Association between ultrasonographic appearance of urine and urinalysis in dogs and cats.

OBJECTIVE

To evaluate association between ultrasonographic urine echogenicity and sediment examination in dogs and cats.

MATERIALS AND METHODS

Dogs and cats undergoing ultrasound-guided cystocentesis at a multidisciplinary referral hospital. Ultrasonographic images were stored and reviewed by a single, blinded, board-certified radiologist. Urine appearance was described as "echoic" or "anechoic". Urine sediment was examined for bacteriuria, pyuria, haematuria, crystalluria and urine-specific gravity and then classified as "active" or "inactive."

RESULTS

Of the 194 cases included in this study, urine was echoic in 52 and anechoic in 142. Sediment was active in 52 and inactive in 142 samples. Sensitivity and specificity of echoic urine for active sediment were 40% (95% CI: 27 to 55%) and 78% (95% CI: 70 to 85%), respectively. Positive predictive value and negative predictive value of echoic urine for active sediment were 40% (CI 30 to 52%) and 78% (CI 74 to 82%), respectively. If urine-specific gravity was <1.015 urine was always described ultrasonographically as anechoic.

CLINICAL SIGNIFICANCE

Association between sediment analysis and ultrasonographic appearance of urine is poor. Echoic urine had low positive predictive value for active sediment in this study, suggesting that echoic urine alone should not prompt urinary investigations in the absence of other clinical suspicion. Despite a negative predictive value of 78%, urinalysis is still indicated for anechoic urine, especially if urine specific gravity is low.