Kidney Failure in Cats: Symptoms, Diet and Treatment of CKD

Medically reviewed by: Kinga Wojtczak, Doctor of Veterinary Medicine, specialist in canine and feline diseases

It is currently estimated that about 30% of cats over 7 years of age suffer from kidney failure. Kidney failure is one of the most common diseases. What is kidney failure? How is it treated? Is it a death sentence for your cat? I will try to answer these and other questions in this article.

What is kidney failure?

Imagine that your cat's kidneys are an efficient filter that cleans its body. When this filter stops working properly, the kidneys cannot adequately clean your pet's blood and then produce urine. Kidney failure lets harmful metabolites build up and poison the body. The amount of urine also decreases. In advanced stages of kidney failure, urine production may stop completely.

There are three forms of kidney failure:

1. Acute kidney injury (AKI)—it usually results from poisoning or prolonged vomiting.
2. Chronic kidney disease (CKD)—the most common form of kidney failure in cats. It is often the result of a previous episode of acute kidney injury, but it can also be caused by: * some viral diseases (FIP or FeLV), * urinary tract infections, * kidney tumors, * some autoimmune diseases, * often the problem is idiopathic—we do not know what caused it.
3. Congenital kidney failure—associated with defects such as narrowing of the ureters, polycystic kidneys, or abnormal embryonic development; such kittens often die young, but they can live as long as 5–6 years without showing any signs.

Now you know the forms of the disease. But what causes it? Read on to learn the causes of kidney failure.

Causes of kidney failure

Which animals are predisposed, and is your cat at risk?

Factors that influence the development of kidney failure include:

The cat's age

The older the cat, the more susceptible it is to kidney failure. The risk of developing kidney failure is highest in cats over 7 years of age. Although kidney failure mainly affects older cats, this does not mean the disease cannot occur in a young kitten.

Breed

Some cat breeds are predisposed to kidney failure:

• Maine Coon,
• Abyssinian,
• Siamese,
• Persian,
• Russian Blue.

Improper feeding

A cat's diet is extremely important in preventing and treating the disease. Kidney failure is promoted by too little water in the diet, too much protein or poor-quality protein.

Other diseases and treatment

Some diseases can contribute to impaired kidney function. These include frequent bacterial infections, immune disorders, pancreatitis and diabetes in cats.

Giving certain groups of drugs can also induce the disease:

these include nonsteroidal anti-inflammatory drugs (NSAIDs) and steroids.

Stress in cats

Because of their living conditions and crowding, animals living in shelters and rescues are more at risk of the disease.

Acute kidney injury in cats

As I mentioned earlier, acute kidney injury in cats (AKI) is an emergency. It is usually caused by toxic substances or a change in blood flow to the kidneys. So if your cat is the type that nibbles on balcony flowers and you suddenly notice it is behaving strangely, go to the vet immediately.

In most cases, a quick response guarantees the animal's recovery. However, if the condition becomes chronic—which, unfortunately, happens in many cases when owners react too late—the damage to the kidney cells cannot be reversed. The animal may have to take medication and eat a renal diet for the rest of its life.

Symptoms of acute kidney injury in cats

When you look into kidney failure, you need to realize how complex a process it is. The signs of acute kidney injury (AKI) fall into 4 phases.

Phase 1

In the first phase, which lasts 1–2 days, there are no signs. This is when glomerular filtration decreases and kidney damage begins.

In short:

Your cat will not let on that anything is happening, but that does not mean everything is fine.

Phase 2

In phase two, signs such as these may appear:

• oliguria (reduced urine output),
• azotemia/uremia,
• increased concentrations of kidney values.

So if your cat is passing less urine than usual and its breath smells of urine, see the vet immediately for blood tests.

Phase 3

The third phase is the polyuric phase, a period when large amounts of dilute urine are passed.

Phase 4

Phase four is the period when the kidney recovers.

