General Practice Appointment Hours:

Mon-Fri: 8:00AM – 5:00PM,
Sat: 8:00AM – 12:00PM
 

Urinalysis

UrinalysisThe urinalysis is an important part of any database of laboratory tests. It is an important screening tool whether or not an infection is suspected. The urinalysis examines chemical properties of the urine sample such as the pH, specific gravity (a measure of concentration), and amount of protein or other biochemicals. It also includes a visual inspection of the urine sediment to look for crystals, cells, or bacteria. This test often precedes the culture or lets the doctor know that a culture is in order. Indications that a culture of a urine sample should be done based on urinalysis findings include:

  • Excessive white blood cells (white blood cells fight infection and should not be in a normal urine sample except as an occasional finding).
  • Bacteria seen when the sediment is checked under the microscope.
  • Excessive protein in the urine (protein is generally conserved by the urinary tract. Urine protein indicates either inflammation in the bladder or protein-wasting by the kidneys. Infection must be ruled out before pursuing renal protein loss.
  • Dilute urine. When the patient drinks water excessively, urine becomes dilute and it becomes impossible to detect bacteria or white blood cells so a culture must be performed to determine if there are any organisms. Further, excessive water consumption is a common symptom of bladder infection and should be pursued.
  • If the patient has symptoms suggestive of an infection, a urinalysis need not precede the culture; both tests can be started at the same time.

BLADDER INFECTION: WHAT DOES IT LOOK LIKE AND WHERE DID IT COME FROM?

The kidneys make urine every moment of the day. The urine is moved down the ureters and into the bladder. The urinary bladder is a muscular little bag that stores the urine until we are ready to get rid of it. The bladder must be able to expand for filling, contract down for emptying, and respond to voluntary control.

The bladder is a sterile area of the body, which means that bacteria do not normally reside there. When bacteria (or any other organisms for that matter) gain entry and establish growth in the bladder, infection has occurred and symptoms can result. People with bladder infections typically report a burning sensation during urination. With pets we see some of the following signs:

  • Excessive water consumption.
  • Urinating only small amounts at a time.
  • Urinating frequently and in multiple spots.
  • Inability to hold urine the normal amount of time/apparent incontinence.
  • Bloody urine (though an infection must either involve a special organism, a bladder stone, a bladder tumor, or be particularly severe to make urine red to the naked eye).
  • Sometimes there are no symptoms at all so it is important to periodically screen patients at risk (such as elderly patients and patients that use cortisone-type medications long term).

The external genital area where urine is expelled is teeming with bacteria. Bladder infection results when bacteria from the lower tract climb into the bladder, defeating the natural defense mechanisms of the system (forward urine flow, the bladder lining, inhospitable urine chemicals etc.). A bladder infection is not contagious.

  • Bladder infection is somewhat unusual in cats under age 10 years.
  • Bladder infection is somewhat unusual in neutered male dogs.

URINE EVALUATION

The first part of a urinalysis involves gross inspection of the urine itself, as well as measurement of the urine’s concentration.

Color

Urinary color is analyzed by visual inspection. Change in urinary color from its normal appearance – light yellow to amber – indicates the presence of pigments in the urine which can indicate lower urinary tract disease or systemic disease.

Normal urine is pale yellow to light amber, and is generally clear to slightly cloudy. Urine that is dark yellow usually suggests the pet needs a drink of water or may be dehydrated. Urine that is very pale yellow or clear suggests the pet is drinking a lot of water and urinating frequently; this may signal underlying kidney disease, or a disorder that interferes with the pet’s ability to pass concentrated urine. Urine that is any color other than yellow (for example orange, red, or brown-black) may contain substances not normally found in healthy urine and may reflect injury or underlying disease.

Clarity

Clarity is analyzed by visual inspection of the urine sample. Change in urine clarity is most often due to the presence of red blood cells, white blood cells, or crystals in the urine. Increased turbidity or cloudiness indicates that there are cells or other solid material in the urine.

Examination of the sediment will determine what is present and whether it is significant. Increased turbidity is typically associated with the presence of blood, inflammatory cells, crystals, mucus, or debris.

Specific Gravity

The specific gravity is a measure of the urine’s concentration. Specific gravity varies in normal dogs and cats, and when well hydrated any specific gravity may be normal. This is one of the most important parameters we measure in urine. Water has a specific gravity of 1.000. A dilute urine sample has a specific gravity less than 1.020 (often less than 1.010). A concentrated urine sample would have a specific gravity over 1.030. A failing kidney by definition cannot make a concentrated urine and the patient must drink excessively to get enough water to excrete the day’s toxic load.

URINE CHEMICAL ANALYSIS

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.

pH

The pH of urine is an index of acid-base balance but is not a reliable indicator of blood pH. Urine pH is a measure of how acidic or alkaline the urine is. The pH can change with diet, but can also signal the presence of infection or metabolic disease. Normal urine in the cat and dog ranges from mildly acidic to mildly alkaline. Extremes in urine pH beyond this range are more likely to be associated with disease.

Urine Protein

Protein in the urine, also known as proteinuria, can be an indicator of renal disease (interpret in conjunction with urine concentration) or lower urinary tract disease, when pre-renal causes of proteinuria have been ruled out. Mild proteinuria in a concentrated urine may not be 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

Glucosuria is an indicator of increased blood glucose or an inability of the proximal renal tubule to reabsorb 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 or in pets under significant stress.

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 (referred to diabetic ketoacidosis), but can also be found in healthy animals during prolonged fasting or starvation.

Blood/Hemoglobin

Blood/hemoglobin on the reagent strip is most often an indicator of hematuria (red blood cells in the urine). 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 blood in the urine does not appear to be due to the sampling method, further investigation is recommended.

Occasionally the blood test pad will show positive for blood when there is immune-mediated disease or muscle inflammation or injury. Typically when this occurs, there is already cause for suspicion of these conditions and therefore further diagnostics will be recommended.

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 (“hemolysis”) and should always be investigated.

URINE SEDIMENT EVALUATION

Why do we evaluate the urine sediment? A lot of information can be gleaned from the particles of material within the urine itself, including red blood cells, white blood cells, crystals, bacterial, and tissue cells. This information adds to the puzzle pieces that help to diagnose many conditions.

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. White blood cells can also be an indication of cancer within the urinary tract.

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.

Bacteria (rods, cocci)

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 bacteria are present and which antibiotic should be used to treat the infection.

Epithelial Cells

Epithelial cells in the urine can indicate inflammation, infection, or neoplasia in the urinary tract. The type of epithelial cell can provide information about the disease process. Casts Casts in the urine are an indicator of renal injury/disease. The type of cast can provide information about the disease process.

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, the veterinarian may wish to examine a fresh sample immediately after it has been collected to determine if the crystals are significant.

Share this Content