Odds are pretty good if you walk into an emergency room anywhere, it's going to be run by a company based in Tennessee. In roughly two-thirds of ERs, the doctors don't work for the hospital. Instead, they work for a physician services firm, and the biggest are Envision and TeamHealth.
Those companies treat the patients and handle the billing. And that has made them prime targets in the growing rage against "surprise medical bills," which has resulted in legislation being considered by Congress.