How do you know if your anus needs reconstructive surgery? because the bottom of my anus is loose and smells like poop

Surgery Experts: This is exactly why there are colo-rectal surgical experts to consult. If you have a loose or a pro-lapsing rectum this can and often is fixed surgically.

See gastroenterology: You should see a gastroenterologist. It may be possible you have a fissure or fistula but it is highly unlikely you have a "loose" anus from natural causes.