Updated December 21, 2023 – How many of us have trailed our dog with a pie plate to secure a urine sample or orchestrated a feline separation just to collect urine from a specific litter pan? We've all been there, hoping for a seamless visit to the vet, fingers crossed that our four-legged friend won't make a pit stop before we enter the clinic. But amidst this juggling act, one question persists: "Is this effort truly worthwhile?"
The answer is a definite yes.
The humble urinalysis is one of the critical elements of what veterinarians often refer to as the “minimum database.” Understanding what a urinalysis can tell us about our pet’s health is vital for pet owners to know.
A urinalysis comprises several elements, mainly involving urine production and the intricate function of the kidneys.
Kidneys play a vital role in:
- Expelling waste products and drugs from the body
- Maintaining fluid balance
- Regulating electrolytes
The urinalysis encompasses the physical, chemical and microscopic evaluation of urine. Pet owners must comprehend the information their veterinary care team relays, fostering proactive pet health care. (For an in-depth understanding of the urinary tract, explore our YouTube video on urinary tract anatomy and disease).
The urinalysis comprises various facets:
- Color: Normal urine is transparent and yellow or amber on visual inspection. Abnormal urine color may be caused by pigments or blood, but it does not provide specific information about abnormalities.
- Clarity: Urine is usually clear. When pigment, infection, crystals, or fat are present, urine can become cloudy.
- Specific Gravity: This test measures how concentrated the urine specimen is – in other words, how much water is present. Variations in water content reflect body water balance. The kidney plays a pivotal role in regulating these adjustments, making specific gravity an essential marker for kidney function.
- Urine pH: Urine is typically acidic in animals but can vary greatly depending on diet, medication administration, and/or disease. For example, some bacterial urinary tract infections can result in alkaline urine. Urine pH affects the formation of crystals and stones in the bladder and kidneys. Some kidney or bladder stones can be treated or prevented by feeding diets that manage urinary pH.
- Protein: Generally, normal urine should have only a small amount of protein or none.
There are many reasons protein can be present in the urine, some serious and some not. The most common causes of proteinuria (reported in dogs and cats) include:
- Strenuous exercise,
- Kidney disease affects the glomerulus (a filtering structure in the kidney).
- Acute pancreatitis
- Hyperthyroidism (impacts cats)
- Hyperadrenocorticism (Cushing’s Disease), which impacts dog
Interpreting proteinuria requires considering its context within the broader urinalysis. For instance, a slight amount of protein in concentrated urine is less significant than in diluted urine.
When proteinuria lacks an obvious explanation, such as dehydration or evidence of infection, further testing becomes necessary.
Glucose: Ordinarily absent in urine (glucosuria), glucose's presence is commonly linked to diabetes mellitus. Less frequent causes include excessive blood glucose due to IV infusion or kidney tubule damage leading to glucose excretion.
Ketones: Normally, ketones aren’t found in urine, arising from abnormal fat burning instead of carbohydrates. Although primarily associated with diabetes, ketones can also emerge from low-carb diets, prolonged fasting, or starvation.
Bilirubin/Urobilinogen: Bilirubin, a byproduct of red blood cell breakdown, is liver-excreted. While small urinary bilirubin amounts are average in concentrated urine, elevated levels often signal liver disease or conditions accelerating red blood cell breakdown. Urobilinogen tests lack clinical specificity despite being typically present in minimal quantities.
Occult Blood: A positive result for blood in urine could stem from hemorrhage, rapid red blood cell degradation, or myoglobin, a byproduct of severe muscle breakdown. Discolored urine might yield false-positive outcomes, requiring microscopic examination to confirm red blood cell presence.
The final step involves a microscopic urine evaluation. This process separates heavier elements from the urine (sediment) and is examined under a microscope.
The sediment analysis includes:
- Red Blood Cells: Few red blood cells in urine are normal. Elevated counts signal bleeding in the urinary or genital tracts.
- White Blood Cells: A minimal presence is typical; increased levels (pyuria) may result from inflammation, infection, trauma, or cancer.
- Epithelial Cells: Transitional cells, typically found in urine sediment, may indicate certain bladder cancers.
- Casts: A few casts are considered normal, but high numbers suggest kidney damage, often an early sign of toxic kidney cell effects.
- Infectious Organisms: Urine typically contains minimal bacteria. Their presence may signify infection, but the collection method should be considered to differentiate between normal skin/genital tract bacteria.
- Crystals: Various types can form based on urine pH, temperature, and time between collection and examination. While not always problematic, certain crystals may indicate illness or metabolic issues. Crystals also can be associated with a stone in the urinary tract, and further diagnostic tests such as an X-ray or ultrasound might be indicated.
- Spermatozoa: Normal in urine from intact male dogs. Spermatozoa's presence is expected.
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