Source: https://vcahospitals.com/know-your-pet/urinalysis
What is a urinalysis?
A urinalysis is a routine test that examines urine properties, helping assess the health of the urinary system, kidneys, and other organ systems.
Urinalysis is a valuable test for both healthy and sick animals to find any underlying issues and provide early detection of problems in the organ systems.
How is the urine collected?
There are two main ways the urine is collected: mid-stream flow and cystocentesis.
- Mid-Stream Flow – Often referred to as “free catch” or “free flow”, this sample collection method involves allowing the pet to urinate as they naturally would, collecting the urine in a container as they do. Ideally, the collection happens mid-stream, so that most foreign debris present near the area is washed away before collection. This sample collection has its advantages and disadvantages. It is non-invasive and can even be collected at home. However, collecting mid-stream can be difficult with some pets, and there is always a higher risk of foreign debris entering the sample container.
- Cystocentesis – This collection method involves drawing urine directly from the bladder by inserting a sterile needle through the abdominal wall. The patient is gently placed on their back or side and held to facilitate safe collection. The needle is then inserted, and the sample is collected. Advantages of this method include minimal risk of foreign debris contamination, making cystocentesis ideal for assessing the bladder and kidney functions and detecting bacterial infection. Disadvantages are the need for a full bladder and patient compliance for a productive sample collection. In some cases, particularly those with urinary discomfort, your veterinarian may use an ultrasound to locate abnormalities such as stones, crystals, or masses on the bladder wall.
What a Urinalysis Tests For
There are four different tests performed during a urinalysis:
- Assess color and cloudiness (turbidity)
- Measure the specific gravity (or concentration)
- Measure the pH and chemical composition
- Examine the cells and solid material (called sediment) present under the microscope
Assessing color and turbidity – Normal urine is pale yellow to light amber in color and clear to slightly cloudy. Darker coloring can suggest that the pet is dehydrated. Very pale to clear coloring can suggest that the pet is drinking a lot of water and urinating frequently, which can also indicate possible kidney disease or other underlying disorders. Urine that is not yellow (red, black, brown, or orange) suggests the urine contains substances not typically found in healthy urine and can also indicate underlying diseases, injuries, or disorders.
An increase in turbidity indicates that cells or solid material (sediment) are present in the urine. Examination under the microscope is required to determine what the sediment contains (blood, other cells, crystals, or foreign debris) and if the presence is concerning.
Measuring specific gravity – Healthy urine should be concentrated. Specific gravity is the concentration, or density, of the urine. Diluted urine can suggest an underlying disease. A refractometer is a device used to measure the specific gravity. Occasionally, healthy pets pass diluted urine, so a single sample is no cause for concern. However, if your pet consistently passes diluted urine, there can be an underlying disease, and further examination is required.
Urine pH and chemical composition – The pH is the measure of the acidity or alkalinity of the urine. Normal levels for cats and dogs range from mildly acidic to mildly alkaline. Extremes beyond the range are likely associated with disease. Measuring the chemical composition involves using a dipstick test. The dipstick has a series of testing pads that measure different chemical components. The testing pads will react and change color. The coloring is then compared to a chart that translates the colors’ intensities to actual measurements.
Examining sediment – The most common foreign bodies found in urine sediment are red or white blood cells, tissue cells, bacteria, and crystals. Mucus or other debris is common in free catch samples.
– Red blood cells can be found in small numbers in urine collected with cystocentesis or catheterization. An excessive amount of red blood cells can indicate internal bleeding, commonly caused by bladder stones, infection, trauma, cancer, etc.
– White blood cells can be found in small numbers in urine collected during free catch. An excessive amount of white blood cells typically indicates inflammation of the urinary system. This inflammation is often caused by bacterial infection.
– Other tissue cells are often seen in urine collected by catheterization. While typically not associated with any disease, an increase in tissue cells can also be seen with diseases such as cancer, prostate issues, bladder stones, or urinary tract inflammation. If cells appear abnormal, further testing may be required to determine if there is any underlying disease.
– Bacteria present in the urine indicate a very high chance of a bacterial infection somewhere in the urinary system. The urine is cultured to determine the types of bacteria present and which antibiotics should be used to treat the infection.
– Crystals found in urine can vary in size, shape, and color, and they do not always indicate disease. Some crystals can help diagnose certain conditions, such as bladder infections or kidney stones. Crystals can also provide information to help determine how the found conditions should be treated or managed.