Comparison of routine urinalysis and urine Gram stain for detection of bacteriuria in dogs

Objective To determine the utility of performing urine Gram stain for detection of bacteriuria compared to routine urine sediment examination and bacterial aerobic urine culture. Design Prospective, observational study. Setting University teaching hospital. Animals Urine samples acquired via cystocentesis through convenience sampling from 103 dogs presenting to a tertiary referral institution. Interventions All samples underwent routine urinalysis, including sediment examination, as well as urine Gram stain and quantitative bacterial aerobic urine culture. Measurements and Main Results The urine Gram stain demonstrated improved sensitivity (96% versus 76%), specificity (100% versus 77%), positive predictive value (100% versus 83%), and negative predictive value (93% versus 69%) when identifying bacteriuria, compared to routine urine sediment examination. Conclusions The urine Gram stain is highly sensitive and specific when detecting the presence of bacteria in canine urine samples. Gram staining should be considered when bacteriuria is highly suspected and requires rapid identification while bacterial culture is pending.