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Chronic Kidney Disease in Cats (Part 1)

This is the first part of a 2-part series dealing with Chronic Kidney Disease in Cats. Part 1 addresses the role of the kidneys, a discussion of the signs and effects of CKD and how veterinarians diagnose the condition. 

Part 2 describes management of CKD, the role of a “renal diet”, the importance of ongoing monitoring by the veterinarian and by owners at home, and brief case studies of two of the author Candice Drew's own cats diagnosed with CKD.

The Role of the Kidneys:

The kidneys are multi-talented and hard-working organs, serving numerous vital functions in the body. These include:

 Filtering the blood and removing toxins such as urea and creatinine from circulation, which are then excreted from the body as urine. These toxins are produced when the body’s cells metabolise nutrients such as protein for energy

✔️ The blood-filtering process also retains important substances and sends them back to the body. (Think of the kidneys as gate-keepers which protect the body. Harmful waste is filtered out of the blood and beneficial substances are kept and returned to circulation).

Other jobs performed by the kidneys include:

✔️ Maintaining water balance in the body

✔️ Maintaining blood pressure

✔️ Balancing blood pH (level of acidity)

✔️ Balancing electrolytes such as potassium and sodium, which enables the body’s cells to function properly.

✔️ Secretion of hormones such as renin, which helps control blood pressure, and erythropoietin, which stimulates the bone marrow to make red blood cells.

What is Chronic Kidney Disease (CKD)?

Chronic kidney disease is a gradual, progressive and irreversible deterioration of the kidneys. It is usually diagnosed in older cats, especially those over 15 years, with up to half of cats >15 years being affected. However, it can occur in cats of any age. CKD also occurs in dogs, but it is around 3 times more common in cats. There are many potential causes of CKD which include:

✔️ Polycystic Kidney Disease (PKD) which is an inherited condition in Persians and similar breeds (only Persian-type cats which inherit the gene will have this condition)

✔️ Exposure to toxins such as lilies or ethylene glycol (antifreeze), causing Acute Renal Failure (ARF) which can sometimes progress to CKD

✔️ Tumours (cancer)
✔️ Infection
✔️ High blood pressure
✔️ Impairment of blood flow to the kidneys
✔️ Impairment of urine output (eg: urinary tract infection or “blocked bladder”)

What happens to my cat when the kidneys aren’t working properly?

Because the kidneys are such amazing organs, they are able to continue doing their valuable work even when they are in the early stages of damage. This means that by the time they are no longer compensating for their reduced function and clinical signs become apparent in your cat, a significant level of irreversible damage has already occurred (up to 75% reduced function). 

These signs are related to the above-mentioned functions of the kidneys, either directly or indirectly. The process of filtering and excreting toxins and keeping valuable substances, control of blood pressure and balance of fluids in the body, and production of hormones are all impaired.

The most commonly-recognised signs of CKD, which you might notice in your cat, include:

✔️ urinating a lot more (increased frequency and/or volume), which results in your cat drinking more to make up for this increased fluid loss.

✔️ loss of appetite and weight loss, vomiting or nausea, caused by an increased level of toxins in the blood.

✔️ lethargy, caused by reduced potassium levels, anaemia and other factors

✔️ depression

✔️ dehydration due to increased urination and an inability to take in enough fluid orally.

✔️ mouth ulceration and bad breath, caused by an accumulation of waste products in the mouth.

If you notice any of these signs in your cat, you should seek veterinary advice immediately. The presence of any of these signs does not necessarily mean your cat has CKD, but they are an indication of ill-health and should be investigated. Additionally, not all cats with CKD will experience all of these signs.

How is CKD diagnosed?

Diagnosis is made by your vet considering the abovementioned signs, as well as blood and urine testing and blood pressure measurement. Sometimes abdominal x-rays or ultrasound are also utilised, if the veterinarian believes they will assist in reaching a diagnosis. Your vet might conduct tests such as:

✔️ Haematology – this assesses the number, size and quality of the cells in the blood

✔️ Biochemistry – this assesses substances and electrolytes in the blood. More recently, measurement of Symmetric Dimethylarginine (SDMA) in the blood has been shown to identify CKD up to 18 months earlier in cats, and is a more reliable diagnostic indicator, compared with measuring creatinine levels only.

✔️ Urinalysis – this might include a “Dipstick” test, a “Urine Specific Gravity” (USG) and a “Urine Protein to Creatinine Ratio” (UPCR) to assess the urine.

These blood and urine tests can identify toxin levels in the blood, determine whether protein is being lost in the urine and whether your cat’s kidneys are able to filter blood and concentrate urine sufficiently.

Your vet should also determine whether your cat is suffering from high blood pressure (hypertension), or from anaemia (a decrease in the number of red blood cells, which carry oxygen around the body). 

Among other effects, untreated hypertension can lead to damage of the retina at the back of the eye, and subsequent blindness. Anaemia results from reduced kidney production of erythropoietin, as mentioned above.

