What is a urinalysis?
A urinalysis is a form of diagnostic testing that your vet will use to test the physical and chemical properties of urine. The main focus of your dog having urinalysis done is to determine the health of their kidneys and urinary system, but it may also be used to show concerns with other systems and organs within your dog's body. Urinalysis is an important diagnostic tool for the ongoing preventive care of your dog.
How is Your Dog's Urine Collected for Urinalysis?
Your vet will utilize one of three main ways to collect your dog's urine.
Cystocentesis: This process utilizes a sterile needle and syringe as the method of collecting urine from your dog's bladder by puncturing the abdominal wall and collecting the urine directly from the bladder. This method allows the urine to be collected without possible contamination from debris within the lower urinary passage. Cystocentisis is most commonly used when detecting bacterial infections and other issues with the kidneys and bladder. Unfortunately, this method can only be used when your dog has a full bladder and is cooperative which can be difficult as it is a more intrusive method of collecting urine.
Catheterization: This method of urine collection uses a catheter passed through the urethra and up into the bladder which then has a syringe attached to extract the urine from the bladder. This option may be easier than cystocentesis as it is less invasive and easier to utilize. The downside is the possible irritation that may occur within the urethra and the chance of bacteria moving from the urethra and into the bladder during the process.
Mid-stream free flow: Possibly the easiest method of urine collection is while your dog is voluntarily emptying their bladder. It is recommended that the urine collected during this method occurs halfway through their voiding. Other terms for this method of collection are free-flow or free-catch. This way of collecting the urine sample is easiest as you can do the collecting in your own time. There is the possibility however that the sample could become contaminated during collection.
How Will Your Vet Perform Your Dog's Urinalysis?
Urinalysis happens in four parts:
- Your vet will assess the cloudiness of the urine.
- They will measure the concentration of your dog's urine.
- Your vet will determine the acidity or PH of the urine.
- They will utilize a microscope to explore the cells and solid material present in the urine.
For the most part, your vet will perform the analysis on whole urine as it is collected, although if your vet decides to complete a microscopic examination of the cells and solid material they will need the urine sample to be concentrated or sedimented. In order to create a concentrated urine sample, your vet will place the sample of your dog's urine in a tube and then run it through the centrifuge at very high speeds which will cause the heavier materials to move to the bottom of the sample and this sample will then be analyzed using a microscope.
How is the Chemical Analysis of Your Dog's Urine Performed?
The chemical analysis of urine is performed using a dipstick, which is a small strip of plastic that holds a series of individual test pads. Each test pad measures a different chemical component and changes color to indicate the amount of that substance in the urine. The dipstick is dipped into the urine, and after a short waiting period, the color of the test pads is compared to a chart that translates the intensity of the color to an actual measurement.
What Substances Will be Detected by the Chemical Analysis of Your Dog's Urine?
- Protein: The presence of protein in urine is called proteinuria. Mild proteinuria in concentrated urine may not be a cause for concern, but proteinuria in dilute urine should be investigated since it may signal developing kidney disease. The significance of proteinuria is often determined by doing a second test called the protein: creatinine ratio.
- Glucose: Glucose should not be present in the urine of healthy cats and dogs. The presence of large amounts of glucose usually indicates the pet has diabetes mellitus. Small amounts of glucose in the urine may also be found in pets with kidney disease.
- Ketones: Ketones appear in urine whenever the body breaks down excessive amounts of stored fat to meet its energy needs. This occurs most frequently in diabetes mellitus, but can also be found in healthy animals during prolonged fasting or starvation.
- Blood: Blood in the urine usually indicates there is bleeding somewhere in the urinary system. Sometimes this is due to how the sample was collected; for example, small amounts of blood are often found in samples collected by cystocentesis or catheterization. Blood in the urine is associated with diseases such as bacterial infection, bladder stones, trauma, or cancer, so if the blood in the urine does not appear to be due to the sampling method, further investigation is recommended.
A positive reading for blood can also be seen with a disease called hemolytic anemia, in which red blood cells are destroyed and a protein called hemoglobin is released. Hemoglobin passes into the urine and causes the blood test pad to show positive, even though there is no actual bleeding in the urinary system.
Occasionally the blood test pad will show positive for blood when there is muscle inflammation or injury. This is because damaged muscle fibers release a protein called myoglobin, which is very similar to hemoglobin. Myoglobin will also cause the blood test pad to show positive, even though there is no actual bleeding in the urinary system. A specific test for myoglobin can be done if muscle injury is suspected.
- Urobilinogen: The presence of urobilinogen in urine indicates that the bile duct is open, and that bile can flow from the gall bladder into the intestine. A negative urobilinogen result has no interpretation and does not mean the bile duct is obstructed.
- Bilirubin: Bilirubin is a substance that is produced in the liver and normally excreted in the bile. Bilirubin is not found in the urine of healthy cats but may be found in small quantities in the urine of healthy dogs. Abnormal amounts of bilirubin in the urine are associated with liver disease or red blood cell destruction (called hemolysis), and should always be investigated.
What is the Benefit of Examining Your Dog's Urine Sediment?
Urine sediment is the material that sediments out or settles into the bottom of the tube when a urine sample is spun in a centrifuge.
The most common things found in urine sediment are red blood cells, white blood cells, crystals, bacteria, and tissue cells from different parts of the urinary system. Small amounts of mucus and miscellaneous debris are often found in free-catch samples. Rarely, parasite eggs are found in urine.
- Red Blood Cells. Small numbers of red blood cells are often found in urine collected by cystocentesis or catheterization, but large numbers of red blood cells usually indicate bleeding. This may be caused by conditions such as bladder stones, infection, coagulation problems, trauma, cancer, etc.
- White Blood Cells. Small numbers of white blood cells in a free-catch sample may not be significant, but in general, an increased number of white blood cells indicates inflammation somewhere in the urinary system. Inflammation is often secondary to bacterial infection.
- Bacteria. The presence of both bacteria and inflammatory cells in the sediment indicates there is likely bacterial infection somewhere in the urinary system. Ideally, the urine should be sent to the laboratory for culture and sensitivity testing to find out what types of bacteria are present and which antibiotic should be used to treat the infection.
- Crystals. There are many different types of crystals and they vary in size, shape, and color. The significance of crystals also varies. Some crystals are unique and help to pinpoint a specific diagnosis. In more common conditions such as bladder infection and bladder stones, the crystals provide information that can influence how the disease is managed.
Crystals in the urine do not always indicate disease. Some crystals form when a pet is given certain types of medications. Crystals can also form in urine after it has been collected, especially if there is a long delay before the urinalysis is done. If this happens, your veterinarian may wish to examine a fresh sample immediately after it has been collected to determine if the crystals are significant.
- Tissue Cells. Increased numbers of tissue cells are often seen in samples collected by catheterization. While this is not a sign of disease, increased cellularity can be seen with a variety of disorders, including urinary tract inflammation, bladder stones, prostate problems (in the male dog), cancer etc. If the cells look abnormal, your veterinarian may recommend a cytological preparation of the sediment, which allows for a more detailed examination of the tissue cells.