Introduction
Kidney failure, also known as chronic kidney disease (CKD), is a common condition in cats where the kidneys are no longer able to filter waste products from the blood effectively. Kidney disease affects over 30% of cats aged 15 years or older, making it one of the most prevalent geriatric diseases in cats[1].
Kidney failure in cats can have many causes, including congenital defects, infections, toxins, cancer, and general wear and tear associated with aging. While kidney disease is not reversible in cats, recognizing the early warning signs and making appropriate diet and lifestyle changes can significantly slow its progression and extend a cat’s quality of life.
That’s why it’s critical for cat owners to understand the common symptoms of feline CKD. Catching kidney failure early allows for interventions that can help cats live comfortably for months or even years after diagnosis.
[1] https://elibrary.ru/item.asp?id=47355836
Changes in Water Consumption
As a cat’s kidneys start to fail, they are less able to concentrate urine and regulate body fluids. This leads to increased thirst and water intake, a condition known as polydipsia. According to research, cats with CKD drink over 100 mL per kg body weight per day, which is more than double the amount of a healthy cat.
Owners may notice their cat starts drinking water more frequently and from sources they did not drink from before, like the bathtub or sink. Cats may also start drinking their own urine. This increased thirst is the body’s way of compensating for impaired kidney function. As the kidneys fail to remove toxins and concentrate urine, the cat feels constantly dehydrated, even if they are drinking more. Left untreated, this can lead to potentially fatal dehydration and electrolyte imbalances.
Changes in Urination
One of the most common signs of kidney failure in cats is increased urination, also known as polyuria. As the kidneys become impaired, they are no longer able to concentrate urine effectively. This results in larger volumes of dilute, watery urine being produced and excreted [1]. Cats with kidney disease will often visit their litter boxes more frequently and have larger volumes of urine each time.
Owners may notice their cat urinating in locations outside of the litter box as well. Since the urge to urinate comes on more suddenly and frequently, cats may not always make it to the litter box in time. Puddles of urine found around the house can be indicative of this loss of bladder control. Cats that were previously well-housed trained may start having repetitive urinary accidents [2]. This increased urgency and frequency of urination is a classic sign of declining kidney function.
Weight Loss
Weight loss is one of the most common signs of kidney failure in cats. As the kidneys lose their ability to function properly, toxins accumulate in the bloodstream which can lead to a loss of appetite and nausea (Freeman, 2016). This condition, known as uremic anorexia, can cause cats to eat less even though their body needs extra calories and protein. The inability to properly digest food coupled with a poor appetite leads to muscle wasting and rapid weight loss (Ormond Cat Clinic).
In advanced kidney failure, cats are unable to properly utilize the protein and fat stores in their body. This leads to depleted muscle mass and fat, resulting in significant weight loss and emaciation. The kidneys help regulate the metabolism and use of protein, so when they fail, the body starts breaking down its own muscle tissue for energy. Even if the cat continues to eat, lean muscle mass and body fat are progressively lost. Severe weight loss is a telling sign the cat’s kidney function is declining.
Gastrointestinal Signs
As kidney disease progresses in cats, it often leads to gastrointestinal issues like vomiting, diarrhea, constipation, and loss of appetite. These occur because failing kidneys cannot adequately remove toxins and maintain fluid balance in the body, leading to a condition called uremic gastropathy. According to VCA Animal Hospitals, common gastrointestinal signs of kidney disease in cats include:
- Vomiting – Cats may vomit bile or food undigested from previous meals. Vomiting is caused by toxin buildup and metabolic changes from kidney failure.
- Diarrhea – Loose stools and diarrhea can develop from uremic gastropathy. Diarrhea exacerbates dehydration and nutrient losses.
- Constipation – Dehydration and electrolyte imbalances can slow motility of the gastrointestinal tract leading to constipation.
- Loss of appetite – Toxins, nausea, mouth ulcers, and metabolic changes often suppress a cat’s appetite. This exacerbates muscle wasting and weight loss.
According to a study in the National Center for Biotechnology Information, over 50% of cats with chronic kidney disease experienced vomiting and 41% had diarrhea. Appetite loss occurred in 36% of cats studied (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4895456/). While gastrointestinal signs have many causes in cats, their presence along with other symptoms could signal kidney problems. A veterinarian can run tests to check kidney values and determine if kidney disease is present.
