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Clinical Case 104: FAST Thinking

This is a trauma case.  I want to use this case to illustrate something about the way we think about trauma when it comes to making calls using ultrasound – specifically the FAST exam.  FAST exams are ubiquitous in modern ED practice – but if executed and interpreted poorly – they are potentially a source of error.

Now you may be aware that I am an US tragic – and when it comes to trauma I have been seriously drinking from the gel fountain.  OK – onto the case.

Typical Broome case:  a lot of unknown unknowns.  30 y.o male who is brought in by the Ambos after being found on the roadside.  Appears to be very drunk.  There wis a vague history from the Ambos that a few “innocent bystanders” saw our patient getting a “proper flogging” [being kicked and punched by a group of fellows].

On initial assessment there is not much to find externally – no bruises or lacerations .  His Obs are really very normal [BP 110/70,  pulse 80, RR = 12, breath alcohol level 0.3%…. normal for Broome].  He has a normal neurological examination [ which is of course the bluntest test in Medicine! ] And equally reassuringly has equal and reactive pupil responses.

Now it is a few hours since the injury and his belly is sore.  Despite his relatively pickled state he is really not wanting you to examine his belly at all.  He seems very tender though there is no distension or bruising.

So being me – it is time to get some gel onto the patient and find the badness.  The scan is basically negative, well almost.  The LUQ, pelvis and subxiphoid views are all normal… but. The RUQ view is just not quite right. Take a look and think – is this a positive, a tiny bit of free fluid? Or is it OK?  This is the sort of call you need to be really sure about when doing these bedside scans.

Because it would be easy to look at this and say – “it is OK” and move on, but if you cannot convince yourself of normality – then you need to act.  So what is it going to be?
RUQ FAST view
So – here is the summary: a Very drunk man with normal obs.  Not a clear mechanism of injury – but we think he has been “flogged”.  Not much to find on examination.  And his FAST exam looks pretty good – but is that RUQ view as it ought to be?  It all hinges on this!

OK I ma going to leave it hanging there and wrap up the case in a few days.

Let me know – what will you do next?

If you are interested in the finer points of the FAST exam then I highly recommend Dr Laleh Gharabaghian’s Sonospot website, or check out her podcast with Scott Weingart on “Don’t Half Ass your FAST”

OK, after a few days to consider the FAST  – here is the conclusion to the case.  But first a rant about “half-arsing the FAST” [Love that line from Dr Laleh]

Obviously it would be a bad idea to make a call on a single still image from a FAST protocol – and yet I see this a lot!  I see a lot of Docs getting a little too focussed on getting a “text book picture” on the screen.  I think we should be exploring the area, as Laleh says: fanning through the whole potential space around Morison’s pouch and into he paracolic gutter if the gas allows.

Lots of folk use a single angle of attack – this often gives a nice image – but to be sure that you are not missing something down at the inferior edge of the liver – you need to look at it from a few sides.  This requires one to have a few tricks in the quiver – not just 4 “standard” points to cover.

Now – point number 2.  FAST (and a lot of bedside US) is not the most sensitive test – it requires a decent volume of haemoperitoneum to be present before you notice it.  So what does that mean in practical terms?  Well I looked at the image above – and thought: “it is nearly normal”.  There just might be a slip of blood there anterior to the kidney.  On a second fan through – I was convinced that there was something “not right”.  It was not clearly NEGATIVE.  Now human nature makes us want to think like this:  ‘if it is close to normal – it can’t be too bad.  Could it?’  But that is wrong – FAST is insensitive, so any subtle abnormality could potentially mean serious pathology.  When you interpret a FAST – you need to be certain of normality.  There is no room for “close enough” here.  And when I rescanned this patient – I was not certain.  So I decided to go onto CT.

A slice from the CT

liver cT

Liver laceration with associated pancreatic contusion. No fresh blush of contrast

So – as you can see.  A small anomaly on the FAST can bely serious injury.

So – our patient remained stable and was managed conservatively.  HE did have a lipase bum and went onto develop some traumatic pancreatitis.  [ we would never blame the alcohol! ]

And for the record he had serial FAST scans which become more obviously positive over time.  One could even see the laceration with the aid of the CT!.  But that is not what FAST is about – you should not be looking for solid organ injury.

And here is the liver lesion on the subsequent UltrasoundLiver laceration

So remember – DON’T HALF_ASS YOUR FAST

Have a low threshold to call it “not normal”.

