Got ultrasound on leg-groin for leg pain suspecting dvt found nothing but would like second ultrasound for assurance how do i get second without refer?

You need: a physician order/prescription to get it done. But unless there is some reason to believe the ultrasound was improperly performed, there shouldn't be a reason to repeat it.

You will need a: physician's order to obtain a repeat and if you are insured it is unlikely that the second one will be paid for. In other words you will have a big bill to pay. It is not reasonable to obtain a second study as the likelihood of it being any different is extremely small. Talk to your health care provider about your concerns.