Chronic kidney disease (CKD) is the name now used to refer to cats with kidney failure (or chronic kidney failure).
CKD is one of the most common conditions affecting older cats, and in most cases is progressive over time so that there is a gradual decline and worsening of the disease. The rate of decline varies considerably between individual cats.
The kidneys are responsible for helping maintain fluid balance in the body, for producing certain hormones, for regulating many electrolytes in the body and for excreting waste products (via urine). In CKD, all these regulatory processes can be interfered with causing a wide range of different signs.
Although CKD is not a curable or reversible disease, appropriate support and treatment can both increase the quality of life, and also prolong life by slowing down the progression of the disease.
How is CKD managed?
If a specific cause for the CKD is identified (eg, bacterial infection of the kidneys), treatment may be possible to arrest the progression of the disease. In most cases though, treatment is symptomatic and supportive. Some cats may require initial intravenous fluid therapy to correct dehydration (and perhaps electrolyte abnormalities), but once stable, treatment is aimed at supporting kidney function and minimising the complications of CKD. Despite therapy, CKD cannot be reversed and in most cases will also progress over time.
Optimal management of renal failure usually requires repeat investigations at regular intervals (including blood pressure assessment, blood and urine tests) to identify treatable complications as they arise, eg, anaemia, low potassium, high phosphate, urinary infections, and hypertension. Dietary modification is important in cats with CKD to improve quality of life and slow progression of disease, but a variety of other treatments may be valuable also, depending on individual needs. Sometimes multiple drug therapies may be needed, but if it is difficult to administer medications to your cat, these may need to be prioritised.
Diet and the management of CKD
Dietary management is critical in cats with CKD, and there are three main aspects to this:
Cats with CKD are more likely to become dehydrated (due to the reduced ability of the kidneys to conserve water). Maintaining a good fluid intake is therefore very important, and may help to slow progression of CKD. As cats obtain much of their water intake from their food, whenever possible, cats with CKD should be fed tinned (or sachet) foods rather than dry foods.
An ideal diet for a cat with renal failure should have a restricted protein content. Many of the toxic products that accumulate in the blood in CKD are a result of protein breakdown, and feeding a reduced protein diet will help to minimise this and improve quality of life. Protein restriction has to be performed with care though as too little protein can be extremely detrimental to general health.
Low phosphate content
Restricting the phosphate content of the diet appears very beneficial in protecting the kidneys from further damage in cats with CKD. While restricting protein in the diet helps maintain quality of life, restricting phosphate thus appears to prolong the life of cats with CKD. Studies suggest this effect may be quite dramatic in cats. If blood phosphate concentrations remain high despite being on a low phosphate diet, further treatment with drugs known as 'phosphate binders' to reduce the amount of phosphate absorbed from the intestine may also be indicated.
Other dietary measures
Other aspects of the diet may also have an important role to play in helping manage cats with CKD. These include the addition of anti-oxidants to try to protect the kidneys against further damage, essential fatty acids to help maintain blood flow through the kidneys and reduce inflammation, added potassium to prevent hypokalaemia (low blood potassium), and added bicarbonate (or similar) to help prevent acidosis (a build up of acid in the body which can also occur in CKD).
All these measures may help and have a role to play in keeping cats with CKD as healthy as possible for as long as possible. Because of the exacting nutritional demands in cats with CKD, feeding a specific veterinary therapeutic diet designed to manage all these aspects is strongly recommended. These diets are only available through your vet, but have a vital role to play in managing the disease.
Managing the change to a new diet
Cats will often develop a strong preference for particular diets, and low protein diets tend to be less palatable. This means that changing cats with CKD to an appropriate therapeutic diet can sometimes be difficult. These tips may help:
- Always may a change in diet gradual - per several days at least and sometimes over a few weeks if your cat is quite fussy
- Start by mixing a very small amount of the new food with your cats old food, and make sure it is well mixed
- Only increase the amount of the new food slowly, once your cat is happy to eat the old mixture. Make each step where you replace old food with a greater amount of new food slow
- Warming the food to body temperature (around 30C) may help increase the palatability
- If necessary, talk to your vet about using drugs to increase the appetite to make the transition easier
In most cases with sufficient care and time, cats can be very successfully transitioned to a new diet, and as this is such an important part of managing CKD it is worth taking the time to do this properly. If cats absolutely refuse to eat any of a new diet, it is important that they eat something, so keep offering their old diet in this situation and contact your vet for further advice.
