Kidney Disease In Your Cat
Chronic Renal Failure (CRF, CKD)
Ron Hines DVM PhD
All bodies suffer the wear and tear of time. In people, our hearts are our weakest link. Heart disease is #1 and kidney disease is #10 on the list of causes of human death. No one has added up the numbers for cats in the United States, but I suspect the two issues would be reversed. In cats in the UK, kidney disease is #2 (surpassed only by car accidents) and heart disease is #8). ( read here & see here Despite the many things today’s marketers attempt to sell you to combat age-related issues in your cat and you, treatment improvements and cures for kidneys and hearts aren’t going to happen before more important new discoveries in basic medical science have been made. (read here) Public expectation tends to be greater than your veterinarian’s viable options. For human heart disease physicians have so many proven procedures and medications that have been proven to extend lifespan. For kidney disease people have the option of dialysis and kidney transplants. But for cats, transplants, where available cost $18,000-20,000 dollars + the cost of lifetime immunosupressive drugs with mixed success and quality of life issues. Other than low-phosphorus nutrition and assuring adequate levels of calcitriol, medications scientifically proven to extend the lives of cats with failing kidneys do not exist. (read here)
A study by Banfield Pet Hospitals reported that kidney disease is 7 times more common in cats than in dogs. One in every 12 older cats presented to them had evidence of kidney problems. When the diagnosis was made at a point early in the disease, cats treated by Banfield lived an average of 2-3 years past that point. When cats were brought in later in the disease (blood creatinine >5.0 mg/dl >440 µmol/l ) they lived fewer than six additional months. Twenty nine percent of cats that came in due to kidney problems also had bad teeth and gums (periodontal disease ). How or if one of those problems contributes to the other remains unclear. The same situation exists in people. (read here)
What Happens When My Cat’s Kidneys Fail?
First, you need to know something about the critical work your cat’s kidneys do. They keep its body free of the wastes that accumulate during normal metabolism. They are continually “scrubbing” your cat’s blood free of excess salts, water, excess metabolites and toxins and depositing them in the urine for elimination.
The actual removal of wastes occurs in tiny systems within your cat’s kidneys called nephrons . There are almost one million of these structures in a single human kidney. How many there normally are in your cat is unknown. Each nephron contains a small sieve-like filtering structure called a glomerulus. These glomeruli (plural form) prevent normal blood proteins, cells and critical constituents in the bloodstream from escaping into the cat’s urine, while allowing extra fluid and wastes to pass through to eventually end up in your pet’s urine. A complicated chemical exchange takes place, as waste materials and water leave the blood and enter the urinary system. That requires very specialized gatekeeper cells called podocytes ; and throughout the animal kingdom, specialized cell are never good at regenerating once they have been injured. Your cat’s kidneys also regulate its body’s acidity and, through regulation of body salt content, the kidneys help control your cat’s blood pressure.
Cells associated with healthy nephrons produce an important hormone called erythropoietin and and enzyme called renin. Erythropoietin is necessary for your pet’s body to manufacture and maintain red blood cells, while renin activates another hormone (angiotensin) to helps control your cat’s blood pressure. In addition, healthy kidneys are required to convert vitamin D into calcitriol which preserves calcium reserves in bones and maintains normal calcium balance throughout the body. In chronic kidney disease these glomeruli have been scarred and lost, or plugged up with proteins and inflammatory cells. Without enough functioning glomeruli, none of the processes I mentioned work normally.
But My Cat Is Still Producing Plenty Of Urine – More Than Before!
The body is marvelous in sensing when it has a problem and attempting to correct it. In an attempt to keep its blood waste-free, your pet’s kidneys work overtime, using their small remaining capacity to remove waste as fast as they can. This accounts for the increased thirst and urination you might have see in your cat. For a while, this compensation keeps it’s body clean enough of wastes to function normally. But with time, your cat cannot consume enough water to keep those waste levels in its blood in check. That is the time your veterinarian might suggest that fluids be given to your cat by injection. By that time your pet might already be experiencing weight loss, anemia, and abnormal blood work results. When that time arrives, over half of its precious kidney glomeruli are thought to have been lost. You pet cannot replace them and nothing veterinarians have at their disposal today (short of a kidney transplant) can either.
What Are The Signs Of Kidney Disease In My Cat?