Remember, however, that in some cases the kidney never fully regains its function:

Your cat may have urinary problems for the rest of its life…

But what does it look like in practice?

Typically, the owner who comes to the vet describes their cat as terribly lethargic and listless.

Signs you may often notice include:

• the cat eats less,
• the cat starts vomiting,
• the cat develops diarrhea,
• the cat is dehydrated,
• its breath smells bad.

The signs appear suddenly and run a very acute course.

Chronic kidney disease in cats (CKD)

Chronic kidney disease is one of the most common conditions for which owners of house cats bring them to the vet. Unfortunately, it is incurable. Appropriate treatment can extend the cat's life by about 3 years. But what exactly is CKD?

It is a kidney dysfunction that causes the kidneys to stop performing their most important functions:

• Cleaning the blood of harmful metabolic waste products.
• Regulating the body's water and electrolyte balance.
• Producing the hormones erythropoietin (responsible for the production of red blood cells) and renin (responsible for normal blood pressure).
• Maintaining the proper blood pH.

As you can see, kidney diseases in cats are very serious conditions. Below you will find information on how to recognize them in your pet.

Symptoms of chronic kidney disease in cats

Signs of chronic kidney disease can develop over as long as several years. Owners of such cats usually come to the vet "because the cat is acting kind of strange, and on top of that he has lost a lot of weight lately." Such cats often drink more than usual, also pass more dilute urine, and visit the litter box more often. Only additional tests performed at the veterinary clinic give a definitive diagnosis.

It also happens that owners notice certain problems in their cat but do not suspect that it may have a kidney problem.

Chronic kidney disease can cause signs in these body systems:

1. Digestive system: * stomatitis (inflammation of the mouth), * diarrhea, * vomiting, * loss of appetite, * weight loss.
2. Circulatory system: * anemia, * a tendency to bleed.
3. Nervous system: * drowsiness, * seizures, * altered consciousness (even coma), * abnormal sensation in the limbs.
4. Skeletal system: * soft tissue calcification (hard lumps in the cat's soft tissues), * bone demineralization, * bone degeneration.
5. Endocrine system: * insulin resistance, * secondary hyperparathyroidism, * high blood pressure.
6. Skin: * itching, * dehydration, * edema (swelling).

Chronic kidney disease in cats can go on for a long time without any signs. Unfortunately, kidney disease is often detected only when the changes in the body are already considerable. This is because the damage must affect about 75% of the kidney tissue (parenchyma) before the effects of kidney failure show at all. The first signs that bring a worried owner to the vet are increased urine output and increased thirst.

A healthy cat should pass about 30–50 ml of urine per kg of body weight per day. If you think your cat is passing more dilute urine than usual, or, on the contrary, noticeably less urine, see a veterinarian immediately.

Other signs of kidney disease may include:

• loss of appetite,
• listlessness,
• frequent urination,
• vomiting, often persistent,
• polydipsia (increased thirst),
• bad breath,
• an unpleasant smell of the cat's coat,
• changes in coat quality and color,
• inflammation and ulceration of the mouth,
• gum inflammation,
• diarrhea,
• weight loss and severe emaciation,
• neurological problems: body tremors, seizures, difficulty moving, changes in the animal's behavior.

If your cat visits the litter box more often than usual, it may be a sign of kidney failure.

Diagnosing kidney disease in cats

When the vet suspects kidney failure in your cat, their first step will most likely be blood tests and urinalysis. Tests such as ultrasound and X-rays are also often helpful. They are done to find the cause of kidney failure (tumors) or to assess kidney damage (the ratio of the renal cortex to the medulla).

Blood tests

A standard kidney panel may include values such as:

• complete blood count (CBC),
• creatinine level,
• urea (BUN) level,
• total protein,
• potassium level,
• sodium level,
• chloride level,
• phosphorus level.

However, keep in mind that creatinine and urea levels change only once 3/4 of the cells have already been damaged.

