Bladder debris on ultrasound as a predictor for urinary tract infections in a pediatric population
Scott M. Stevenson, MD, William C. Andolsek, MD, Angela P. Presson, Ph.D., Glen A. Lau, MD, Patrick C. Cartwright, MD.
University of Utah, Salt Lake City, UT, USA.
BACKGROUND: Debris within the bladder is commonly seen on ultrasound and its presence or absence is often reported by radiologists. The etiology of bladder debris is varied and includes urinary tract infection (UTI). The likelihood that urinary debris represents a UTI is not defined, thus limiting the usefulness of this finding. We hypothesize that bladder debris will increase the likelihood that a UTI is present compared to those without bladder debris.
METHODS: We tested our hypothesis with a retrospective review performed on children age 0 to 17 years who had a VCUG with a catheterized urinalysis or urine culture performed on the same day, 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. Positive UTI was defined as a single bacterial strain ≥50,000 cfu/mL. Presence of bladder debris was reliably documented on ultrasound reports, including a subjective determination of the bladder debris severity. Baseline demographic information, including findings of reflux and hydronephrosis were compared. Sensitivity, specificity, and risk ratios were calculated in usual fashion for predicting UTI in patients with urinary debris on ultrasound.
RESULTS: A total of 445 patients met inclusion criteria between January and December 2014. The overall UTI rate was 20%, and the overall rate of bladder debris was 22% for the population. Median age for those with and without bladder debris was 6.6 years and 5.5 years, respectively (p=0.02). 23% of girls had bladder debris, compared to 12% of boys (p=0.04). The sensitivity and specificity for bladder debris in detecting UTI was 52% and 86%, respectively. 47% of those with bladder debris were infected, compared to 12% of those without bladder debris (p<0.01). The relative risk of infection if debris is present is 3.90 (95% CI: 2.73-5.55). Only minor differences were observed comparing the subjective assessment of bladder debris severity (mild, moderate, or severe). Presence of hydronephrosis or vesicoureteral reflux does not affect the positive relationship observed between bladder debris and presence of urinary tract infections.
CONCLUSIONS: Nearly half of pediatric patients undergoing urological evaluation and found to have bladder debris on ultrasound will have a UTI. Debris is noted more commonly in girls and at a slightly higher age. The presence of debris increases the risk of UTI by nearly 4-fold, regardless of debris severity, hydronephrosis, or vesicoureteral reflux. Given this, it is of value for radiologists to routinely document 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.
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