Cats with kidney disease tend not to groom themselves as well as they used to. They tend to have less energy and are less playful. Another early sign that often goes unnoticed is when your cat begins to drink water and urinate excessively (polydipsia). At first, it is normal for owners to ignore this. It might just be that your cat’s litter box is damper and smellier than it used to be or that its water bowl had to be filled more frequently than before. Not all cases of increased thirst are due to kidney issues. Fever, diabetes, severe diarrhea or vomiting. (read here) , corticosteroids and increased salt intake can all produce similar effects.
As kidney problems advance, pet with failing kidneys tend to become more finicky eater and begin to loose weight. About this time energy levels tend to decrease. These cats play less, romp less and sleep more. This is often when cats are first taken by their concerned owner to see their veterinarian. An exception are cats that have both kidney issues and hyperthyroidism. It is common for both health issues to coexist in a single cat. Those cats also loose weight, but their high thyroid hormone levels (T4) keeps them very active.
In advanced kidney disease cats just peck at their food. They often gag as they would with fur balls and may have digestive disturbances such as nausea and diarrhea. Their apathy causes their water intake to decrease so they become dehydrated. They might stand over their water and/or food bowl without attempting to eat or drink. These cats have all developed uremia – an intolerably high level of nitrogen-containing metabolic waste products in their bloodstream. Because many of these toxic waste products contain the azo-molecular group of nitrogen, another term for uremia is azotemia.
Why Did This Happen To My Cat?
Veterinarians know a lot about the things that can make your cat’s kidneys fail suddenly: a kidney stone , other blocks to the passage of urine, something eaten that was toxic, a bad reaction to a medication, etc. But veterinarians do not know why kidneys fail gradually. We know that a slow but steady loss of kidney function is part of the normal aging process of cats. Why the process of decline proceeds faster in one cat than in another remains unknown. Human nephrologist ponder the same questions. (read here) Many causes have been discussed that seem logical – but none of them have been scientifically proven to be true. Regardless of the cause(s), all cases of chronic kidney disease develop the same signs and pass through the same stages. Usually, your veterinarian will just tell you after a routine health screen that your cat has early blood indicators of CRF (chronic renal failure). That is because in most cases there is no way for your veterinarian to determine the original cause. The exception is polycystic kidney disease that I’ll write about a bit later.
The Wear And Tear Of Time
There was a time not so long ago when infectious diseases and dietary deficiencies ended the lives of many cats early. But with advances in vaccination, pet nutrition, antibiotics and sophisticated surgery, cats now have the potential to live much longer. Nothing lasts forever and every organism has its weakest link. I mentioned that the critical cells of the kidney, the podocytes, cannot replace or regenerate themselves as other cells do in the liver, lungs, bone and skin. Once a glomerulus ages and is lost, it is lost forever. That is the most common cause of kidney failure in cats. When you have a “wellness” checkup on your 15-18 year old cat and are told that laboratory tests (BUN, creatinine, SDMA) point to kidney disease you could just as well have been told that you are the owner of an old cat. (see here) and repeat.
Polycystic Kidney Disease
Some cats were destined from birth to loose kidney function prematurely in their life. These pets inherited genes that cause fluid-filled sacks (cysts) to form within their kidneys. As these cysts gradually grow in size, they crowd out and destroy the functional tissue (glomeruli) within the pet’s kidneys. This is an inherited problem in certain purebred cats, It is due to inbreeding. It is a much less common problem in random bred house cats because they have a larger and healthier gene pool. (read here) That is one of the many reasons I suggest your next cat be a run-of-the-mill cat from your local humane society.
Chronic interstitial Nephritis
Chronic interstitial nephritis is the pathologist’s term for the microscopic damage seen in the most common forms of kidney disease in older cats and dogs. It is thought to be the end result of many different inflammatory processes – not just one. Nephritis is a term for inflammation of the kidneys. The tissue that surrounds the nephron filters is called the interstitial tissue. It is the matrix that suspends the nephrons and gives shape to the kidneys – much like stars are suspended in space. Pathologists that examine kidney tissue from pets with failing kidneys have noticed that many of these pets have a higher than normal number of inflammatory cells ( your cat’s WBCs) invading this area. This low-grade, chronic inflammation is thought to cause the scaring that eventually destroys most of the pet’s nephron filters. What draws these inflammatory cells to the kidneys remains unknown.
