Findings: The VCUG demonstrates filling of the bladder with Grade II vesicoureteral reflux (VUR) involving both ureters of a duplicated left collecting system. The two distal ureters may empty into the bladder separately or may conjoin approximately 1 cm before the ureterovesical junction. Renal sonography reveals two separate central sinus echoes involving the left kidney confirming partial duplication of the left collecting system. No hydronephrosis is identified on either study.

Diagnosis: Duplicated left collecting system with Grade II vesicoureteral reflux.

Discussion: Duplication of the collecting system is secondary to premature branching of the metanephric duct. Different forms of renal duplication exist with a spectrum from a bifid renal pelvis to complete duplication of the ureter and kidney to the level of the urinary bladder. The incidence is more frequent in girls than boys (4-5:1). With complete duplication, the lower pole moiety is more prone to vesicoureteral reflux, while the upper pole moiety (which inserts medial and caudal to the ipsalateral normal ureteric orifice) is more prone to obstruction secondary to a ureterocele (Weingert-Meyer rule). The upper pole moiety may insert ectopically into the uterus, vagina, epididymis or urethra.

Urinary tract infection (UTI) in children is often an indication of an anatomic and/or functional urinary tract disorder in 35-50% of patients (i.e. VUR, UPJ, UVJ). Vesicoureteral reflux (VUR) is present in approximately 30-35% of these patients. VUR is believed to be a primary ureteral abnormality or incompetence of the ureterovesical junction and is not secondary to obstruction or infection. VUR is particularly common in the neonate and infant where it is thought that there is immaturity or maldevelopment of the longitudinal muscle of the submucosal ureter at the ureterovesical junction.

GRADES OF VESICOURETERAL REFLUX

• I. Reflux into the distal ureters
• II. Reflux into collecting system without caliceal dilatation/blunting
• III. All of the above plus mild dilatation of pelvis and calices
• IV. All of the above plus moderate dilatation with clubbing of calices
• V. All of the above plus sever tortuousity of the ureters

Children under the age of five with a well-documented history of UTI should be evaluated with both VCUG and renal ultrasound. Further evaluation with excretory urography or radionuclide renogram is appropriate if the VCUG shows VUR or other anatomic abnormalities.

References:

1. Blickman H. Pediatric Radiology: The Requisites, 2nd edition,1998.

2. Danhert W. Radiology Review Manual, 2nd edition, 1993.

3. Kirks D. Practical Pediatric Imaging: Diagnostic Radiology of Infants
   and Children, 2nd edition, 1991.