A 4-month-old girl presented for evaluation of her urinary tract following a urinary tract infection. A renal ultrasound and voiding cystourethrogram were obtained. The ultrasound demonstrated dilatation of the left-sided collecting system, with dilatation of the entire left ureter.
A voiding cystourethrogram was subsequently obtained. Initially, following catheterization, it was noted that the catheter tip was positioned high within the left side of the abdomen. The catheter was partially withdrawn, and infusion of contrast was started. It was immediately noted that the catheter tip was located within the distal left ureter and did not appear to pass into or through the urinary bladder (see Figure 1). The catheter was repositioned into the bladder, and additional images were obtained, clearly demonstrating an ectopie insertion of the left ureter into the proximal urethra (see Figure 2, page 86). During voiding, contrast refluxed into the more proximal portion of the collecting system, which was moderately dilated, consistent with the ultrasound findings (see Figure 3, page 86).
Figure 1.Oblique view of the pelvis showing the catheter tip (white arrow) within the contrast-filled, moderately dilated, distal left ureter (black arrows). Some contrast has entered the urinary bladder (*), the result of the side hole of the catheter being located more distally in the urethra.
The incidence of ectopic ureters is approximately 1 in 1,900 and occurs more commonly in girls.1'2 Ectopie ureteral insertion is the result of abnormal migration of the ureteral bud, and the ectopie ureteral orifice can be present anywhere along the path of migration of the mesonephric duct.3 If the ureteral bud fails to separate from the Wolffian duct, it is pulled into a more caudal location than normal. In females, this can result in ureteral insertion into the lower bladder, urethra, or vagina. Approximately one third insert into the bladder neck or proximal urethra, one third into the vaginal vestibule adjacent to the urethral orifice, and one fourth into the vagina. Insertion into the cervix, the uterus, or the rectum is significantly less common.1'4
Typically, insertion of the ureter into the urethra or vagina presents after toilet training, with persistent wetting (continuous dribbling), and an otherwise normal voiding pattern. This is due to insertion of the ureter distal to the urethral sphincter. Approximately half of girls with an ectopie ureter will present with this history.1'5 Vaginal discharge may also be a presenting complaint.
In this case, with ureteral insertion into the urethra, the abnormality is easily identified. In fact, the initial placement of the urinary catheter resulted in positioning of the catheter tip in the left ureter itself. More often, with catheter placement in the bladder, the urethral insertion of an ectopic ureter is visualized only during voiding. In cases of vaginal insertion of the ureter, no abnormality may be seen on voiding cystourethrogram, but may be demonstrated by vaginogram.2
Figure 2. Oblique view of the pelvis. The catheter has been repositioned, wit h its tip now in the urinary bladder. The insertion of the ureter into the urethra, below the level of the bladder outlet, is clearly demonstrated (arrow).
Figure 3. Post-void image of the abdomen showing contrast in the proximal portion of the ureter (white arrows), the renal pelvis (*),and the calyces (black arrows), all of which are moderately dilated.
Ectopic ureteral insertion into the bladder is often accompanied by an ectopie ureterocele, which presents as a filling defect during the early filling phase of the cystogram. Later, when the bladder is completely filled and intravesical pressure is increased, the ureterocele may invert and have the appearance of a diverticulum.2 A large ureterocele may cause bladder outlet obstruction or prolapse through the female urethral meatus.3
Ureteral ectopia may be bilateral, seen in approximately 1 0% of cases. There is also a high incidence of associated renal anomalies, including hypoplasia and dysplasia.1 This is felt to be due to the relationship between the ureteral bud arising from the Wolffian duct and the adjacent metanephric mesoderm.6
A high number (70% to 85%) of ectopie ureters in girls are associated with completely duplicated urinary collecting systems.1'2'4 In the majority of these cases, the insertions of the duplicated ureters follow the Weigert-Meyer rule: the upper pole ureter inserts ectopically (medially and caudally) into the bladder or urethra, and the lower pole ureter inserts in a relatively normal location. The upper pole, if inserting into the bladder, is typically associated with an obstructing ureterocele, and the lower pole ureter has vesicoureteral reflux.
1. Gillenwater JY, ed. Adult and Pediatrie Urology. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins 2002:2176-2181.
2. Kühn JP, Slovis TL, Haller JO, eds. Caffey's Pediatrie Diagnostic Imaging, 10th ed. Philadelphia, PA: Mosby; 2004:1842-1853.
3. Nelson WE, ed. Textbook of Pediatrics, 15131Cd. Philadelphia, PA: WB. Saunders Company; 1996:1538-1539.
4. Berrocal T, Lopez-Pereira P, Arjonilla A, Gutiérrez J. Anomalies of the distal ureter, bladder, and urethra in children: embryologie, radiologìe, and pathologic features. Radiographies. 2002; 22(5):1139-1164.
5. Bemard-Bonnin AC. Diurna! enuresis in childhood. Can Fam Physician. 2000;46: 1109-1 115.
6. Pope JC, Brock JW, Adams MC, Ichikawa I. How they begin and how they end: classic and new theories for the development and deterioration of congenital anomalies of the kidney and urinary tract, CAKUT. JAm Soc Nephrol 1999;10(9):2018-2028.