Cats suffering from chronic interstitial nephritis, like the one in my top diagram, have small, shrunken and hard kidneys due to scarring and the tissue contraction that follows it. If your cat is mellow and not too chubby, it would be easy for me to palpate and identify these shrunken, firm kidneys during a routine veterinary exam. I drew that cat’s kidneys larger that they would be only for visual effect. Some veterinarians associate chronic interstitial nephritis in dogs with possible exposure to leptospirosis carrying rodents. Leptospirosis is thought to be quite rare in cats, so most veterinarians believe that it is unlikely to account for this type of chronic kidney damage in felines. But others disagree. (read here) Some also believe that cats are genetically resistant to leptospirosis – due to cats having to relying on rodents (common lepto carriers) as a food sources in the wild.
Chronic Over-stimulation Of Your Pet’s Immune System
Your cat’s kidney glomeruli act as sieves, straining and filtering blood as it passes through them. Very large molecules in the blood have a tendency to collect there. When they do they appear to slowly damage the kidney’s filtering-ability. Some of these large molecules are antibodies combined with antigens (immune complexes). Many chronic infectious and auto-immune diseases produce immune complexes. These include bartonella , chronic skin infections and chronic intestinal disease . Among these rare causes of kidney failure in cats is another situation where destructive proteins sometimes accumulate in the kidneys. It is called amyloid (amyloidosis). In a few cats, this is a genetic disease. But it has also been know to occur subsequent to long-term over-stimulation of the immune system. Abyssinians and Siamese cats have a higher than normal incidence of amyloidosis which in some can lead to kidney failure. (read here) A similar form of kidney damage in pets occurs in auto-immune diseases that are similar to lupus in humans. In this disease, run-away antibodies are produced against the pets own body. In some cases, these antibodies are directed at the pet’s kidneys themselves, in others, they may only accumulate there causing physical damage.
Hyperthyroidism And High Blood Pressure
An overactive thyroid gland (hyperthyroidism) is a common problem in older cats. Veterinarians are uncertain why it appears to be occurring more frequently. But we do know that it often occurs concurrently with kidney disease. Hyperthyroidism often masks the signs of kidney failure making the results of blood tests appear less serious than they actually are. It is only when your veterinarian resolves your cat’s thyroid problem that it becomes apparent that the cat’s kidneys had already lost much of their blood-cleansing ability.
Most veterinarians believe that hyperthyroidism might cause your cat’s blood pressure to be abnormally high. No studies in cats have ever been conducted, but we assume it might occur based on studies in hyperthyroid people. (read here) We also know that high blood pressure often leads to kidney failure. Perhaps that is why hyperthyroidism and kidney failure go hand-in-hand in cats. The biggest problem is in getting accurate readings of your cat’s blood pressure during veterinary hospital visits. Blood pressure readings in cats are notoriously inaccurate. (read here & here) If you cat was diagnosed as having an overactive thyroid gland, its heart and kidney function need to be carefully scrutinized. Of the tests currently available, I rely on the microalbuminuria test of your cat’s urine, considered along with its other urinalysis results , as being the most sensitive for detecting the possibility of early kidney damage related to elevated blood pressure. A cat’s “normal” blood pressure increases slowly as it ages. That is due to loss of elasticity (increased stiffness) of its vascular system – the same reason we get wrinkles.
Lower Urinary Tract Disease
Feline Urological Syndrome (FUS) is another disease that has become more common as our cats live their lives indoors with little exercise and unlimited calories. When a cat develops FUS, a pasty grit (struvite crystals) sometimes plugs the cat’s urethra, preventing normal urination and increasing urine pressure in the bladder, ureters and kidneys. Abnormally high urine pressure in a cat’s kidneys slowly destroys them. This situation is called hydronephrosis. Obstructing urinary tract stones (calculi) and defects in the ureters are other possible causes. However the vast majority of cats that suffer from bouts of FUS do not show changes in their kidney function once the blockage has been removed.
How Do Veterinarians Diagnose Kidney Disease In Cats?
The history you give your veterinarian, your pet’s age and your veterinarian’s physical examination of your cat often make him/her suspect a chronic kidney problem. As I mentioned, as glomeruli are replaced by scar tissue, the kidneys become small, hardened and lumpy (pitted). In lean pets, they have a characteristic feel when felt through the abdominal wall or when observed using renal ultrasound. A standard blood chemistry and urinalysis panel usually confirms their initial suspicions. Bringing your cat in for its examination on an empty stomach makes successful kidney palpation considerably easier.
