Defining CRF in Cats
Chronic renal failure (CRF) is a progressive disease caused by long-term insult to the kidneys. This over time, damages their ability to concentrate urine and remove waste products from circulation.
The word “renal” means anything pertaining to the kidneys. Chronic renal failure is one of the most common causes of death in domestic cats. Unfortunately, most owners don’t notice the symptoms of CRF until their cat’s kidneys have been damaged beyond repair.
Usually, by the time CRF is diagnosed, about 70% of functional kidney tissue has already been destroyed. Once clinical signs appear, the kidneys have lost most of their ability to filter waste products.
This includes circulating blood, excreting the end-products of metabolism in the urine, regulating blood pressure, contributing to red blood cell production and regulating the concentrations of hydrogen, sodium, potassium, phosphate and other electrolytes in the cat’s system. Chronic renal failure is always progressive, irreversible and eventually fatal.
Causes of Chronic Renal Failure in Cats
Causes of Chronic Renal Failure in Cats
Chronic renal failure (CRF) involves a long-term insult to the kidneys that causes them to gradually deteriorate, losing their ability to concentrate urine and remove waste products from the bloodstream.
The reason cats get this condition isn’t well-understood, although advancing age is considered to be the biggest risk factor. It seems that as cats get older, their kidneys simply start to wear out.
Most cases of chronic renal failure in cats happen when they are 7 years or older. Genetics almost are always involved, because certain cat breeds and family lines have an increased preponderance of chronic renal failure as composed to the normal domestic cat population. Other reported contributing factors include:
- Exposure to nephrotoxic poisons (nephrotoxins are substances that destroy kidney cells, which are called “nephrons”)
- Congenital kidney disorders (“congenital” means something that exists at birth)
- Prior episodes of acute renal failure
- Chronic urinary tract obstruction (narrow urethra, chronic infection, kidney or bladder stones)
- Drugs (especially nonsteroidal anti-inflammatory drugs [NSAIDs] and nephrotoxic antibiotics)
- Polycystic kidney disease (a common congenital kidney defect)
- Lymphoma (a type of cancer; also called lymphosarcoma)
- Infectious diseases (especially feline leukemia virus [FeLV] and feline infectious peritonitis [FIP])
- Exposure to heavy metals (mercury, lead, thallium)
- Abdominal trauma (especially when the pelvis is fractured and the bladder is ruptured)
A number of different kidney diseases can contribute to chronic renal failure in cats, including glomerulonephritis, pyelonephritis, tubulonephrosis, amyloidosis and tubulointerstitial nephritis.
A veterinarian is in the best position to discuss these diseases with cat owners. Unfortunately, the cause of a cat’s chronic renal failure usually remains a medical mystery.
Preventing Chronic Renal Failure in Cats
Because the underlying cause of chronic renal failure is elusive, it is difficult to identify ways to prevent this disease. Most cases of feline CRF can’t be prevented, and unfortunately they are not particularly responsive to treatment.
Many cats diagnosed with chronic renal failure can be managed with medication and supportive care for some period of time, but none can be cured. Companion cats – especially those over 7 years of age – should have an annual veterinary examination with blood and urine screening to monitor kidney function and the health of their other vital organs.
Dietary management can also be helpful. There are a number of good commercial kidney diets that are available with a veterinarian’s prescription. Of course, free access to fresh water is always important, especially for cats with kidney problems. Cats that are known to have kidney disease in their family probably should not be used as part of a responsible breeding program.
Cats with chronic renal failure often show no symptoms of their condition for months or even years. Early diagnosis of CRF and conscientious supportive care can delay progression of the disease and help maintain the cat’s quality of life.
Symptoms of Chronic Renal Failure in Cats
Effects of Chronic Renal Failure – From the Cat’s Point of View
Chronic renal failure (CRF) is caused by some long-term insult to the kidneys. Most cats with chronic renal failure don’t show any signs of being sick during the early phase of their disease; this is considered to be renal “insufficiency,” rather than renal “failure”.
