Work-up of urinary tract infection in infants and children.

Urinary tract infection (UTI) in infants and children demands rapid differentiation between upper UTI (pyelonephritis) and lower UTI (cystitis) for prompt treatment to be initiated so that renal damage is minimized. This pictorial review presents a wide gamut of structural and functional abnormalities of the urinary tract that may predispose infants and children to UTI, including vesicoureteral reflux, upper urinary tract obstruction (ureteropelvic junction obstruction), lower urinary tract obstruction (primary megaureter, ureterovesical junction obstruction, posterior urethral valve, ectopic ureterocele with or without associated duplex collecting system), neurogenic problems (dysfunctional voiding), calculi, and parenchymal scars. Sonography (ultrasound [US]) is the imaging modality of choice for assessment of renal size, growth (serial sonograms), texture, and blood flow. Other modalities used to work-up UTI in the pediatric patient include fluoroscopic voiding cystourethrogram, nuclear voiding cystourethrogram, and nuclear renal scintigraphy (NRS). Excretory urography is no longer recommended in the routine evaluation of childhood UTI because information regarding anatomy and function (qualitative and quantitative) can be better assessed with US and NRS, respectively. Computed tomography and magnetic resonance imaging are primarily reserved for complex cases in which a definitive diagnosis cannot be made with routine imaging. Algorithms for work-up of UTI in various pediatric age groups are presented.