Recently, veterinarians have also gained a new weapon in the fight against kidney failure:

It is a new laboratory parameter: SDMA. It is measured in blood serum or plasma. And why is it a good weapon against kidney failure? First, it makes it possible to diagnose chronic kidney disease before full clinical signs develop and before often irreversible kidney damage occurs. It is therefore much more sensitive than measuring creatinine and other values—a change in their levels indicates advanced disease, while an abnormal SDMA level indicates the onset of kidney failure.

Which blood test results may indicate kidney failure?

Blood chemistry tests make it possible to detect the first abnormalities in kidney function. Elevated urea and creatinine may point to emerging urinary tract problems. Another worrying sign is a large amount of protein in the urine, because healthy kidneys should not let it pass. Below you will find the blood test results of a cat with kidney failure.

Urinalysis

In a standard urinalysis result, a vet who suspects kidney failure will first check:

• specific gravity,
• color,
• protein content,
• glucose content.

Urine that is too dilute or too concentrated may indicate kidney failure. The presence of glucose or protein may also mean that renal filtration is impaired. The creatinine level is also important. Reduced creatinine excretion may indicate kidney failure.

There are also other values that can be assessed from urine tests:

• daily urine output,
• glomerular filtration rate (GFR),
• urine protein-to-creatinine ratio (UPC)—it measures protein loss in the urine in a single, preferably morning, urine sample and is more reliable than measuring protein alone,
• urine protein electrophoresis—assessing the types of protein.

Below you will find the urinalysis results of a cat with kidney failure.

Ultrasound and X-rays

During an ultrasound or X-ray examination, the vet assesses:

• the structure of the kidneys,
• their morphology,
• any tumors,
• patency of the ureters,
• the ratio of the renal cortex to the medulla.

This is used to determine the causes and the stage of the disease.

Example results in a cat with CKD

Urinalysis:

• low specific gravity
• proteinuria (elevated urine protein-to-creatinine ratio)
• casts
• possibly bacteria and pyuria

Blood test (complete blood count):

• anemia,
• signs of inflammation.

Blood test (chemistry):

• azotemia (increased urea, creatinine),
• hyperphosphatemia,
• abnormal sodium and potassium levels,
• possibly hypoalbuminemia.

Blood pressure:

• elevated

Urine culture:

• possibly positive

X-ray/ultrasound:

• smaller or enlarged kidneys,
• abnormal cortex/medulla ratio,
• soft tissue calcification,
• osteodystrophy.

If the signs of kidney disease have been confirmed by testing, treatment should start as soon as possible.

Treatment of acute kidney injury in cats

The treatment of acute kidney injury is meant to support the organ's own recovery. The cornerstone here is giving antidotes (in poisoning) and fluid therapy as quickly as possible. You must remember that this form of kidney failure requires an immediate response. The first 6 hours of therapy are crucial. That is why frequent (even 2–3 times a day) intravenous infusions are used.

The volume of fluid to give is calculated with the formula:

fluid volume (ml) = % dehydration × body weight (kg) × 10. The infusion fluid should be isotonic, so vets, taking the electrolyte panel into account, often choose lactated Ringer's solution or 0.9% NaCl. In metabolic acidosis, that is, when blood pH is <7.2, they may add sodium bicarbonate to the treatment. In acute hyperkalemia, they may add calcium gluconate, which must be given as a very slow intravenous infusion.

Often, however, during treatment of acute kidney injury the opposite situation occurs: a potassium deficiency (hypokalemia) caused by the body excreting too much of this element. In that case, the veterinarian replaces potassium, most often by adding potassium chloride to the IV fluids. Sodium bicarbonate and glucose, given with or without insulin, lower potassium levels—they are used in hyperkalemia, not in potassium deficiency. In treating AKI, it is also helpful to check phosphorus and, if the level of this element is too high, to give phosphate binders.

