Laboratory Studies
Urinalysis and urine culture are important in evaluating any young child with an unexplained fever, and the diagnosis of urinary tract infection (UTI) should prompt further radiological evaluation to identify urologic structural anomalies. When structural anomalies are identified in a patient with a febrile illness, it is essential to evaluate for a UTI and, if found, to provide early treatment to minimize the risk of kidney injury.
Imaging Studies
Renal and bladder ultrasound is a first-line imaging study to evaluate the upper urinary tract (eg, for duplication, dilatation of collecting system, character or thickness of the renal parenchyma) and the lower urinary tract (eg, for bladder wall thickness, ureterocele, diverticulum, posterior urethral dilatation, degree of bladder emptying).
Voiding cystourethrogram (VCUG) permits evaluation of the bladder and urethra (eg, for vesicoureteral reflux [VUR], diverticulum, ureterocele, bladder trabeculation, bladder emptying, urethral anatomy during voiding) as well as assessment of the ureters if VUR is present.
Diuretic nuclear renography is an excellent study to objectively establish differential renal function, cortical scars, and to evaluate the drainage efficiency of the dilated collecting system (eg, washout times).
Intravenous pyelogram (IVP) is a useful study, although it has been largely replaced by ultrasound and nuclear renography. IVP delineates anatomy (eg, dilatation of collecting system, renal or ureteral displacement, bladder wall characteristics) and provides subjective estimation of relative renal function.
Magnetic resonance urography (MRU) provides excellent anatomic and functional evaluation of the renal parenchyma, collecting system and vasculature without exposure to radiation. However, MRU is sensitive to motion artifact and consequently necessitates anesthetic sedation of young children. [5]
See the images below.
Intravenous urogram demonstrating left primary megaureter in comparison to normal right collecting system.
Ultrasound image of a normal right kidney in a child with a febrile urinary tract infection. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
Ultrasound image of the same patient (in Picture 2), demonstrating that the left kidney has a duplex collecting system. Note the lower-pole hydronephrosis. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
Voiding cystourethrogram from the same patient (in Picture 2), demonstrating right vesicoureteral reflux into a single system and left vesicoureteral system into the lower pole of a duplicated system. Note the deficiency of upper-pole calyces on the left side and the "drooping lily" appearance of the left lower-pole system, which suggest the duplication anomaly in this case. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
Voiding cystourethrogram that illustrates a right ureterocele characterized by the round filling defect at the right bladder base. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
Other Tests
Urodynamic studies (eg, flow study, cystometrogram) assess voiding and bladder functional characteristics that are essential in the evaluation of a suspected neurogenic bladder.
Cystoscopy, vaginoscopy, and retrograde pyelogram are endoscopic procedures that allow direct visualization of the genital and lower urinary tracts and may include radiographic visualization of the upper urinary tract (eg, retrograde pyelogram).
Pressure-perfusion studies (eg, Whitaker test) measure differential pressures of the renal pelvis and the bladder. This invasive study, which requires percutaneous renal access, may be useful in evaluating equivocal urinary tract obstruction but is seldom used in the modern era of nuclear renography.
Histologic Findings
Ureteral ectopia
Single-system ureteral ectopia reveals widespread renal dysplasia in 90% of affected kidneys.
Duplicated-system ureteral ectopia reveals renal dysplasia in approximately 50% of affected renal moieties.
Megaureters
Light microscopy of megaureters demonstrates a predominance of circular smooth muscle; muscle fiber hypoplasia and atrophy, with collagen deposits separating the muscle cells; and mural fibrosis with scant muscle fibers.
Electron microscopy of megaureters demonstrates increased collagen deposition within the adynamic segment.
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Intravenous urogram demonstrating left primary megaureter in comparison to normal right collecting system.
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Ultrasound image of a normal right kidney in a child with a febrile urinary tract infection. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
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Ultrasound image of the same patient (in Picture 2), demonstrating that the left kidney has a duplex collecting system. Note the lower-pole hydronephrosis. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
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Voiding cystourethrogram from the same patient (in Picture 2), demonstrating right vesicoureteral reflux into a single system and left vesicoureteral system into the lower pole of a duplicated system. Note the deficiency of upper-pole calyces on the left side and the "drooping lily" appearance of the left lower-pole system, which suggest the duplication anomaly in this case. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
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Voiding cystourethrogram that illustrates a right ureterocele characterized by the round filling defect at the right bladder base. Image courtesy of Steven Kraus, MD, Cincinnati, Ohio.
