A young male presents with abdominal pain 24 hrs after an assault where he was punched and kicked to the flanks. he is mildly tachycardia but walked into the ED and appears from the end of the bed to be clinically stable. He has marked tenderness in the left and right upper quadrants.
- no free fluid was noted by the person interpreting the scan
- Clinical concern remained for intraadominal injury and he proceeded to CT. Selected images are shown below
- this is reported as a small liver laceration a renal laceration and some free fluid in the pelvis. He is managed conservatively
- FAST scans have lots of limitations. The old adage in USS holds – that if positive it’s probably right but if negative then all bets are off. This is reflected in the diagnostic characteristics showing a high specificity and low sensitivity.
- A superficial, rushed FAST exam will often mislead in subtler cases. Laleh Gharahbaghian, from sononspot has a great series on making your FAST exam better. It was also featured on EMCrit as a podcast.
- In this case there are several pitfalls
- the LUQ does not image above the superior portion of the spleen, from a prior case we know that this is where free fluid will lie
- the RUQ is incompletely visualised. While Morrisson’s pouch is nicely seen the inf pole of the kidney is not visualised.
- in the pelvis a sliver of free fluid is actually seen at the very end of the sweep through the bladder. The sweep is so quick that it can be easily missed (as it was in this case)
- Ultimately a quality assurance programme with review of images by trainees can be a really helpful adjunct to ensure that we make the best use of our scanning.
- Importantly in this case (as in all cases with POCUS) the operator used good clinical judgement and was well aware of the limitations of POCUS