A patient can sue for any reason. They can be wrong and sue.
It's then up to the physican to pay costs for legal defense (i.e. medical malpractice insurance). If the patient is wrong, then the physican can counter-sue. This whole dance is very expensive and, worse, time consuming (which, for a doc, is the ultimate resource). This cost ends up on the patient ad the doc must raise prices to account for the new insurance.
Patients normally sue a hospital system though. My partner has been involved in dozens of malpractice lawsuits over the years because every person who interacted with the patient during their stay is named in the lawsuit, not just the doctor(s) who treat them.
Hospitals have staff lawyers whose job it is to deal with lawsuits. So it's not terribly time-consuming for doctors outside of depositions.
It's safe to say that this is one of the reasons that doctors move from private practice into working in a hospital system. But it's also not a major one (dealing with insurance companies is the major factor).
Hacker news readers may not realize that joint liability exists in many states. Under this doctrine, the plaintiff can collect all awarded damages from even very peripherally involved people. A person with deep pockets can end up paying for others mistakes.
For example, a plaintif’s attorney might drag everyone into a lawsuit they can over a disappointing surgical result. The jury could be persuaded that an operating room nurse is 1% liable for a failed operation and the surgeon 99% responsible. If the surgeon can’t pay their part of a two million dollar judgement (brand new doctor perhaps) the nurse may end up paying the two million (maybe the nurse is married to a software engineer).
> the doc must raise prices to account for the new insurance
As I understand it, the portion of additional costs that the doctor eats and the portion that they charge to their patients actually depends on the elasticity of the market for the doctor's medical services. I can't comment on the market for the hypothetical doctor's medical services (in the U.S. AFAIK that market is very complex and opaque, and it probably depends on the doctor, location, and the specific service), so speaking generally about sellers and buyers:
The portion of a cost increase that is eaten by the seller or charged to the buyer depends on elasticity. Computer memory is highly elastic: If your costs go up and you try to increase your price $10/DIMM, then I'm going to buy my DIMM someplace else (unless your DIMMs are very special); a small change in price causes a large change in demand. Superstar developer salaries are highly inelastic: If the developer's costs increase (a new baby!) and they ask for more money, I probably have to give it to them because I'm not going to find a replacement. You see that more publicly with superstar athletes: Cristiano Ronaldo is irreplaceable; the market for his services is at the extreme of inelasticity; he can almost name his price for running around in shorts, playing games.
It's then up to the physican to pay costs for legal defense (i.e. medical malpractice insurance). If the patient is wrong, then the physican can counter-sue. This whole dance is very expensive and, worse, time consuming (which, for a doc, is the ultimate resource). This cost ends up on the patient ad the doc must raise prices to account for the new insurance.