Urinalysis Explained by Dr. Jones If you have ever received a phone call from us about your pet’s urine test, you know it can be a long conversation – crystals and protein and blood, Oh My! Hopefully the following entry will help explain why we check urine and why we are concerned, as your pets’ doctors, about the changes. “Normal” urine in dogs and cats is well-concentrated, slightly acidic, and free from protein, crystals, glucose (sugar), blood, white blood cells, bacteria, and other cells. Normal, healthy kidneys filter the blood to remove waste and medication by-products and maintain the body’s water balance. The part of the kidney that filters the blood is called the glomerulus (from Latin meaning “little ball of yarn”), a tiny tangled tuft of blood vessels. A single cat kidney has hundreds of thousands of glomeruli all filtering the blood and creating urine! Normally only water, waste products, and electrolytes can pass through the tiny holes in the glomerulus and enter the urine. Larger items in the blood such as proteins and red and white blood cells are too big to pass through the holes and stay in the blood. Congratulations! You made it through your first foray into kidney function! Now what you really want to know: what do the changes in the urine mean and why does my veterinarian care? For that you must read on! ---Why is there protein in my pet’s urine? One of the common conversations we have with owners is about protein. As you know from our previous discussion, there shouldn’t be protein in normal urine because it should not pass through the glomerulus. On our urine test, protein can come from several places: it can come from the kidneys (renal), it can come from the bladder, urethra, and vulva or prepuce (post-renal), or it can be artifact (false positive). Renal sources of protein can be from primary renal disease (kidney failure, protein-losing nephropathy, and infectious causes of kidney disease), systemic (whole body) inflammation, or high blood pressure. In these cases, we try to use the rest of your pet’s blood work and his or her clinical signs at home to figure out where the protein is coming from. Post-renal sources of protein include urinary tract infections, blood in the urine, and a few other that are scary (and rare!) and I won’t discuss right now. In these cases, there are usually other changes on the urinalysis such as bacteria, crystals, and red and/or white blood cells, and the extra cells are the source of protein. We will likely discuss treating the infection with antibiotics or discussing ways to resolve crystals – but that is a discussion for next month! If your pet’s urine is too basic (i.e. the opposite of acidic), or if it is very very concentrated, those can cause a “false positive” for protein. If your pet is a first-time offender for protein in the urine with no other changes (no blood, bacteria, crystals, or white blood cells), we may just want to recheck the urine to see if it is repeatable – it could have been a fluke! If we see protein in the urine over and over, we will likely want to run additional tests. Possible causes of protein loss through the kidneys (as mentioned above) include metabolic disease, tick-borne diseases, high blood pressure, and kidney infections, and primary glomerular damage. It is important that we diagnose and treat the underlying cause for the urine protein because chronic protein loss can damage the kidneys over time. Thanks for tuning in! Come back next month for our foray into urine crystals!
Posted on: Fri, 17 Oct 2014 12:26:30 +0000
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