Vets don’t rely on single readings of blood, urine and blood pressure when making a diagnosis of CKD. Rather, serial readings (at least two) taken a few weeks apart will tell your veterinarian if there is ongoing, rather than short-term/acute dysfunction. Veterinarians follow an important set of guidelines by the International Renal Interest Society (IRIS) when diagnosing and treating CKD. Fortunately, the body of evidence for treating the disease is growing all the time, which means better treatment protocols leading to prolonged life and increased quality of life for affected cats.

“Cee” was diagnosed with CKD at age 15

It is important to realise that CKD cannot be cured; the damage already done to the kidneys is irreversible.

However, the earlier the disease is diagnosed and treatment begins, the sooner disease progression can be slowed and your cat can enjoy an improved quality of life for longer, often for many years. 

The rate and severity of disease progression is different for every cat, and specific treatments are tailored to a cat’s individual condition and level of stability. 

CKD is divided into 4 stages by IRIS, depending on progression of the disease. Cats in stages 1-2 can often appear quite well for a long time, with minimal or no obvious signs. One benefit of cats 7+ years of age receiving regular health checks is to enable signs of age-related diseases, such as CKD, to be diagnosed early. 

This gives veterinary teams and cat owners more treatment options than if the disease is left undiagnosed and untreated until the later stages (IRIS stage 3-4).

What complications can occur with CKD?

Possible complications of CKD, some of which I’ve already mentioned above, include: 
  • dehydration or electrolyte imbalance: cats which are dehydrated have a loss of fluid in the blood vessels or have excessive waste products in the blood stream (see azotaemia, below) and they sometimes need intravenous (IV) fluids in hospital. Alternatively, some cats can be given subcutaneous (under the skin) fluids in hospital or at home. 

One way of checking your cat’s hydration is to gently pull up the skin between the shoulder blades (only if your cats allows this). If the skin is slow to return to normal position, your cat could be dehydrated. Other factors such as the amount body fat can also affect skin return.
  • azotaemia / uraemia: this is the build-up of waste products in the bloodstream, such as urea and creatinine and other nitrogens, due to an inability of the kidneys to remove them from the body. Azotaemia can cause problems with blood clotting, vomiting, diarrhoea and other gastro-intestinal signs.
  • low blood potassium (hypokalaemia): this occurs commonly in cats with CKD and supplementation is sometimes necessary, usually in combination with IV fluids. Cats with severe low potassium will have difficulty in standing, walking and holding their head up due to weakness. They also have a plantigrade stance, meaning their hind legs walk on the hocks rather than the paws, making them appear flat-footed.
  • deficiencies of water-soluble vitamins: such as the B vitamins due to increased loss in urine, which can be replaced by a vitamin B injection under the skin.
  • high blood pressure (hypertension): this occurs in 20-30% of cats with CKD. Your vet or nurse will monitor blood pressure at each visit and medication to lower blood pressure is commonly prescribed for cats with CKD. Signs of hypertension include dilated pupils, blindness and other changes in the eyes, and neurological signs such as disorientation, circling and seizures.
  • anaemia: a reduction in the number of red blood cells can occur due reduced production by the kidneys of a hormone called erythropoietin. This can affect the delivery of oxygen to the tissues, resulting in lethargy and intolerance to exercise.
  • mouth ulceration: when waste products are converted into ammonia by bacteria in the mouth, ulceration of the gums can occur, sometimes with associated bad breath, pain, salivation (drooling), pawing at the mouth and reluctance to eat.

Some cats might have other conditions at the same time as CKD, such as polycystic kidney disease (PKD), or hyperthyroidism, the latter of which can “hide” renal disease until treatment for hyperthyroidism begins.

If this all sounds a bit much, don’t despair! Although CKD is incurable, there’s a lot that can be done to extend life and maintain quality of life, without resorting to heroic measures.

In part 2 of this article, I’ll discuss treatment of CKD and how you can actively help your own cat. I’ll also share the stories of my previous cat “Cee” and my current cat “Maggie”, both of whom had/have a diagnosis of CKD.

written by Candice Drew, March 2021 for Australian Cat Lover (all rights reserved).

About the Writer

Candice qualified as a veterinary nurse in Australia in 2005, being awarded the Novartis Award for Outstanding Achievement in Veterinary Nursing in her qualifying year. 

She has worked extensively in Australia and the UK, and is a UK Registered Veterinary Nurse. Candice is experienced in general practice, shelter nursing and referral nursing (Surgery and Emergency & Critical Care [ECC]). 

She attained the Diploma of Veterinary Nursing (surgical) in 2009, qualified as a trainer & assessor in 2015, and completed the ISFM Diploma in Feline Nursing in 2018. Candice is interested in most aspects of veterinary nursing but her passions are feline nursing, ECC and working with students. 

Candice is the happy slave of an 11-year-old rescue cat named “Maggie”, whom she adopted in January 2018.


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