Scan like you are hunting for blood – not just taking a snapshot!

Repeat the scan if in doubt.  And remember to interpret in the clinical context – i.e.. a NORMAL FAST in a crashing patient means little.  You need to find the badness when the pressure is dropping – either in CT or the operating room!

Happy scanning – Casey

Comments

  1. Victoria Stephen says:

    Hi Casey.

    Great case. I too love ultrasound and am particularly interested in learning to apply the ultrasound findings to the clinical context. I second what you said about Laleh’s emcrit podcast-helped me be a lot more careful than I used to be.
    The case: the patient was found several hours after the injury. This means the free fluid had plenty of time to clot. There could be plenty of clots in that abdomen which you can’t see now as they are grey. This patient may have an intestinal perforation due to the blunt trauma, a sliver of fluid may be all that it produces, if you are lucky. The patient has a lot of abdominal pain out of proportion to exam findings, that concerns me, and increases my suspicion of injury.

    I would look at the haemodynamics, the blood gas, the lactate. I assume he’s haemodynamically stable, so i would CT scan him. Don’t think there’s one in Broome though?

    EFast is easy in the hypotensive patient, much trickier in the stable patient. Interpret with caution. repeat it if necessary. If he had no abdominal pain and tenderness, and other investigations were normal, that black stripe may be fat, in which case i would keep him over and do serial examinations in an area where I could watch him closely.

  2. Nitin Bijwe says:

    sir
    can we do an xray abdomen standing ?
    should rule out bowel perforation.
    fast and quick.

    thanks.

  3. Excellent case Casey, thanks !!

    What’s my interpretation of the image? I’m not too sure! Ultrasound is so much easier when you’re the person holding the probe at the bedside….

    Regardless, this scenario really highlights our need to appreciate the limitations (or test characteristics) of point-of-care ultrasound – in this case the FAST exam. Reproducibly, it has excellent specificity (95-99%) and rapidly improves our decision making in the unstable trauma patient (both penetrating & blunt trauma), ie. laparotomy now!! However; the sensitivity of FAST seems to be capped in the mid-to-high 80’s; and we need to keep this in mind when we have a ‘negative’ study but either a concerning mechanism of injury or a concerning physical exam. There still could be significant pathology !

    This is where the pre-test ‘concern’ enters the game. For this guy, our index of suspicion is already pretty high (drunk, difficult to assess, ongoing severe abdominal pain with minimal findings). Before I’ve laid the probe on his belly I’m considering the potential pathology which includes small bowel injury, duodenal haematoma (on top of the usual splenic or liver injuries) & I have to accept that for some of these; USS won’t clinch the diagnosis for us.

    If this guy came through my tertiary ED, he would get a CT without flinching !!

    As an aside; in a case such as this with such an unreliable story we should really consider the non-traumatic causes of belly-pain. Pancreatitis, perforated viscous, ischaemic bowel….

    Thanks again,
    Chris.

  4. The equation depends on the following:
    1) How sore is he and how long will it take for him to become unpicked?
    2) How far is the closest CT scanner and who will go with him?
    3) Where is your closest general surgeon and what is he able to deal with?
    4) How long will it take to get him to a major trauma centre if things go pear-shaped?
    5) If the patient destabilises, what kind and how much blood product do you have?

    Although most stable patients with solid organ injuries are managed conservatively and CT is not a great modality to detect hollow viscus injuries, a delay in repair in the latter has significant morbidity. By the time his acid-base and lacate to go off he would be pretty sick by then.

    Even if CT is normal, but he is still pretty sore or follow-up is not assured, keep under observation. Ideally you want the person doing the serial examinations to be the one who is deciding to do the cutting.

  5. Great case Casey! …. and thanks for the shout out!
    Its always the drunks that make the exam go to S***! Not sure about over there, but every single alcoholic that comes into our emergency department has belly pain – no matter what brought them in.
    Looking forward to case finale in a few days!
    Of course, Ill say what Ive said before on emcrit and everywhere else – need to fan widely, deliberately, and use multiple rib spaces to especially visualize the caudal tip of the liver in that right upper quadrant! Keep that patient you are observing flat – at least as best as you can (lots more difficult to do that when they have had a few….. 🙂

  6. Here is the conclusion to the case. Enjoy.

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