Pediatric urinary tract infection: imaging techniques with special reference to voiding cystoerethrography

Urinary tract infection (UTI) is the second most common infection in childhood. Large hospital-based pediatric series report an incidence of 3-5%. Dickinson prospectively determined that 1.7/1000 boys and 3.1/1 000 girls annually present with a UTI. This corresponds to about 780 girls and 430 boys per million population aged 0-14 years. Under age 6 years, a UTI furthermore is an indicator of an anatomic and/or functional urinary tract disorder in 35-50% of these patients. Vesicoureteral reflux (VUR) is present in 30-35% of these, but is present in 85% of children with evidence of renal scarring.4•5 This scarring, in turn, is responsible for 20-40% of end-stage renal failure in patients under 40 years of age. From these figures it can be estimated that the risk for hypertension or renal failure after a first, laboratory and clinically proven (index) UTI is about 1% for boys and 0.5% for girls. The imaging evaluation of these children has a dual purpose. On the one hand, it is intended to establish that the kidneys, bladder and urethra are normal, so that subsequent UTis can be treated by a 10 day course of antibiotics without risking renal damage. This affords the opportunity to make sure that normal kidneys remain normal. On the other hand, appropriate imaging is intended to a) identify and grade the severity of VUR, b) to define the extent of renal scarring and to c) determine the site of obstruction, if any. This allows for minimizing renal damage.8 Early identification of these abnormalities, the anatomic basis of which will be discussed later, thus offers the prospect of preventive medicine and sound advice to the clinician regarding antibiotic (for lower grades of VUR) or surgical (for higher grades of VUR and obstructive etiologies) therapeutic measures. The available imaging modalities (VCUG, EU, US, Urodynamics and Radionuclides) all have different capabilities and limitations and should not be used indiscriminately as some employ ionizing radiation, others are invasive, uncomfortable and expensive.