Can someone get a surgery without going through a doctor or an emergency room?

He will have to see a doctor at some point...who else is going to do the surgery? If he doesn't have insurance then there won't be the requirement of getting a referral to a surgeon from his primary care doctor, since that is a requirement of some insurance companies. He is free to try to make an appointment with a neurosurgeon or spine surgeon, however, without insurance they may not take him as a patient, but it is certainly worth making some calls to various surgeon's offices. You cannot just show up a a hospital, besides in the ER, and ask to check in, it doesn't work like that. He would meet with a surgeon in their office, and if they decide to do the surgery then they would admit him to the hospital. Don't bother going to the emergency room, we don't take patients from there to surgery unless the surgery is an emergency, which his is not. He won't even get an MRI while in the emergency room. They MIGHT do a CT scan but since he has a known condition that is causing his symptoms they would likely just give him something for the pain and send him on his way with instructions to follow up with a surgeon. So now he is back in te same situation that I previously discussed, calling around trying to find a surgeon to take him, but on top of that you will be getting a $1000+ bill from the ER. It is unfortunate the way access to health care is so limited, but that's the way it is in the US. Best wishes to your family.

A quick addition to Rafael's excellent answer: He should call your nearest teaching hospital and ask about free or low cost surgery clinics. Also, not all sciatica is a surgical problem. He will need imaging studies to determine whether it is or not, as well as an exam by the surgeon.

You need to go through a doctor and any surgery no matter will cost a lot of money.