X-ray of pelvis, taken after injecting two ml of Ioversol (OPTIRAY 300) through balloon channel of Foley catheter and 50 ml of diluted contrast through the main lumen of Foley catheter in order to visualise Foley balloon and urinary bladder respectively: The outline of urinary bladder is seen clearly. A smaller circular opaque shadow, situated below the urinary bladder, represents the. Foley balloon. The Foley balloon is lying in posterior urethra. When a Foley catheter is positioned correctly, the Foley balloon should lie within the cavity of urinary bladder.