Imaging Strategy for Infants with Urinary Tract Infection: A New Algorithm

The Journal of UrologyVolume 185, Issue 3 , Pages 1046-1052, March 2011

Link to article:
http://www.sciencedirect.com/science/article/pii/S0022534710049220

Article Review:

Starting in June 2002, pediatric researchers at Sweden’s University of Gothenburg performed a 3-year prospective investigation on 161 male and 129 female infants under 1 year of age with a first-time urinary tract infection. Ultrasound and DMSA scans were performed on all infants with a positive urine culture, and a VCUG was done within two months on these patients.

Diagnostic criteria used were “any growth of bacteria in urine from suprapubic bladder aspiration, or greater than 100,000 colony-forming units in urine from 2 midstream or bag samples.”

The objective was to identify those patients with renal scarring following their first febrile UTI.  A follow-up DMSA scan was performed one year later on infants with an abnormal initial DMSA scan and/or recurrent febrile UTI.

Of the initial 290 infants, 270 were followed through the first year of the study. From this group, 70 were found to have renal scarring.  The researchers applied a multiple regression analysis to assess risk of renal scarring.  Variables such as C-reactive protein, anteroposterior diameter of kidneys on ultrasound, serum creatinine, fever, non- E. Coli bacteriuria, and recurrent febrile urinary tract infections were all studied.  Infants with a CRP of 70 mg/L or greater, combined with a A-P kidney diameter on ultrasound of 10 mm or more, had the highest risk of renal scarring. 

Together, these two variables had 87% sensitivity and 59% specificity.

The authors offered an algorithm for imaging based on their findings:

If anteroposterior kidney diameter is < 10mm on ultrasound AND  CRP < 70 mg/L  >> No further imaging necessary

If anteroposterior diameter ≥ 10 mm  -OR- CRP ≥ 70 mg/L  >> DMSA scan should be performed

If DMSA is normal >> No further imaging

If DMSA is abnormal >> A VCUG should be performed

Commentary by Andrew Huang, MD, Pediatric Urology, Roseville:

DMSA renal scan and C-reactive protein may have a role in helping to delineate children at highest risk of renal scarring or who already have scarring. These children are more likely to have high grade reflux and therefore may benefit from early diagnosis and antibiotic prophylaxis.

Children with an elevated lead level should be referred via eConsult to the Toxicology service in San Jose or South Sacramento.  Specialists from those departments will evaluate each case by TAV or in the clinic if deemed appropriate.