Ultrasound to detect leaky expander?

I have an ultrasound on Friday to see if my expander on the left side is leaking. It seems smaller than the right side. But when the nurse called to set up the appt she said it was to “aspire fluid.” 😳 Has anyone had this? I told her I thought it was to see if the expander is leaking and then she said they would sample the fluid if it is. I don’t want another needle poke! Yikes! Getting anxious. Thanks for reading! I’m so thankful for this forum.