Proteinuria

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By Dr Bing Yun Zhu

What is proteinuria?

Proteinuria, protein losing kidney disease, or protein losing nephropathy (PLN) are interchangeable names given to a condition where kidneys leak excess protein into the urine. If untreated, the adverse outcomes include:

  • Kidney failure (inability to expel toxins from the blood into the urine)
  • Build up of fluid in the body and inability to excrete the fluid (changes such as skin swelling and abdominal fluid build up)
  • Predisposition to blood clots forming in blood vessels (which can be fatal if occurring in the brain or lungs). 

What to do with a pet with proteinuria

When protein is first detected in the urine, the first step is to make sure that the problem is truly at the level of the kidneys. Some animals have other medical conditions that make protein loss normal, or have a urinary tract infection or bladder stone that can be increasing protein levels. You can ask your veterinarian for a referral to an Internal Medicine Veterinarian at SASH to help evaluate this. Internal Medicine Veterinarians and Specialists have had additional training to diagnose and treat these specific conditions.

What causes proteinuria?

If we do determine the problem is at the level of the kidneys then protein losing nephropathy (PLN) may be due to:

  • Glomerulonephritis – when the body’s own immune system erroneously attacks (auto-immune) the glomerulus, the sieve portion of the kidneys, which is meant to KEEP proteins in the body. This disease can respond to immune suppressant medications. Generally, a diagnosis for glomerulonephritis is favourable, as it is relatively treatable.
  • Glomerulosclerosis or non-immune glomerular diseases – This is often scarring of the glomerulus or other diseases where there is no particular medication to reverse the protein loss.
  • Amyloid – when a certain deposit forms in the kidneys that is also irreversible and cannot be fixed with medication.

How is glomerulonephritis diagnosed?

The only way to truly determine whether there is immune-mediated disease (e.g. glomerulonephritis) is to biopsy the kidneys (renal biopsy). The benefit of renal biopsy is that we will know what we are truly dealing with and can confidently start immune suppressant therapies. We will also be better able to gauge an idea of how much permanent damage is done. Sometimes we find conditions such as excess fat droplets in the kidneys that actually require a low fat diet. Without biopsy, we do not know for sure how to treat your pet. 

The risks of renal biopsy include bleeding (in rare circumstances, this can be significant and may require a blood transfusion) and general anaesthestic risks.

How is proteinuria treated?

Regardless of the cause for proteinuria (protein in the urine), there are supportive medications we can give to try and reduce the degree of protein loss such as:

  • Feeding a low protein diet, as long as there are no other medical conditions that will prevent this
  • Giving medication to reduce the blood flow pressure on the glomeruli
  • Giving anti-oxidants for the kidneys (e.g. fish oils)
  • We can also give blood thinners to try and prevent a clot

Sometimes, if it is not safe to biopsy the kidneys, or biopsies are declined due to financial constraints or personal reasons, then we may consider giving your pet immune suppressant drugs just in case they have immune-complex disease (because this is the one treatable condition). Keep in mind that immune suppressant drugs have adverse effects (vomiting, diarrhoea, poor appetite, suppressing the immune system so predisposing to secondary infections) and your pet may not actually need it.

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