FAST – Focus on the RUQ – False +ve

Text and images  Genevieve Carbonatto

There is a BAT call. A young 35 year old has fallen from a 3 story building and essentially landed on his feet.  He has extensive leg injuries and possible chest and abdominal injuries. BP 95/60 HR 110/min RR 25/min Saturating 96% on RA.

The trauma team is called. The patient gets wheeled in. He has both legs in splints and a pelvic binder on.  He has extensive injuries to his legs, femoral, fibular and tibial fractures with ankle fractures on the right. Probable foot fractures on the left.  He is pale and complaining of pain. The history is taken while the patient is transferred to the bed. His BP is 90 systolic his HR 120/min.  IV lines are inserted fluids are started. The massive transfusion protocol is activated.

Ultrasound of RUQ:

This is perihepatic fat, not fluid. There is no fluid  at the tip of the liver

It is possible to compare the above with a positive FAST below

The hypoechoic areas are well defined. The liver edge is clearly visible as separate from the fluid.

Now try the following 2 images : Fat or fluid?

Perihepatic fat is seen in the first image and fluid at the tip of the liver in the next


Small volumes of free intraabdominal fluid can be difficult to distinguish from perihepatic fat. Free fluid is usually completely anechoic (may be hypoechoic or hyperechoic  if coagulated blood) and has a characteristic shape; stellate, sharp edges.  Perihepatic fat on the other hand is not usually completely anechoic and has a more regular shape at the liver edge






Leave a Reply

Your email address will not be published. Required fields are marked *