Little guidance is available regarding the optimal imaging for older children and adolescents presenting with urinary tract infection. We sought to determine the imaging yield from renal bladder ultrasound (RBUS) and voiding cystourethrogram (VCUG) in patients over age 5 presenting with urinary tract infection. We also examined the ability of RBUS to predict VCUG results.
We analyzed 153 patients aged 60 months – 18 years who underwent RBUS and VCUG on the same day. This same-day restriction avoids bias that might be induced if patients underwent RBUS first, and then VCUG only if the RBUS revealed an abnormality. We excluded patients with prior GU imaging or known abnormalities, including antenatal hydronephrosis. This allows us to narrow our focus to a cohort of unscreened patients with respect to prior imaging. We classified urinary tract infections as febrile or nonfebrile and initial or recurrent. Median age was 6.3 years (IQR 5.5, 8.1). Of the 153 patients, 113 (74%) were 5-7 years old, 32 (21%) were 8-11 years old and 8 (5%) were 12-17 years old. A total of 118 patients (77%) were female, 120/153 patients (78%) had a febrile UTI, and 84/153 (55%) had a history of recurrent UTIs.
Overall, no patients had hydronephrosis of moderate grade or greater. There were no abnormal findings on RBUS for 97/153 children (63%). Vesicoureteral reflux was found in 52/153 cases (34%), with 15/153 (9.8%) having reflux of grade III or higher. Findings such as hutch diverticuli or other bladder anomalies were found in 19/153 (12.4%). There was no difference in VCUG or RBUS yield contingent on the urinary tract infection being febrile versus nonfebrile, or initial versus recurrent.
We analyzed the performance characteristics for RBUS in predicting VCUG, and conducted this at four different levels of RBUS positivity and five levels of VCUG positivity; for VCUG at some levels all reflux was included and at others only high grade reflux was included. At all combinations the predictive ability of RBUS was poor with an area under the receiver operating characteristic (ROC) curve of 0.61-0.63 (a value of 1 indicates perfect predictive power and 0.5 indicates predictive power no better than a coin toss).
Imaging findings were common in older children and adolescents with UTI. Severe ultrasound abnormalities were rare. While reflux was found in approximately 1/3rd of the cohort, it was grade III or higher in 1/10th of the children. As in infancy, the correlation between RBUS and VCUG is poor. RBUS should not be used as screening tool in place of VCUG if determination of reflux status is important to the clinician or family.
Written by: Michael Kurtz, MD, MPH Fellow, Pediatric Urology
Reference
J Urol. 2015 May;193(5 Suppl):1778-82. doi: 10.1016/j.juro.2014.10.119. Epub 2015 Mar 25.
Imaging after urinary tract infection in older children and adolescents.
Kurtz MP1, Chow JS2, Johnson EK2, Rosoklija I2, Logvinenko T2, Nelson CP2.