Where is the Foley balloon positioned during a retrograde urethrogram?
The balloon is positioned in an outpouching of the distal urethra called the "fossa navicularis". Overdistention of the balloon in the urethra is extremely painful, but underdistention allows the balloon to slip out when contrast is injected. In order to get a good distention amount, contrast should be instilled *slowly* into the balloon while one holds the distal penis in the region of the fossa navicularis. One should be able to feel it fill slowly and prevent it from overdistending. Very gently tugging at the Foley after filling can ensure that the balloon is snug in the fossa.