Your Cat’s Urine Specific Gravity SpGr
Veterinarians often request that you to bring them a urine specimen from your cat so that its specific gravity and constituents can be checked. (read here) Placing some Saran wrap™ over your cat’s litter might makes urine collection easier. Purchasing non-absorbing plastic beads that replace litter is considerably more successful. For certain other analysis, it is better if the sample is collected by your veterinarian. Specific gravity measurement tells your veterinarian how concentrated the urine sample is. Cats -that have weakened kidneys can no longer produce concentrated urine. So its specific gravity, a measure of concentration, is low. Cats with normal kidneys produce urine with a specific gravity of about 1.015 to 1.060. When your cat’s kidney nephrons have suffered substantial damage, the urine your cat produces is essentially the same as blood plasma minus blood’s protein content. (= isothenuric urine = <1.015 SpGr) The lower your cat’s first-of-the-morning specific gravity is, the more serious its kidney problem is likely to be.
Anything that causes your cat to drink excessively will shortly thereafter lower its urine specific gravity. That is why it is wise to collect your pet’s urine specimen as soon as possible after you get up in the morning – before your cat has had a chance to drink. Unless your cat is already ill, remove its access to water over the previous night time hours. Your veterinarian might have different thoughts on that. I personally find it cruel and unnecessary to collect urine through a needle inserted through your cats abdomen (cystocentesis) unless it is to determine the antibiotic sensitivity of a confirmed urinary tract infection or to lower urine pressure in a cat with a urinary tract obstruction. Would your physician do that to you to obtain a urine specimen? To do so painlessly, your cat must be anesthetized. Urine samples obtained that way often report the false presence of blood in the urine from the needle penetration as well.
Your Cat’s Urine Protein Content And Microscopic Urine Examination
Failing kidneys leak blood proteins into your cat’s urine. Most of that protein is albumin. Although a urinary tract infection or sudden trauma can also cause high urine protein content, excess urine protein is often an early sign of long-term kidney damage in older cats. The presence or absence of white and red blood cells and debris in the urine specimen help your veterinarian tell the difference between sudden (acute) and chronic (long-term) kidney disease. Of the many tests available to detect protein in the urine, the urine microalbuminuria test appears to be the earliest to give accurate warning.
Your Cat’s Blood Urea Nitrogen ( BUN ) Level
Blood urea nitrogen ( BUN ) is a waste product of all cellular metabolism. BUN rises in the blood of cats with failing kidneys. Your cat’s liver creates the BUN from ammonia-containing residues as the safest method to convey those residues through its bloodstream to its kidneys for elimination in the urine. The urea ammonia in BUN is what gives the pee in your cat’s litter box its distinctive odor. BUN level stays within a relatively narrow range in the blood of healthy cats – although it fluctuates during the day depending on your cat’s ingestion of high-protein meals and hydration status. BUN level in the blood of kidney-problem cats begins to rise when not enough healthy kidney tissue remains to excrete it into the cat’s urine. The higher its persistent level remains in your cat’s blood – the more serious its kidney problem is likely to be. The blood urea nitrogen and creatinine results in your cat’s blood profile are also the prime ways veterinarians decide if their treatment of kidney disease in your cat is working. You will have many of those tests run on your pet during therapy.
Your veterinarian knows that lack of hydration, over-hydration, impending heart or liver failure, urinary tract obstruction, high protein diets, fasting and vigorous exercise also influence your cat’s BUN (and SDMA) levels. Your cat’s other blood panel results as well as your veterinarian’s physical examination of your cat and the history you provide will help him/her rule those other causes out one-by-one.
