Imaging Kidneys and the Urinary Tract

Abstract

Diagnostic imaging is an essential component of the routine evaluation of children with kidney disease. Ultrasound, due to low cost and absence of side effects, is the most common modality, with special importance in evaluating a child with acute kidney injury or hematuria and diagnosing and following children with congenital anomalies of the kidney and urinary tract. Voiding cystourethrograms remain important for diagnosing vesicoureteral reflux and assessing the urethra, but radiation exposure can be reduced or eliminated in some patients via radionuclide cystography or contrast-enhanced voiding urosonography, respectively. CT, ideally with protocols that reduce radiation exposure, provides excellent anatomic resolution, with applications that include assessing children for renal artery stenosis and acute nephrolithiasis, and evaluating a child following trauma to the urinary tract. MRI provides excellent anatomical detail without radiation but is expensive and may require sedation in young children. Magnetic resonance urography enables determination of split differential renal function and transit time of contrast through the kidney, making it an effective technique for assessing hydronephrosis. A variety of nuclear medicine modalities are used to assess renal scarring, locate ectopic kidneys, decide if a hydronephrotic kidney is obstructed, locate a pheochromocytoma, and determine differential renal function. Retrograde urethrography, often utilized after trauma, evaluates urethral caliber and integrity.