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Are Imaging Studies Useful Predictors of Renal Scarring After Febrile UTI?

Ultrasonography, voiding cystography, and DMSA scintigraphy performed immediately after a first UTI provided little clinical value.

Questions persist about treatment of febrile urinary tract infections (UTIs) in children. Although oral antibiotics have been shown to be as effective as parenteral antibiotics, prophylaxis for low-grade vesicoureteral reflux remains controversial, and no consensus exists about which radiologic studies should be performed.

Investigators prospectively compared the accuracy of routine imaging studies for predicting renal scarring after a first febrile UTI among 300 children (age range, 1 month to 2 years) at 28 pediatric centers in Italy. Children with abnormal renal anatomy on prenatal ultrasounds were excluded. Children underwent ultrasonography and dimercaptosuccinic acid (DMSA) scanning within 10 days after starting treatment and underwent voiding cystourethrography (VCUG) within 2 months. Patients with DMSA scans positive for acute pyelonephritis underwent repeat scintigraphy 1 year later to detect scarring (63 were lost to follow-up and not included in the analysis).

Only 38 children (13%) had abnormal ultrasound results, and 66 (22%) had vesicoureteral reflux detected by VCUG (4 had grade IV or V reflux). Of 161 children (54%) with initial DMSA scans consistent with acute pyelonephritis (showing focal or diffuse areas of uptake), 45 of the 98 patients available for follow-up had evidence of renal scarring at 1 year. Both ultrasonography and VCUG had low positive predictive values (31.6% and 34.8%, respectively) for renal scarring.

Comment: The study authors conclude that DMSA scans are clinically useful only when conducted 6 to 12 months after a first febrile UTI, and that other imaging studies are warranted only for subsequent UTIs or if prenatal ultrasound results are not available. However, if radiologic exams are postponed, some patients could be lost to follow-up, and some parents might not want their children to undergo invasive VCUG or DMSA scans many months after symptoms have ceased. Before we drastically change our protocol for febrile UTIs, we need to know if and how the results of these three radiologic studies change after a second febrile UTI and whether age affects risk for renal scarring.

— Robin Drucker, MD

Published in Journal Watch Pediatrics and Adolescent Medicine February 25, 2009

Citation(s):

Montini G et al. Value of imaging studies after a first febrile urinary tract infection in young children: Data from Italian Renal Infection Study 1. Pediatrics 2009 Feb; 123:e239. (http://dx.doi.org/10.1542/peds.2008-1003)

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