What is kidney disease in cats?
Kidney disease, also known as chronic kidney disease (CKD), refers to gradual loss of kidney function over time. The kidneys are responsible for filtering waste products from the blood, regulating fluid balance, and producing hormones. As kidney function declines, waste builds up in the body, causing symptoms like increased thirst, vomiting, and weight loss.
There are two main types of kidney disease in cats: acute kidney injury, which comes on suddenly, and chronic kidney disease, which progresses slowly over months to years. Chronic kidney disease is most common, affecting 2-20% of cats and up to 30% of cats over age 10 [1].
Common symptoms of kidney disease include increased thirst, increased urination, weight loss, poor appetite, vomiting, bad breath, and lethargy. In later stages, ulcers in the mouth may develop along with bleeding disorders. The kidney disease may eventually lead to kidney failure.
Kidney disease is more prevalent in older cats, certain breeds like Persians and Abyssinians, and cats with other health conditions like diabetes or hyperthyroidism [2]. Overall prevalence in cats is estimated at 2-4%, rising to 30-40% in cats over age 10 [2].
Causes of kidney disease in cats
There are several potential causes of kidney disease in cats. Some of the most common include:
Congenital defects
Some cats are born with congenital kidney defects or underdeveloped kidneys that can lead to kidney disease later in life. Examples include polycystic kidney disease, renal dysplasia, and renal agenesis 1.
Infections
Kidney infections, also known as pyelonephritis, can damage the kidneys over time. Bacteria, viruses, parasites, or fungi may spread to the kidneys through the bloodstream or urinary tract 2.
Toxins
Exposure to toxins like antifreeze, lilies, pesticides, or cleaning products can cause acute kidney injury. Repeat exposure may lead to chronic kidney disease 3.
Cancer
Cancerous tumors in the kidneys or urinary tract can obstruct urine flow, leading to kidney damage. Lymphosarcoma, squamous cell carcinoma, and transitional cell carcinoma may spread to the kidneys 1.
High blood pressure
Chronic high blood pressure (hypertension) can damage the small blood vessels in the kidneys over time, leading to kidney disease 2.
Age and kidney disease
Kidney disease is more common in older cats. According to a 2014 study published in the Journal of Veterinary Internal Medicine, over 50% of cats aged 11-15 years were diagnosed with chronic kidney disease (CKD) [1]. As cats age, their kidneys undergo natural changes that reduce the kidney’s ability to concentrate urine, leading to increased water consumption and urination. Additional age-related changes include decreased blood flow to the kidneys, lower kidney mass, and fewer functioning nephrons (kidney’s filtering units). These age-related changes reduce the kidney’s overall function and ability to respond to kidney injury or disease [2].
Genetics and breed predispositions
Certain cat breeds are more prone to developing kidney disease due to genetic factors. For example, Persian cats are more likely to develop polycystic kidney disease, a genetic disorder where fluid-filled cysts develop on the kidneys over time and impair kidney function. According to one study, Persians had a 3.5 times higher risk for polycystic kidney disease compared to other breeds.[1]
In addition to Persians, other breeds like Maine Coons, Abyssinians, Ragdolls, and Burmese have shown a predisposition for chronic kidney disease.[2] The underlying genetic factors are still being researched, but it’s clear that genetics play a role in certain breeds’ susceptibility.
Beyond specific breed predispositions, there may be other genetic factors that can increase a cat’s risk. For example, some research suggests a familial inheritance pattern in some cases of feline chronic kidney disease where multiple cats in the same family are affected. More studies are needed to fully understand the genetic components involved in kidney diseases.
Diet and kidney disease
A cat’s diet is extremely important for supporting kidney health and preventing disease progression. Kidney disease leads to an accumulation of phosphorus in the blood, so it’s critical to feed a low phosphorus diet. This helps reduce strain on the kidneys and prevent secondary issues like hyperparathyroidism. Feeding wet food is ideal as the high moisture content helps flush toxins from the body and prevent dehydration. Cats with kidney disease should be fed a veterinary therapeutic kidney diet to ensure balanced nutrition with restricted phosphorus. Maintaining an ideal body weight is also important, as obesity is a risk factor for kidney disease. Lean body condition reduces demand on the kidneys.
Toxins and medications
Many common toxins and medications can have severely damaging effects on a cat’s kidneys. Some of the most dangerous substances include:
Ethylene glycol, more commonly known as antifreeze, is extremely toxic to cats if ingested. According to The Veterinary Nurse, antifreeze poisoning is a common cause of renal failure in cats [1]. The chemical metabolizes into toxic compounds that can crystallize in the kidneys, causing irreversible damage.
