Renal scarring in children with urinary tract infections

Urinary tract infections (UTI) are among the common acute bacterial infections in childhood accounting for a significant amount of morbidity. Concern with childhood UTI focuses not so much on the morbidity of acute infections but on the risk of delayed clinical outcome resulting from renal parenchymal damage. Chronic atrophic pyelonephritis is the main cause of sustained hypertension and renal insufficiency in children and young adults.


Introduction
Urinary tract infections (UTI) are among the common acute bacterial infections in childhood accounting for a significant amount of morbidity.Concern with childhood UTI focuses not so much on the morbidity of acute infections but on the risk of delayed clinical outcome resulting from renal parenchymal damage.Chronic atrophic pyelonephritis is the main cause of sustained hypertension and renal insufficiency in children and young adults.

Objective
To assess factors associated with renal scarring in children with urinary tract infections.

Design
A prospective study.

Method
This study was done in the Professorial Paediatric unit, Teaching Hospital, Peradeniya since September 1993 to date.During this period 290 children below the age of twelve years with a bacteriological proven urinary tract infection were screened to detect renal scars and underlying abnormalities.

Results
A total of 290 children with bacteriologically proven urinary tract infections were screened.Of the total sample 114 (39%) had detectable renal scars.59 (52%) of them were males and 55 (48%) were females.The male to female ratio was almost 1:1 Patterns of renal scars observed in these patients are shown in Table 1.The left upper pole was more frequently scarred than the right.50(43%) Vs. 36(31%) while a quarter had multiple bilateral scars.70% of those patients with scarred kidneys were below age of 5 years (Table 2).Out of the 114 patients with scarred kidneys 105 (92%) have had no previously recorded urinary tract infections (Table 3).Of those with scarred kidneys 75 (66%) patients presented with specific symptoms and 39 (34%) presented with non specific symptoms (Table 4).Vesico-ureteric reflux was the main underlying abnormality detected in patients with scarred kidneys (Table 5).Coliforms sensitive to most of the commonly used antibiotics was the commonest organism identified in 99% of patients with scarred kidneys (Table 6).90% of children with renal scars presented with the first episode of urinary tract infection.A thorough evaluation of the histories showed that some of them have had recurrent febrile episodes in early infancy.
It is possible that they may have had UTIs during infancy which were undetected and masked by indiscriminate use of antibiotics for febrile episodes.Even through 65% of those with scarred kidneys presented with specific symptoms related to the urinary tract it is important to note that 34% presented with non specific symptoms.Therefore a high degree of suspicion of urinary tract infection is necessary to identify these patients who are at risk of renal damage.
Underlying abnormalities were detected in 45% of patients with renal scars and the main abnormality detected was vesico-ureteric reflux (VUR) in 75% of patients.Although vesico-ureteric reflux or structural abnormality has been considered as a prerequisite to the development of renal scars only 33% of patients in our study group had demonstrable VUR.This study confirms the observations made by Jacobson et al 2 that renal scarring occurs more often without demonstrable reflux or obstruction and there may be other unidentified host or bacterial factors responsible.In some of these patients VUR may have resolved before they presented to us.
E. coli was the commonest organism cultured from these patients.This is in agreement with other studies.Four patients who have had Klebsiella infection had underlying abnormalities.Previous observations have shown that children with underlying urinary tract abnormalities are susceptible to get infections by more virulent organisms.

Conclusions
A high degree of suspicion, early detection and treatment, identifying risk factors and prevention of recurrences are important to prevent permanent renal damage in children with urinary tract infections.

Table 5
70% of children with renal scars in the study group were below the age of five years and more than 50% were below the age of two years.This finding is in keeping with previous studies which have shown that infants and children younger than 5 years are at greater risk of developing renal scars 1 .