▶ Longitudinal ultrasound image (left) shows a cyst (arrowhead) in the bladder. Arrow indicates bladder wall.
▶ Early-filling view from a voiding cystourethrogram (VCUG) shows a smooth-walled filling defect (arrowhead).
Foreign objects, such as Foley catheter balloons, may also cause bladder filling defects but are uncommon.
▶ A ureterocele is a dilation of the distal ureter, usually due to ureterovesical junction (UVJ) obstruction, which invaginates into the bladder.
▶ Ureteroceles may be ectopic (associated with an ectopic ureter) or simple. Ectopic ureteroceles are more common in girls with duplex kidneys. These are often large and may cause obstruction of the bladder outlet or the contralateral UVJ or they may herniate through the urethra and present as an interlabial mass.
▶ Ureteroceles in boys are often small and asymptomatic. These have the appearance of a cobra head or spring onion. When there is contrast in the distal ureter and the bladder, there is a lucent rim or halo around the ureterocele as it is lined by two layers of urothelium—that of the bladder and that of the ureter.
▶ Ureteroceles are dynamic in size and shape. With bladder filling, they become less apparent, in part due to obscuration by dense contrast, but also due to change in relative pressure in the bladder compared to the ureterocele. As the bladder fills, the pressure in the bladder exceeds that in the ureterocele and the ureterocele is compressed. With further filling, the ureterocele may even evert and mimic the appearance of a bladder diverticulum. For these reasons, ureteroceles are best visualized on early-filling views.
1. Berrocal T, López-Pereira P, Arjonilla A, Gutiérrez J. Anomalies of the distal ureter, bladder, and urethra in children: embryologic, radiologic and pathologic features. Radiographics. 2002 Sep–Oct;22(5):1139–1164.Find this resource:
2. Fernbach SK, Feinstein KA, Schmidt MB. Pediatric voiding cystourethrography: a pictoral guide. Radiographics. 2000 Jan–Feb;20(1):155–168.Find this resource: