One in six children with initial urinary tract infection will have renal scarring on follow-up

Article Outline

• Question
• Design
• Data Sources
• Study Selection and Assessment
• Outcomes
• Main Results
• Conclusions
• Commentary
• Copyright

Shaikh N, Ewing AL, Bhatnagar S, Hoberman A. Risk of renal scarring in children with a first urinary tract infection: a systematic review. Pediatrics 2010;126:1084-91.

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Question 

Among children with an initial urinary tract infection (UTI), what is the risk of renal scarring?

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Design 

Systematic review.

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Data Sources 

Medline and Embase were searched for articles that addressed the prevalence of dimercaptosuccinic acid (DMSA) scan abnormalities in children 0 to 18 years of age after a first UTI.

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Study Selection and Assessment 

Of 1533 articles found by the search strategy, 325 full-text articles were reviewed; 33 studies met all inclusion criteria. A standard abstraction tool was used to collect data for each study. The authors assessed study quality by examining whether enrollment was consecutive and whether each study was done prospectively.

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Outcomes 

Data on the prevalence of abnormalities on acute-phase (≤15 days) or follow-up (>5 months) DMSA renal scans.

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Main Results 

Among children with an initial episode of UTI, 57% (95% CI, 50-64) had changes consistent with acute pyelonephritis on the acute-phase DMSA renal scan and 15% (95% CI, 11-18) had evidence of renal scarring on the follow-up DMSA scan. Children with vesicoureteral reflux (VUR) were significantly more likely to develop pyelonephritis (relative risk [RR]: 1.5 [95% CI, 1.1-1.9]) and renal scarring (RR: 2.6 [95% CI, 1.7-3.9]) compared with children with no VUR. Children with VUR grades III or higher were more likely to develop scarring than children with lower grades of VUR (RR: 2.1 [95% CI, 1.4 -3.2]).

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Conclusions 

Children with an initial UTI showed evidence of renal scarring on follow-up DMSA scan 15% of the time. The risk was higher in children with VUR, particularly those with grades III or higher.

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Commentary 

Shaikh and co-workers conducted a meta-analysis to assess: (1) prevalence of acute abnormalities on DMSA scans performed within 2 weeks of a first UTI; (2) the prevalence of scarring on DMSA performed at least 5 months after an initial UTI; and (3) the likelihood of recurrent UTIs during the interval between the two DMSAs. Only 33 studies with 4891 children were eligible for analysis. Definitions of UTI included measures of bacteriuria; there was no requirement for evidence of pyuria. Studies in which urine specimens were collected by bag were included. Collection of urine specimens using a sterile plastic bag is generally discouraged because of the frequency of falsely positive specimens especially in uncircumcised boys and infant girls. The overall prevalence of VUR in these studies was about 25%. Children with VUR, not unexpectedly, showed higher rates of abnormal initial and final DMSA scans than children without VUR. Furthermore, those with the highest degree of reflux showed the greatest likelihood of scarring, although scarring also occurred in children without reflux. The results were not different when studies including children from whom bagged specimens were obtained were excluded. One very interesting finding of the study was a decrease in the overall frequency of scarring that was documented in more recent investigations. Although the authors speculate that this may be on the basis of detection of children with renal dysplasia on prenatal ultrasound, and their subsequent exclusion, it is more likely a function of earlier diagnosis of UTI, which is common in the last decade since UTI has been recognized as a frequent cause of fever in young children who have been appropriately immunized against respiratory pathogens.