This question was asked during a recent CE session: In checking for bacterial UTI on urinalysis, is doing a slide where urine is spread in monolayer (like a blood smear) and staining in diff-quick - can this technique be used to look for bacteria?
YES preparing a DIFF QUICK stain of a spread of the urine sediment is a good idea to increase one’s confidence that bacteria are really there (or not). Staining with Gram stain can also provide meaningful information as to whether bacteria are there, and if so, are they Gram negative or Gram positive.
Many things in cat urinary sediment look like real bacteria but they are something else - small crystals, small lipid droplets, cellular detritus, etc. Brownian motion of these small particles adds to the suspicion that they may be bacteria.
In the absence of an increase in the WBC in the urinary sediment and in the face of concentrated urine above 1.035 - it becomes way less likely that a real bacterial UTI exists. Quantitative urine culture (cfu/ml) is still the gold standard as to whether there is really a bacterial UTI or more likely NOT.
