Canine Proteinuria 101: A Guide for General Practitioners

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Annual physical exams are a cornerstone of maintaining our patients’ health through early intervention. During a patient’s annual physical exam, I recommend collecting blood and urine samples which gives us valuable information on your pet’s overall health.

We can gather a lot of information in a urine sample! Detecting the presence of ketones in urine would alert us to investigating for diabetes, observing crystals could indicate bladder stones, detection of red blood cells and bacteria can help us screen for urinary tract infection, and much more!

I highly recommend utilizing the urinalysis, as it can tell us so much about their overall health. This blog post will focus on protein detected in urine, or “proteinuria”.

What does proteinuria mean?

Proteinuria is defined as the presence of abnormal protein in the urine. Proteinuria itself is not a disease, but rather a sign that there is a serious underlying condition that needs attention. Normally, circulating proteins are blocked by the glomerulus, reabsorbed by the renal tubules, or broken down by renal epithelial cells. In a pet with impaired filtration function, proteins inappropriately pass through the kidneys and into the urine.

Proteinuria can be related to kidney disease, infection, inflammation, cancer, diabetes mellitus, genetics, high blood pressure, breed predilection, tumors, and other conditions.

In cases where proteinuria is related to conditions other than kidney disease, the proteinuria will resolve when the underlying condition is treated.

In cases of kidney disease, proteinuria is a sign that the pet’s kidneys are not filtering waste from the bloodstream or balancing levels of important nutrients and is associated with a poorer prognosis.

How is proteinuria detected?

There are several methods to detecting proteinuria in pets.

urine dipstick – the most common but limitations due to lower specificity.
sulfosalicylic acid turbidimetric test (SSA) – should be used to confirm the urine dipstick
Urine Protein Creatnine Ratio (UPC) – quantifies proteinuria. Keep in mind that gross hematuria and active sediment can affect this value.
The early renal damage test (ERD) – this is a simple rapid test that detects microalbuminuria. This is the most sensitive in detecting small amounts of protein in urine and is helpful in detecting early proteinuria.

What to do next if protein is detected in a pet’s urinalysis?

Proteinuria should always be assessed in light of a pet’s urine specific gravity, and sediment activity.

In a normal dog or cat, small amounts of protein being passed in the urine through the kidneys is a normal finding.

If proteinuria is 1+ but the pet is concentrating their urine appropriately (i.e. USG of 1.04), it is unlikely that this is a significant finding.

With elevations in UPC, I recommend confirming that UPC is clinically significant by repeating test 2-3 times over a 2 week period.

Normal UPC values are <0.2 for both dogs and cats, but it is possible to see a value above this called a “grey-zone” between 0.2-0.4/0.5. Current recommendations are as follows:

For UPC between 0.4/0.5-0.9 – investigate and monitor once you have ruled-out pre-renal and post-renal causes and have established that your patient is normotensive.
For UPC 1-1.9 – investigate cause and consider treatment based on diagnostic work up
For UPC 2 or greater – investigate and TREAT!

If significant proteinuria is confirmed, I recommend a workup including urine culture, blood pressure, blood cell counts, internal organ function screening, testing for tickborne disease, and x-rays of the abdomen and thorax.

If indicated, the next steps may entail a referral to an internist for a consultation and abdominal ultrasound and renal biopsy.

Differentials for proteinuria

It is important to look at the full diagnostic picture when faced with a proteinuria case. There are many rule-outs to consider when doing your work-up.

Hemolysis
Strenuous exercise, or Rhabdomyolysis
Certain cancers
Inflammatory Bowel Disease
Pancreatitis
Kidney failure or injury
High blood pressure
Cushing’s disease (hyperadrenocorticism)
Genetics or breed
Diabetes Mellitus
Amyloidosis
Idiopathic
Systemic Lupus erythematosus

What are current recommended therapies for proteinuria?

In cases where proteinuria is related to conditions other than kidney disease, the proteinura will resolve when the underlying condition is treated.

In cases where proteinuria is related to kidney disease, there are ways we can manage progression by prescribing therapeutic renal diets, addressing dehydration, nausea, and vomiting, and prescribing anti-proteinuric therapies such as Ace Inhibitors (ACEI) and Angiotensin Receptor Blocker (ARB). “Telmisartan”, is an ARB, and is a first-line treatment and an alternative to ACEI if response to ACEI is inadequate. It is important to note, first line treatment for hypertension in cats is a calcium channel blocker such as Amlodipine as opposed to an ACE inhibitor. ARB’s are an effective anti-hypertensive in both dogs and cats.

How can you as a pet owner detect proteinuria?

Monitor for signs that are related to underlying disease; increased thirst and urination, reduced appetite, vomiting, diarrhea, lethargy, foul smelling urine or breath.

Visit your vet annually for preventive check-ups! Yearly physical exam and diagnostics tests (CBC, Chemistry and Urinalysis) can help prolong your dog or cat’s life and keep them happy and healthy.

Unfortunately, there is no cure for chronic kidney disease in dogs and cats, but we have tools to slow progression and keep your pet comfortable and happy. If your pet is experiencing any abnormal signs, please visit your veterinarian for testing and advisement.