Your Cat’s Blood Creatinine Level
I mentioned that your cat’s BUN has substantial daily fluctuations in its level in the blood. In a research setting your cat could have many repeated BUN blood tests run throughout the day and they could be averaged. That is asking a lot from your cat and impractical: your cat would be upset, not drink or eat, and the results would be meaningless. However non-specific, throughout-the-day, fluctuation are much smaller when it comes to creatinine. Like BUN, creatinine is also a waste byproduct of cellular protein metabolism (primarily muscle metabolism). However creatinine diffuses through your cat’s body slower than BUN. So its level throughout the day is more stable than BUN (less subject to hourly fluctuations). Sometimes diagnostic laboratories report BUN and Creatinine also as a ratio, the BUN:Creatinine ratio. Because creatinine results from normal muscle metabolism, your cat’s lean body weight does have some influence on the creatinine content of its blood. As cats age, many loose muscle mass and consequently their blood creatinine level is naturally a bit lower. So in cats with advanced kidney disease and wasting, the reported creatinine level may not sufficiently indicate the seriousness of the situation. Some claim that the highly-marketed SDMA test avoids this problem. However your cat’s SDMA level is affected by so many non-kidney issues (read here) that I believe that creatinine is still the best marker of kidney health that veterinarians and cat owners have. When it comes to your kidneys, human physicians agree. When last I corresponded with the American Kidney Foundation’s physician team, I was told that they just didn’t feel that the test was worth doing.
Your Cat’s Blood Phosphorus & Calcium Levels
Phosphorus (as phosphate) is one of the mineral constituents of blood. The foods your cat prefers (meat and fish) are naturally high in phosphorus. A cat with failing kidneys has difficulty preventing leakage of blood calcium into its urine. Healthy kidney tubules reabsorb almost all the calcium that pass through its kidney’s filtering units . Healthy kidneys also aid in the discharge of excess phosphate. Calcitriol , formed within healthy kidneys is also necessary for proper absorption of calcium from your cat’s diet and for the release of calcium stored in its bones. So an elevated blood phosphorus level in your cat often another sign of failing kidneys. Phosphorus and calcium exist in tandem in you and your cat’s body. As one goes up, the other goes down. So as the ratio of phosphorus to calcium in its blood becomes abnormally high, your cat’s bones will weaken as they are leached of calcium. They other much rarer signs of high blood phosphorus (hyperphosphatemia) also relate to a lack of sufficient calcium in the blood stream (possible cramps, seizures and neuropathy). This is why pets with kidney failure need to be fed diets that are lower in phosphorus or given oral phosphate binders or both.
Your Cat’s Blood Potassium Level
Proper internal levels of potassium are very important for your cat’s well-being. When a cat’s kidneys fail, its body potassium level tends to drop. The sign of this problem, called hypokalemia, is muscle weakness. These cats are often slow to rise and wobbly in their gait. Holding their head properly erect becomes an effort. Picky eating, depression, constipation, a lack of interest in grooming and scruffy hair coat also occur. But it is hard to know if those issues are due to low blood potassium or another of the many imbalances and toxicities that accompany kidney failure. A few cats reaches a point where they no longer produces sufficient urine. In those situations its blood potassium level can actually rise too high (hyperkalemia).
It is very important that your cat eat enough to maintain a healthy body weight. If it doesn’t like the taste of the food your animal hospital provides – make the diet yourself (best accomplished with the aid of a veterinary nutritionist). In kidney disease, body weight and longevity go hand in hand. The most important characteristics of a good kidney diet are that your cat finds it tasty, that it fulfill your cat’s vitamin/mineral needs, be as low in phosphorus as possible and not furnish protein in excess of what your cat requires to maintain its muscle mass.
Packed Cell Volume (= hematocrit, Hct, PCV)
Your cat’s packed cell volume (PCV) is a measure of possible anemia. When a cat with kidney failure has a PCV that is abnormally low, it means that is not manufacturing sufficient red blood cells in its bone marrow. One of the hormones involved in red blood cell formation is produced in its kidneys. It is called erythropoetin. When your cat’s kidneys deteriorate, not enough of that hormone is produced.
Your Cat’s Blood Pressure
You veterinarian will probably also measure your cat’s systolic blood pressure. Your cat’s systolic blood pressure is the first (highest) number – the second number (the diastolic pressure) is difficult to obtain in cats and dogs with the technology that practicing veterinarians currently have access to. Abnormally high blood pressure (hypertension) is thought by many to be common in cats with chronic kidney disease. We know that occurs in humans, it is less well documented in cats. It is still unknown if high blood pressure is the cause of the cat’s kidney damage, or the result of that kidney damage. High blood pressure is known to damage the kidneys in rodent models – but kidney disease is also known to elevate blood pressure. When the second occurs it is called secondary hypertension. What limits veterinarian’s understanding is the blood pressure-raising effect of your cat’s trip to the animal hospital. BP readings at animal hospitals – even when averaged – are highly untrustworthy and may have little to do with your cat’s blood pressure at home in its more relaxed situation. That is why I suggest that you have your veterinarian check your cat’s blood pressure regularly during its lifetime so that the vet has a historical record to compare it to. It is also normal for blood pressure to creep upward as a part of the normal aging process. (read here)
What Treatment Options Are Available For My Cat?
