The Skinny on Urinalysis

Many days in practice, I see clients with the following concern - “My cat is peeing everywhere” or “My dog has to go out 10 times a day!” Either the pet is urinating in the wrong place, urinating more than normal, or the urine looks abnormal.  These are symptoms of problems with the urinary tract, which includes the kidneys, ureters (tiny tubes that drain urine from the kidneys to the bladder), urinary bladder, and/or urethra.

Urinary problems are a big deal. Apart from skin and dental problems, urinary issues are one of the most common concerns of pet owners that come to our practice. Inappropriate urination is also a significant cause of surrender and/or euthanasia in pets. It can be an  incredibly difficult problem for people to manage – causing significant property damage and even worse, frustration with the issue can be very damaging to the human / animal bond.

There are 4 main reasons why pets urinate inappropriately:

  • Anatomic – young animals who inappropriately urinate may have developmental problems of the urinary tract that cause urine leakage (e.g. ectopic ureters)
  • Neurologic – damage to the nerves that control the process of urinating can lead to inappropriate urination for a number of different reasons (e.g. older female dogs with urinary sphincter mechanism incompetence or USME).
  • Disease- infectious, inflammatory, metabolic, endocrine and cancerous diseases can all affect the urinary system and cause inappropriate urination (e.g. bladder stones, diabetes, Cushing’s disease, transitional cell carcinoma, renal disease…)
  • Behavior – some pets may develop inappropriate urination habits secondary to poor early training (sometimes seenin older adopted dogs), territoriality, boredom, fear or even obsessive / compulsive types of problems.

An accurate diagnosis is critical to effective treatment when it comes to urine.  Remember, though tests may be a little costly, treating the wrong thing is ultimately even more expensive.  Imagine treating a behavior problem for several months when actually the problem was an infection that could have been treated with a single round of antibiotics!

For starters, ALL pets that present with inappropriate urination need to have a urinalysis. My vet school clinical pathology professor, Dr. George, used to call it a “liquid renal biopsy”.  There is a lot of information we can get from the urinalysis, which is comprised of three parts:

1) The test strip – this is a color based chemical test that looks for the presence of blood, white blood cells, glucose, protein, ketones, bilirubin (blood breakdown) and checks the pH.  Although not perfectly accurate, they are a good screening test for diseases such as urinary tract infections and diabetes mellitus, to name a couple.

2) The sediment exam – for this the urine is centrifuged, and the cells are examined under a microscope. This is a more sensitive test for the presence of blood, renal casts, fungal organisms and bacteria in the urine, and it also allows us to determine if there are urinary crystals, which can be an indicator of stone formation in the bladder.

3) The urinary specific gravity – This is a number, usually between 1.002 and 1.060, that essentially indicates the density of urine as compared to water. When there is an excess of water in the body, the kidney produces a diluted urine, and the specific gravity will be less than 1.008.  If not, then it produces a concentrated urine, which is indicated by a specific gravity of 1.025 or greater.  The specific gravity will change throughout the day depending on hydration. If the urine is in the middle range, neither concentrated nor dilute, it’s called isosthenuria. If the kidneys are only able to produce isosthenuric urine, it means that the kidneys have lost about 60 – 70% of their functional capability and the pet is in early renal failure. If we can detect renal failure early, before there are changes in the bloodwork, we have a much better chance of managing it successfully for a longer period of time.  If urine is isosthenuric the doctor will often ask you to submit a urine sample from the first morning urine, when it should be more concentrated.

The other test that can be very important in determining the cause of urinary problems is called a urine culture and antibiotic sensitivity. This is where we collect urine in a sterile manner, usually with a needle directly in to the bladder wall (cystocentesis). We then submit it to our reference laboratory, whose technicians apply the urine to a bacterial culture medium. Urine should normally be sterile, so if any bacteria grow, then that is a positive test for a bacterial urinary tract infection.  The lab then tests the bacteria against a number of commonly used antibiotics to determine which ones it is sensitive to so that we know the best antibiotic to use. False negatives can sometimes occur if the pet has been on antibiotics.

Once we have information from the preliminary urine tests, we may move on to secondary testing. For example, if test results indicate the possibility of stones in the bladder, urethra or kidneys, we may do an x-ray or ultrasound to look more closely.  Many other tests exist for following up on urinalysis and culture results that can help us make sure we make the right diagnosis and get the right treatment started for your pet.

I hope this helps give you an idea of how we look at the world of inappropriate urination in dogs and cats. If you have a pet that you suspect of a urinary problem, please bring him or her in for evaluation as soon as possible. If you can bring us some urine that is great, but our veterinary technicians and assistants are pro’s at obtaining urine, so if you can’t, don’t worry, we’ll catch it!