The article referenced doesn’t give many details but for over thirty years open heart surgery has been done without blood transfusions and with good results.
So serious surgical procedures can be done without transfusions and thus avoid any side effects from transfused blood. But maybe this guy is too ill to consider it in his case.
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.