Depends on how long. Most often, you will not be able to hold it long enough to do damage to your body, however there are rare occasions where holding your urine can cause damage to your bladder and kidneys.
i ALWAYS do this. but i do it for like over an hour sometimes, i think i go way to far with this. i hold it for hours at a time sometimes, even when it does hurt...so maybe holding it in is not bad, but when you get to my extent, it probably is
Yes. It backs up and the urine is poison to your kidneys. The liquid that becomes pee is what you drink. It goes through kidneys to be filtered and cleaned so you won't get some infection. If you hold it it will spread germs to kidneys and eventually get weak and shut down slowly. So DON'T HOLD IT! (8th grade health and my biology book helps!)