It depends on what those risks were. Doctors must fully inform their patients about serious risks involved in any proposed medical procedure or treatment so that the patient can decide whether to go forward, in light of the danger. In both medical and legal terminology, this is called "informed consent." However, doctors don't have to inform patients about every single risk involved in a procedure, only the important ones. In determining what a doctor must disclose in terms of the risk linked to certain treatment, states generally use one of two standards:
In some situations (like emergencies), a doctor is not required to get informed consent before treating a patient. To learn more about what constitutes informed consent and when it is required, see Nolo's article Medical Malpractice: Informed Consent.