Chronic Kidney Disease (CKD)

Chronic kidney disease is one of the more common illnesses we see in our geriatric patients, especially cats.  It is not a disease that we can cure, but there are various ways that we can help protect the parts of the kidneys that are still functioning.

Kidney Function

The kidneys are responsible for:

1. 'Filtering’ the blood of various waste products
2. Moderating the amount of water and salts (or electrolytes) lost into the urine from the blood. This means that when kidney function is decreased, waste products tend to build up in the blood and more water than normal is lost into the urine
3. Helping to moderate blood pressure 
4. Production of red blood cells

What happens when kidneys start to fail?

The kidneys are made up of many tiny units called nephrons, which filter toxins out of the blood and re-absorb water to keep the animal hydrated. In many types of CKD, these nephrons are lost due to scarring or changes in the makeup of the kidney. Once a nephron is lost it cannot be replaced – this is why kidney disease cannot be reversed.  Luckily for all of us, the kidney has a huge functional reserve – this means that an individual can function perfectly well with only a small percentage of functioning kidney – in fact, we often don’t see signs of kidney disease until at least 66% of kidney function has been lost!! (This is why you can live normally if you only have 1 kidney).

How do we diagnose CKD?

The history given to the vet can ring alarm bells straightaway as there are often certain signs that an owner spots.  Once the vet is suspicious of CKD, he or she is likely to recommend a blood test along with a urine test – these are usually sufficient to rule CKD in or out.  If you as an owner are suspicious of kidney disease, it is very helpful to the vet if you are able to bring a urine sample in with you to the initial consultation – the fresher the better!

Signs of Kidney Disease

When kidneys start to fail there are usually signs to look out for – these are related to the jobs that the kidneys are no longer performing –

1. Waste products start to build up in the blood stream, (the ones we measure are proteins called Urea and Creatinine).  This can make the animal feel nauseous (sick) and can put them off their food.  With time, this will cause weight loss.
2. A build-up of these toxins can also cause gingivitis (inflammation of the gums).  This can make the animal’s mouth very sore, hence also leading to a reluctance to eat
3.  As the kidneys lose their ability to reserve water, the animal will start to urinate more than normal (as the water is lost in the urine).  In order to replace the extra water being lost through the kidneys, drinking is increased.
4. Because the kidneys are involved in the production of red blood cells, animals with CKD become anaemic - this can make them feel lethargic and depressed.
5. In cats especially, blood pressure can increase quite dramatically – this can cause some heart problems and can often lead to blindness as the higher blood pressure tends to cause retinal detachment at the back of the eyes.

As an overview, animals with kidney disease tend to go off their food and drink/urinate more than normal

What we can do to help

CKD cannot be reversed.  Treatment aims to make the most of the remaining kidney function and also to give the kidneys as little work as possible to do.

1. Diet – lower levels of high quality easily digestible protein within the diet mean that the kidneys have less work to do in filtering waste proteins from the blood.  Unfortunately for us, feeding these sorts of diets is not always easy as we are often faced with an animal that has a reduced appetite and is very picky with what he/she will eat.  In these instances, it is always worth trying a prescription kidney diet initially, resorting to feeding whatever the animal will eat if this is refused.  Specialist kidney diets also contain lower levels of potassium, which can help retain kidney function as well.
2. Blood flow through the kidney – if blood pressure in the kidneys is reduced, filtering out the waste products is easier work.  Medication can be given which is able to do this.
3. If necessary, medication can be given to ease any sickness the animal may be feeling and to increase the appetite – it is very important that an animal with any chronic disease keeps their calorie intake up.