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Southern Pines areas of North Carolina

Chronic Kidney Disease in Cats

While CKD is a progressive and potentially fatal disease, we can do a LOT to slow the progression and improve your pet’s quality of life, especially with early intervention. In the early stages, many cats do not have any symptoms, and we have diagnosed the disease because of lab work results. It takes 66% of kidney function to be lost by the time we can see decreased urine concentration. And by the time we see elevations in the BUN, creatinine, and SDMA, over 75% of kidney function is already lost. So when we say “early” disease, we are actually being quite ridiculous, as so much kidney function is already gone. Unfortunately, there is nothing we can do to reverse the lost function. But there is a lot we can do to preserve existing function and protect the kidneys from further damage.

Kidney Functions

Let’s look at all the things the kidneys do and why they are so important for your cat’s health.  

  1. Elimination of wastes.  The kidneys filter wastes and toxins from the blood and eliminate them in the urine.  The liver breaks down proteins into ammonia and excretes it into the bloodstream as urea.  The kidneys filter urea from the blood and excrete it into the urine.  The kidneys also excrete creatinine from the normal breakdown of muscle tissue.  We measure BUN (blood urea nitrogen) and creatinine in the blood to estimate kidney function.  
  2. Production of red blood cells.  The kidneys produce erythropoietin, a hormone that signals the bone marrow to make red blood cells.  Without erythropoietin, the cat can become anemic.
  3. Regulates the amount of calcium and phosphorus in the blood.  
  4. The renin-angiotensin-aldosterone system is a crucial mediator of cardiac, vascular, and renal physiology through the regulation of vascular tone and salt and water homeostasis.  This system helps maintain normal blood pressure.
  5.  Maintains acid-base balance.

Causes of Chronic Kidney Disease in Cats

Tubulo-interstitial nephritis of unknown origin is the most common cause of CKD in dogs and cats.  

Various infectious agents can cause CKD including feline leukemia (FeLV), feline immunodeficiency (FIV), and feline infectious peritonitis (FIP) viruses, and possibly feline morbilliviruses (diseases like canine distemper virus, Newcastle Disease, measles, and mumps are in this group).   Infectious agents that cause pyelonephritis or glomerulonephritis can also be responsible for the progression of acute renal disease to CKD.

Two congenital diseases in cats, polycystic kidney disease and renal dysplasia, can lead to CKD. Abyssinians, Siamese, Burmese, Tonkinese, Devon Rex, and oriental shorthair breeds are at increased risk of amyloidosis which can lead to CKD.  

There are several types of cancer that can cause CKD.  

Anything that causes acute kidney disease that the cat survives can lead to chronic kidney disease.  These include certain toxins and drugs such as lillies, non-steroidal anti-inflammatory drugs, antifreeze, aminoglycoside antibiotics, vitamin D overdose, grapes, and raisins; anything causing urinary blockages such as feline lower urinary tract disease/sterile cystitis or stones; ascending bacterial urinary tract infections, and more.

Diagnosis and Staging of CKD in Cats

Diagnosis

Ideally, we diagnose CKD before your cat shows any symptoms of the disease through routine screening senior laboratory tests.  We recommend that cats 12 years and older have annual lab work with a CBC, chemistry panel, T4, and urinalysis.  Unfortunately, as already mentioned, we don’t have sensitive tests for CKD.  The most sensitive test we have is urine specific gravity (USG).  In clinically normal well-hydrated cats, the urine specific gravity should be greater than 1.045.  Repeated lower USG without another cause is most likely due to CKD.  But that means already 66% of kidney function is lost.  

Increased BUN and creatinine, waste products that should be excreted by the kidneys, are another way to diagnose CKD.  However, it’s important to note that these will also increase if your cat is dehydrated for any reason, such as GI disease.  BUN can increase if your cat eats a particularly high-protein meal (like a steak).  

If your cat is dehydrated, has a high BUN and creatinine, AND also has lower than 1.045 USG, they most likely have kidney disease.  Whether it is acute kidney injury (AKI) or chronic kidney disease depends on the history.  Cats with AKI are sick; cats in the early stages of CKD typically are not sick.  That said, AKI can lead to CKD so it’s always worth follow up lab work if your cat presents with high BUN, creatinine, and low USG.

Many clinicians ignore BUN and focus on the creatinine to diagnose CKD; there is nothing wrong with this approach.  In fact the IRIS (International Renal Interest Society) Guidelines do not include BUN for diagnosing, staging, or monitoring CKD. 

