Kidney problems in cats are one of the most common health issues that affect them. While kidney (renal) problems and failure are among the leading causes of death in cats, early detection and management can help cats live many years beyond their initial diagnosis.
The kidneys are vital organs in the body. Cats have two kidneys, which are responsible for constantly filtering the blood, separating waste products from the bloodstream, and expelling them through the urine. This process keeps unwanted waste products from accumulating in other organs, ensuring those organs function efficiently. The kidneys’ role is essential to life and is a constant process within the body.
Many factors, or a combination of factors, can cause parts of the kidneys to stop functioning properly. Diet, genetic predisposition, injury, and old age are all common causes of kidney failure. As kidney function declines, waste products begin to accumulate in the cat’s body, leading to symptoms such as weight loss, decreased appetite, depression, increased thirst, increased urination, and severe dehydration.
Types of Kidney Failure in Cats
There are two types of kidney failure: chronic and acute. Acute kidney failure in cats most often occurs as a secondary result of a major injury or illness that places significant strain or stress on the kidneys. As a result, the kidneys may stop functioning almost immediately, leading to a complete failure of the body’s filtration system. Acute kidney failure can be caused by cats ingesting toxins or other nephrotoxic substances. Exposure to even a small amount of some substances—such as ibuprofen, lilies, or antifreeze—can cause acute kidney failure, which is an immediate and life-threatening emergency. Treatment for acute kidney failure depends on the cause of the shutdown, the ability to remove the toxin from the cat’s body, and the extent of kidney damage. In some cases, dialysis may be required to artificially filter toxins from the blood for several days or weeks, allowing the kidneys time to recover and potentially resume normal function.
Chronic kidney failure in cats is much more common, and a high percentage of cats over the age of 12 have some degree of chronic kidney failure. As the term “chronic” implies, this condition develops over an extended period, and many cats with chronic kidney failure do not show strong clinical signs until they have had the problem for months or even years. In these cases, the most common cause of chronic kidney failure is simply age— as cats age, their kidneys do too, and eventually, they may wear out completely.
Recently, studies have also shown that diet can significantly impact the prevention of kidney failure in cats. By nature, cats are carnivores, and their bodies evolved to eat meat to survive. In the wild, cats eat nearly the entire content of their prey. Their protein comes from the bulk of the animal they catch, and most of their water intake comes directly from the kill. Cats evolved from desert animals, where water was scarce, so they had to rely on their prey as a primary source of hydration.
A cat’s diet should naturally contain around 65% water, which helps the kidneys filter more efficiently. However, domesticated cats are often fed dry food with minimal water content. To compensate for this dry food, cats need to drink supplemental water. Unfortunately, many cats do not drink enough, which leads to chronic dehydration, making the kidneys work harder to filter blood and potentially causing them to wear out faster than the rest of the body.
While there’s no way to completely prevent kidney failure, offering your cat a diet with higher moisture content, such as canned food, can help reduce the risk of kidney problems. Additionally, encouraging your cat to drink more water (e.g., using a water fountain) is beneficial in counteracting the conflict between their evolutionary needs and modern feeding habits.
Identifying kidney failure in its early stages is often difficult. The kidneys are resilient and can continue functioning at nearly normal levels until at least 70% of their function has been lost. For this reason, symptoms of kidney disease often appear only after the kidneys have already experienced significant damage. As your cat ages, routine veterinary exams, blood work, and urine analysis can detect kidney disease before severe damage occurs.
The main ways to identify and assess kidney failure are through two blood tests and a urine test. Blood urea nitrogen (BUN) and blood creatinine levels help evaluate kidney function, but they are less effective in determining whether the problem is acute or chronic, or in detecting early kidney failure. To diagnose early kidney failure, a urinalysis is also needed.
When the kidneys’ filtration process becomes compromised, the body adapts by increasing blood flow to the kidneys, which leads to more urine production. To prevent dehydration from the increased urine output, the cat drinks more water. This is reflected in the urinalysis as a drop in the concentration of waste products in the urine. As kidney function declines, the concentration of urine decreases.
If your cat is diagnosed with kidney failure, there are several common changes you can make to help ease the kidneys’ workload and support their function. Diet changes may be prescribed to reduce the protein levels in the food, which can be a stressor for the kidneys. Wet food may also be recommended over dry food. Fluid therapy, administered at home daily under the skin, is another excellent way to help ease the burden on the kidneys and improve their function.
With early diagnosis and treatment, many kidney problems in cats can be managed for months or even years. The most important aspect of diagnosing and treating kidney issues is to work closely with your veterinarian to determine the best treatments and actions for your cat.
