- Written by Ethan Abbott
For this week’s question:
A 25 yo male with no PMH presents to the SBH emergency department with abdominal pain after an MVC. He undergoes rapid evaluation by the trauma team which includes a FAST exam. The FAST exam appears to have free fluid in the RUQ, but on closer inspection you note a “FAST Double-Line sign.” What is this finding?
Answer: The FAST Double-Line sign is a false positive finding when scanning the RUQ or Morrison’s Pouch. The perinephric fat pad can mimic free fluid. Per below reference, “the echogenic lines are caused by fascial planes encasing the hypoechoic fat pad, which can have a sharp corner, a finding classically associated with free fluid.”
Example here: https://www.youtube.com/watch?v=GE4r8owli2o
Reference: Paul R. Sierzenski, Joel M. Schofer, Michael J. Bauman, Jason T. Nomura, The Double-Line Sign: A False Positive Finding on the Focused Assessment with Sonography for Trauma (FAST) Examination, The Journal of Emergency Medicine, Volume 40, Issue 2, February 2011, Pages 188-189.