Roughly 18% of children exhibit renal scarring 5-24 months after their first urinary tract infection, although only 2.5% have severe grade IV or grade V vesicoureteral reflux – long considered the main risk factor for scarring in this population.
The finding means that while “the identification of VUR may be important, VUR is neither necessary nor sufficient for the development of renal scarring,” wrote Dr. Nader Shaikh and colleagues (Pediatrics 2010;126:1084-91). Moreover, “a sole focus on VUR, as has been the dominant strategy for decades, is unlikely to result in large reductions in rates of renal scarring,” they added.
Dr. Shaikh and associates at the University of Pittsburgh looked at 1,533 articles found in Medline (between 1950 and January 2009) and Embase (between 1974 and January 2009) that included the terms “technetium Tc 99m dimercaptosuccinic acid (DMSA),” “pyelonephritis,” or “urinary tract infection.”
Studies were included only if all patients were 18 years of age or younger, and had DMSA scans – “the current gold standard for the detection of renal parenchymal involvement.” A total of 328 studies were retrieved for full-text review. Thirty-three of these, comprising 4,891 children, were assessed.
Overall, the authors found the pooled prevalence of any VUR to be 24%. However, only 2.5% of the children had severe VUR, rated as grade IV or V. Nevertheless, in 14 studies that included data from follow-up DMSA scans, 18% of children exhibited renal scarring 5-24 months after the UTI. That was despite a 0.6% incidence of pre-existing renal scarring, according to the four studies that had that data available.
The authors did find that children with VUR had a 2.6 times higher prevalence of renal scarring, compared with children without VUR (41% vs. 17%; P = .001), and that prevalence was 2.1 times higher among children with VUR grades III-V at 53%, versus 25% in children with grades I and II (P = .001), reported Dr. Shaikh and associates.
However, the results show that “VUR is not the only risk factor for renal scarring,” wrote the authors.
They also sought to characterize the link between VUR and acute pyelonephritis (APN). They found that VUR patients were 1.5 times more likely to exhibit findings consistent with APN on the acute DMSA scan, compared with children without VUR (67% vs. 49%, respectively; P = .004).
The authors conceded that “identification of VUR can be a practical method of identifying children who are at risk for renal scarring.” However, a top-down approach of scanning every UTI patient is likely not feasible, because scans are “expensive, invasive, and expose children to radiation.”
“Furthermore, it is unclear how to best manage the large numbers of children with a positive acute phase DMSA scan … most of whom (85%) will not scar,” they wrote. So, “additional research is warranted to help determine management strategies for children with UTIs.”
Dr. Shaikh and associates reported having no relevant financial disclosures.