Sometimes when something is so familiar to me, I incorrectly assume it is familiar to others. In particular, when I talk to my clients about their pet's urinalysis results sometimes I fail to comprehend that they are not in the medical field and have no idea what I'm talking about. I suspect they are just respectfully waiting for my concluding remark to understand what just happened. Like, " This is great news. Your pet does not have a urinary tract infection." Or, " We found sugar in your pet's urine and your cat may have Diabetes Mellitus."
I strongly believe an educated client is my best client and pet owner. It is my goal today to educate you about your pet's urine so that when your veterinarian discusses your pet's urinalysis results with you, you understand it and can make the best decision on your pet's medical care.
Why would your veterinarian recommend a Urinalysis?
A urinalysis is a simple test to assess your pet's overall urinary tract (kidneys and bladder) health and insight on your pet's glucose regulation and liver function. As a proactive healthcare advisor, the veterinarians at Animal Medical Center of Chicago recommend a yearly urinalysis on all pets eight years of age or older. If your pet has increased water intake, increased frequency in urination, pain on urination, or visible blood in the urine, then a urinalysis is indicated.
Collection of the Urine:
The best urine sample to be evaluated is a sterile or "clean" sample. In human medicine they frequently supply you with sterile wipes to clean your genitalia and advise you to collect a midstream urine sample. This is a fair quality sample but it is the simplest and least invasive collection method. In veterinary medicine, we have the advantage of our patient's willingness to cooperate for a cystocentesis. This is a diagnostic procedure where we place a small needle attached to a syringe directly into the lumen of the bladder and collect a urine sample. This method avoids contamination of the urine with debris from your pet's genitalia. This urine collection technique is sterile and relatively pain-free.
For your information, never allow any technician to squeeze your pet's bladder to collect a urine sample. This is painful and potentially traumatic to the bladder.
Timing of Evaluation
The urine sample is best read within 30 minutes of collection otherwise certain factors (like crystals, bacteria and cells) may alter their composition (dissolve or multiply) over time. If you collect a urine sample at home, please drop it off at your veterinary clinic as soon as possible. At Animal Medical Center of Chicago, we always recommend that a professional staff member collect your pet's urine sample at our clinic where it can be collected in a sterile manner and immediately analyzed.
Actual timing of urine collection is usually not significant unless we are assessing your pet's ability to concentrate urine or if we are looking at your pet's urine cortisol levels when screening for Cushing's disease. In both these cases we desire first morning urine sample.
A veterinarian or certified veterinary technician will visually examine the urine for color and clarity. A bright red or brown colored urine sample may indicate blood. A burnt orange colored urine may be suggestive of liver disease or a potential side effect of a drug ingested. A cloudy urine may suggest that an infection or protein is present in the urine. Although this may seem elementary in investigation, this knowledge can be crucial when interpreting the Dipstick results. The color and clarity can adversely affect some of the readings on the Dipstick giving false test results. For instance, if the urine is bright red, it will falsely elevate the readings on the dipstick for protein, acidity and specific gravity.
The Dipstick Test
A dipstick is a narrow piece of plastic with small strips of chemically impregnated pads that change color depending on the presence of a substance in the urine. A dipstick test can check the following:
- Acidity (pH): The pH level indicates the acidity of the urine. In healthy pets, the urine pH is typically in the 6.5 to 7.0 range. If the pH is acidic (pH below 6) or alkaline (pH above 7) it may allow bacteria to thrive and crystals or stones to form. However, do not be alarmed if your pet's urine pH is not 6.5. Throughout the day there are normal pH variations in the urine, especially associated with eating certain foods and medications. So, one single slightly higher or lower urine pH reading is not alarming if the rest of the urinalysis is within the normal range. If it is consistently abnormal, your veterinarian may wish to investigate further.
- Specific Gravity: The specific gravity is a measurement of your pet's urine concentration, which is a kidney function. It is based on a numerical range of 1.000 to 1.040 or higher. A urine specific gravity of 1.001 is very dilute. On the other hand, a urine specific gravity of 1.040 is very concentrated.
Your pet's urine specific gravity will vary throughout the day. For illustration purposes, if your dog were swimming and drinking lots of lake water, I would expect your pet's urine to be dilute (low specific gravity). If your dog were exercising on the beach and not drinking water, I would expect its urine to be concentrated (high specific gravity).