Lilies are extremely poisonous to cats, and even ingesting a small amount can lead to acute kidney injury. All parts of the plant are toxic, including the leaves, flowers, pollen and water in a vase [2]. Kidney failure can occur within 2-3 days of exposure.
Certain medications like NSAIDs and chemotherapy drugs can have damaging kidney side effects in cats. It’s important to follow dosing guidelines and monitor kidney values when giving medications [3].
Melamine toxicity occurred in 2007 after tainted pet food from China caused kidney failure in thousands of cats and dogs. Melamine had been added to boost the apparent protein content [1]. This tragic incident highlighted the need for better regulation and quality control of pet foods.
Catching toxin exposure early and providing aggressive treatment can potentially reverse kidney damage. Preventing access to toxins is the best way to protect a cat’s kidney health.
[1] https://www.theveterinarynurse.com/review/article/poisons-affecting-the-kidney
[2] https://www.webmd.com/pets/cats/kidney-failure-uremia-symptoms-cats
[3] https://wagwalking.com/cat/condition/kidney-toxicity
Injuries and Physical Trauma
Physical trauma from injuries can also lead to kidney disease in cats. Blunt trauma, such as being hit by a car, can damage the kidneys and cause internal bleeding. Surgeries involving the urinary tract, kidneys, or abdomen also pose a risk of accidental injury to the kidneys. Rarely, surgical complications like ischemia (restricted blood flow) or inadvertent ligation of the ureters can occur, leading to acute kidney injury.
According to one source, “Blunt trauma is reported as the most common cause of postrenal ARF (acute renal failure). Damage results from contusions or transaction of the ureters or urinary bladder” (https://vcahospitals.com/know-your-pet/kidney-failure-acute-in-cats).
Cats that suffer trauma or injury to their kidneys are at higher risk for developing chronic kidney disease later in life. Therefore, it’s important for cat owners to monitor their pet closely after any blunt force trauma or surgery involving the urinary system.
Diagnosing kidney disease
There are several tests veterinarians use to diagnose kidney disease in cats:
Blood and urine tests – Blood tests check levels of waste products like creatinine and BUN (blood urea nitrogen) that are filtered by the kidneys. Increased levels indicate decreased kidney function. Urinalysis checks for protein loss, blood, and concentration issues. According to VCA Animal Hospitals, the urine protein to creatinine ratio helps quantify protein loss.
Imaging tests – X-rays, ultrasound, or CT scans allow veterinarians to visualize the kidneys and look for issues like small, shrunken kidneys, tumors, cysts, or stones, according to Cornell University Veterinary Specialists.
Kidney biopsies – Biopsies remove small samples of kidney tissue for analysis under a microscope. This helps identify specific causes of kidney disease like inflammation or abnormal structures, according to PetMD.
Treating kidney disease
There are several approaches for treating kidney disease in cats:
Fluids: One of the most common treatments is providing subcutaneous fluids, which helps flush toxins from the body and prevent dehydration. Fluids can be given at home under the skin. Vets may recommend daily fluids or fluid therapy multiple times per week. Chronic Kidney Disease in Cats – VCA Animal Hospitals
Diet changes: Prescription kidney diets lower protein, phosphorus, and sodium levels. Feeding wet food increases water intake which is beneficial. Feeding kidney diets early in the disease process helps slow progression. Chronic Kidney Disease – Cornell Feline Health Center
Medications: Drugs like ACE inhibitors help control blood pressure and reduce strain on the kidneys. Antacids help control stomach ulcers. Medications to control anemia may also be prescribed. Causes of and Treatments for Kidney Failure in Cats
Dialysis: In severe cases, dialysis filters wastes from the blood. This intensive treatment is uncommon since most cats don’t tolerate the process well. Chronic Kidney Disease in Cats – VCA Animal Hospitals
Preventing kidney disease
There are several ways to help prevent kidney disease in cats:
Get annual vet checkups to monitor kidney function and catch any issues early. Blood and urine tests can identify kidney problems before signs appear (1).
Avoid exposing cats to toxins like antifreeze, heavy metals, lilies, and toxic plants. Keep all chemicals and medications out of reach (2, 3). Kidney toxins can cause irreversible damage.
Feed a high quality diet low in protein, phosphorus, and sodium. Kidney-friendly diets support kidney health (1, 3).
Ensure cats have fresh, clean water available at all times. Increased water intake helps flush toxins from kidneys (1, 2). Consider adding extra water bowls around your home.
With diligent care and routine vet visits, kidney disease can often be detected early and managed to improve quality of life.
