Objective: To determine up to what age children remain at risk of developing a new renal scar from a urinary tract infection.
Design: Follow up study. Families of children who had normal ultrasound scans and scanning with dimercaptosuccinic acid (DMSA) after referral with a urinary tract infection when aged 3 (209) or 4 (220) were invited to bring the children for repeat scans 2-11 years later. A history of infections since the original scan was obtained for children not having a repeat scan.
Setting: Teaching hospital.
Subjects: Children from three health districts in whom a normal scan had been obtained at age 3-4 years in 1985-1992 because of a urinary tract infection.
Main outcome measure: Frequency of new renal scars in each age group.
Results: In each group, about 97% of children either had repeat scanning (over 80%) or were confidently believed by their general practitioner or parent not to have had another urinary infection. The rate of further infections since the original scan was similar in the 3 and 4 year old groups (48/176 (27%) and 55/179 (31%)). Few children in either group known to have had further urinary infections did not have repeat scanning (3/209 (1.4%) and 4/220 (1.8%)). In the 3 year old group, 2.4% (5/209) had one or more new kidney scars at repeat scanning (one sided 95% confidence interval up to 5.0%), whereas none of the 4 year olds did (one sided 95% confidence interval up to 1.4%). The children who developed scars were all aged under 3.4 years when scanned originally.
Conclusions: Children with a urinary tract infection but unscarred kidneys after the third birthday have about a 1 in 40 risk of developing a scar subsequently, but after the fourth birthday the risk is either very low or zero. Thus the need for urinary surveillance is much reduced in a large number of children. Key messages Urinary tract infections can cause renal scars in young children that may lead to hypertension or renal failure, often years laterScars can be detected immediately on scanning with dimercaptosuccinic acid (DMSA) but may not be apparent for years if only intravenous urography is usedPrevious studies based on intravenous urography have suggested that new scars may develop in children up to the age of 10 years. This study, which used DMSA scanning, shows that there is little or no risk of new renal scars developing in children aged 4 and older.