Behavioral Changes
Cats with kidney disease often experience behavioral changes as the toxins build up in their bodies. Some of the most common behavioral changes include:
Lethargy: Cats may become increasingly inactive and sleep more often as kidney failure progresses. They simply don’t have the energy for their usual activities. According to PetMD, lethargy is one of the most common symptoms of kidney failure in cats.1
Irritability: Cats with kidney disease may become irritable or aggressive, especially when touched or handled. The Kidney Chek blog notes that cats often don’t show overt signs of pain but kidney disease can cause chronic discomfort.2
Hiding: Sick cats tend to hide as an instinctual behavior. Cats with kidney failure may hide more often, only coming out reluctantly for food or attention. This withdrawal behavior can progress as kidney disease gets worse.
Aggression: The buildup of toxins can cause confusion, anxiety, and aggression in cats with kidney failure. A cat that previously enjoyed attention may start to bite or scratch due to this discomfort and disorientation.
Poor Coat Condition
As kidney disease progresses in cats, their coats often become dull, rough, and unkempt. This is because the kidneys play an important role in regulating vitamins, minerals, and nutrients in the body. When the kidneys start to fail, imbalances in these substances can occur.
Specifically, cats with kidney disease may have deficiencies in proteins, fatty acids, and vitamins like vitamin B12. This can lead to a dry, brittle, and ragged coat texture. The coat may also become matted and unclean since ill cats tend to groom themselves less. Skin problems like dandruff, scaly skin, and bald patches may arise too. Kidney Disease in Cats: Symptoms and Treatments notes that poor coat health may include skin infections as well as thinning and patchy hair loss.
A dull, unkempt coat is usually one of the earlier visible signs of kidney problems in cats. So owners should be alert for any deterioration in their cat’s coat quality or skin condition as it could indicate underlying kidney issues. Addressing diet and nutrition can help improve coat health in kidney disease cats. Medicated shampoos may also be prescribed for skin conditions. But the dull coat is a symptom of the larger kidney problem, so treating the kidney failure itself is key to restoring good coat quality.
Anemia
One of the most common symptoms of kidney failure in cats is anemia, which is a reduction in red blood cells or hemoglobin. This happens because diseased kidneys produce less erythropoietin, the hormone that stimulates red blood cell production in the bone marrow. Anemic cats will have pale gums, noticeable fatigue, weakness, and exercise intolerance. They may also have faster breathing and heart rates as their bodies try to compensate for decreased oxygen carrying capacity. In May 2023, the FDA approved the first drug, Elanco’s Varenzin-CA1, specifically for the treatment of nonregenerative anemia associated with chronic kidney disease in cats, which can help stimulate red blood cell production. Treatment of the underlying kidney disease is still essential for managing anemia in these patients (FDA approves anemia drug for cats with chronic kidney disease, 2023).
Diagnosis
Diagnosing kidney disease in cats begins with a complete physical examination by a veterinarian. The vet will check for signs like dehydration, oral ulcers, pale gums, and an enlarged abdomen.
Common diagnostic tests include:
Blood and urine tests: These are used to check kidney values like blood urea nitrogen (BUN) and creatinine. Elevated levels indicate poor kidney function. A urinalysis can detect protein in the urine and an abnormal specific gravity, which are signs of kidney problems (https://www.vetinfo.com/chronic-kidney-failure-in-cats.html).
Imaging: X-rays, ultrasound, or CT scans of the abdomen may reveal small, shrunken kidneys or abnormalities. These help rule out obstructions or masses putting pressure on the kidneys.
Kidney biopsy: Taking a tissue sample from the kidney for analysis can confirm damage and identify the underlying cause, like inflammation or cancer (https://www.vetamerikan.org/health-information/cat-diseases/kidney-failure-in-cats).
Conclusion
In summary, there are several key signs that cats exhibit when suffering from kidney failure, including increased thirst, increased urination, weight loss, gastrointestinal issues, poor coat condition, lethargy, and anemia. The earlier kidney disease is detected, the better the prognosis when proper treatment is started. It is critical to have annual bloodwork and urinalysis performed on older cats to screen for kidney issues, even before outward symptoms appear. If kidney values start to increase, vets can put cats on kidney diets and medications to help slow the progression of kidney failure. While kidney disease cannot be reversed, timely veterinary care and following the prescribed treatment plan can help extend and improve quality of life. Prognosis depends on the underlying cause and how early treatment begins, but cats can live for months or even years with proper management of chronic kidney disease.