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Proteinuria: frequently asked questions

Updated: 21 hours ago

Protein in the urine, known as proteinuria, is one of the most common complications of Cushing’s disease. Approximately 50 percent of dogs with Cushing’s disease have proteinuria. Below are answers to frequently asked questions about this condition and potential treatments. As always, the content provided is for informational purposes only and does not replace the advice or diagnosis of a veterinary professional.


What is proteinuria and how does Cushing’s cause it?


Proteinuria is the presence of protein in the urine. Normally, when blood moves through the kidneys, its waste products pass through glomerular filtration barriers and into urine, while proteins and other nutrients stay in the bloodstream. Long-term elevation of cortisol can damage the kidney’s filtration barriers, causing proteins to escape from the blood and into the urine.


Is proteinuria harmful to dogs?


Multiple studies have linked persistent proteinuria to the development and progression of chronic kidney disease. Proteins that escape from the bloodstream are toxic to kidney cells and tissue, causing them to become inflamed and damaged. Meanwhile, the kidneys become increasingly strained and weakened as they work overtime in an effort to reabsorb the protein and prevent its loss from the body. When kidneys are unhealthy, their filtration barriers allow even more protein to flow out of the blood, and the cycle of damage continues.


NOTE: certain types of inflammation and infection, including urinary tract infection, can cause temporary rises in urine protein. This type of proteinuria usually resolves once the illness is treated and normally does not harm the kidneys.


Does treatment for Cushing’s decrease proteinuria?

Although treatment with Vetoryl (trilostane) or Lysodren (mitotane) can potentially reduce protein loss, many dogs continue to experience proteinuria even after cortisol levels are under control. In one study, proteinuria persisted in 5 out of 13 percent of dogs after a year of trilostane treatment.


What are the medical options for proteinuria?


In cases where controlling cortisol does not reduce proteinuria, many veterinarians will prescribe either an ACE inhibitor or an ARB. The most common ACE inhibitors for dogs are Enalapril and Benazepril, and the most common ARB is Telmisartan. Veterinarians often use these medications to treat high blood pressure, but they are also useful for proteinuria. They reduce protein leakage into the urine by lowering pressure inside the kidney’s filtering units.


NOTE


ACE inhibitors and ARBs should be used with caution, especially when given in addition to Vetoryl (trilostane). Vetoryl not only lowers cortisol but also aldosterone, a hormone that regulates potassium level and blood volume. Since ACE inhibitors and ARBs also lower aldosterone, giving an ACE inhibitor or ARB to a dog that is also on Vetoryl can lower aldosterone too much. Risks of low aldosterone include:


  • High potassium, a serious and potentially life-threatening condition.

  • Low blood volume and reduced blood flow to the kidneys, which puts dogs at risk of acute kidney injury.

  • Due to these risks, veterinarians should monitor potassium levels and kidney values in dogs taking Vetoryl along with an ARB or ACE inhibitor.


Are there any supplements or foods that can help to reduce my dog’s proteinuria?


Yes, for dogs with persistent proteinuria, dietary modifications can be beneficial. For example, there’s evidence that reducing protein in the diet lessens the workload on the kidneys and decreases proteinuria over time. Your veterinarian can help you determine your dog’s ideal protein intake and other dietary needs.


As far as supplements, omega-3 fatty acids and certain probiotics have potential to support kidney health. Probiotic products formulated for kidneys include Azodyl and Nephrodyl.


For general nutrition guidance, see:


Nutritional Management of Protein-Losing Nephropathy in Dogs, by Tufts School of Veterinary Medicine

Therapeutic Nutrition, by Purina Institute


References



Long-Term Follow Up of Renal Function in Dogs After Treatment for ACTH-Dependent Hyperadrenocorticism, Journal of Veterinary Internal Medicine, Volume 26, Issue 3, May-June 2012


Proteinuria: What’s New in the Management of this Silent Killer? by Shelly Olin, DVM, University of Tennessee, College of Veterinary Medicine


Proteinuria in Pets, by AMC Schwarzman Animal Medical Center


Proteinuria in Dogs, by MSPCS Angell



 
 
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