What on Earth is the point in asking a question to form an argument and then answering it incorrectly?
The answer to your question "Does your abdomen bulge before you pee?" is yes. When the urine leaves the bladder, the bladder shrinks (like a balloon shrinking when you untie the neck and let some air out). The bladder is surrounded by a variety of soft squidgy organs like the intestines and the liver and kidney. When the bladder shrinks, the surrounding organs adjust their position slightly. The total volume of the bladder reduces which means that the other organs crowd in around it more closely, and the skin surrounding all of these things shrinks in abit as well. The reduced volume of the urine which has been expelled is therefore matched by an equal reduction of the volume of the whole abdomen. One pint of pee spread out all over someone's abdomen and chest would be hardly noticeable in terms of depth or thickness or volume.
There is no truth in the absurd suggestion that the bladder "doesn't touch the sides" as if it were somehow hanging in an empty chamber of air and somehow separated from the other organs. There is also no truth in the absurd suggestion, made earlier, that the urine in the bladder is somehow magically replaced by an equal volume of "air" or "void" (whatever that means), or that the bladder's shape does not change. It is obvious to me that the bladder is like aballoon which stretches and shrinks accordingly.
The point about name-calling is that EVERYTHING which I have written in this thread is completely obvious to anybody who has any reasonable amount of intelligence or common sense, and the fact that the question was even asked in the first place was completely absurd.