What happened when Elie needed surgery?

Due to the harsh conditions and inadequate clothing, Elie develops a serious infection in the bottom of his foot that causes his leg to swell; it gets so severe that he can no longer even stand on it. Elie is at first conflicted; in the hospital things seem a little better. He is given more food, time to rest, and even sheets to sleep on. However, a very sick Hungarian in the bed next to him reminds him that the Germans have no use for sick Jews and sternly instructs him to "leave the infirmary before the next selection."
The surgery goes well, and Elie finds the doctor trustworthy and comforting. When he awakes, his doctor tells him that he must rest for two weeks. However, after two days, the lines of battle are rumored to be nearing Auschwitz, which sends everyone into a frenzy of activity in preparation to desert the camp. Those in the hospital are told that they can remain behind, but Elie becomes convinced that everyone left there will be killed.
More than impending death, Elie fears losing his father: "We had already suffered so much, endured so much together. This was not the moment to separate." Unsure if his foot will make the journey impossible, he sets out with determination to prepare for departure in order to remain together.

While imprisoned in the Auschwitz concentration camp, Elie Wiesel recounts experiencing swelling in his foot. He approached an imprisoned doctor for advice, and the doctor advised him to get surgery on his foot immediately to avoid amputation. Elie decides to go to the hospital and try to get the surgery, but throughout his stay he worries about being chosen to be killed because he is sick. The surgery goes well and Elie is told to stay in the hospital and rest for two weeks. However, he soon hears rumors from other patients that the Russians are approaching the camp and planning on evacuating the camps and killing everyone in the hospital. Elie decides to escape from the hospital and, despite the advice of his doctor, travel on foot to return to the camp and try to find his father.