If you need a cystometry test, you may be asked to lie down, sit, or stand.

A thin tube (catheter) will be gently placed into your urethra with a numbing gel to make it more comfortable.
Another small tube will be inserted into your rectum. These tubes measure the pressure in your bladder and belly.
Small stickers with sensors will be placed on your skin to track your muscle activity.
Your doctor will slowly fill your bladder with a sterile liquid through the catheter and ask you to cough or push to see how your bladder reacts.
They will check if any urine leaks and ask if you feel the urge to go.
When your bladder is full, you will be asked to urinate while the pressure is measured. Once the test is done, everything will be removed.

This video shows how a standard urodynamic test is done.