There is another test called SDMA or sometimes SDA (stands for symmetric dimethylarginine) that is the product of protein breakdown and is excreted by the kidneys.  Elevations in SDMA are typically due to kidney disease but in some cases due to cancer.  When this test was first introduced, it was touted as not affected by dehydration and was supposed to detect CKD when as little as 20% of kidney function was lost- WAY better than USG and creatinine!  But that’s not how it all panned out.  Unfortunately, SDMA has a large RSV (reference change value- see What Screening Lab Work Can Do For Your Pet).  This means the number produced by the laboratory can be very different from the true value, and that changes in your cat’s results are likely to be meaningless unless they are BIG changes, even if that pushes your cat over the “normal” cutoff.  Also, it takes 17 measurements to determine your cat’s true values.  I don’t think I’ve measured the SDMA in one cat 17 times- ever.  So I’m not that impressed with SDMA as a diagnostic tool.  I use it for monitoring and staging according to IRIS guidelines.  In other words, if a clinically normal cat has normal BUN and creatinine, USG >1.045, and a mildly elevated SDMA, I doubt your cat really has CKD.  It’s another tool in the box, and doesn’t replace creatinine, USG, examination, and history.  

If we don’t get a urinalysis when we do blood work, we’ll come back and try again.  It’s that important!  You can use non-absorbable litter in the box to help us.

 

Staging

We use the IRIS Guidelines because they are well-researched and standard throughout the world.  This makes communication with experts in the field clearer and easier.  Note that this guideline is to stage, not to diagnose CKD.  

 

IRIS stages of CKD with clinical signs
IRIS feline CKD substages for proteinuria and hypertension

Within each stage of CKD, there are specific treatment recommendations.  IRIS relies on research and the experience of millions of veterinarians around the world to maintain reasonable recommendations and updates.  We also use VIN (Veterinary Information Network), which employs specialists to help with specific cases.  This way, your cat is treated with the most current science-backed medications, supplements, and foods. 

Effects of Chronic Kidney Disease in Cats

Kidneys are involved in so many processes in the body, that when they start failing, we see major impact.  We treat the problems as they develop, which means we have to monitor cats with CKD regularly, including lab work.  

1. The first function that kidneys generally lose is the ability to concentrate urine. This leads to increased urination, which drives kitties to drink more water. Eventually, even though your cat may be drinking constantly, they won’t be able to keep up with the water loss and will become chronically dehydrated.  

2. Kidneys are important in maintaining normal blood pressure. When the kidneys start to function poorly, they demand more blood flow through the Renin-Angiotensin-Aldosterone System (RAAS). The kidneys release hormones that cause an increase in blood pressure. Unfortunately, just like in humans, hypertension causes damage to the heart, blood vessels, and eyes (can cause blindness).  

3. Kidneys are involved with the regulation of calcium and phosphorus in the bloodstream. When the kidneys can’t excrete excess phosphorus, it causes mineralization of tissues including the heart, blood vessels, and the kidneys themselves, worsening kidney function. Excess phosphorus also increases parathyroid hormone (PTH), which in turn causes problems in calcium regulation. When a cat has too much or too little calcium in the blood, it can cause problems with muscle contraction, leading to tremors, seizures, and heart arrhythmias. Hyperphosphatemia is directly correlated to increased morbidity (illness) and mortality (death).  

 

4. The kidneys are also responsible for filtering out the by-products of protein metabolism. The elevations in BUN and creatinine are a consequence of the kidney’s impaired ability to do their job. These metabolites disrupt neurotransmitters, making kitties feel lethargic, and can cause nausea.

5. When the kidneys are supposed to keep good things like certain proteins in the blood. When they can’t do that, protein is able to get into the urine, a condition called protein-losing nephropathy. This causes muscle loss. If there isn’t enough protein in the blood, it can also cause blood clots. Also, the protein in the urine directly damages the kidneys, worsening the disease.

This is why there are so many things to monitor and treat with chronic kidney disease. If the kidneys can’t function, we have to provide medications, supplements, and special diets to help them out. Not only will doing all of these things improve your cat’s quality of life, but they can also extend their life.

