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Chronic Kidney Disease in Pets

What is chronic kidney disease?
Kidneys are responsible for filtering the chemicals you want to keep in the body from chemicals that need to be removed in the urine, balancing salts and mineral levels (e.g. electrolytes), and maintaining appropriate water levels within the body. When the kidneys fail to function properly, waste products do not get removed and an unhealthy level of toxins can build up and circulate in the bloodstream.

Chronic kidney failure is different from acute kidney failure. Acute kidney failure has a very sudden onset and usually has a specific treatable cause, whereas chronic kidney failure is a gradual degenerative process over time that cannot be cured, only managed.

What are the clinical signs of chronic kidney disease?
Kidneys have a large reserve capacity so often 2/3rds of the kidneys must be dysfunctional before clinical signs are seen. This means, in many cases, early damage from chronic kidney disease may have been occurring for many months to years before diagnosis.

Some of the clinical signs of chronic kidney failure are:

  • Loss of appetite
  • Increased urination (polyuria)
  • Increased thirst (polydipsia)
  • Weight loss
  • Depression
  • Vomiting
  • Diarrhoea
  • Bad breath (sometimes they can also get ulcers in the mouth)

How is chronic kidney disease diagnosed?
Diagnosis of chronic kidney disease is made by:

  • Urine test

One of the earliest indicators of kidney disease can be detected on a urine test or urinalysis and so it is often recommended as part of a complete senior health check. A complete urinalysis often includes measuring the following:

    • Urine specific gravity (USG) which assess urine concentration
    • Urine dipstick test to detect levels of certain chemicals in the urine (e.g. red blood cells, white blood cells, protein, glucose)
    • Urine sediment exam to assess for the presence of crystals, cells and/or microorganism

Depending on the initial urinanlysis results, further urine tests may be required such as:

    • Urine culture and sensitivity test to assess for any concurrent urinary tract infections (if present, what type and which antibiotic use). Patients with chronic kidney disease often produce diluted urine making them more susceptible to recurrent urinary tract infections.
    • Urine protein: creatinine ratio (UPC) to quantify the amount of protein being excreted in the urine. Protein is a very valuable resource so the body shouldn’t be getting rid of it in the urine unless the kidneys aren’t filtering properly. This will help stage kidney disease and determine if certain medications are required.
  • Blood test

Given most patients do not present with any clinical signs of chronic kidney disease until damage is quite advanced, a regular annual routine blood test, especially for senior pets, is often recommended to get a quick ‘screenshot’ of their overall health. A full body health blood test (total annual health profile) includes the following:

      • Haematology or complete blood count (CBC) which assess all the cells within the blood such as red blood cells, white blood cells, platelets, etc. The kidneys also have an important role in the production of red blood cells, so a low blood cell count (anaemia) may be detected as a complication of chronic kidney disease
      • Chemical biochemistry which looks at markers of several organs (e.g. kidney, liver, pancreas), as well as blood sugar, electrolyte levels, protein levels, thyroid levels
        • Kidney markers
          • SDMA which is a relatively new marker that reflects the filtration ability of the kidneys and can increase with as early as 25% loss of kidney function
          • Creatinine and urea which are two major waste products filtered through the kidneys, however these markers often do not increase until up to 75% of kidney function is lost
        • Electrolytes (especially phosphorus, calcium, etc.) which if too high or low due to inappropriate kidney filtration, can contribute to appetite loss and lethargy
      • Blood pressure which if uncontrollably high, can cause further damage to the kidney’s filtration system
  • Abdominal ultrasound

Abdominal ultrasound allows for the architecture of the kidneys to be assessed and to also investigate for any structural abnormalities that could be contributing to kidney disease. If required, taking a sample of the kidney via a needle aspirate or biopsy can also be performed at the same time.

How is chronic kidney disease managed?
When kidneys are permanently damaged, it’s difficult for them to bounce back. However, with appropriate treatment, we can hopefully help your furbaby live many more comfortable years by supporting the kidneys as best as possible.

Depending on the presenting condition or clinical signs, the first phase of treatment is to ‘restart’ the kidneys by giving large amounts of intravenous fluids. This flushing process is called diuresis. Fluid therapy includes replacement of various electrolytes, especially potassium. Other important aspects of initial treatment include proper nutrition and medication to control other clinical signs like vomiting and diarrhoea.

The second phase of treatment is to keep the kidneys functioning as long as possible.

  • Special kidney prescription diet – When protein is broken down in the body, it becomes amino acids. Excess amino acids ultimately become urea and are filtered through the kidneys. There are many kinds of amino acids and not all of them are required at the same amount by the body. By giving just enough of each amino acid, we can minimise the amount of by-product and as a result, the kidneys do not have to work as hard.
  • Controlling electrolyte levels (especially calcium and phosphorus levels) – phosphorus can accumulate when the kidneys aren’t functioning properly, contributing to lethargy and poor appetite. A special diet (as mentioned above) can help but eventually other medications may be required to help ‘mop’ up certain excess electrolytes.
  • Medications – there are some drugs that will help to decrease blood pressure and increase blood flow to the kidneys.

Your veterinarian will advise which drugs are best suited for your pet depending on the results of their diagnostics tests.

Prognosis and outcome
Chronic kidney disease is a disease that we manage so your furbaby is comfortable for as long as possible. The earlier the detection and intervention, the better the outcome is likely to be. Please talk to your veterinarian about any concerns or questions you have about the disease. We are always here for you and your furbaby.