To limit further dehydration, antiemetics and drugs that reduce inflammation of the stomach and intestines are also given, such as:

• maropitant (Cerenia),
• metoclopramide,
• chlorpromazine.

Gastric hyperacidity is also treated with H2 receptor blockers such as ranitidine (Ranigast, Solvertyl). If, despite rehydration, the cat still produces less than 1–2 ml of urine per kg of body weight per hour, we may be dealing with oliguric kidney failure. In that case the veterinarian may decide to give diuretics—osmotic (mannitol, dextrose) or loop diuretics such as the popular furosemide—or dopamine as a slow, careful intravenous infusion.

Treatment of chronic kidney disease in cats

Cats diagnosed with CKD will most likely be treated for the rest of their lives. First, they should receive fluid therapy to rehydrate them. The vet may also decide on symptomatic treatment depending on how advanced your cat's disease is. The vet may recommend switching to a renal diet (kidney diet food). In some advanced cases, force-feeding may also be necessary…

In severe cases, multimodal treatment should be started as soon as possible. It involves several basic measures:

• lowering the urea level (fluid therapy),
• if the cat will not eat—an appropriate diet, appetite stimulants, sometimes "force" feeding,
• if vomiting or diarrhea is present—stopping it,
• if the cat is thin or cachectic—nutritional supplements for cats,
• rehydrating the cat with intravenous and subcutaneous fluids,
• controlling anemia—whenever possible,
• if there is inflammation of the mucous membranes (mainly of the mouth and stomach)—controlling the inflammation (topical ointments, gels such as Dentisept, anti-inflammatory drugs),
• fighting acidosis—if present,
• giving diuretics only in specific situations, e.g. fluid overload (too much fluid in the body)—in chronic kidney disease they are not used routinely, because they worsen dehydration and can increase azotemia; the veterinarian decides whether to use them,
• lowering phosphorus levels and raising potassium and calcium levels if blood tests show a deficiency,
• if there is hypertension—lowering it.

Remember, however, that every case is different and it is the vet who must decide on the treatment.

What will the vet do once CKD is diagnosed?

Depending on the signs, their severity and the animal's condition, the vet will first:

• Replace fluids—more fluid is needed because of the increased volume of dilute urine. If the cat cannot take in its daily water requirement on its own, daily subcutaneous fluids become necessary. Usually the owner gives them at home. Over time, and once the cat's general condition improves, the vet may also recommend giving fluids less often, e.g., 1–2 times a week.
• Give vitamin C and B vitamins by injection or by adding them to the cat's diet.
• If the cat has high blood pressure, try to lower it with cardiac drugs such as Lotensin, Enarenal or others.
• Possibly, if phosphorus is elevated, give phosphate binders that act in the intestine.
• Give antiemetics and drugs that reduce inflammation of the stomach and intestines (mentioned above).
• Try to treat anemia with anabolic steroids or erythropoietin.

Later on, a change of diet will also be necessary, to one with reduced protein and phosphorus. Many foods that meet these requirements are now available, so feeding such food to your cat will not be a problem.

In some cases, the vet will also use dietary supplements such as:

• Renalvet,
• Urinovet,
• Ipakitine,
• Rubenal.

To reduce the protein level, products such as Semintra are used.

Preventing kidney disease in cats

To prevent kidney disease in cats, it is very important to have regular check-up blood and urine tests done in cats over 5–7 years of age. Diet also matters—older cats should eat food with a moderate phosphorus content, and a diet lower in phosphorus and protein is used in cats diagnosed with kidney disease. As a preventive measure, you can also give them dietary supplements that affect kidney function. You also must not forget to treat urinary tract diseases and other conditions that may contribute to kidney failure.

Diet for a cat with kidney failure

A special diet is a very important part of treating kidney disease. A cat with kidney failure should be fed a diet with reduced protein content. On the one hand, such food will support treatment of the disease, and on the other, it will provide the right nutrients, benefiting the health of the whole body and the cat's well-being. In the first phase of the disease, it is also a good idea to pay attention to how palatable the food is—foods with "increased palatability" are available.