Graphic representation of how everything that kidneys do when they are diseased worsens the disease in a vicious cycle

Treatment for Cats With Chronic Kidney Disease

TREATMENT FOR CATS IN ALL STAGES OF CKD:
1. Ensure access to fresh water at all times.  Even though your cat is drinking and urinating excessively, they can become dehydrated quickly and this causes serious harm to already compromised kidneys.  If your cat is urinating outside of the litter box, add more litter boxes to different areas of the house to ensure they always have access to a clean one.  You may consider an automatic scooping litter box as well.  But do not withhold water to reduce the amount of urine produced.  
2. Treat potential dehydration immediately.  Cats that stop eating typically stop drinking too.  For your cat, even 12 hours without food is an emergency.
3. Discontinue potentially nephrotoxic medications if possible.  There are few medications that can exacerbate CKD, meloxicam being one that I prescribe for cats with arthritis.  Thankfully, we can switch to Solensia, a once monthly injection, to treat arthritis instead.  
4. Omega-3 fatty acid supplementation to reduce inflammation.  We’ll give you the dose of fish oil to provide for your cat based on their weight and their current food (kidney-specific diets have extra omega-3 fatty acids already). 

Monitoring

Cats with CKD can develop any consequence of their disease at any time.  Frequent monitoring including lab work at LEAST every 6 months is important to maintain your cat’s optimal health and quality of life.  Cats diagnosed and treated in Stage 1 or 2 can live for many years with an excellent quality of life.  My own cat, Greta, lived 12 years with CKD- the entire time I had her.  Those diagnosed and treated later tend to die to the disease a lot earlier and don’t enjoy a good quality of life.  That’s why we recommend annual senior screening lab work in cats starting at 10 years of age.  Once your cat shows signs of CKD, they’re already in stage 2 or 3 at least.  We can’t reverse CKD but we can dramatically slow it down and give you more quality time with your feline friend.

Ultrasound image of urinary calculi (bladder stones) which can cause or exacerbate CKD
Ultrasound image of bladder stones that can cause or exacerbate CKD

RULE OUT AND TREAT CAUSES OF CKD

The first thing we do is to rule out cancer, stones, and infection as a cause of CKD.  Treatment for CKD is destined to fail quickly if these diseases are present and untreated.  We use abdominal ultrasound to see the structure of the entire urinary system- bladder, ureters, and kidneys.  If a urinalysis was not obtained already we get one now.  

Cats with CKD are more likely to suffer from urinary tract infections due to their decreased USG.  We have to monitor the urine closely for signs of infection during all stages of the disease, as infection worsens CKD.  Usually a urinalysis is enough to rule out infection, but sometimes we have to culture the urine.

HYPERTENSION and PROTEINURIA

We measure your cat’s blood pressure for staging.  And when we do get a urine sample, we run a Urine Protein to Creatinine Ratio (UPC) unless there is infection.  The UPC is always high when there is infection, so we have to wait until the infection is clear and we have a new urinalysis to run that test.

If blood pressure is high, there are several medications that can help lower it.  One is a class of drugs called ACE Inhibitors that work by interrupting RAAS that causes hypertension.  If there is also proteinuria or borderline proteinuria, I generally use telmisartan, an angiotensin-2 receptor blocker that treats both hypertension and proteinuria.  Some cats with severe hypertension need multiple medications.  Amlopidine, a calcium-channel blocker is helpful in these cases.  

recommendations for foods for cats with chronic kidney disease include purina nf, hills k/d, and royal canin renal support.

HYPERPHOSPHATEMIA

Our target phosphorus range for cats with CKD is 2.7-4.6 mg/dl.  This is below the “normal” values given by our laboratory but it is important for cats with CKD to have lower than normal phosphorus.  There are several ways to decrease serum phosphorus, depending on how high it is.  We can switch to a prescription diet specially formulated with lower phosphorus.  We always prefer canned food for cats, especially those with CKD.  You can read more about that in our blog “Don’t Make These Mistakes When Feeding Your Cat.” We can use a variety of phosphorus binders in the food, depending on your cat’s calcium levels.  Calcium carbonate (Tums) is a poor choice for cats with hypercalcemia, but we can use aluminum hydroxide or phos-bind powder instead.  Phos-bind powder has the benefit of being tasteless and readily accepted by cats when mixed with food.  

 

There is a risk to starting phosphorus-reduced prescription diets in cats that don’t have hyperphosphatemia.  In a recent but very small study, 2/16 cats developed hypercalcemia immediately after starting a prescription renal diet, which resolved after the cats switched back to a regular diet.  We rarely recommend diet change in Stage 1 of CKD, sometimes in Stage 2, and usually in Stages 3 and 4.   

