Kidney Disease in Cats

What Is Kidney Disease in Cats?

A cat has two kidneys, one on each side of the abdomen, and they play a vital role in filtering waste from the body. Additionally, the kidneys serve to regulate the body’s balance of fluids, minerals, and electrolytes. They conserve water and protein and play an important role in maintaining blood pressure and red blood cell production by making a hormone called erythropoietin.

There are different types of kidney disease in cats and various underlying causes. These often develop into one of two categories: acute or chronic.

Examples of acute kidney disease:

• Viral infections (feline infectious peritonitis, feline immunodeficiency virus, feline leukemia virus)

• Parasitic infections (toxoplasmosis, kidney worm Capillaria plica)

• Bacterial infections, often caused by an ascending bladder infection, which can lead to pyelonephritis (kidney infection)

• Tick-borne diseases

• Toxins, such as antifreeze, ingestion of lilies, and certain antibiotics

• Shock and hypotension (low blood pressure)

• Obstructive uropathy, often seen in male cats that are unable to urinate. This is considered a medical emergency

Examples of chronic kidney disease:

• Immune-mediated diseases

• Stroke-like events or hypertension (high blood pressure)

• Clotting disorders

• Cancer, lymphoma is most common in cats.

• Amyloidosis, seen primarily in Persians and Abyssians, is an inherited condition that causes abnormal protein deposits that lead to kidney damage.

• Polycystic kidney disease is another inherited condition seen in Persians. It consists of cysts developing within a kidney and leads to progressive kidney failure.

• Congenital kidney dysplasia is a condition that leads to small, nonfunctional, or underdeveloped kidneys.

• Consequence of acute kidney injury

Cats cannot survive without their kidneys. Many of these conditions are progressive in nature and debilitating which can lead to death. When enough damage has occurred (losing about two-thirds of kidney function), signs become apparent and regeneration will not occur, leading to chronic kidney disease. Chronic renal failure (CRF), renal insufficiency, and chronic kidney disease (CKD) are medical terms used interchangeably to describe the same condition.

Symptoms of Kidney Disease in Cats

Clinical signs are often related to the severity of the kidney disease and underlying cause. Most cats will exhibit symptoms including:  

• Increased thirst and urination

• Intermittent vomiting

• Dehydration

• Sores in the mouth

• Foul breath

• Weight loss

• Decreased appetite

• Fever and decreased activity

• Urinary accidents, incontinence, or inability to urinate

• Lower back pain

• Edema (fluid-filled swelling in the limbs)

Some cats may show muscle-wasting and signs attributed to high blood pressure, such as vision loss and weakness.

Causes of Kidney Disease in Cats

Kidney disease can be caused by a variety of factors:

• For some cats, the disease could have occurred after a serious kidney injury, from a severe infection (including feline infectious peritonitis, feline immunodeficiency virus, and pyelonephritis), ingestion of a toxic substance (like antifreeze or lilies), and from certain medications.

• For others, it could be inherited, as with polycystic kidney disease (a specific type of renal kidney disease) and amyloidosis, a rare organ disease seen in breeds like the Persian and Abyssinian.

• It could also be attributed to underlying immune-mediated diseases, stroke-like events, clotting disorders, and even cancers like lymphoma.

Even with the best testing, in some cases, the underlying cause remains unknown.  Progression of chronic kidney disease will continue with no possible cure.

How Veterinarians Diagnose Kidney Disease in Cats

Kidney disease is often diagnosed based on routine blood work and a urinalysis, looking specifically at such kidney markers as:

• Blood urea nitrogen (BUN): is a by-product of protein metabolism. Higher values can often indicate kidney failure.

• Creatinine (CREA): measures how well kidneys are filtering waste from blood.

• Phosphorous: elevated phosphorous levels typically indicate kidney damage.

• Electrolytes (sodium, potassium, chloride) are often affected by the primary disease—but also by secondary factors such as vomiting and a lack of appetite.

• Calcium: elevated levels, though not as common, are often seen with kidney damage.

• Red blood cell count: if low, it may indicate kidney failure.

• White blood cell count: if high, it may indicate infection or inflammation.

• Symmetric dimethylarginine (SDMA): an additional test to help determine if kidney disease is present. It can be used for early detection of kidney disease.

