All about urine: Longitudinal examination of urine pH, specific gravity, proteins, culture, and resistance profiles in healthy dogs

Background Urine is routinely evaluated in dogs to assess health. Reference ranges for many urine properties are well established, but the scope of variation in these properties over time within heathy dogs is not well characterized.

Objectives Longitudinally characterize urine properties in healthy dogs over 3 months.

Animals Fourteen healthy client-owned dogs.

Methods Dogs were evaluated for health; then, mid-stream free catch urine was collected from each dog at 12 timepoints: Mornings / afternoons of Days 1, 2, 3; end of Weeks 4, 5, 6, 7 and Months 2 and 3. Urine pH, urine specific gravity (USG), protein, cultures, and antimicrobial resistance profiles were evaluated at each timepoint.

Results Urine pH varied significantly within and between dogs over time (Friedman’s test: within p = 0.031; between p < 0.005). However, USG, protein, and bacterial richness of urine were consistent within dogs over time, and only varied significantly between dogs (Kruskal-Wallis: between all p < 0.005). Antimicrobial resistant isolates were identified in 13 out of 14 dogs with 71% (34 of 48) of the isolates demonstrating resistance to amoxicillin.

Conclusions and clinical importance 1) Urine pH should be assessed at multiple timepoints via pH meter prior to making clinical decisions. 2) Mid-stream free catch urine from multiple healthy dogs yielded high concentrations of bacteria in culture (>10⁵ CFU/mL) and should not be considered the only indicator of urinary tract infection. 3) Bacterial isolates demonstrated widespread resistance to amoxicillin / oxacillin underscoring the need for antimicrobial stewardship.