Why is finding protein in urine a cause for concern?
Protein is used throughout the body in a variety of ways, and is especially important for growth and repair. Maintaining adequate levels of protein is critical for the long-term health of an animal, and any persistent loss of protein in the urine represents a waste of a precious resource that is difficult to replace.
What are the causes of protein in urine?
The presence of protein in urine is called proteinuria. The most common cause of proteinuria is inflammation or bleeding somewhere in the urinary system, usually in the bladder, but sometimes in the kidneys, the prostate (in the male dog), or the vagina (in the female). The most serious cause of proteinuria is a primary problem within the kidneys that results in the loss of protein without either inflammation or bleeding being present.
Is all proteinuria important?
Proteinuria is almost always a sign of underlying disease and should be investigated. However, proteinuria caused by bleeding or inflammation is a little less worrisome, because the underlying condition can usually be treated and cured. Unfortunately, when proteinuria is caused by a primary kidney problem, the underlying disease is often complex, difficult to diagnosis, and hard to treat. Therefore, protein loss from the kidney always warrants further testing.
What tests are required to determine the origin and significance of proteinuria?
The first test is a complete urinalysis, including sediment evaluation (see handout “Urinalysis”). This test provides a preliminary estimate of how much protein is in the urine, and determines if there is substantial inflammation or bleeding that could explain the proteinuria.
If proteinuria is not present on routine urinalysis, is further testing needed?
If proteinuria is not detected on routine urinalysis, there may still be a kidney problem, and the Early Renal Disease test may be recommended (see handout “Early Renal Disease Testing”). This is a very sensitive test that detects tiny quantities of protein that cannot be detected with routine urinalysis. A positive test result may indicate the presence of early kidney disease.
If the urinalysis reveals proteinuria with signs of bleeding and inflammation, what then?
If the urinalysis reveals inflammation or bleeding, the proteinuria is likely the result of a fairly specific problem, and your veterinarian may suggest further testing. This may include sending a urine sample to the laboratory to be tested for bacterial infection (called culture and sensitivity testing), or doing diagnostic imaging (x-rays and/or ultrasound) to assess the urinary system for a variety of conditions including bladder stones, prostatic disease (in the male dog), or cancer. Following treatment, a repeat urinalysis is often recommended to determine if the inflammation, hemorrhage, and proteinuria have disappeared.
What if proteinuria is present in the absence of inflammation or bleeding?
If proteinuria is present, and there is no detectable inflammation or bleeding, then a serious problem may exist in the kidney. The best test to determine the seriousness of the problem is the Urine Protein:Creatinine Ratio(see handout “Urine Protein:Creatinine Ratio). A substantial elevation in the protein:creatinine ratio is a reliable indicator of kidney disease, and further testing may be recommended, including ultrasound of the kidneys and kidney biopsy. Once there is a definitive diagnosis, effective management of the problem may be possible.
This client information sheet is based on material written by Kristiina Ruotsalo, DVM, DVSc, Dip ACVP &
Margo S. Tant BSc, DVM, DVSc.
© Copyright 2004 Lifelearn Inc. Used with permission under license. December 9, 2011