Mon, 04/11/2022 - 9:20pm

All About Proteinuria

Excess protein in your dog's urine can signal kidney failure

 

Should I be worried if there is protein in my dog’s urine?

 

The presence of protein in urine is called proteinuria. Protein is an important component of body function, and the kidneys play a vital role in preventing it from being lost in the urine. When protein is detected in a urine sample, it may be a sign that the kidneys are not working properly. In some cases, it may even be an indication of kidney failure.

However, proteinuria is not always a sign of serious kidney disease. It may occur for a number of other reasons. Bleeding or inflammation in the urinary tract secondary to a urinary-tract infection is a very common cause of proteinuria. Problems with the prostate gland in male dogs and vaginal diseases in female dogs may also lead to proteinuria.

The presence of protein in the urine may resolve with treatment of the underlying condition. If repeated urine samples continue to test positive for protein, then it is more likely a sign of kidney disease. Further testing is recommended.

 

What tests are required to determine the cause of proteinuria?

 

The first test is a complete urinalysis, including an examination of the sediment, or solid particles, present in the urine. This test provides a preliminary measurement of the amount of protein in the urine. A urinalysis will also determine whether there are red or white blood cells present, indicating bleeding, infection or inflammation that would explain the proteinuria.

Once proteinuria is confirmed to be a persistent finding, determining the amount of protein will help your veterinarian decide what tests should be run next. The urine protein: creatine ratio (UPC) is the test most commonly utilized for this purpose.

If an elevated value of the UPC is identified, rechecking the value in two to four weeks on at least two occasions is recommended to confirm the high levels. Since there can be a significant day-to-day fluctuation in the UPC, collecting two to three individual samples and mixing them together in equal portions will help obtain the most accurate UPC.

Other testing to determine the cause of proteinuria involves screening for infectious diseases to which the patient may have been exposed, such as Lyme disease, leptospirosis, heartworm or Rocky Mountain spotted fever. Evaluation for endocrine disorders such as Cushing’s syndrome, which is excess adrenal-gland function, cancer and immune-mediated disease, would include bloodwork, radiographs and ultrasound, as well as CT and/or MRI imaging.

All dogs with proteinuria should have their blood pressure tested. The scope of the diagnostic work-up is tailored to the needs of the patient based on history, physical-examination findings and the results of the initial lab tests.

Dogs with a high magnitude of proteinuria, low blood protein and elevated kidney values might require a more exhaustive battery of tests. This may include performing a biopsy of the kidney, especially if there is progressive disease and a lack of response to treatment.

 

Is there treatment for proteinuria?

 

The goal of treatment for proteinuria is to reduce the protein to the lowest possible level. Any existing infectious, inflammatory, metabolic or cancerous underlying condition should be treated. Blood pressure should be evaluated and treated if found to be elevated. The goal is to achieve at least a 50 percent reduction in the level of protein in the urine.

Diets that have a lower level of protein can be helpful in reducing proteinuria. If the protein intake can be limited, it eases the burden on the kidneys. Commercial diets formulated for dogs with kidney disease are moderately restricted in protein content and contain low amounts of salt.

For cases where diet alone is not effective, medications are prescribed. Angiotensin converting enzyme (ACE) inhibitors are drugs that help relax the veins and arteries to lower blood pressure. ACE inhibitors prevent an enzyme in the body from producing angiotensin II, a substance that narrows blood vessels. This narrowing causes high blood pressure, forces the heart to work harder, and puts more strain on the kidneys. Some examples of ACE inhibitors are benazepril, enalapril and lisinopril.

Angiotensin II receptor antagonists (ATRA) protect the kidneys and reduce proteinuria when used alone or together with ACE inhibitors. The ATRAs work on alternate pathways in the production of angiotensin II. The most commonly used ATRA is losartan.

Newer research has shown that the aldosterone agonist spironolactone reduces proteinuria up to 34 percent even when used at low doses. Since spironolactone is well tolerated by dogs, it can be prescribed alone or in conjunction with ACE inhibitors for dogs that are not responding to ACE inhibitors and ATRAS.

High doses of omega-3 polyunsaturated fatty acids (n3 PUFA) reduce proteinuria as well as inflammation, and relax blood vessels. Dogs consuming n3 PUFAs show increased kidney function and lower cholesterol.

Chemotherapy drugs that suppress the immune system are used when a biopsy of the kidney shows immune-mediated glomerular nephritis. This is a life-threatening disease of the kidneys and may be associated with Lyme nephritis. Cyclophosphamide, azathioprine, chlorambucil and cyclosporine are some of the drugs in this category.

Low doses of acetylsalicylic acid (aspirin) act as an anticoagulant by reducing fibrin deposits in the kidneys and prolonging blood clotting time.

Dogs started on medication for proteinuria should have their blood pressure, kidney values and potassium levels checked in two weeks. After two to four weeks of treatment, the response to the medication can be determined by rechecking the urine protein: creatine ratio in a sample composed of three separate urinations. The ideal goal of therapy is to have a normal UPC, but a more realistic goal is to reduce the UPC by at least 50 percent. Blood-pressure monitoring is also important to avoid hypotension (low blood pressure).

 

What is the prognosis for dogs with proteinuria?

 

The prognosis for dogs with persistent proteinuria is variable. It depends on the underlying cause and magnitude of the proteinuria. Dogs with a low level of proteinuria that is responsive to therapy have a good prognosis. Those dogs with severe proteinuria that are showing signs of kidney disease have a more guarded prognosis. Early recognition with appropriate diagnostics and therapy will help prolong the lives of these patients.

 

 

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