Closer friends usually want more info, not out of nosiness, but because they care. I'm pretty open and don't have anything to hide. However, I also do not want to scare people. Usually a simple general sentence suffices. Then they understand my terror of touch.
Medical professional in the ER rarely care about anything other than treat and release me. They won't listen to very important diagnoses, essential for treating me. Being Deaf, having no balance, and having PTSD makes treatment rather difficult. They often just write it up as "the patient was being rather uncooperative." So in the meantime I just go with someone so my rights aren't trampled on and the visit does not become traumatic.
The only person who knows the details is my therapist. After almost a year we're just touching on more and more of my history. She learned the most important pieces early on: It started as a young age and continued throughout my teens. It involved every type of abuse (i.e. physical, emotional, sexual, neglect, and medical).
The medical abuse still happens regularly, even if I bring a supporter along. Luckily I have a great family practice doctor, a great psychiatrist, and a wonderful therapist. As I always have a witness, there's no question as to what happened.