By Jennifer Kvamme, DVM
Kidney disease is a challenge for both veterinarians and pet owners. It can be hard to tell when your dog or cat has kidney problems and the underlying cause can be difficult to diagnose. Fortunately scientists and researchers are continually looking for new ways to identify the issue.
What is Kidney Disease?
There are two forms of kidney disease in dogs and cats — acute and chronic. In the acute version, your pet’s kidneys immediately stop working correctly. This could be due to infection, injury, ingestion of a toxic substance, or a problem within in the kidney (tumor or kidney stones).
Chronic kidney disease has been present for some time (several months), without the animal showing specific symptoms. This disease can progress into kidney failure, which is life-threatening.
Symptoms of Kidney Disease in Dogs and Cats
The kidney is made up of thousands of microscopic units called nephrons. Because there are so many nephrons to carry the workload, symptoms will not appear until a significant percentage of the kidney is diseased.
In the initial stages of kidney disease, normal filtration that should take place in the nephron slows down, leading to the build-up of waste products in the body. Normally, the animal’s body excretes these substances in the urine. Without proper filtration of these toxins, illness will result. Non-specific signs may include depression, vomiting, decreased appetite, weight loss, and diarrhea.
How is Kidney Disease Typically Diagnosed?
Following a physical examination of your pet, a veterinarian will run blood tests and a urinalysis. If there is kidney disease, a blood chemistry panel will typically show increased levels of substances called blood urea nitrogen (BUN) and creatinine. The urinalysis will show if any protein is being released into the urine, as well as any signs of infection. Additional testing such as X-rays or an ultrasound to look at the size and structure of the kidneys may be considered. These tests are not always conclusive. Your veterinarian may need to do additional testing.
Research into New Methods of Diagnosis of Kidney Disease
Recent research conducted at Oregon State University has led to the discovery of an indicator produced by cats and dogs with kidney disease. This biomarker is called symmetric dimethylarginine (SDMA).
SDMA is a form of amino acid created through the breakdown of protein and released into the bloodstream to be sent out of the body through the kidneys. An increased level of SDMA in the blood can be seen much earlier than an increase in other indicators of kidney disease (increased BUN and creatinine levels). SDMA is important because it is not affected by other conditions that may cause elevated creatinine levels in a sick animal (liver disease, heart disease, Cushing’s disease, etc.).
It was determined that SDMA levels could be used approximately 17 months earlier to indicate the presence of kidney disease than by measuring creatinine levels (Yerramilli, et al). Another study conducted in dogs with chronic kidney disease showed that SDMA could be detected approximately 9.5 months earlier than elevated creatinine levels (Hall, et al).
New Test for Detecting Onset of Kidney Disease in Dogs and Cats
The discovery of this biomarker has made it possible for a screening test to be developed to diagnose kidney disease in its earliest stages. IDEXX Reference Laboratories has developed such a diagnostic tool which is to be included on all the routine blood chemistry panel testing for dogs and cats.
This test will help veterinarians recognize the potential for kidney disease in dogs and cats much earlier. Monitoring and treatment protocols at this stage will potentially add several months to years to a pet’s lifespan.
Managing Kidney Disease in Dogs and Cats
The goal of treatment in kidney disease cases is to reduce the workload of the functional kidney tissue. When the disease is diagnosed earlier, there will be a larger percentage of functioning nephrons available to maintain overall health. Initially, pain medications, intravenous fluids, and anti-nausea drugs may be used to stabilize the animal’s condition. Bacterial infections can be treated with antibiotics, while stones/blockages can be treated with surgery and dietary changes. In severe cases, kidney dialysis or kidney transplant may be indicated.
Once stabilized, kidney damage can be controlled through dietary changes to reduce the amount of protein filtering through the nephrons, allowing them to work better. Depending on the severity of the damage, animals with this condition will have different prognoses. If caught early enough, animals may stabilize and the kidneys may compensate well enough to only require dietary modification and routine monitoring. If the disease has progressed, animals may require periodic fluid therapy along with medications as needed to control symptoms. Diets for kidney disease patients are generally low in protein, sodium, and phosphorus; are enhanced with high-quality protein and carbohydrate sources; and enriched with antioxidants and fatty acids.
While there is no cure, the symptoms of chronic kidney disease can be treated and further damage prevented to give you and your pet more quality time together. This is why the discovery of the SDMA biomarker is a significant advance in the diagnosis and treatment of kidney disease in dogs and cats.
Yerramilli M, Yerramilli M, Obare E, Jewell DE, Hall JA. Symmetric dimethylarginine (SDMA) increases earlier than serum creatinine in dogs with chronic kidney disease (CKD). [ACVIM Abstract NU-42]. J Vet Intern Med 2014;28(3):1084-1085. http://onlinelibrary.wiley.com/doi/10.1111/jvim.12361/abstract. Accessed January 14, 2015.
Hall JA, Yerramilli M, Obare M, Yerramilli M, Melendez LD, Jewel DE. Relationship between lean body mass and serum renal biomarkers in healthy dogs. J Vet Intern Med 2015;29(3):808-814.
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