Kidney Disease

Kidney disease is a common and frustrating ailment in our mature pets. The bad news is that, unfortunately, once kidney disease is advanced enough to show up on bloodwork, 75% of kidney function is already gone and cannot be regained. Your pet is now functioning with 25% kidney function or less. The good news is that there are several things that can be done to not only make your pet feel better but also to prolong the remaining kidney function.  

Your veterinarian will use your pet’s bloodwork results to classify his or her renal disease into one of four categories developed by the International Renal Interest Society (IRIS). This grading system will help your veterinarian better tailor a treatment plan for your pet’s specific medical needs, and help to arrive at a prognosis.  

Allow me to explain a little about what kidneys do, and why kidney disease is so troublesome. Kidneys are not only responsible for making urine and thus flushing toxins out of the body, but they are also important for conserving water in times of dehydration. When a healthy individual is dehydrated, their kidneys make smaller amounts of more concentrated (darker) urine in an effort to conserve body water. When a healthy individual is well-hydrated, their kidneys make larger amounts of more dilute (paler) urine because more water is available to flush toxins from the body.  

In individuals suffering from any degree of kidney disease or renal insufficiency, the kidneys are no longer able to conserve water during times of dehydration. Even in a severely dehydrated pet, unhealthy kidneys will produce large volumes of dilute urine in the same way they would if the pet was well-hydrated. As you can imagine, producing large amounts of dilute urine in the face of dehydration will rapidly worsen the existing dehydration.  

Because renal disease patients produce too much urine, they are constantly in a state of dehydration. This is why you may have noticed your pet drinking excessive quantities of water in a futile attempt to become better hydrated. 

Renal disease has a number of side-effects: 

1. Constipation – Constipation is due to the chronic state of dehydration. Patients suffering from constipation often benefit from once- or twice-weekly subcutaneous fluids. You can learn to give these quite easily at home. Some patients also require stool softeners. 

2. Nausea – Nausea is due to the buildup of toxins in the blood that the kidneys are not able to remove. The toxins are called uremic acids. They give the pet an overall feeling of illness, nausea, and fatigue, not unlike a bad hangover. They may also give the pet headaches. Again, frequent administration of subcutaneous fluids seems to help alleviate this symptom. Nausea can also result from excessive acid (uremic) in the stomach. Pets with renal disease may feel as if they have heartburn or acid reflux. Such patients often benefit from antacids that can be dispensed by your veterinarian. 

3. Anemia – The kidney is heavily involved in the production of red blood cells. The kidney produces a hormone called erythropoietin. This hormone stimulates the bone marrow to churn out new red blood cells when old ones are destroyed. In the absence of this hormone, as in renal disease, the bone marrow loses its motivation for producing red blood cells. Consequently, the animal becomes anemic, which contributes to the overall feeling of fatigue. Depending on the degree of anemia (confirmed with bloodwork), your pet may benefit from dietary supplements that stimulate and support the production of red blood cells. Advanced cases require expensive injections of erythropoietin. 

4. Dental disease, bad breath, uremic ulcers – In part, these symptoms are due to the chronic dehydration. A lack of saliva in the mouth will promote the growth of certain dental disease-causing organisms. Additionally, uremic acids (toxins) are excreted in the saliva. These acids destroy enamel on the teeth and can even lead to painful ulcers on the tongue. They also contribute to bad breath. 

5. Weight loss – Any type of chronic disease can lead to weight loss. It is important to try to maintain a healthy weight in renal disease patients. This is most effectively accomplished by providing antacids when necessary, maintaining adequate hydration on a daily basis, and providing high-quality, easily digestible food that is “kidney-friendly”.

When a protein-rich meal is digested and absorbed, the body packages up the proteins and amino acids and stores them in muscle tissue. One of the leftover byproducts of this protein metabolism is nitrogen molecules such as urea. Because the kidney is no longer effective at ridding the body of urea, it builds up to toxic levels in the blood and contributes heavily to the overall feeling of illness as described above. One way to minimize the amount of urea that can build up in the blood is to minimize the amount of protein fed to the pet. Protein-restricted diets result in less nitrogen buildup in the blood, and also relieve the kidneys of their nitrogen-clearing duties to a certain degree, thus prolonging their existing health. Examples of protein-restricted diets include Hill’s k/d, MediCal Reduced Protein, and MediCal Renal LP. Canned diets are typically preferable to dry diets because they have more moisture in them, and are therefore better able to combat dehydration than dry diets are. Your veterinarian can help you choose an appropriate diet for your pet’s degree of renal disease. 

Additional assistance comes in the form of dietary supplements. A newly released supplement called “Renal Advanced” can be helpful. This product provides electrolyte supplementation, reduces absorption of nitrogen substances from the digestive tract, increases blood flow to the kidneys, and counteracts anemia to some degree with vitamin B12 and folic acid. This supplement is not a cure for renal disease, however, a recent study has shown that 50% more patients survived one year of renal disease when provided the supplement than those patients who did not use the supplement. 

Please contact your veterinarian for more information if you have any questions about this handout, or about your pet’s specific medical needs.