What Urine Can Tell Us: Interpreting the Urinalysis

Following up after our discussion in September on blood work, this month I will be discussing how to interpret the basic urinalysis.

There are many reasons why your veterinarian may wish to run a urine sample on your cat or dog.  Often times you have noticed a change in urine quantity, colour, reluctance to use the litter box, frequent squatting, or an increase in water consumption to name a few.  Overall urine samples can tell us a lot about what is going on with the kidney and bladder and can help narrow down the reason behind your pet’s clinical signs.

Common rule-outs that a urinalysis can help with include: cystitis (inflammation of the bladder), urinary tract infections, sometimes uroliths (bladder stones), kidney disease, diabetes mellitus, bladder cancer, protein losing nephropathy and more.

Collection of urine can also factor into result interpretation.  The most sterile sample is via a cystocentesis.  This is done by using a needle and syringe and directly collecting urine from the bladder through the body wall, often using an ultrasound to help guide the sample collection.  This method avoids the potential of bacteria entering the urine sample as it travels down the urethra and into the external environment.  Some samples are collected from a urinary catheter, though this is often saved for hospitalized patients that already have a catheter in place.  Commonly a free catch sample is what we have to work with.  This is a non-invasive and generally easy way to collect a sample (holding a container under your dog or cat while they pee), with the main downside being likely contamination of the sample with bacteria as it exits the body, so interpretation of results must be taken with that in mind.

Timely running of the urine sample is beneficial to get the most accurate results.  As urine sits often crystals form, falsely elevating them in the analysis, along with some other changes in parameters.  Refrigeration of the sample is ideal if it cannot be run right away, and even after refrigeration it is best to run the UA within a couple hours to a day.

So let’s go through what we can test for and what those parameters mean.

To begin with we look at the properties of the urine

·      Such as its colour (yellow, pink, orange)

·      Clarity (clear, hazy, turbid)

·      The method of collection when reflecting on the results.

Urine Specific Gravity:

·      This is a test of how concentrated a urine sample is

·      It can vary depending on how hydrated your cat or dog is at the time of sample collection

·      It is also a good indicator of kidney function, highly concentrated urine the kidneys can do their job, dilute urine can indicate kidney dysfunction

pH:

·      Urine pH is important to assess as more acidic or basic urine can promote the formation of various bladder stones or crystals

·      Dogs and cats tend to have more acidic urine as they are carnivores

·      pH may also factor in on the overall bladder environment and how that impacts bacterial growth

Protein:

·      A normal urine sample should have no protein in it, some dogs may have a normal low level in their urine

·      Elevated protein can indicate the kidneys are not filtering the protein properly and allowing it through into the urine, thus suspicious for kidney injury or dysfunction

·      There can be a slight elevation in protein if there is blood in the urine when the red blood cells are broken down, they release their protein that is then detected on the urine stick

·      Other causes of protein presence include fever, stress, high protein diet, steroid administration and extreme exercise

·      Proteinuria can be a serious issue and if found on a urine sample, follow-up urinalysis is generally recommended to see if it resolves or if further investigation is warranted

·      Loss of protein can cause your pet to replace that protein from catabolizing their muscle, causing muscle wasting, weakness, and loss of overall health

Glucose:

·      The kidneys do a great job not letting glucose, an important energy source to our bodies, leave via the urine

·      Therefore, when glucose is present in urine, we become suspicious of diabetes

·      Low levels of glucose may show up in urine as a stress response of the body, often seen in cats when stressed out coming to the clinic

Ketones:

·      When the body starts having to use energy sources that are not glucose, such as in diabetic ketoacidosis, we would see elevated ketones in the urine

·      Also seen in cases of negative energy balance (not eating enough for the bodies’ metabolism requirements) or a tumour of the pancreas called an insulinoma (very rare)

·      Further work-up should be done, especially when a pet is presenting as sick and ketones are found in the urine

Bilirubin:

·      A small amount of bilirubin in the urine can be normal for dogs, but any present in cats is abnormal

·      Need to consider liver disease, bile duct obstruction, hemolysis (breakdown of red blood cells), or fever and further investigation is warranted in most cases

Blood and RBC:

·      Somewhat obvious, but indicates blood and red blood cells specifically in the urine

·      This is common with many urinary issues, such as bladder infection, kidney infection (pyelonephritis), cystitis, cancer, bladder stones, trauma, etc.

·      Sometimes the urine will be pink to red in colour when a lot of blood is present, but other times it may look normal yellow and still contain blood that we can’t see with our naked eye

WBC:

·      These are the white blood cells when found in urine

·      Likely to indicate inflammation or infection

Bacteria:

·      Urine containing bacteria is an indication of active infection or sample contamination, such as with a free catch sample

·      Most machines that test urine with categorize bacteria into two columns based on their shape, known as rods or cocci

Crystals:

·      There are many types of crystals that can form within the urinary bladder

·      Large numbers of crystals may indicate urine that is not as dilute and flushing through the bladder as it should be, leading to accumulation and “sludge” that can risk a urethral plug and blockage (an emergency when your pet cannot urinate!)

·      The type of crystal can be determined based on their shape when the urine is analyzed

·      pH and diet can factor into the formation of particular crystals and their dissolution

·      Other crystals can indicate more pathological causes, such as anti-freeze ingestion

Miscellaneous:

·      Casts in the urine are clumps of cells or other debris that may be benign or indications of something worse going on

·      May indicate kidney disease

·      May consist of epithelial cells, fat, blood cells, and other components

·      Sometimes cancerous cells from a bladder mass may be shed in the urine and identified

Well, that concludes the urinalysis interpretation.  I hope you find it helpful when discussing results with your veterinarian or going over them yourself afterwards.

Enjoy your spooktacular October!

Dr. Hillary