Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Urine: It's Not Just Waste!

Pet Column for the week of July 7, 2003

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Ann Marie Falk
Information Specialist

You can learn a lot from urine. This smelly yellow liquid provides a variety of clues that help a veterinarian solve the mystery of your pet's health.

Like people, pets should have urine that is yellow and has an unmistakable odor. Most pets develop a pattern and will urinate with the same frequency each day.

"Changes in frequency of urination, blood in the urine, and pain upon urination are common signs of infection. Owners are very good at picking up on these signs and mentioning them to their veterinarian," says Dr. Anne Barger, a veterinary clinical pathologist at the University of Illinois College of Veterinary Medicine in Urbana.

There are three ways of collecting urine. Your veterinarian may ask you to bring in a urine sample collected with the 'free catch' method. Take your dog for a walk and when he lifts his leg, deftly catch the urine in a plastic container. To speed up the process you can feed your dog several ice cubes before setting out on the walk. Free catch does not require intensive labor, money, or time, nor does it upset your pet.

The other two methods are done at a veterinary clinic. A urinary catheter can be placed to collect urine directly from the bladder. The other method, called cystocentesis, requires a veterinarian to direct a needle through the abdominal wall into the bladder to collect a sample. These two collection procedures require the animal's cooperation and often require sedation.

"It is important that the urine sample is fresh. Urine can be preserved for a short time in the refrigerator," advises Dr. Barger. The first thing examined is the urine sediment, which refers to cells floating in the urine. "An increased number of white blood cells signals inflammation and helps diagnose a bladder infection. A decrease in urine flow is the No. 1 cause of bladder infections, allowing bacterial growth. Sometimes the bacteria may be present in the sediment," says Dr. Barger.

Female dogs are more prone to urinary tract infections. This is due to the long length of their urethras. Male cats are at risk of developing a blockage. Diabetic animals have an increased amount of glucose in urine, which may promote bacterial growth and resulting infection.

Animals can form bladder stones if urine flow is decreased or the bladder wall is irritated. Stones can be seen on radiographs (X rays) and with ultrasound. If surgery is required to remove stones, a dietary change may be instituted to help prevent stone formation.

Examining the urine can help diagnose renal disease, which means functional problems with the kidney. Your veterinarian will check the specific gravity of the urine. Specific gravity compares the weight of urine to the weight of water. It tells us how well the animal is concentrating its urine. Urine is concentrated as blood is filtered through the kidney. If the kidney is abnormal, the concentration of urine may be altered.

Casts and crystals can also be found in urine. Various minerals can solidify in urine to form crystals. The presence of calcium oxalate crystals, for example, can be found with ethylene glycol toxicity. Ammonium biurate crystals are red flags for liver disease. Silica crystals can be formed in the presence of bladder stones.

The kidney is composed of a series of tubules that aid in making urine. Substances are either absorbed or excreted in the tubes. Formation of casts highlights a problem with the tubules in the kidney. Casts are solid clumps of protein cells or red and white blood cells. These cells collect in the tubules and are shed sporadically. These casts are tube-like in shape and can be seen with a microscope.

Urine is so much more than a waste product. It provides many interesting diagnostic clues that help determine what's going on inside your pet!

Contact your local veterinarian for more information or if you are concerned about your pet has a bladder infection.