In the future, we might be able to regenerate failing organs. But for now, there is no known way to mend damaged kidneys. What veterinarians can attempt to do is to slow the rate at which your cat’s kidney tissue is lost, and deal to with the side effects of that loss. Kidney failure is a progressive disease. That means that with time it will become worse. The key to gaining time for your cat is to use its remaining kidney tissue as efficiently as possible. We try to do this through diet, medications and, when necessary, fluid injections (diuresis).
A Specially Formulated Diet
Commercial diets, designed for kidney failure in cats are a bit lower in protein and sodium than ordinary cat food. Dogs can tolerate even lower protein diets than cats can. These renal cat diets also have added omega-3 fatty acids and compounds such as potassium citrate to counteract body “over-acidity ” . Most importantly, they are drastically lower in phosphorus.
On any of these protein-restricted diets your cats body weight and kidney test parameters need to be monitored carefully. It is particularly important that your cat’s blood albumin protein level not drop too low and that your cat’s body weight remains stable. When you do that, and your pets BUN and Creatinine levels drop or remain stable, not providing protein in excess is a very positive step. But there are periods in a cat’s ongoing fight with renal disease when restricting protein might not be a good thing to do. (For example, when 7/8th of its kidney’s filtering apparatus has been lost) (read here & ask me for Madison2010)
Cats do not tolerate low protein diets as well as dogs do. And cats do not metabolize added carbohydrates as well as dogs. It might be wiser to depend more on added fat and fiber for dilution of your cat’s protein and phosphorus consumption rather than a large amount of added plant carbohydrates. Experimentally, higher fat diets can also be beneficial to kidneys . (read here) In certain instances, ketoacids, as sold through body building outlets, can also act as substitutes for dietary protein. (read here) But I know of no veterinarians that use them in a treatment plan for kidney disease in cats or dogs.
I believe that the most important thing you can do in modifying your cat’s existing diet or preparing a homemade diet is to slowly increase the amount of added water to the limit that your cat will accept. Keep track of its fasting body weight; we do not want that to drop in a cat that is lean already. The more water, broths and fluids your pet consumes, the more toxic waste products it will be able to flush from its body with the fewer health kidney filter units (nephrons) that remain. You can also experiment with Hydra Care™
We still want to limit your cat’s consumption of phosphorus. The foods naturally highest in phosphorus are the common high-protein foods, meat, poultry, fish, dairy products, peas and beans.
Limiting the amount of sodium your cat ingests might also wise when its kidneys are failing. Although there is little scientific data that pertains to cats, commercial-prepared feline kidney diets limit the amount of sodium-rich ingredients in their foods on the suspicion that it might be helpful. (read here) As I mentioned, kidney diet producers also add omega-3 fatty acids that are found in cold-water fish and fish oils, some combining it with flax seed. Again, no cat data, but some believe that these particular fatty acids reduce inflammation throughout the body – including any inflammation that might be occurring in your cat’s kidneys. (read here) You might also explore offering your cat Hydra Care™.
Cats with kidney problems often have poor appetites, weight loss and anemia. They might suffer digestive disturbances as well. That could limit their absorption of vitamins. So B-vitamins are often given as appetite stimulant and to ward off any B vitamin deficiencies they might have. I mentioned earlier that for your cat to convert sufficient vitamin D into its active form, calcitriol , it needed sufficient healthy kidney tissue. Unfortunately the doses of calcitriol suggested for supplementation of cats by various sources and suppliers differ widely. I can’t find my copy of the article at the moment but I would go with the ones suggested for cats in renal failure by Dr. Chew at Ohio State here.
ACE Inhibitor Medications
An organ as critical to life as the kidney does not vary much at the cellular level between mammals. Today, experiments in the treatment of kidneys disease are most acceptable to animal welfare advocates when they are performed on rats. The cells that researches zero in on in declining kidney function are the podocytes , specialized cells in the kidney’s filtering apparatus that underlie its blood-cleansing abilities. Once podocytes loss begins, like a tree bent to a severe angle by a storm, it will continue to slowly fall even after the winds cease even though the remaining kidney filters “super nephrons” enlarge (=hypertrophy) and work harder. There is considerable evidence that medications called ACE inhibitors can slow that podocyte loss. (read here) The ones most often chosen by veterinarians for cats and dogs are benazepril and enalapril .
