Bladder debris on ultrasound as a predictor for positive urine culture in a pediatric population

Debris within the bladder is commonly seen on ultrasound. The etiology of bladder debris is varied and the likelihood that urinary debris represents positive urine culture is under investigation. We hypothesize that bladder debris will increase the likelihood that a urine culture is positive compared to those without bladder debris.

We performed a retrospective review on children aged 0-17 years who had a voiding cystourethrogram with a catheterized urinalysis or urine culture, and who also had a renal and bladder ultrasound up to 1 week prior, the day of, or up to 2 days after their urine studies. Presence of bladder debris and debris severity was recorded. Positive urine culture was defined as a single bacterial strain ≥50,000 cfu/mL. Demographic information, including findings of reflux and hydronephrosis were compared. Sensitivity, specificity, and risk ratios were calculated for predicting positive urine culture in patients with urinary debris on ultrasound.

A total of 445 patients met inclusion criteria between January and December 2014. The positive urine culture rate was 20%, and the rate of bladder debris was 22%. The mean age for those with and without bladder debris was 6.6 and 5.5 years, respectively (p = 0.02). 23% of girls had bladder debris, compared to 12% of boys (p = 0.04, see results table). The sensitivity and specificity for bladder debris in detecting positive urine cultures was 52% and 86%, respectively. Forty-seven percent of those with bladder debris had positive cultures, compared with 12% of those without debris (p < 0.01). The relative risk of positive urine culture if debris is present is 3.90 (95% CI 2.73-5.55). Hydronephrosis or vesicoureteral reflux did not affect the relationship between bladder debris and positive urine cultures.

Nearly half of pediatric patients undergoing urological evaluation found to have bladder debris on ultrasound will have a positive urine culture. Debris is noted more commonly in girls and at a slightly higher age. The presence of debris is associated with a fourfold increase in detecting a positive urine culture, regardless of debris severity, hydronephrosis, or vesicoureteral reflux. Given this, it is of value to routinely document and look for the presence of any amount of bladder debris seen on ultrasound, as this finding can be used to augment clinical decision-making and warrants strong consideration for obtaining urine culture.