A urine specific gravity in the range of 1.008 to 1.012 is like the concentration of water. In this narrow range, the kidneys neither are producing concentrated nor dilute urine. If your pet's urine falls in this range on testing day, I would recommend that your veterinarian recheck the urine specific gravity on the first urine sample of another day to confirm this finding. (The first urine sample of the day tends to be the most concentrated sample). If your pet's urine specific gravity repeatedly falls in this range, your pet's kidneys may not be functioning properly and your veterinarian will recommend further tests.
- Protein: On a dipstick test, protein should not be routinely found in urine. A positive test for protein in urine may be an indication of a bacterial infection, kidney disease or blood in urine.
- Sugar: Sugar should not be detected in urine. The presence of sugar in urine may be a red flag for underlying Diabetes mellitus.
- Ketones: Ketones are abnormal byproducts produced by your pet's cells when they do not have an adequate energy source. If your pet tests positive for ketones in its urine, a medical work up for Diabetes Mellitus will be performed.
- Bilirubin: Bilirubin is the yellow-staining breakdown product of hemoglobin found in red blood cells. Bilirubinuria (bilirubin in urine) is an abnormal finding and indicative that red blood cells in your pet's blood stream are being destroyed at a higher rate than normal. It can be found in pets with liver disease and autoimmune diseases. Remember, that pets with blood in their urine from a bladder infection can falsely stain the bilirubin pad on the dipstick causing a false concern for a more serious liver problem.
- Blood: The dipstick can identify red blood cells or other components of the blood, like hemoglobin or myoglobin, that are present in your pet's urine. Blood in the urine must be investigated further by microscopic evaluation of the urine. Blood in the urine may be indicative of an infection, inflammatory problem or stones in bladder or kidney.
There may be other pads on the dipstick, like leukocytes (white blood cells) and nitrites, but these aren't relevant tests for pets.
Microscopic Evaluation of Urine Sediment
Every urine sample collected should not only be evaluated by a dipstick but also evaluated microscopically. A dipstick does not reveal the whole picture. It may mislead the diagnostician that the urine is "normal" when indeed pathology may exist. When the urine sample is microscopically evaluated the urine is centrifuged (spun down at tremendously high speeds) such that any cells or abnormal elements in the urine are deposited into the bottom of the test tube (called the urine sediment) where they are collected and viewed under the microscope.
For a normal pet - the technician may see only a few (less than 0-5 per high powered viewing site) red blood cells and white blood cells. Anything beyond these values needs further evaluation.
Elements that may be found in abnormal urine sediment:
- White Blood Cells - may be a sign of an infection or an inflammatory process within the bladder or kidney.
- Red Blood Cells- may be a sign of trauma or irritation to the bladder wall or kidney. The technician will find red blood cells in the urine in pets with bladder or kidney infections, bladder or kidney stones, interstial cystitis (inflammation within the lining of the bladder) or cancer within the urinary tract system.
- Bacteria - may be an indication of an infection. If bacteria are found in the urine sample, a urine culture and sensitivity may be recommended to further identify the bacteria and aid in the selection of the best antibiotic to resolve the infection.
If the technician does not see bacteria in the urine sediment, it does not definitively mean that your pet does not have a bacterial infection in the bladder or kidney. In dilute urine samples or in urine samples that contain tremendous numbers of white or/and red blood cells, the bacteria may not be seen. Always request a urine culture for clarification if the sediment does not initially support the diagnosis of a urinary tract infection and your pet is showing classic signs of a urinary tract infection, like urinating more frequently and pain on urination.
- Casts - are not usually found in healthy pets and may be an indication of damage to the kidneys. My best explanation for what casts are is the following -- imagine the kidney is made up many tubes. The kidney tubes are lined with cells and when irritated, they cast their interior lining into the urine like snakes shedding their skin. Casts found in the urine are an indication that there is some kind of insult to the kidneys. It may be infectious, inflammatory or a result of a toxin ingested. Your veterinarian should investigate casts in the urine further.
- Crystals - When the urine pH strays from the normal range, it is possible that the normal elements that are naturally suspended in urine bind together to form crystals or stones. In dogs, the seed of a stone may be bacteria.
In concentrated urine or urine analyzed greater than one half hour after collection, finding occasional struvite or calcium oxalate crystals in the sample is not unusual. If the number of crystals in the urine is dramatic, it may be clinically significant and your veterinarian may recommend a radiograph or ultrasound of your pet's abdomen to look for bladder or kidney stones.
- Other Cells: Occasionally in pets with bladder tumors, atypical cells can be seen in their urine. Pets with irritated bladder walls will exfoliate cells into the urine called transitional epithelial cells.