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Tests used to Diagnose Kidney Disease in Dogs

This section will go over the more common tests for kidney disease, as well as some of the more complex ones. I find that people are often told that their dogs have "renal failure", with no indication of whether it is chronic or acute, early stage or end stage, and without proper information about what should be done based on the diagnosis. In addition, too often no one looks to see if there might be a treatable cause for the kidney problem. This section will review a number of different tests to help you better understand what your dog's diagnosis may mean, and what additional tests you may want to have done. Also see IRIS Staging of CKD and Relevant Diagnostic Tests for Chronic Kidney Failure for more information.


Disclaimer: I am not a veterinarian, nor do I have any formal training in any medical field. The information presented here is not meant to replace your vet's advice or prescribed medications, but only to suggest additional options to explore, based on your dog's condition.


Blood Tests

The most common blood tests used to diagnose kidney disease are Creatinine and BUN (also called Urea Nitrogen). However, several other standard blood test results also provide information about kidney disease, including Phosphorus, Calcium, and the Sodium:Potassium ratio.

Note about measurements: I refer to the standard US measurement of Creatinine and BUN in mg/dL, but have also supplied the converted numbers in mmol/L (BUN, or Urea) and µmol/L (Creatinine) for those outside the US. To convert BUN (Urea) from mmol/L to mg/dL, divide by 0.357 (or multiply by 2.8). To convert Creatinine from µmol/L to mg/dL, divide by 88.4. See  Unit Conversion for more info and a calculator that will do the conversion for you..

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Urine Tests

A urinalysis can be important in diagnosis of kidney disease. Often, low urine specific gravity (1.020 or below) will be the first indication that your dog's kidneys are not functioning properly (to be accurate, this test should be performed on the "first catch of the day", the first time your dog urinates in the morning after being in all night). Other signs of kidney disease can include excess protein in the urine, although a very small amount of protein coupled with a high urine specific gravity (1.035 or above) is considered normal. Also be aware that if the urine is collected by cystocentesis (needle in the bladder), catheterization or by expressing the bladder manually, there may be blood in the urine which will show up as trace amounts of protein. For this reason, I prefer to test urine that is free caught -- just use a ladle or small bowl to catch a little of your dog's urine when she pees. If you do this at home, refrigerate right away, then take to the vet as soon as possible. It is best to let the dog start to urinate before catching the sample (mid stream), to avoid getting bacteria in the sample.

Azotemia (elevated BUN and Creatinine) combined with normal urine specific gravity (1.030 and above) may indicate prerenal problems, such as Addison's Disease, or postrenal problems, such as kidney or bladder stones. see Localization of azotemia: Test your skill for more information.

It is also important to do a urine culture and sensitivity when you have indication of kidney disease. A urine culture is the only way to rule out a urinary tract infection, this cannot be done by simple urinalysis and observation of whether there is bacteria in the urine or not. A culture and sensitivity will also help you determine the best antibiotic to use for treatment, if an infection is present. Bacterial infections can cause kidney disease (pyelonephritis), so it is important to rule this out when dealing with kidney problems. Dogs with kidney problems are also at greater risk of developing urinary tract infections. Although vets prefer to do a urine culture using a sterile urine sample (cystocentesis), I hive had good luck doing cultures on free caught samples.

Proteinuria: If more than a trace amount of protein is found in the urine, you should do a urine protein:creatinine (UPC) ratio to determine how significant it is. Significance to some extent is related to the stage of kidney disease: for dogs with normal kidney function (creatinine < 1.5), a UPC of 2.0 or less should be investigated for an underlying cause and closely monitored, while those with UPC > 2.0 should be treated. For dogs with creatinine levels above 1.4, UPC over 0.5 should be treated.

Certain types of kidney disease, particularly glomerulonephritis (GN), are associated with high amounts of protein in the urine (UPC > 3.0), and this may be the first sign of kidney problems  in dogs affected with these diseases. See the Links section for more information on GN. Note that Antech offers a Urine Profile (see SA570 under Diagnostic Profiles) that includes a urinalysis, UPC ratio and numerous other values that can be helpful for only about $30 more than a UPC alone, so this might be something to ask your vet about if you are dealing with a dog that has or is suspected to have kidney problems. This article on Proteinuria is technical, but has a great deal of information about the meaning of protein in the urine, and what these additional tests may mean. There can be many causes of protein loss in the kidneys -- according to the article Protein Losing Nephropathy: An Overview, "Some of the more common infectious agents to keep in mind when diagnosing protein losing kidney diseases include: Brucellosis, Ehrlichiosis [Tick Disease], Leptospirosis, Borreliosis [Lyme Disease], Leishmaniasis [uncommon in the U.S.], chronic bacterial infections, and heartworm disease. Noninfectious causes include inflammatory bowel disease [IBD], systemic lupus erythematosus [SLE] and hyperadrenocorticism [Cushing's Disease], among others." See below for more information on testing for Leptospirosis and Tick Disease.

There is a new test that can find trace amounts of protein in the urine and serve as an early warning of kidney disease. This test is called the Heska ERD (Early Renal Disease Detection). See The E.R.D.-Screen™ Urine Test for information on this test specifically related to the Chinese Shar-Pei. There is additional information about the meaning of this test in the E.R.D. Healthscreen Urine Test Clinic Lab Book.

There is also a urine test called Electrophoresis that can provide diagnostic clues to the source of protein in the urine. See the following sites for a little more info:
Urinary and Serum Protein Alterations in Dogs with Natural Ehrlichia Canis Infection using Electrophoresis
Total Protein Electrophoresis
Glomerulonephritis

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Additional Tests

It can be important to do additional tests to try to determine the cause of kidney disease, especially in younger dogs or when kidney problems come on suddenly. Acute Renal Failure (ARF) can be caused by bacterial infection, such as from Leptospirosis or Tick Disease, or by poisoning, especially Antifreeze or Rat Poison. Grapes and raisins have also been linked to kidney failure in dogs if consumed in quantity. See this article on Acute Renal Failure for more specific information about this problem. While ARF is more dangerous in the short term, it is often curable, especially if caught early, and your dog may have a completely normal life afterwards (although ARF can also cause CRF, chronic renal failure). Here are some of the tests to consider:

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