidney disease (CKD).

Chronic Kidney Failure in Cats

Chronic kidney failure, or chronic kidney disease (CKD), eventually leads to end-stage renal failure, or ESRF, which is considered stage 4 of kidney disease.

In CKD, a gradual loss of kidney tissue occurs over a period of months (must be >2 months to be considered CKD) or years due to underlying genetic factors, chronic infections, age, cancer, or other underlying medical conditions.

Clinical signs of chronic kidney disease show up when about two-thirds of normal kidney tissue has been lost.

As it worsens, medical management becomes ineffective in helping the kidneys perform their crucial roles. 

Symptoms of Kidney Failure in Cats

Clinical signs of kidney failure in cats differ slightly, depending on if the condition is acute or final stages of CKD.

In cats with acute kidney failure, symptoms include:

• Sudden onset of decreased appetite or anorexia

• Lethargy or listlessness 

• Vomit, sometimes tinged with blood

• Diarrhea or bloody diarrhea

• Weight loss

• Ammonia-like odor to the breath (due to uremic toxins building up in the blood)

• Changes in urination (increased frequency, large amounts or cessation)

• Drinking more water than normal, usually excessive

• Abdominal pain due to swollen kidneys (seen in cases of acute kidney failure in cats)

• Seizures

In cats with end-stage kidney failure associated with chronic kidney disease, clinical signs include:

• Anorexia/refusal to eat 

• Vomiting

• Weight loss

• Lethargy, excessive sleepiness 

• Dehydration

• Confusion (possibly pacing and restlessness)

• Changes in behavior (withdrawn, irritability)

• Uncontrolled urination or defecation

• Drinking more water than normal

• Ammonia-like odor to the breath

• Seizures

• Decreasing body temperature

• Greasy, unkempt, thin hair coat

Stages of Kidney Failure in Cats

Stages of kidney failure in cats is determined by their lab values as well as the symptoms they have.

Let’s look at each stage of kidney failure in cats.

Stage 1

Kidneys are damaged but no azotemia present. Azotemia is the measurement of waste accumulation in the blood as evident by increased creatinine and blood urea nitrogen (BUN).

No clinical signs or symptoms noted.

This stage has the greatest chance of successful treatment. However, since there are no signs or lab value changes, it’s very rare to diagnose a cat with stage 1 kidney disease.  

Stage 2

Kidneys have started to decrease in their ability to filter waste out of the blood and azotemia is noted in blood work. The urine starts to become more diluted (containing more water) from poor kidney function.  

Urine specific gravity (USG) will decrease on urinalysis.

Most cats have no signs or symptoms at this stage, but some cats will start to drink more water and urine more frequently/increased volume of urine produced (PU/PD).

Stage 3

The kidneys continue to have decreased filtering ability. Azotemia becomes worse as more waste is concentrated in the blood.

Cats will begin to show clinical signs.

Stage 4

This final stage of kidney disease continues to worsen the kidneys’ ability to filter waste from the blood. This toxin buildup in the blood not only affects the kidneys but will start to affect other organs of the body.

Cats begin to feel and act very sick.

A cat’s bones can become soft and break easily. Brittle jaw bones can cause young cats’ teeth to fall out.

What Causes Kidney Failure in Cats?

Acute kidney failure has numerous causes, but it can be categorized as due to toxins or from an underlying medical issue.

Toxin exposure may be caused by ingesting:

• Ethylene glycol (antifreeze)

• Lilies (all parts of the plant and the water in the vase are toxic by ingestion or inhalation)

• NSAIDs for people, such as acetaminophen or ibuprofen

• Heavy metals like arsenic, lead, or mercury

• Rat poisons

Underlying medical issues can include:

• Urethral obstructions (inability to urinate)

• Low blood pressure

• Clotting disorders

• Heart disease

• Pyelonephritis (infection in the kidneys)

• Parasitic infections (toxoplasmosis or kidney worms)

• Tick-borne diseases

• Feline infectious peritonitis (FIP)

• Trauma or severe allergic reactions that result in shock

Chronic kidney disease eventually progresses to end-stage kidney disease and kidney failure.