The word “renal” refers to anything having to do with the kidneys. However, as chronic renal failure progresses, affected cats become very ill. Circulating toxins are building up in their bloodstream, which adversely affects the function of all of their key organs. Affected animals just feel lousy.
They become weak, lethargic and sluggish. They lose their appetite and lose weight, often being referred to as “skin and bones.” They develop painful sores (ulcerations) on their gums and tongue, and they also become nauseous and have increasingly severe abdominal pain.
Symptoms of Chronic Renal Failure in Cats – What the Owner Sees
Unfortunately, most cats with chronic renal failure don’t start to show signs of being sick until their kidneys have lost approximately 70% of their functional ability. When the symptoms of CRF do become apparent to an affected cat’s owner, they typically include one or more of the following:
- Marked increase in thirst and water intake (polydipsia; the kidneys are no longer able to conserve water efficiently)
- Marked increase in urine output (polyuria; dilute urine; increases the chance of developing bladder and kidney infections)
- Urination in inappropriate places (outside the litter box; around the house)
- Urination at inappropriate times (sometimes during sleep)
- Decreased or even complete absence of urination (anuria; usually occurs in end-stage disease)
- Hunched body stance (due to abdominal pain)
- Stiff gait (due to abdominal pain)
- Blood in the urine (hematuria)
- Loss of appetite (inappetance; anorexia; likely due to nausea and abdominal pain)
- Weight loss
- Bad breath (halitosis; uremic breath odor – smells like ammonia)
- Oral ulceration (painful sores on the gums and tongue)
- Drooling/excess salivation (ptyalism)
- Brownish discoloration of the surface of the tongue
- Poor hair coat (dry; flaky; thinning)
- Decreased self-grooming activities
- Poor body condition
- Pale gums and other mucous membranes
- Bleeding/clotting problems
- Altered cognition (changes in mental state)
- Elevated blood pressure (hypertension)
- Blindness (typically sudden in onset)
Cats at Increased Risk of Chronic Renal Failure
Chronic renal failure is more common in companion cats than in domestic dogs. Certain breeds seem to be predisposed to developing this disease. These include the Maine Coon, Abyssinian, Persian, Siamese, Russian Blue and Burmese.
Almost all elderly cats have some degree of renal insufficiency or failure, depending on how long they live. Hyperthyroidism and chronic renal failure are often seen in the same aging cat, as both are considered to be geriatric feline diseases.
Cats with earlier episodes of acute renal failure are also at an increased risk of developing chronic renal failure.
Diagnosing Chronic Renal Failure in Cats
Most cats that are feeling and showing symptoms of chronic renal failure (CRF) are very sick and already have lost about 70% of their kidney function. The veterinarian will be presented with an older cat who “ain’t doin’ right” (called “ADR” in veterinary lingo).
Any aging cat that is progressively weak and lethargic, losing weight and body condition, and drinking a lot and urinating a lot probably will be suspected of being in end-stage chronic renal failure.
The veterinarian will take a complete history from the cat’s owner and perform a thorough physical examination. The initial evaluation will also include drawing blood and urine samples for routine analysis.
The results of these tests will identify the levels of circulating waste products that healthy kidneys would normally filter out, such as blood urea nitrogen (BUN), phosphorus and creatinine.
Consistently elevated levels of these substances in blood reflect declining kidney function. A blood panel can also help identify or eliminate other causes of the cat’s clinical signs, such as anemia, diabetes or hyperthyroidism.
Most veterinarians recommend that routine blood work (a complete blood count and serum biochemistry profile) and a urinalysis be performed yearly on cats after 7 years of age. A urinalysis is a simple diagnostic tool that can provide a great deal of information about a cat’s kidney function and overall health.
The results of a urinalysis can identify a urinary tract infection and can show the concentration of the cat’s urine. Cats in chronic renal failure usually drink lots of water and urinate frequently, because their body is trying to flush out accumulating waste products. Cats with CRF have very dilute urine.
