The urinary tract infection (UTI) is one of the most common bacterial infections in children; incidence is relatively more in males (3.7%) than females (2%) during infancy. Thereafter, incidence is higher in females (3%) than males (1%). Risk factors identified are female gender, high grades of vesicoureteral reflux, catheterization, presence of bladder bowel dysfunction, phimosis and underlying congenital anomalies of kidneys and urinary tracts (CAKUT). Febrile UTI in younger children can lead to renal scarring and subsequently hypertension and chronic kidney disease. E. coli is responsible in 85-90% of cases and non-E. coli pathogens are Klebsiella pneumoniae, Proteus mirabilis, and Enterococcus species. The organisms which are associated with CAKUT are Pseudomonas, group B Streptococcus and Staphylococcus aureus [1].

Early diagnosis is important so that timely antibiotic therapy and evaluation can be done to prevent further kidney damage. Ultrasonography (USG) of kidney, ureter and bladder is a non-invasive imaging without any radiation exposure. However, there are differences in recommendations of International Guidelines as regard to specific age group and timing of USG screening. The National Institute for Health and Care Excellence (NICE) recommends USG screening in children with first UTI at age younger than 6 mo during acute infection, if a child does not respond to treatment within 48 h or presenting with atypical or recurrent UTI [2]. In children between 6 mo to 3 y and older, USG is recommended during acute infection with atypical UTI or within 6 wk with recurrent UTI. American Academy of Pediatrics recommends USG in children aged 2-24 mo during first 2 d of treatment in cases with severe illness or if there is no clinical improvement after therapy, to detect complications like renal or perirenal abscesses or pyonephrosis associated with obstructive uropathy [3]. Indian Society of Pediatric Nephrology recommends USG in all children and further evaluation, if abnormality is detected [4].

In this issue of the journal, Kayak et al. reported regarding usefulness of USG in detection of underlying abnormalities in children with first UTI and tried to answer that which cases should be subjected for screening [5]. USG was done within 7 d after diagnosis of UTI. Anomalies were detected in 27.5%; hydronephrosis being the commonest and the detection rate was higher in children below 5 y. The non-E coli pathogens were found in 61.8% of cases with renal anomalies, and significantly higher in children under 5 y (30.4-48%) than older children (17.2%). It was concluded that UTI in children below 5 y and presence of atypical UTI were significant independent predictive factors for presence of underlying renal anomalies. However, limitations of study were that it was a retrospective single-centre observation and conducted on relatively smaller number of cases.

Since the USG is readily available and cost effective, it can be used in children with first UTI to detect underlying abnormalities such as hydronephrosis, hypoplasia/dysplasia, ectopic kidney, multicystic-dysplastic kidney, horse- shoe shaped kidney, duplex collecting system, renal stones, and bladder wall thickness and diverticula. Presence of underlying CAKUT complicates the course of UTI especially in younger children. Therefore, initial USG evaluation is warranted in UTI to detect anomalies, especially in children below 5 y or with recurrent/ atypical UTI and those having infection with non-E. coli pathogens [1, 5]. It can be considered 4-6 wk after an episode of UTI or early during acute infection in non-responders, so that measures can be undertaken for correctable forms of anomalies, prevention of recurrent UTI and further kidney damage.