The method of urine sampling is not a valid predictor for vesicoureteral reflux in children after febrile urinary tract infections

Abstract

Introduction: The likelihood of detecting vesicoureteral reflux (VUR) after febrile urinary tract infections (UTI) in children logically should correlate with the correct diagnosis of the UTI. Beneath the unspecific symptoms of fever urine analysis is the main diagnostic criterion for the exact diagnosis of febrile UTIs in children. Use of inadequate urine sampling techniques during diagnosis may lead to impaired accuracy in UTI diagnosis. This could lead to the assumption that children, having diagnosed their UTI by the use of possibly inadequate urine sampling techniques should not be evaluated as consequently compared to those, where the diagnosis relied on sterile urine sampling techniques. We hypothesized that children with possibly contaminated urine samples during the initial diagnosis may show a lower rate of VUR in subsequent VCUGs because of a wrong diagnosis initially compared to children, where accurate urine sampling techniques were used.

Patients: Between 2009 and 2014, a total of 555 patients underwent a primary VCUG at our department indicated because of febrile UTIs. Patients with urine collection methods other than bag urine and catheter/suprapubic aspiration (SPA) were excluded from this study (mid-stream urine, potty urine, n = 149). We evaluated 402 patients (male/female 131/271, mean age 1.91 years), VUR rates and grades were compared between patients where urine was sampled by the use of a urine bag only at the time of diagnosis (n = 296, 73.6%) and those where sterile urine sampling (catheter, suprapubic puncture) was performed (n = 106, 26.3%). 4 patients were excluded due to equivocal data on urine sampling.

Results: VUR rate in children after sterile urine sampling using a catheter or SPA accounted to 31.1%. In those where urine samples acquired by the use of urine bags were used, 33.7% showed VUR on subsequent VCUG (p = 0.718). There were no significant differences as to VUR grades or gender, although VUR was much more commonly diagnosed in female patients (37.0% vs 28.2%, p = 0.227) (Figure).

Conclusion: Children diagnosed with their UTI by use of bag urine in our experience carried the same risk of showing a VUR in a subsequent VCUG compared to those, where the initial diagnosis relied - beneath clinical criteria - on urine samples acquired by suprapubic puncture or catheterization. Consequently urine-sampling technique during initial UTI diagnosis alone should not be used as predictor for the reliability of UTI diagnosis and should not influence the further management after UTI.

Keywords: Urinary tract infection; Urine sampling; Vesicoureteral reflux.