The FAST exam is an examination that is ubiquitous in emergency medicine, and the more I do them, the more I realize that their correct interpretation takes some training.  If you don’t know how to properly do a FAST exam, START HERE. The following is a list of things that will cause you to have a false-positive or false-negative FAST:

Right upper quadrant:

Perinephric fat

Gallbladder

Not looking at the inferior pole of the kidney/caudal tip of the liver interface

Pelvis

You’re too high (probe should sit right above the pubic symphysis)

Iliac vessels

Probe not oriented sagitally

Left upper quadrant

Perinephric fat

Stomach

Not looking superior to the spleen