Question is not about someone with gas in part of their digestive system, or air in their lungs.
I’m wondering if there are empty spaces in people’s bodies due to the fact that organs don’t fit exactly alongside each other, and so on. Or if someone has an organ removed, for that matter. Or does any available empty space fill up with some sort of fluid, or other squishy substances in there?
If so, where, and also what proportion of a typical person’s body would be hollow?