You’ll get more infections, probably, and need antibiotics fairly regularly. The spleen is a major immune organ.
Complete hemispherectomies are rare, but they have been successfully performed. Has anybody ever had even more than half of their brain removed, aside from Spock?
(groan)
I vote for tonsils, adenoids, spleen, thymus, reproductive organs, gallbladder, and there may be others. Anything else, and its absence will seriously impact one’s quality of life.
If you count bones, muscle or skin as an organ, you can survive long-term losing quite a bit of muscle or bone (and a fair amount of skin), though obviously you’ll need medical intervention in the short-term (and probably medium-term if you lose much skin).
I was surprised to learn that huge numbers of people are polysplenic- probably 10% or more of everybody has multiple spleens.
Nobody ever notices until one or more ruptures and a surgeon has to go in there and look around.
I had some sweat glands removed! The apocrine ones in my armpits (you also have apocrine sweat glands in your nether regions - and so do I). According to Wikipedia they are not useful in humans, they are more useful in camels.
The desending colon can be removed with no sequelae, but removal of other parts of the colon require a colostomy. Removal of more than a few inches of the small intestine requires an ileostomy. These are both externalized stomas requiring a bad to collect intestinal contents.
Skin is an organ, bone and muscle are not. One’s skin must remain intact. Third degree burns or major skin sloughing requires grafting and extended hospitalization.
Removing the stomach does have sequelae. Even gastric by-pass requires on-going care, including special diet, vitamin supps and electrolye replacement.
Bladder removal requires externalization of the ureters into a false bladder made of part of the intestine. It has to be emptied by hand.
I could go on if you like, but I have to run some errands.
I don’t think anyone’s mentioned the prostate (though I guess that’s part of the reproductive system). My body is my cite.
What counts as an organ?
For some reason, a sex organ is an organ, but an arm or leg is not, in common speech. But an arm is a set of tissues working together for a purpose or purposes, so if arms are organs or legs are organs, you could live without those.
Rather broad statement; untrue at least by exception. My father had a significant chunk of (i.e., most of) tranverse colon removed and resected, and as far as I can tell he’s as totally not full of shit as he ever was. And no bag on the side, as it were.
<claps> 