Chronic Kidney Disease (CKD) in cats

The kidneys are important organs, which help cats and other mammals to maintain fluid and electrolyte balance in the body, produce hormones that help regulate blood pressure and red blood cell production, and remove waste products by producing urine.

Symptoms of CKD

In most cases CKD is a progressive disease, which is reflected in the clinical signs that cats show as kidney function declines. This leads to an increased production of urine because cats lose the ability to concentrate their urine, therefore they also drink more to compensate. It is estimated that up to 50% of cats over the age of 15 years have some degree of CKD. To start with, the signs are often vague and non-specific. Mild signs will gradually become worse over time.

Common signs:

• Weight loss
• Increased thirst (polydipsia)
• Increased urination (polyuria)
• Poor appetite (inappetence)
• Lethargy
• Dehydration

Other signs may include:

• Anaemia - pale gums, shortness of breath
• Poor coat
• Vomiting
• Muscle weakness
• Bad breath (halitosis) - often metallic
• Weakness
• Collapse, seizures

Causes of CKD

As an organ, the kidneys have a high functional reserve, which means that signs of CKD will only be seen if a large proportion of the kidney tissue has been affected. This is important as it allows an individual to survive despite a significantly reduced kidney function. Biopsies from affected kidneys often show a combination of inflammation and scarring.

The most common cause of CKD in cats is as a result of natural ageing, even in the most well cared for cats. Cats are obligate carnivores and as such, their diet must contain a large amount of protein in the form of meat to survive. Removing the waste products of protein digestion over time is hard work and causes progressive kidney degeneration. However, due to their high functional reserve, the signs of this degeneration will never be seen in some cats.

CKD in cats is commonly idiopathic - the cause is unknown, despite extensive testing. Other causes of CKD include infection, toxins, tumours, as well as Polycystic Kidney Disease in certain breeds, for example Persians. can all cause chronic kidney disease in cats.

Diagnosis of CKD

Regular screening checks in mature and older cats will help to spot signs of CKD early so that appropriate management can be started promptly.

Your vet will use a combination of blood and urinalysis will be used to look for evidence of kidney failure and make a diagnosis. Blood tests will look for a build up of waste products that the kidney is not managing to process. Urinalysis will check the kidneys ability to concentrate urine. SDMA is a newly discovered marker in the blood, and elevated levels are indicative of CKD.

The same tests are used to monitor progression of the disease, together with blood pressure measurements.

What can you do to help your cat?

There are two things that you can do to help your cat: manage diet and dehydration. Your vet will be able to provide guidance on the use of medication, including phosphate binders.

1. Change their diet

Cats can be fussy and trying to change an older cat’s diet is not often easy. However, dietary management is an important part of managing CKD, in particular feeding a diet that is low in phosphate. If your cat refuses their new diet, offer their old diet and contact your vet for further advice. Here are some tips that may help:

• Make the change gradually
• Warming the food to increase the smell and palatability
• Ask your vet about appetite stimulating medication

2. Manage dehydration

• Feed a wet diet rather than a dry diet to increase water intake
• Ensure fresh water is always available
• Encouraged drinking: offer different bowls, flavoured water (chicken or tuna) or water fountains
• Adding water to the food (if tolerated without affecting the appetite)
• Intermittent subcutaneous or intravenous fluid therapy fluid therapy at your vet clinic (may be administered at a home visit if appropriate)

Treatment of CKD

Unfortunately, CKD cannot be cured. Treatment is aimed at managing the disease and the complications that can come with it, including dietary management and medication. In combination, these elements help to improve a cat’s quality of life and slow down the progression of the disease.

1. Diet

Cats with CKD are more likely to become dehydrated due to the reduced ability of the kidneys to concentrate their urine, therefore water intake should be increased.

Restricted dietary protein reduces the workload on the kidneys and reduces the amount of waste products entering the bloodstream. A restricted protein diet can improve quality of life and extend your cats survival time. Protein restriction must be performed under veterinary supervision as too little protein can also be dangerous. A renal diet is recommended for cats with renal disease for this reason. Some options include: Royal Canin, Purina and Hill's Pet.

A build up of phosphate in the bloodstream can speed up kidney damage. If, despite feeding a low phosphate diet, blood phosphate levels remain high, your vet may recommend adding a phosphate binder to the diet (such as lanthanum or calcium acetate). Controlling blood phosphate levels appears to have a protective effect on the kidneys in cats with CKD. Milk and cheese should be avoided as they are high in phosphate.

Renal diets often contain other benefits. For example: antioxidants, essential fatty acids, low sodium, added potassium to prevent low blood potassium (hypokalaemia) and added bicarbonate to help prevent acid buildup (acidosis).

2. Medication

Some cats with CKD develop low blood potassium levels. This can cause muscle weakness, can contribute to inappetence, and worsen CKD. If this is identified, potassium supplementation (tablets, gel or powder) of the diet is important.

Cats with CKD are at risk of developing high blood pressure (hypertension). This can cause several damaging effects, including blindness and worsening of the CKD. Blood pressure should ideally be monitored in all cats with CKD.

Reducing blood pressure and protein loss through the kidneys is managed using ACE inhibitors, such as benazepril or enalapril, or ARBs (angiotensin receptor blockers), such as telmisartan. Hypertension can also be treated using specific vasodilators (dilate blood vessels), such as amlodipine.

Anaemia in advanced CKD is quite common. This may be due to their inability to produce erythropoietin (EPO), a hormone that stimulates production of red blood cells in the bone marrow. Other factors can also contribute to anaemia. Severe anaemia can cause lethargy, weakness and a poor quality of life. Depending on its cause and severity, several treatment options may be available, including anabolic steroids, iron supplementation, anti-ulcer medication and EPO supplementation.

Nausea and vomiting are common in advanced CKD. They can cause inappetence and significantly affect quality of life. Various anti-nausea and anti-ulcer drugs can be used to control these signs including maropitant, famotidine and ranitidine.

Read more: International Cat Care

When to see your vet

• If you have any notice any of the signs of kidney disease
• If you have any concerns about your cat

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