A urinalysis (UA) is a series of tests performed on a urine sample. We test for pH, specific gravity, the presence of blood, protein, glucose, bilirubin, and ketones, and microscopically look for cells, bacteria, crystals, and casts.
The pH lets us know if the urine is too acidic or alkaline or in the normal range. When the urine pH is abnormal, it may alert us to potential problems (such as formation of crystals and/or stones OR metabolic problems in the body) and guide us to make some changes, specifically in the diet.
Urine Specific Gravity (USG) is basically the level of solids in relation to liquid. It lets us know how well the kidneys are doing at concentrating the urine and is especially useful with older cats. There can be problems if it is too high or too low.
Glucose in the urine along with glucose in the blood (samples taken approximately the same time) alerts us about diabetes. With complicated diabetes and some other problems, the urine may also contain ketones (breakdown products of lipids).
Bilirubin may be present when there is a problem with the liver or when large amounts of broken down blood has gotten into the urine.
Cells may be present in the urine for various reasons. Generally white blood cells (WBCs) are present when a urinary tract infection is occurring. Red blood cells (RBCs) may be present for many different reasons, often involving inflammation of the bladder and/or urethra. Epithelial cells (Epi) may also be present for different reasons, depending on the type of epithelial cells present and method of urine collection.
Crystals may be normal in small amounts, depending on the crystal type. They also may be pathologic and indicate that crystals and possibly formed stones may be present in the urinary tract, causing pain and inflammation. If they are found on a urine sample in a kitty that has frequent attempts at urination with only small amounts produced (and often bloody), they are most likely pathologic and some treatments and diet change may be necessary. (Usually in younger kitties.)
Casts may be an indication of kidney pathology.
At The Cat's Meow, the first step of a UA is measuring the specific gravity on a refractometer. The urine is next tested using a "dipstick" to check for the presence of glucose, bilirubin, ketones, protein, and blood as well as the pH. The urine is then centrifuged and the sediment is examined under a microscope for cells (RBCs, WBCs, epithelial) as well as crystals, casts, bacteria, and other things that should not be present. As you can see from the picture of the dipstick below, there are several different values that can be measured. Some of these may not be accurate in cats, so we do not rely solely on dipstick results. For instance, some human dipsticks will produce results for specific gravity and leukocytes (white blood cells). While these tests work great for humans, they are frequently inaccurate in cats due to different enzymes and chemical makeup, so we use a refractometer to measure the specific gravity and look for white blood cells under the microscope instead. This particular sample has normal results. Yea!
When to collect a sample:
It is best to obtain a urine sample at approximately the same time as the blood sample is collected. This is because the results of the tests should correlate for a good picture of what is occurring in the body at that particular time. For instance, if a blood sample is taken one day and the cat gets stressed about being at the hospital and having to "donate" blood, the urine the next day may have glucose (sugar) in it purely because the cat's blood glucose increased from stress, and the extra blood glucose leaves the body later in the urine. It would not be a good situation to have this scenario and then diagnose the patient as diabetic when, if the samples were taken at the same time, there may have been NO glucose in the urine.
How to collect a sample:
When getting a urine sample, the best way to obtain it is by cystocentesis. This involves inserting a very small needle into the urinary bladder and collecting the sample...it's just like drawing blood from a vein, but it's from the bladder using a smaller needle. Even though it may sound scary, since cats do not get mentally worked up about needles like people frequently do, they usually do not mind cystocentesis any more than they mind blood collection. This method allows the sample to be "sterile" and not have contaminant cells and/or bacteria from the urethra, outside of the body, or collection container. The second best collection method is "free-catch," where the urine is collected in a sterile or clean container as the urine is leaving the body. The least desirable method is collecting the urine out of a container or off the counter or floor after it has been voided.
When we are trying to obtain a urine sample, we may wish (depending on the scenario) to get the sample by cystocentesis if the bladder is full enough and the patient is cooperative. We may need to keep the cat for a few hours to allow the bladder to fill up with urine. At The Cat's Meow, we may use aquarium gravel in a litter box rather than conventional litter (because gravel does not absorb liquid) in an attempt to get the kitty to urinate in it. If a cystocentesis is not an option and the cat absolutely will not urinate at the hospital, we may even request for you to try to get a sample at home. Some of the constituents in the urine (especially the pH) may change over time, so the sooner tests can be performed after the urine is voided, the better. Keep the urine in the refrigerator until it can be brought and analyzed.
Amazing how much information is gained by a urine sample!