system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens with the remaining cavity when someone donates/loses a body organ?

Do they stuff it with something or is there left air? Does the body fill it up with new tissue?

For example, it seems a lung might leave a fairly big *hole*. They don't just leave it and staple it closed, do they?

Please assume a good process of healing without problems for this example. No need to go into a (mine-)field of medical what-ifs.
gpt
There is no air or fluid that fills the space. The organ is removed and depending on the organ, its size, and its location there are internal stitches put in to hold the walls of the organ cavity together. Like all tissue the flesh surrounding the organ will eventually grow together. Basically after it is healed it is like there was never an organ there to begin with. From the outside there may be a noticeable "dent" or cavity. It is very easy to feel when an organ has been removed if you rub over the scar. it sort of feels like a hole but it is solid.