What is Chronic Renal Failure in Dogs?
Chronic Renal Failure, also known as chronic kidney disease (CKD), is a condition in which the kidneys are slowly losing the ability to do their job. Symptoms, such as drinking more water and urinating more frequently, usually are only apparent once the kidneys have lost 75% of their functioning ability. Chronic renal failure is different from acute renal failure in that acute normally has sudden onset and is often the result of infection or other trauma, whereas chronic kidney disease comes on gradually.
What do the kidneys do?
Your dog’s kidneys are responsible for removing waste products from the blood, keeping sodium and other mineral levels balanced, and regulating blood pressure, among other functions. They produce urine, which contains lots of stuff that the body needs to get rid of to remain healthy. Since the kidneys provide so many important functions for the body, loss of kidney function greatly hinders the normal function of many other organs.
The kidneys are made up of functional units called nephrons. The nephrons are the units that do the filtering of the blood. When a nephron is destroyed, it cannot be replaced or repaired. Thus, chronic kidney failure is irreversible, as the kidneys cannot regain lost nephrons. The cause of chronic renal failure generally isn’t determined and knowing the cause of CKD normally isn’t necessary to treating it (this is not true of acute kidney failure). Treatment of CKD is aimed at preserving function of the remaining nephrons for as long as possible. This is normally done through diet and other measures. (See Sample Diets for Dogs with Kidney Disease)
Signs and symptoms of kidney disease in your dog:
As mentioned above, the first sign that something is wrong with your dog when he has kidney disease is often increased urination and thirst. Many people are surprised that there is anything wrong with their pet’s kidneys in this case, because the dog is producing so much urine. But it is the lack of the kidneys ability to concentrate the urine that causes the dog to pee so much. Because the dog loses so much water in every time he goes potty, he feels extremely thirsty and can easily become dehydrated. This is why it is very important that dogs with CKD have constant access to water, since they are at increased risk of dehydration.
Other changes are common. The dog’s coat may become dull, and his behavior may change. Loss of appetite and weight often result. In some cases the dog may develop an ammonia like odor to the breath as waste products continue to build up in the body. Vomiting is very common and very problematic as well, since vomiting can put the dog at an even higher risk of becoming dehydrated. (Dog Owner’s Home Veterinary Handbook). Proper treatment can help postpone these symptoms, and many medications can help the dog feel better once they are present.
Other diseases can cause these symptoms, so it is imperative to have your vet properly diagnose your dog as soon as changes in his normal appearance and behavior develop.
How is CKD disease diagnosed?
Kidney disease can be diagnosed with a blood test that will let the veterinarian look at the blood urea nitrogen (BUN) and creatinine levels in your pet’s blood. Creatinine and urea are both normal waste products that the body produces that the kidneys get rid of, but when the kidneys stop working properly, both of the substances can build up in the blood. Both of these values are elevated with kidney disease. Normal creatinine is between 0.5 – 1.6 mg/dL, and normal BUN is between 6 – 31 mg/dL. Higher creatinine levels correspond with more progressed kidney disease.
Urine tests can also indicate kidney disease. As the kidneys lose more of their functional ability, they cannot concentrate urine properly. The specific gravity content of the urine will indicate how well the kidneys are able to concentrate urine. The range of normal values can be rather broad, and interpretation of the results will many times be dependent on the particular animal. (http://www.iris-kidney.com/education/urine_specific_gravity.html) Dilute urine can indicate kidney disease, as can extremely concentrated urine (Dog Owner’s Home Veterinary Handbook). Generally to get accurate information for the urine specific gravity, vets recommend getting urine from the first time the dog potties in the morning.
Urine tests can also show whether or not the kidneys are losing protein in the urine. Protein in the urine (called proteinuria) indicates kidney problems. You can find more information on proteinuria here: (http://www.iris-kidney.com/education/proteinuria.html).
A relatively new test is the symmetric dimethylarginine (SDMA) test. This test is very beneficial because it can detect kidney problems even before changes in creatinine happen. More information on this test can be found on this website: http://iris-kidney.com/index.html. The drawback it that this test does not seem to be nearly as accurate as other tests of kidney function. Consequently, an abnormal SDMA doesn’t necessarily mean that your dog has early kidney disease, because while early kidney insufficiency can cause an abnormal SDMA, other things can also cause an abnormal value (https://www.2ndchance.info/test.php?page=SDMA2018).
Many other values can be unbalanced in kidney disease. Low red blood cells (anemia) and high amounts of phosphorus in the blood are very common in kidney disease. In routine blood work, your veterinarian can check these values and the others listed above to determine how well your dog’s body is functioning.
Changes to your pet’s eating, drinking, urination, and behavior should never be brushed off. CKD, like many other diseases, has the best chance of responding to treatment when it is caught sooner rather then later. There is an abundance of information available on kidney disease that can help you give your dog the best care possible.
Dog Owner’s Home Veterinary Handbook, 4th edition