Bladder debris on renal and bladder ultrasound: A significant predictor of positive urine culture

SummaryBackgroundRenal and bladder ultrasound (RBUS) is recommended in evaluation of children after an initial, febrile urinary tract infection. Although it is not uncommon to observe debris within the bladder lumen on sonography, the significance of this finding is uncertain. Debris may be interpreted as an indication of ongoing infection, but there have been no studies to date investigating the association of bladder debris with a positive culture.ObjectiveThe aim of this study was to evaluate the association of bladder debris noted at the time of RBUS with positive urine culture results obtained from a catheterized specimen, among patients undergoing RBUS and voiding cystourethrogram (VCUG) on the same day.Study designWe performed a retrospective cross-sectional study of 3995 patients who presented for same-day RBUS and VCUG. RBUS reports were reviewed for the presence of bladder debris, and analysis was limited to patients under 60 months of age with a catheterized urine specimen sent for culture at the time of the studies. Those with prior postnatal imaging or a diagnosis of prenatal hydronephrosis or other GU abnormalities were excluded. Thirty-four subjects with bladder debris on RBUS were identified and matched to 155 controls based on age, gender, circumcision status, and presence of vesicoureteral reflux. A positive urine culture was defined as ≥50,000 colony forming units per mL of at least one organism. A conditional logistic regression model was used to evaluate the association between debris on RBUS and positive urine culture results.ResultsIn conditional logistic regression stratifying by matching age, gender, circumcision status, and presence of vesicoureteral reflux, there was a statistically significant association between bladder debris on RBUS and positive urine culture result collected on the same day during VCUG (OR 7.88, 95% CI 1.88-33.04, p = 0.0048). This corresponds to a 688% increase in odds of positive urine culture for patients with debris (Table).DiscussionThis is the first study to evaluate the association between bladder debris on RBUS and positive urine culture, and it should serve as a starting point for future investigations. The study is limited in its generalizability to the sampled population; further work should evaluate the predictive value of RBUS debris among children without UTI history, with prior imaging or known genitourinary anomalies, or older children.ConclusionAmong children younger than 60 months old undergoing initial imaging for history of UTI, there is a significant association between bladder debris and a positive urine culture.Table. Urine culture results for patients with and without bladder debris on renal bladder ultrasound (p = 0.0048).Bladder debris (n = 34)No bladder debris (n = 155)Urine culturePositive5 (14.7%)E. coli (1)Enterococcus (1)P. mirabilis (2)P. vulgaris (1)3 (1.9%)E. coli (1)Enterococcus (1)E. cloacae (1)Negative29 (85.3%)152 (98.1%)