To Pee or Not to Pee…
A few months ago, one of my blog posts discussed the myriad of reasons why we want to examine your pet’s poop each year. Equally as important as checking your pet’s poop is to check their other waste product- their urine. It’s not that we’re fascinated by your pet’s bodily functions- trust me. In the case of their urine, we are interested in knowing how your pet’s organs are functioning- specifically the kidneys and the urinary tract including their bladder. You’d be surprised at how much a few ounces of the yellow stuff can tell us.
The kidneys act as a filter removing waste products as well as other metabolized products from your pet’s blood. Without going into too much biology, the waste travels from the kidneys into the bladder through the ureters where it is stored until your pet urinates. The urine your pet passes holds what we call ‘sediment’- which is one of the many things the complete urinalysis will test. More on this later.
The sediment will tell us the health of the cells and many of the structures contained within the urinary tract. The complete urinalysis will also give us information about how the kidney’s components are functioning and your pet’s metabolic and fluid status as well as check for other substances which may indicate potential underlying disease.
How do you collect the urine?
This is probably the least scientific part of the process- at least for dogs. For most of our dog samples, we will use the ‘free catch’ method- where we use a large soup ladle (or something similar) to collect the sample as your dog urinates. The sample is then transferred to a sample jar or urine tube and then sent to the testing lab. You may be thinking that this is not a ‘sterile’ sample. You’re right, although the ladle is clean, the sample is not completely sterile. The urine has passed all the way through their system, through the urethra, and since we cannot clean the penis or vulva of a dog, it can get contaminated by bacteria which are not associated with a true bladder infection. There is always the potential for bacterial contamination in a naturally collected urine sample, which is called a “free catch” or “voided sample”.
We usually try to get a direct sample from the bladder (known as a “cystocentesis”), using the ultrasound to guide us to obtain a sterile urine sample. This sample via cystocentesis is a more accurate representation of what is going on inside of your pet and where in the urinary tract the problem is happening. If there any bacteria in this sample, we know that it is a true bladder infection. Most pets tolerate this sample collection technique well, pending their temperament.
Rarely, we may opt to catheterize your pet to collect their urine- but this is usually done with sedation to help keep your pet comfortable. We want to make this as comfortable as possible for your pet.
A urine culture and sensitivity may also be needed at your visit to tell us the name of what bacteria is growing in your pet’s bladder. Depending on the bacteria, the sensitivity tells us which antibiotic works best for your pet’s infection. The Urine culture and sensitivity is especially helpful in pets with bladder stones and/or urinary tract infections. We also recommend doing urinalysis and urine culture and sensitivity testing prior to some surgeries.
What are you looking for?
The easiest thing to analyze is the color. It’s not like going to your paint store and looking for a specific shade of yellow. We generally categorize the colors into three categories.
Clear to light yellow
Bright or dark yellow
We’re wanting to see clear to light yellow. This indicates that your pet is getting proper hydration. Some yellow is good, since that means your pet is concentrating their urine- while clear urine could mean they’re drinking too much water or is not able to concentrate their urine- which could be a sign of trouble.
If your pet’s pee is bright or dark yellow, it is most likely due to dehydration or other issues with the kidneys. It could be caused by a lack of adequate drinking water or because of other medical conditions. If you notice that your pet’s urine is bright or dark yellow, consult your veterinarian immediately.
Brown, orange or reddish-pink urine is also troublesome. If your pet has suffered an injury, or is stressed for any reason, their body may produce a protein called Myoglobin. Your pet’s muscles release this protein and it is excreted through their urine, causing it to turn brown or a shade of orange depending on the concentration.
Other issues such as kidney/bladder stones, infections and blood resulting from such could also stain your pet’s urine. If you notice a brown or pinkish hue to your pet’s pee, it may be a result of blood in the urinary tract. A trip to your veterinarian is needed.
Other items we will check when doing a complete urinalysis:
What is Specific Gravity and how does it help detect disease?
It may help to think of urine specific gravity as the density of the urine. A healthy kidney should produce dense (concentrated) urine, while watery (dilute) urine may signal underlying disease.
One of the kidney’s jobs is to maintain the body’s water level within relatively narrow limits. If there is an excess of water in the body, then the kidneys allow the excess water to pass out in the urine, and the urine becomes more watery or dilute. If there is a shortage of water in the body (as in dehydration), then the kidneys reduce the amount of water lost in urine, and the pet passes more concentrated urine.
Normal animals may pass dilute urine from time to time during the day, and a single dilute urine sample is not necessarily a cause for concern.If a pet continues to pass dilute urine, then there could be underlying kidney or metabolic disease and further investigation is recommended.
What is urine pH and why is it measured?
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.
How is the chemical analysis of the 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 are detected by the chemical analysis of urine?
The presence of protein in urine is called proteinuria. 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 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 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 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.
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 hemoglobinis released. Hemoglobin passes into theurine 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 fibres 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.
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 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.
Why examine the 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.
What sorts of things can be found in a urinary sediment and what do they mean?
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.
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 forculture and sensitivity testingto find out what types bacteria are present and which antibiotic should be used to treat the infection.
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.
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 acytological preparation of the sediment, which allows for a more detailed examination of the tissue cells.
Sometimes, we’re not really interested in everything that we’ve listed here. Sometimes, we may just be looking for less information to diagnose or rule out a specific disease or illness. A complete urinalysis should be done annually, just like a fecal test- so we can catch any potential issues before they become a bigger problem.