In addition to low protein, food for cats with chronic kidney disease should contain little phosphorus and have the right ratio of omega-6 to omega-3 fatty acids (5:1). A low phosphorus content in the cat's food prevents hyperphosphatemia. This is a condition in which the phosphate level in the blood rises, and it can lead to problems with calcium absorption. A low phosphorus level makes it possible to hold back the disease.

The right ratio of omega-6 to omega-3 fatty acids has an anti-inflammatory effect. It also helps reduce the pressure in the glomeruli. These effects help slow the disease. Ready-made food for cats with kidney disease contains the required ingredients that help excrete nitrogen—among them beet pulp and prebiotics (fructooligosaccharides, FOS). It is also good if the food contains potassium citrate, which helps reduce the risk of metabolic acidosis.

Adequate water intake is also important. Cats with kidney failure pass large amounts of urine, so they need more fluids. The cat must not be allowed to become dehydrated.

Can anesthesia damage the kidneys?

Today, in most veterinary clinics, before a procedure under general anesthesia the vet tells the owner that pre-anesthetic blood tests are necessary, because they make it possible to choose the right anesthetic protocol. Poorly chosen anesthesia, especially the drop in blood pressure that comes with it, may contribute to worsening of the kidneys' condition. Very good and relatively safe general anesthetic agents are now available.

Remember, however, that inhalant anesthesia is the safest and the least toxic to the kidneys; if it can be used, it is a good idea to use it.

Diseases that can harm the kidneys

Some of the conditions your cat may face influence whether CKD develops later, while others are gremlins that make diagnosis and treatment harder for us vets. One such disease is liver failure, because it can mask kidney failure. Urea is produced in the liver. If the liver is failing, we may see a lowered level of urea—a "kidney" value.

Other diseases resemble kidney failure in their signs. One such condition is Addison's disease. A condition that can directly contribute to the development of kidney failure is pancreatitis. We do not fully know what causes it.

Signs may include:

• diarrhea,
• vomiting,
• a distinctive stool appearance (mushy, yellow).

These signs may go away, and the cat's owner may decide it was a passing upset. The inflammation may resolve and the pancreas may regenerate, but it will leave a mark on the kidneys. The treatment of some diseases also has an adverse effect on the kidneys. Kidney tumors are rare, accounting for only about 1% of all tumors, but chemotherapy for other cancers in a cat can itself contribute to kidney failure. Dehydration is also dangerous, because little blood then reaches the kidneys; as a result, they are deprived of oxygen and the urea and creatinine levels rise.

This is where fluids help, as long as serious damage has not yet occurred.

The role of fluids in treating kidney failure

Fluid therapy is meant to rehydrate the cat. Remember that fluids differ in composition, and the composition must be matched to the animal's needs. And here again, we choose the fluid based on blood test results. For example, if we give a glucose drip to a cat with a potassium deficiency, we will lower its potassium even further and make it feel worse. A well-hydrated cat passes more urine, removing toxic products from the body.

My cat has CKD—how should I care for it?

If you care for a cat with CKD, you must remember to:

1. Follow the diet strictly!
2. Keep the cat calm and avoid stress.
3. Watch closely—do not ignore signs that may suggest the cat's results are getting worse, such as loss of appetite, vomiting or drowsiness. If they appear, see the vet immediately.
4. Give the prescribed medications.
5. Have follow-up blood tests done at least once every six months.
6. If in any doubt, contact the vet.

Summary

To sum up, kidney failure is a very insidious disease that can lead to the animal's death. That is why prevention and monitoring of cats in the highest-risk groups are so important. I hope that after reading this article you know how to prevent kidney failure and how to recognize the disease if your cat starts showing the typical signs.

If you would like to learn more about CKD treatment or diet for a cat with kidney disease, leave a comment below the article now, and I will reply as soon as possible.

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