Ureterocele

Abdominal film following contrast enhanced CT scan shows excretion into two ureters on the left (arrows). In the bladder, a characteristic filling defect (yellow arrow) is seen known as the "cobra head" deformity which represents herniation of the dilated distal ureter bulging into the bladder.

 CT scan and  ultrasound through pelvis in patient with known right ureterocele who complains of new right flank and groin pain. Both US and CT show a stone contained within the ureterocele perhaps causing the patients pain from intermittent obstruction. On CT, this stone is radiodense (arrow) and on ultrasound, the stone demonstrates strong acoustic reflection (has a bright interface) and posterior acoustic shadowing (it is black behind the stone because all sound is being reflected at the stones interface).