Abstract
Objective
An uncontaminated urine culture is a prerequisite for the diagnosis of a urinary tract infection. However, this may be difficult to obtain in small children. We have studied the frequency of ballooning of the prepuce in non-circumcised boys and vaginal reflux in girls during voiding as a possible cause of contaminated urine cultures.
Methods
All micturating cystourethrograms (MCUG) performed in our institution over the last 5 years in children aged 0–15 years were reviewed retrospectively for ballooning of the foreskin or vaginal reflux as a potential source of bacterial contamination. The voiding pictures were routinely done with the catheter present for the first voiding cycle and then removed on the second void.
Results
A total of 526 children (77.4 % boys, 22.6 % girls) were eligible for the study. Ballooning of the foreskin was identified on the micturition pictures of 115 (38 %) boys, with the frequency significantly higher in boys aged <12 months [odds ratio (OR) 4.1; 95 % confidence interval (CI) 2.1–7.3)] and boys with vesicoureteral reflux (OR 1.6; 95 % CI 1.06–2.4). Seventeen girls (14.3 %) showed vaginal reflux. No correlation with age or vesicoureteral reflux was found in the girls.
Conclusion
Ballooning of the prepuce or vaginal reflux was seen on a fluoroscopic MCUG in a large proportion of children during their voiding. This normal phenomenon might cause contaminated urine cultures when the urine is obtained by bag or clean catch.


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Contributors’ statement
Nakysa Hooman conceptualised and designed the study, carried out the initial analyses, drafted the initial manuscript and approved the final manuscript as submitted. Marina Easty designed the data collection, reviewed and revised the manuscript and approved the final manuscript as submitted. Kjell Tullus conceptualised and designed the study, coordinated and supervised data collection, critically reviewed the manuscript and approved the final manuscript as submitted.
All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.
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Tullus, K., Hooman, N. & Easty, M. Flushing of the vagina and the prepuce—a cause for contaminated urine cultures in children. Pediatr Nephrol 32, 107–111 (2017). https://doi.org/10.1007/s00467-016-3463-9
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DOI: https://doi.org/10.1007/s00467-016-3463-9