If your cat is placed on an ACE inhibitor, it is wise to be sure that its blood creatinine level does not suddenly increase. In later stage kidney failure when the remaining kidney filters (glomeruli) are filtering way above their normal capacity, ACE inhibitors occasionally drop a cat’s internal kidney pressure so low that the pet’s uremia actually worsens. The best monitoring test in those situations are a 24 hours creatinine clearance test or another test that estimates your pet’s GFR. But those tests are beyond all but the most sophisticated veterinary college teaching hospitals. Over the years I have not seen that the outcomes at those advanced institutions outperform those of local practices that specialize in feline medicine.
The most common side effect of ACE inhibitors in cats are said to be stomach/intestinal upsets, constipation and weakness due to too low a blood pressure. I qualify that because these cats are often taking more than one medication and they are in failing general health. So it can be hard or impossible to sort out which one or ones of the medications are responsible for the side effects. In those cases, the doses needs to be reduced – preferably one by one. Sometimes side effects can be lessened if you begin these medications at a low dose and gradually increase them to the desired dose.
Certain compounds called phosphate binders can block the absorption of phosphorus from your cat’s foods while it is still within its digestive tract. At one time aluminum hydroxide was suggested. Dietitians now think that more modern products that are free of aluminum are safer. Some common ones used today in cats are calcium acetate (PhosLo™) and sevelamer (Renagel®). When your cat won’t eat a therapeutic commercially or home-prepared low phosphorus kidney diet or when those diets no longer control your cat’s blood phosphorus level sufficiently, veterinarians find oral phosphorus binders helpful. Both can produce various digestive tract side effects – so begin gradually.
A Potassium Supplement When Required
Potassium supplements (Tumil K®, etc.) can help when your cat’s blood potassium level drops too low. This sometimes helps combat the listlessness and weakness that accompanies kidney failure. Suspect low potassium (hypokalemia) when your cat does not eat adequately to maintain its former body weight. As I mentioned earlier, in very advanced kidney disease potassium levels can actually be too high. You need to let your veterinarian make these decisions.
An Oral Toxin Adsorbent
When diet, medications and added hydration can no longer control your cat’s BUN and creatinine levels, studies in Japan found that experimental animals and humans with severe kidney disease benefited from consuming an oral carbon adsorbent of uremic toxins, AST-120. (read here & here) Adsorbents prevent the absorption of toxic bacterial products produced by your pet’s resident intestinal bacteria. These toxins are thought to contribute to the list of uremic toxins. As far as I know, the product, AST-120, is still only available experimentally in the United States. (read here)
Erythropoetin – Red Blood Cell Growth Factors
Sold as Epogen®, Betapoietin® or Eporel®, these compounds encourage your pet to produce red blood cells and so combat anemia. Because these compounds were engineered for humans , cats eventually cease responding to them. But they often do raise your cat’s PCV for a time. There is a moderate danger in giving these product. When a pet’s immune system decides to attack human erythropoetin because it is a foreign protein, it not only destroys the human-engineered erythropoetin that was given – it can also destroy the pets natural erythropoetin. So it is possible that it might make the anemia even worse. I would only used these products as last ditch efforts. Some of these potential side effects might be less with darbepoetin. (read here)
Fermentable or soluble fiber, when added to a cat’s diet, also helps remove toxins from its body. Because of this it is often an ingredient in commercial diets sold to manage kidney failure in cats and dogs. In these diets, the source is usually sugar beet pulp. It is the same fiber sold in quantity to stables as a horse feed additive. Too much fermentable fiber in your cat’s diet will cause diarrhea and flatulence. This type of diarrhea is a mess – but not a hazard to your cat’s health.
Extra Flush-Fluid Administration, SC or Subcutaneous Fluids
There comes a time with all cats when they no longer drink enough water on their own to fully utilize their remaining kidney capacity. Early in this period, you can give your cat additional fluids orally with a turkey baster or add additional liquid to its food. I mentioned Hydra Care™ earlier. Leaving faucets dripping for your cat sometimes encourages drinking as do multiple water bowls of various designs.