How quickly this happens is hard to predict. It’s very common in geriatric cats, and some breeds have a higher risk, such as:

• Abyssinians

• Burmese

• Maine Coons

• Persians

• Ragdolls

• Russian Blues

• Siamese

Other risk factors include:

• Tumors and cancer (such as lymphoma)

• Viruses specific to cats, such as feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV)

• Chronic pyelonephritis (a slow-developing infection in the kidneys)

• Underlying genetic disorders like polycystic kidney disease or amyloidosis

• Immune-mediated disorders

• Previous acute renal failure/acute kidney injuries that did not fully respond to treatment

• Underlying medical conditions, like hyperthyroidism

• Use of certain medications

How Vets Diagnose Kidney Failure in Cats

In cases of acute renal failure in cats, blood work, urine samples, and imaging (X-rays and ultrasound) will likely be performed to diagnose the condition and help determine the best course of treatment.

Your cat will be thoroughly examined by their veterinarian and their blood pressure will be obtained as well. Your veterinarian will look for signs of:

• Anemia

• Elevated blood urea nitrogen and creatinine

• Abnormal hydration levels, by measuring electrolyte concentration (sodium, potassium, calcium, and phosphorus)

• Dilute urine or signs of infection in the urine

• High or low blood pressure

• Large or small kidneys

Kidney Failure in Cats Treatment

Options for treating end-stage kidney failure in cats are limited.

They include strategies to manage kidney disease such as special diet, supplements, and anti-nausea medication.

With proper treatment, cats with as little as 5% kidney function can survive for a long time.

One of the most important treatments for cats with any kind of kidney disease is being on a restricted diet to help with their hydration as well as to decrease the toxin buildup in the blood.

The most successful diets are prescriptions like Hills® k/d or Royal Canin® Renal Support.

These diets are restricted in protein and phosphorus to help decrease azotemia and low sodium to help with hydration.

They also contain amino acids (to help muscle mass) and omega-3 fatty acids (to support kidney health and decrease inflammation).

Antinausea medications such as Cerenia® and antacids like famotidine are useful to help control stomach upset stemming from kidney disease.

Depending on your cats' symptoms other medications might be needed—such appetite stimulants (ex: mirtazipine) and blood pressure medication.

Purina® Hydracare™ is an excellent supplement for cats with kidney disease. It’s designed to help your cat drink more water, which promotes kidney function.

Supplements can also be given to cats with kidney disease to help decrease their azotemia and promote kidney function such as AminAvast® and VetriScience®.

Speak with your veterinarian before giving your cat any supplements to ensure it is safe to give to them—they know your cat’s medical history best.

In many cases, hospitalization with intravenous (IV) fluids and the placement of a feeding tube can stabilize the cat.

Some respond well and may be able to return home for continued management of their underlying kidney disease.

For more intensive treatment, hemodialysis (treatment to filter a cat’s blood) is available. This will not cure kidney failure but may improve quality of life. 

However, few veterinary clinics possess the necessary equipment, and the cost of hemodialysis for cats is very high.

This treatment requires working with a board-certified veterinary internal medicine specialist and consultation with a member of the American Society of Veterinary Nephrology and Urology.

Kidney transplant is another experimental route, but this has not widely been used and would require working with specialists to determine if your cat is a good candidate.

When a cat has kidney failure, it’s important to work closely with your veterinarian to discuss prognosis, strategies to monitor quality of life, and when humane euthanasia should be considered.

Recovery and Management of Kidney Failure in Cats

The prognosis for kidney failure in cats is poor. 

At some point, medical management will not keep a cat comfortable and end-of-life planning will need to be discussed with your vet. This is one of the hardest decisions a pet parent can make.

Your veterinarian can help you understand questions about your cat’s quality of life. They’ll also help you develop a plan should humane euthanasia need to be considered outside of normal business hours.

How to Prevent Kidney Failure in Cats

While few types of kidney failure in cats can be prevented, unfortunately, most cases can’t.

However, kidney failure in cats due to toxin ingestion is highly preventable.

Never bring lilies—or bouquets of flowers including lilies—into the home because of their extreme toxicity to cats. All medications and cleaners should be kept in safe containers and away from places where a cat could get into them.

Limit your cat’s time in the garage, as chemicals like antifreeze can cause kidney failure in cats.

Most cases of kidney disease in cats are genetic, therefore the only way to control this is by not breeding affected cats.