Dr David Gething
Kidney Function and Kidney Failure.
A dog or cat's kidneys are one of the most important organs in their body. All animals have two kidneys, located near the liver and stomach in the abdomen. The kidneys have three vital jobs - firstly, they filter the blood to remove any toxins or old chemicals. Secondly, they balance the amount of water in the bloodstream and in the body. Lastly, they produce some special chemicals and hormones, such as EPO, that regulate the blood.
What is Kidney Failure?
The kidneys are made up of millions of tiny filtration units called nephrons. These process the blood and excrete waste, toxins and excess water out in the urine. If these nephrons become damaged, the kidney's ability to do its job becomes affected. Kidney insufficiency or kidney failure results when so many nephrons are damaged that the kidneys can no longer perform their filtration duties effectively. The result is a buildup of toxins in the bloodstream. This can happen very suddenly due to a toxin or infection (called acute kidney failure), or slowly over time as an animal gets older and the nephrons wear out due to old age (called chronic kidney failure).
Pets with kidney failure may display the following symptoms:
Loss of appetite
Increased drinking and urination
Weakness or tiredness
If the vet suspects your pet might have kidney failure they may recommend a blood test.
Patients with kidney failure will often show abnormal blood test readings:
BUN (Urea): This is a by-product of protein metabolism that is excreted by the kidneys. In a healthy animal BUN is below around 13mmol/L.
Creatinine: This is another protein metabolite that indicates kidney function. Healthy patients normally have a Creatinine of under 180mmol/L.
BUN and Creatinine are both affected by the amount of protein in the patient's diet. For patients with kidney failure one of the main treatments is a very low protein diet. Your vet will probably recommend one that is suitable for you. To be effective, your pet should eat only this diet from now on.
Phosphorus: The phosphorus levels in an animal with kidney failure will often rise due to hormone changes and reduced excretion of phosphorus by the kidneys. These increased phosphorus levels can cause significant damage to other organs such as the liver, and can also result in intestinal ulceration and bleeding. Special diets for kidney problems usually have very low phosphorus, and your vet may also recommend special medication to further reduce blood phosphorus levels.
Red Blood Cells: EPO, the hormone that stimulates the production of red blood cells in the body, is produced by the kidneys. The failing kidneys may not be able to produce enough EPO, which can result in dangerous drops in red blood cell counts (called anaemia), weakness and heavy breathing. Your vet may recommend EPO injections to boost this hormone level and restore blood cell counts.
Other Important Treatments for Kidney Failure.
In addition to restoring the body's normal mineral and cell balance as described above, it is also vital to make sure that any animal with kidney issues stays very well hydrated. Water is the kidneys ‘fuel', and as the kidney function is reduced they require more water to continue functioning efficiently. Your vet may recommend a water fountain or extra water bowls to encourage your pet to drink more, or in some cases may give special water injections (Subcutaneous Fluids) under the skin to keep a pet hydrated and improve kidney function. For more advanced cases, the vet may suggest a hospital stay where your pet will be on an IV drip.
What's the Long Term Outlook?
The kidneys are essential for normal balance and metabolism, and any damage or reduction in kidney function is very serious and must be carefully treated and monitored. Treatments for animals with kidney failure have come a long way in recent years and there are many excellent therapies and solutions. Big improvements can be made, even in animals with marked kidney problems. The long term outlook really depends on how widespread the kidney damage is, and if we can reverse this damage with medication and treatment. With the current treatments, many animals with kidney problems can go on to lead a happy life for many years as long as they are carefully treated and monitored. Repeat blood tests are recommended every 6 months (or sooner if requested by the vet), to ensure the appropriate treatments can be given.