Both GI bleeding and kidney failure cause profound anemia.
Surgery on an anemic patient is very dangerous, and most surgeons will not do surgery until the anemia is corrected (and the anesthesiologist would probably not do the anesthesia). The only time you would probably see surgery done on an anemic patient is in a situation where death is imminent if the surgery isn’t done.
Yeah, quite true. Medical procedures on prisoners against their will is not something I want to see in any situation.