Bladder Debris on Renal and Bladder Ultrasound: A Poor Predictor of Positive Urine Cultures
Joseph W. McQuaid, MD, Michael P. Kurtz, MD, MPH, Tanya Logvinenko, PhD, Caleb P. Nelson, MD, MPH.
Boston Children's Hospital, Boston, MA, USA.
BACKGROUND:
Renal and bladder ultrasound (RBUS) is recommended in the evaluation of children after an initial, febrile urinary tract infection. While it is not uncommon to observe debris within the bladder lumen on sonography, the significance of this finding is uncertain. In some cases, debris in interpreted as an indication of ongoing infection, but there have been no studies to date demonstrating this association. The aim of this study is to evaluate the association of bladder debris noted at time of RBUS with positive urine culture results from a catheterized specimen, among patients undergoing RBUS and voiding cystourethrogram (VCUG) on the same day.
METHODS:
A total of 3995 patients were identified with RBUS and VCUG performed on the same day. 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 were excluded. 33 subjects with bladder debris on RBUS were identified and matched to 153 controls based upon age, gender, circumcision status, and presence of hydronephrosis. 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.
RESULTS:
The median age of the cohort was 17 months (IQR = 5-34) and 68.8% were female. No statistically significant association between debris on RBUS and positive urine culture result was detected (OR=2.03, 95% CI: 0.42-9.79, p=0.3791). In a multivariate model adjusting for age, presence of debris on RBUS was still not significantly associated with positive urine culture; however, age had a significant association with positive urine cultures, with odds of a positive urine culture decreasing by 77% for every 1-month increase in age (OR=0.23, 95% CI: 0.07, 0.80, p=0.0208)
CONCLUSIONS:
The presence of bladder debris on RBUS is not predictive of a positive urine culture at time of evaluation for an initial urinary tract infection. Whether these conclusions may be applied more broadly to all children, including those presenting with clinical signs or symptoms of urinary tract infection, remains to be determined. However, this is the only study to date to consider the predictive value of echogenic bladder debris on ultrasound. 
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