Constricting a (usually full) bladder with a belt or similar implement. Either on purpose to cause discomfort or not. If on purpose, the image should probably be also tagged omorashi.

Tag also when the belt or other implement isn't "technically" constricting the bladder but is close enough to it, such that it still causing discomfort to the one with the full bladder. So posts like post #2309544 are still tag bladder_constriction.