When that is no longer sufficient, fluids needs to be give periodically under your cat’s skin by injection. The effect of those fluids is called diuresis– a kidney flushing action. Its effect in flushing out blood toxins from your cat can be dramatic – similar to a human visit to a dialysis center. Many owners learn how to administer these subcutaneous injections of sterile fluids at home. It causes the cat very little pain or discomfort if it is administered at body temperature, slowly and in multiple locations. In most cases, there is no benefit in giving fluids intravenously. Cats with failing kidneys do need emergency intravenous fluids when they are presented severely dehydrated to veterinarians. The psychological hesitancy to inflict pain on a loved pet can be more than some cat owners can overcome. In those cases, find a mobile veterinarian who is willing to visit your home or a veterinarian willing to dispatch one of his/her technicians to your home periodically. Observe the procedure. With time you will probably overcome your hesitancy. In your search, independent veterinarians have more decision making flexibility than those working for conglomerates like VCA, Blue Pearl or Banfield who are discouraged from working off-script.
How Much Longer Will My Cat With Kidney Failure Live?
That is completely dependent on the level of toxins in your cat’s blood. Pets with blood creatinine levels below 2.8 mg/dl usually do well for long periods. Pets with blood creatinine levels of up to about 4 mg/dl have also survived happily for many years with appropriate treatment. But when your cat’s creatinine levels exceed 6-8 mg/dl its quality of life has become quite poor. It is possible to keep these pets alive – but I question the kindness of doing so. Your cat loves you very much. But it is a two way street – it is relying on you to end its life peacefully and humanely when the right time comes. Your veterinarian is, at the most, likely to hint at that. If he/she does, I would take that hint as your vet’s heart-felt advice. That hesitancy among us comes with the experience that cat and dog owners often expect more from us than is humanly possible. When your cat has lost its will to eat, and appetite stimulants like mirtazapine/Mirtaz® and Elura® no longer work, offer it what was its favorite lifetime treat. If it turns its head away at that or sniffs and licks it halfheartedly it is trying to tell you something that you in your heart already know. Cats live in the here and now, they do not fear death the way we do.
A Kidney Transplant?
Kidney transplants are an option for cats if you are fortunate enough to be able to afford them and if your cat is young enough for the results to be successful. Kidney transplants are more successful in cats than in dogs, but not nearly as successful as in humans. Currently a little more than half of the cats that have kidney transplants survive six months. Of those that do, some have lived an additional three years. Success rates for transplant surgery generally go up as specific veterinary centers accumulate more experience with the procedure. Success rates vary markedly from one veterinary center to another. It is not just the expertise of the surgeons that accounts for this. Some veterinary centers are willing to attempt transplant surgery on cats that are already seriously ill. In those locations, the overall success rate will be lower than at veterinary centers that confine their surgery to more healthy cats. None of these university centers are transparent about providing usable success statistics. An article link and thumbnail photo at the top of this page has a more extensive discussion of this subject. (read here)
Is Hemodialysis An Option For My Cat?
Hemodialysis , as it is performed on humans with failing kidneys, is not frequently performed in cats or dogs. A similar blood-cleansing effect for your cat can be obtained through peritoneal dialysis in which fluids are injected, and then removed from your pet’s abdomen. Performing hemodialysis, as done in humans, would be much harder due to the cat’s small size. I discourage peritoneal dialysis for anything but acute (sudden) kidney damage = perhaps the ingestion of something toxic, an overdose of medication, a sudden obstruction of urine flow due to a stone, or a traumatic accident. I believe that the procedure is too traumatic to cats to be subjected to frequently.
I Am Desperate! What About New Experimental Drugs, Homeopathic Remedies And Other Unproven Treatments I Hear And Read About For Kidney Disease?
Undoubtedly, a few of the medications and procedures that are currently being tried by veterinarians on cats with kidney failure will prove to be beneficial. The only way we make progress in medicine is through experimentation. However, as in the case with every disease of humans and animals, the majority of these new medications will be found not to be helpful. If traditional medications and procedures are no longer helping your cat, there is no harm in trying an experimental therapy. We live in a post-truth time. Things that are sold today over the Internet or presented to you with marvelous claims are always worthless. Some veterinarians are not above offering dodgy treatments as well. (read here) The ones Google might choose to advertise on this webpage are no better.
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