Recently a new test called FGF23 became available through Idexx.  FGF stands for fibroblast growth factor.  FGF23 has been used in people to identify patients with CKD who are at risk for hyperphosphatemia even when their serum phosphorus levels are within the targeted range, and it seems to work the same in cats.  Therefore, in cats with Stage 1 or 2 CKD with phosphorus levels in the targeted range, we send the FGF23 test to determine if your cat is at risk.  If so, only then do we recommend a prescription kidney diet for your cat at this stage.  In general, cats in stages 3-4 have hyperphosphatemia and benefit from phosphorus restriction.  

HYPOPROTEINEMIA

Some cats with CKD have an added serious complication called protein-losing nephropathy (PLN).  This condition causes protein loss in the blood.  If serum albumin is less than 2.0 mg/dl, your cat is a risk for blood clots.  We use clopidogrel (plavix) or low-dose aspirin (has to be compounded) to prevent this often fatal disease.  

HYPOKALEMIA

Too low potassium in the blood is called hypokalemia.  This occurs in cats with CKD because their kidneys can no longer reabsorb potassium from the blood.  Hypokalemia causes muscle weakness and pain, decreased appetite, poor haircoat, and nausea.  Cats with hypokalemia are often found weak with the head hanging low as in this picture.  Prescription kidney diets have extra potassium, and it can be supplemented easily.

NAUSEA AND INAPPETENCE

Cats with more advanced stages of CKD often develop nausea and decreased appetite.  Usually, treating hyperphosphatemia and hypokalemia helps, but some cats need more.  Cerenia is a once-daily anti-nausea medication we can prescribe.  Some cats do well with an appetite stimulant such as mirtazipine or entyce.  You can try heating canned food, adding no-salt broth to the food, or switching foods.  We want the cat to eat something; if they won’t eat the prescription diet, we’ll make do with what they will eat.  

ANEMIA

In later stages of CKD, many cats develop anemia because the kidneys don’t produce erythropoietin, the hormone that tells the bone marrow to make red blood cells.  There are medications similar to erythropoietin that we can prescribe to treat this complication of CKD.  Cats with clinical signs related to severe anemia may need transfusions.

Frequent laboratory testing in cats with CKD is important to monitor the various effects of the disease and initiate treatment

DEHYDRATION

At some point, your cat simply won’t be able to consume as much water and they are losing and will become chronically dehydrated.  Dehydration worsens kidney disease in a vicious cycle.  At this point, we can teach you how to administer subcutaneous fluids at home.  

Preventing CKD

Since the treatment of CKD in cats is so complicated, preventing it seems to be the better choice.  I wish it was that easy.  The things you can prevent are any injuries to your cat’s kidneys such as dehydration and toxicity.  If your cat has feline lower urinary tract disease or bladder stones that causes them to become blocked, getting treatment ASAP is very important, as blockages can damage their kidneys.  Keep your cat on the veterinarian-prescribed diet if any to prevent recurrence if possible.  Unfortunately, since we don’t know what causes the vast majority of CKD cases in cats, we don’t have a good way to prevent it.

One thing that may help is to feed your cat a canned food based diet their whole life.  We don’t have studies to back this up, and we never will, because nobody is going to fund a study that feeds 2 groups of cats for 20+ years.  But it makes sense to feed canned food to cats.  Some researchers believe that cats fed mostly dry food are chronically dehydrated, which could lead to CKD.  We know that cats evolved to get most of their water from their prey.  Cats who have a canned food based diet consume more water than cats fed dry food.  I figure that cats have to eat something.  In addition to increasing their water consumption, canned food also prevents obesity because it is mostly water.  And it makes cats feel more full so they don’t over eat or wake up in the middle of the night screaming for food.  So even if canned food doesn’t prevent chronic kidney disease, there are benefits.  Read more about Common Mistake People Make When Feeding Their Cats here.  

 

How Family Veterinary Mobile Clinic Helps You

If you live in the Sanford or Southern Pines areas of North Carolina, you’re in luck!  Family Veterinary Mobile Clinic can treat your cat in the comfort of home.  Our practitioners are Fear Free Elite and Low Stress Handling Silver Certified, and long-time members of the American Association of Feline Practitioners, so they know how to treat your cat with expert loving care.  

Our Premium Wellness Plan includes the recommended 2 complete sets of lab work and unlimited home visits, so you don’t have to worry about surprise fees.  Most of our senior feline patients are on this plan.  Let us know if you have any questions about CKD or our practice in the comments below.  Thank you for reading and loving your cat!

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