While VCUG is mainly safe, some people react poorly to the iodine based dye. This is very rare because the dye goes into the bladder and not into the bloodstream.
Minor reactions include:
- Hot flashes
These are most often treated successfully with antihistamines.
More serious side effects are:
- Trouble breathing
- Low blood pressure
- Swelling of the mouth or throat
- Cardiac arrest
There is also a chance of a urinary tract infection (as with any use of a catheter).
The radiation exposure during this test is relatively low. But women who are or may be pregnant should tell their doctor before the test.