Q: My 14-year-old female cat, Buttercup, has a problem that makes her urinate frequently, and in the tub there is blood in her urine. My veterinarian puts her on antibiotics for two weeks and the problem goes away for a while. But over this past year and a half, the problem has recurred three times. Urine tests reveal bacteria but no crystals, and blood tests show nothing abnormal. What could this be?
A: It seems Buttercup has read the Good Kitty Instruction Manual (and no, I don't have a copy: it's known only to cats). Felines with virtually any kind of problem in the bladder or the urethra usually attempt to urinate more frequently than normal, often spending an inordinate amount of time straining in the litter box - enough so that the problem may be misinterpreted as constipation. They sometimes prefer urinating on a cool, smooth surface like the sink or bathtub, and there may be blood visible in their urine. Many affected cats spend a lot of time licking their genital area. (An obstruction of the urethra, mostly a problem in males and neutered males, can cause similar signs and is a VERY SERIOUS condition that requires immediate veterinary attention.)
As you might imagine, there are lots of different feline lower urinary tract diseases, including infections (bacterial, fungal, parasitic, and probably viral as well); urinary stones of various types, sizes, and locations; and even cancer. The specific cause of many cases of lower urinary tract disease remains elusive despite exhaustive diagnostic testing. In such cases, veterinarians use the term idiopathic cystitis. Some idiopathic cases are similar to a human disease called interstitial cystitis.
So are the bacteria "real"?
Bacterial bladder infections in cats are relatively rare. In young to middle-aged cats, only one to three percent of cases of lower urinary tract disease are found to be caused by bacteria; the number hovers around 10 percent in cats over 10 years of age.
How was the sample collected?
If the answer is, "the cat urinated on the exam table, and my veterinarian sucked some of it up into a syringe," or, "my veterinarian gently squeezed the bladder and collected some urine in a cup as it was coming out," I become skeptical about whether the bacteria are causing an infection. Bacteria normally reside in the lower part of the urethra, so finding them in a "free catch" sample is usually meaningless. The resident bacteria were probably just caught up in the stream on the way out. Likewise, unless the urine is collected into a sterile container, the bacteria may just be innocent bystanders. The most accurate way to know that the bacteria are "real" is by passing a sterile needle attached to a sterile syringe directly into the bladder and withdrawing a urine sample. When properly performed in a relaxed cat, this procedure is safe and simple with virtually no adverse effects, and is the method of choice for collecting urine for bacterial culture.
Another thing to consider is how long and in what manner the urine sample was stored prior to submission to a laboratory for bacterial culture. A lot can happen between the time a sample leaves the cat's bladder and arrives at the laboratory (for example, bacterial counts can double every 20-40 minutes in warm urine). To be on the safe side, veterinarians may choose to check with the laboratory to determine their preferred method of sample handling and submission.
I caution against assuming that Buttercup's temporary response to antibiotics is proof she has a bacterial infection. Many cases of lower urinary tract disease naturally wax and wane, so antibiotics may have nothing to do with the remission. But if it turns out Buttercup does indeed have a bacterial infection, it would be prudent to look for predisposing conditions like bladder stones or diabetes mellitus. Correcting any conditions found, choosing the best antimicrobial medication based on information from the diagnostic laboratory, and treating for an appropriate amount of time - usually a number of weeks - is the best way to assure treatment success.