A thyroid panel (run on a blood sample) can help to rule out hyperthyroidism in aging cats. Hyperthyroidism can exist apart from or in conjunction with renal failure, and if present may affect the treatment options.
The veterinarian will also check the cat’s blood pressure, which often is elevated in cats with CRF. When chronic renal failure is suspected, the veterinarian may recommend an abdominal ultrasound to look at the cat’s kidneys.
This procedure is painless and non-invasive, and the results can provide a tremendous amount of information about the kidneys’ functional status. Ultrasonography also may disclose other abnormalities.
Abdominal radiographs (X-rays) can disclose abnormally small or enlarged kidneys, which often are associated with CRF. These procedures can also help identify kidney or ureter stones (nephroliths, ureteroliths), tumors, cysts or other causes of physical obstruction.
The veterinarian can take surgical biopsies of the cat’s kidneys and submit the samples to a laboratory to identify the extent of kidney damage. However, kidney biopsies are not routinely taken in cats, unless their kidneys are enlarged (renomegaly) or cancer – especially lymphoma – is suspected.
It is important to diagnose chronic renal failure promptly. Unfortunately, it can’t be cured. Treatment options are limited to managing the cat’s symptoms and trying to delay progression of the disease.
Treating Chronic Renal Failure in Cats
Chronic renal failure (CRF) can exist but be asymptomatic in cats for a very long time – even for years. Normally, by the time an owner notices signs of renal failure and a diagnosis is made, the condition is irreversible.
Nevertheless, there are a number of management techniques that can help maintain a cat’s quality of life. The goals of treating feline renal failure are to alleviate the signs of uremia (which is the build-up of nitrogenous wastes in the bloodstream), delay progression of the disease and make the cat as comfortable as possible, for as long as possible.
Treatment Options for Cats with Chronic Renal Failure
The most effective initial treatment for cats with CRF is aggressive fluid therapy. Because the cat’s kidneys can’t perform their normal tasks, circulating waste products must be artificially flushed out.
Over-hydrating the cat by pushing fluids helps accomplish this. Fluid therapy is typically first administered intravenously through a sterile needle inserted into one of the cat’s veins. This is an inpatient procedure.
Once the cat is rehydrated, fluids can be given under the skin (subcutaneously; normally in the scruff of the neck between the shoulder blades). How frequently fluids are given depends on the extent of kidney damage. Most owners quickly learn how to administer subcutaneous fluids at home.
Supportive care is essential to managing cats with CRF. Renal diets are available from several commercial cat food manufacturers.
These diets are designed to reduce the amount of circulating waste products and reduce stress on the cat’s kidneys; they typically are low in protein, sodium and phosphorus, have a high-quality protein source and are high in calories.
Canned food may be a better option than dry food for cats with CRF, because of the greater water content and increased palatability.
Oral and injectable medications are available to help control high blood pressure, address anemia, decrease stomach acidity, sooth the stomach lining and limit protein loss in the urine.
Vitamin and mineral supplements, including vitamin B, sodium bicarbonate, potassium gluconate, potassium citrate, vitamin D and calcitriol, may be recommended. Blood transfusions can help severely anemic cats. Human recombinant erythropoietin is also available to counteract anemia.
Kidney transplants have become a legitimate option for owners of cats with chronic renal failure. Post-surgical survival is reportedly between 70% and 85%, with some cats living for years.
Medication must be given for life after a kidney transplant to prevent rejection of the donor organ. These drugs have many potential side effects. Kidney transplants are only offered at a few veterinary teaching hospitals and specialty referral centers.
The costs associated with this surgery typically exceed $5,000. Transplantation is something for owners to discuss with their veterinarian, particularly if their cat is only mildly to moderately ill and does not have underlying systemic illness.
The kidney donors are often shelter cats that are adopted by the owner of the cat receiving the kidney.
Chronic renal failure is progressive and incurable. How long a cat can live comfortably with CRF is difficult to predict. Many cats have months or years of quality life ahead of them, if they are managed appropriately.