An update on renal scarring after urinary tract infection in children: what are the risk factors?

Summary

Aim

The aim of this study was to present updated information on clinical, laboratory, and imaging risk factors and predictors of renal scarring after first or recurrent febrile UTIs, which may be associated with renal scarring.

Methods

PubMed was searched for current data on possible risk factors and predictors of renal scarring after febrile urinary tract infections in children.

Results

Recurrence of acute pyelonephritis is an independent risk factor for renal scarring, while the duration of fever before treatment initiation is mainly associated with acute pyelonephritis and its severity. Severe vesicoureteral reflux is an important independent risk factor for the development of renal scarring after a febrile urinary tract infection.

Conclusions

Certain clinical parameters could be used to identify children at high risk for renal scarring after febrile urinary tract infection, helping clinicians to reserve dimercaptosuccinic acid scan for selected cases.

Introduction

Urinary tract infection (UTI) is diagnosed in approximately 7% of children who present with fever in the first year of life. In males, the prevalence is higher in the first 3 months of life and declines after that period, and in females, UTI is more common during the whole first year of life [1]. Nearly 8% of children with a first episode of UTI experience recurrence of infection [2]. Almost 17.5% of recurrences occur in the first 3 months after the initial infection, and 53% occur between 9 and 12 months after the initial episode [3].

A systematic review of children with a first episode of febrile UTI found that 57% had acute pyelonephritis (APN), documented by dimercaptosuccinic acid (DMSA) scan. Acute pyelonephritis may damage the renal parenchyma and lead to the formation of acquired renal scars. The average prevalence of renal scarring in children after febrile UTI is estimated to be 15%, a percentage that varies among studies [2]. In the long term, renal scarring may result in proteinuria, hypertension, and impairment of renal function [4,5].

DMSA scan is the gold standard for detecting renal parenchymal involvement in the acute phase of UTI, documenting the diagnosis of APN, or at follow-up, 4–6 months after the UTI, for detecting acquired permanent renal damage (renal scars) [6]. This imaging modality, however, is costly, exposes children to radiation, and is not available at every hospital. Follow-up DMSA scan should therefore be performed mainly for those children considered to be at high risk of renal scarring [7].

Shaikh et al. [8] systematically combined individual patient data from multiple studies (9 studies, including 1280 children) to identify variables predictive of renal scarring after a first UTI. They concluded that children and adolescents with an abnormal renal ultrasonographic finding or with a combination of high fever (≥39 °C) and etiological organism other than Escherichia coli were at high risk for the development of renal scarring.

The aim of this review is to present updated information on clinical, laboratory, and imaging risk factors and predictors of renal scarring after first or recurrent febrile UTIs, which may be associated with renal scarring. To the study authors' knowledge, no similar update review, covering such a wide variety of scarring risk factors and predictors, has been published.