What is the significance of pyuria?
Multiple factors can influence white-cell count; culture for bacteria
May 01, 2006
A voided urine sample was obtained from a 12-year old spayed female Dachshund as part of an annual evaluation of health status. According to the owners, the dog was in good health. The dog had a history of aerobic bacterial lower urinary tract infections on three occasions during the past five years. The three episodes of lower UTI were caused by three different species of bacteria and were eradicated by appropriate antimicrobial therapy. An underlying cause for the recurrent lower UTI could not be found. The most recent episode of UTI occurred one year previously. Urinalysis of a voided sample collected by the owner revealed: specific gravity = 1.025; pH = 7.5; protein = 1+; leukocyte esterase test for white cells = negative; RBC in sediment = 0 to 1 per highpower field; white cells in sediment = 1 to 3 per high-power field. No other abnormalities were detected. Results of a CBC and serum chemistry profile were also normal. Is this magnitude of pyuria of clinical significance in this dog? What is the basis for your answer? Are additional diagnostic tests or treatment warranted?
Points to consider:Leukocyte test pads: Leukocyte test pads frequently give false-negative test results in dogs, even when pyuria is present. Although the test is specific for white cells in dogs, it is very insensitive. In contrast, leukocyte test pads give false-positive test results in most cats in absence of pyuria, and therefore are of no value in this species. Therefore, it is important to evaluate fresh urine sediment to determine the presence or absence of pyuria in dogs and cats.
Urine sediment: Using standardized technique, urine sediment should be evaluated for white cells. Significant numbers of white cells (which may be associated with RBC and protein) in a properly collected sample suggest an inflammatory lesion of the urinary tract. The inflammatory lesion may or may not be associated with infectious agents. The question related to our Dachshund is, "What number of white cells is significant?"
Additional diagnostic points:
2) A positive urine culture in the absence of pyuria should arouse suspicion that the bacteria are contaminants. However, bacterial UTI can occur without detectable concomitant pyuria in patients given glucocorticoids, those with hyperadrenocorticism and those who are immunosuppressed. Therefore, absence of pyuria should not be interpreted as unequivocal proof that bacterial UTI can be excluded.