Using a wet rather than dry diet is important to increase water intake in cats with CKD, but they still sometimes do not consume enough water to compensate for what is being lost in the urine. In these cases, additional measures may need to be taken. These may include:
- Make sure a good supply of fresh water is always available, and cats should be encouraged to drink by offering water from different bowls, etc.
- Using flavoured waters (chicken or tuna, for example) or water fountains to encourage drinking
- Adding further water to the food (if tolerated without affecting the appetite)
- Using intermittent intravenous fluid therapy at your vet clinic
- Using intermittent sub-cutaneous fluid therapy which can be given at your vet clinic or sometime in the home environment
If despite using a low phosphate diet, blood phosphate levels remain high, using a phosphate binder added to the diet (such as lanthanum or calcium acetate) may be valuable. This is important as controlling blood phosphate levels appears to have a good protective effect on the kidneys in cats with CKD.
Some cats with CKD develop low blood potassium levels. This can cause muscle weakness, can contribute to inappetence, and itself can worsen CKD. Where this is identified, potassium supplementation (usually potassium gluconate in the form of tablets, gel or powder added to the diet) is important.
Controlling blood pressure
Cats with CKD are at risk of developing high blood pressure (hypertension). This can have a number of damaging effects, including potentially blindness and worsening of the CKD. Blood pressure should ideally be monitored in all cats with CKD and where hypertension is found it should be treated. This is usually achieved with a group of drugs known as 'vasodilators'. In cats a drug called amlodipine is particularly effective, but other drugs may also be used.
Treatment of anaemia
In advanced CKD in particular, anaemia is quite common. This may be due to lack of production of a hormone by the kidneys (erythropoietin or EPO) that stimulates production of red blood cells in the bone marrow, but can also be due to other factors (such as loss of blood in the intestines). More severe anaemia can cause lethargy and weakness and a poor quality of life. Depending on its cause and severity, a number of treatment options may be available to manage anaemia including the anabolic steroids, iron supplementation, management of any gastrointestinal ulcers and in some cases supplementation with EPO.
Treatment of nausea and vomiting
Nausea and vomiting are more common in advanced CKD and can cause inappetence and significantly affect the quality of life. Various drugs can be used to control these signs including maropitant, famotidine and ranitidine.
Use of 'ACE inhibitors' and ARBs
Blocking activation of a hormone known as angiotensin may be of benefit in CKD. This can be achieved by using so called 'ACE-inhibitors' (angiotensin converting enzyme inhibitors) such as benazepril or enalapril, or using angiotensin receptor blockers (ARBs) such as telmisartan.
These drugs are vasodilators (dilate blood vessels) and help to support blood flow through the kidneys, and may help to lower blood pressure in cats, and also significantly reduce protein loss through the kidneys. Elevated loss of protein through the kidneys in CKD is a risk factor for progression of CKD, and it is possible that lowering protein loss (with ACE-inhibitors or ARBs) may improve survival in some cats with CKD.
In some countries, kidney transplants are offered by some specialist veterinary centres as a means of treating cats with CKD. Although this can be a successful approach, it raises a number of ethical questions including where and how a donor kidney is sourced. Additionally, the procedure is not invariably successful and cats receiving a new kidney may not necessarily survive any longer than cats managed with good medical supportive care.
What is the prognosis for cats with CKD?
Once sufficient damage has been done to the kidneys to cause CKD, the compensatory changes and adaptations that occur to try to maintain normal kidney function usually eventually fail and progressive kidney damage occurs. The disease is usually therefore progressive over time and will eventually lead to the need for euthanasia. However the rate of progression of renal disease varies considerably between individuals and appropriate support and treatment can both increase the quality of life of affected cats and also potentially slow down the progression of the disease.