• Urine specific gravity: a marker of how diluted or concentrated the urine is. Usually, the higher the number, the more concentrated the urine and the greater the ability of the kidneys to conserve water.

• Urine sediment: indicates the presence of protein, bacteria, white/red blood cells, kidney cells and casts. It is an indication of  infection and/or kidney damage.

Your veterinarian will most likely recommend additional diagnostic testing, including:

• A urine protein to creatinine (UPC) ratio to quantify how much protein is being lost in the urine.

• A urine culture, because cats with CKD are more likely to acquire urinary tract infections.

• A blood pressure evaluation to determine if high blood pressure can be a cause or manifestation of kidney disease.

• Radiographs or abdominal ultrasound to screen for kidney stones, infarcts (areas of dead tissue), and cysts.

• A kidney biopsy to determine the type of glomerular (filtering unit of the kidney) disease present

Once diagnosed, kidney disease is then classified into four stages based on the severity of clinical signs and laboratory values:

• Stage I: Clinical signs are usually not apparent

• Stage II: Some clinical signs are noted

• Stage III: Many clinical signs are noted and cats often appear to feel sick

• Stage IV: A majority of clinical signs are noted, and cats often present in crisis

Treatment of Kidney Disease in Cats

Kidney disease is managed mostly with the aid of medications, diet, and hydration. Specific management is geared toward the underlying cause (if known) as well as the stage of the disease. A cat in any stage with an increase in either UPC or high blood pressure will most likely be treated with medication.

Based on the cause, additional therapy may be instituted, such as:

• Aggressive IV antibiotics, if infection is present

• Deworming medication for parasites

• Immunosuppressive-type drugs for auto-immune diseases

• Antithrombotics (to prevent blood clot formation)

• Chemotherapy and/or surgery (if cancer is part of the underlying cause)

If a urinary obstruction is noted, relieving the obstruction would be the treatment of choice.

Throughout your cat’s life, any disease process or illness that could affect hydration should be treated promptly with IV fluids. Drugs prescribed in the future for any other disease process will need to be tailored or substituted for a more kidney-friendly alternative, given that kidney metabolism will be decreased. If not, overdosages and/or worsening of the kidney disease could occur. 

Additionally, for all stages of kidney disease, fresh water should always be available. Drinking should be encouraged and adequate nutrition should be given daily. Cats diagnosed with kidney disease are often prescribed a kidney-friendly diet which may include feeding your cat canned, wet foods that contain additional water.

Recovery and Management of Kidney Disease in Cats

Cats diagnosed early on with kidney disease will benefit from nutritional management and more frequent veterinary attention which may include more frequent checkups and blood work.

Cats in stages I and II may often be monitored for further progression of signs, and some may be given a prescription diet specifically geared to help the kidneys by limiting the amount of work they have to do. Many cats can go on to have a decent quality of life for many months or years, depending on the specific diagnosis.   

Cats in stages III and IV often require more medical and dietary assistance:

• If secondary anemia is present, erythropoietin injections can be given at the direction of your veterinarian.

• Dietary supplements may be prescribed to help with low potassium.

• Phosphorus binders may be prescribed to treat high phosphorus levels.

• Anti-nausea and anti-emetic (anti-vomiting) medications can be given to cats with a poor appetite, vomiting, or nausea.

• Fluids given either intravenously or underneath the skin can help with dehydration, and your veterinarian can show you how to administer these fluids at home.

Because of the severity of signs often seen in cats in stages III and IV and the amount of care and effort required to support these cats, some may be humanely euthanized.

Prevention of Kidney Disease in Cats

Some causes of kidney disease may be preventable (such as toxicologic causes), but unfortunately, most causes are not. Heritable conditions, for example, are not preventable, but affected cats, or cats with the genetic copies of the disease, should not be bred.

To limit your cat’s exposure to toxins, keep lilies out of the home and block off access to the garage, household cleaners, and medications. Limiting exposure to other cats—while keeping your cat up to date on vaccines and monthly heartworm and flea control—is recommended.

If you notice any of the signs above, take your cat to a veterinarian for examination as soon as possible. Early diagnosis and intervention are keys to maintaining quality of life.