Preparing for the Urodynamic Test

If the doctor or nurse recommends bladder testing, usually no special preparations are needed, but make sure you understand any instructions you do receive. Depending on the test, you may be asked to come with a full bladder or an empty one. Also, ask whether you should change your diet or skip your regular medicines and for how long.

source: http://kidney.niddk.nih.gov/kudiseases/pubs/urodynamic/index.htm