Kidney Failure in Cats

Chronic renal failure (CRF) is a progressive and irreversible deterioration of kidney function. It is one of the most common health problems affecting cats, and is a leading cause of death in elderly felines. There are a number of different conditions that have the potential to result in CRF, some are congenital (present at birth), while others develop over time. Fortunately, there are also a number of treatment options available for cats suffering from CRF. It is important for all cat owners to be aware of the signs and symptoms of CRF so that they can ensure an early diagnosis and prompt treatment course. The sooner the disease is treated, the sooner the relief of the affected cat, and the better its prognosis.

What exactly is CRF?

The kidneys are made up of hundreds of thousands of tiny structures called nephrons. These are the functional units of the kidney which are responsible for filtering and eliminating waste products from the bloodstream as well as maintaining water and electrolyte balance within the body. When a nephron is damaged (due to infection, toxins, aging or whatever other cause), it loses its functional capacity. The problem may be acute, as in the case of a urinary obstruction or physical trauma, but in CRF it develops over a relatively long period of time (months to years). As nephrons begin to fail, waste products start to accumulate in the bloodstream and can reach toxic levels. Also, electrolyte imbalances and blood pressure problems may develop. As the kidneys continue to deteriorate a whole spectrum of symptoms present themselves, emphasizing the enormous number of roles the kidney plays in a healthy individual.

What Causes CRF?

There may be one or many reasons that a cat develops CRF; genetics and environment both play a role. Veterinarians tend to describe the causes of CRF as either congenital or acquired. Congenital causes (those that cats are born with) include renal aplasia (when kidneys are not present at birth), renal dysplasia (when kidneys develop abnormally), and renal hypoplasia (when kidneys have a decreased number of normal nephrons). Another congenital cause is the genetic disorder Polycystic Kidney Disease, which causes the development of cysts in the kidneys. Acquired diseases essentially include any disorder that affects the kidneys, such as inflammation, infection, or obstruction. These can predispose cats to the eventual demise of kidney function. Other conditions, such as high blood pressure and hyperthyroidism have also been linked to the development of CRF.

How is CRF Diagnosed?

There are a number of symptoms associated with CRF, the most obvious being increased thirst and urination. With further kidney deterioration, affected cats will often exhibit nausea, vomiting and a loss of appetite. While it is important to be on the lookout for any of these signs, by the time they appear, the disease has already destroyed much of a cats kidney function. Usually, the symptoms of CRF appear only after 75% of the nephrons have been compromised. What this means, is that early detection is crucial. CRF can be diagnosed based on blood results which reveal elevated levels of ‘waste products’ in the blood. The most common markers that veterinarians use are creatinine and blood urea nitrogen (BUN). These molecules are usually filtered out through the kidney, and when they increase in the blood, they are evidence that the kidneys are not doing their job. It is important for all elderly cats to have thorough veterinary exams at least annually (and preferably even more often). Owners should use these appointments to have bloodwork done on their cats as well. Not only can a blood profile catch kidney disease early on, but also a number of other potential problems.

How is CRF Treated?

While there is no cure for CRF, there are a number of ways to help manage the disease in affected cats. Because the worst symptoms are related to the build of waste products in the blood, treatments are targeted to reduce the amount of waste to a level that the kidneys can handle. Through a combination of appropriate nutrition, medication, and hydration, it is possible to improve and extend the life of CRF sufferers.

Cats with CRF should be kept on a low protein diet because most of the waste products are a result of protein breakdown in the body. Research has shown that these diets can allow cats with CRF to live up to twice as long as they might otherwise. These special ‘kidney’ diets are available through prescription and can be purchased through veterinary clinics.

The most common medication prescribed to cats with CRF are ACE inhibitors. These are drugs often used to treat human cases of high blood pressure, but they also work to decrease the protein load on the kidneys. The use of ACE inhibitors has been shown to again double the life span of cats with CRF beyond what may be expected from dietary treatment alone.

Finally, it is important that cats with CRF are adequately hydrated. Cats with kidney problems have the tendency to become dehydrated as they lose the ability to concentrate their urine. Dehydration actually further decreases renal function. This means that cats should always have access to fresh water, and when necessary may need to receive subcutaneous (injections under the skin) fluids from their veterinarian.

What is the prognosis?

Even with the best treatments available, CRF is ultimately a terminal disease. The goal of any owner should be to relieve any suffering their cat may be experiencing as a result of their renal failure and to make sure that their quality of life is the best it can be. As the waste levels reach a toxic level in the body, cats with CRF will feel extremely ill and uncomfortable, especially if they are dehydrated. It is the owner’s responsibility to determine whether their cat’s quality of life is being preserved, and to proceed humanely when it is not.

By Alison Norwich – Pets.ca writer