Tag Archives: chest x-ray

Imaging

Using Chest CT To Detect Occult Injuries

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There are major belief systems when it comes to the use of trauma CT: selective scan vs pan scan. The selective scanners believe that too much radiation can be bad, and that the risk of excess exposure outweighs the value of scanning everything. The pan scanners believe that valuable information might be missed unless they routinely image everything.

Who is right? There’s probably value in each side of the argument. But do we have data? Good data? Two emergency medicine groups from UC-Irvine and UC-San Diego tried to answer this question via a prospective study involving 10 Level I trauma center EDs in California.  They tagged onto data collection underway for the NEXUS chest and chest CT studies from 2009-2012.

Patients with fresh (< 24 hours) blunt trauma who underwent chest imaging in the ED were included. Patients needed to have both CT scan and chest x-ray within 24 hours, at the discretion of the emergency physician. Weirdly, they skewed their sample by enrolling patients from 7am to 11pm daily due to availability of research personnel.

The researchers were looking for minor and major interventions necessitated by data discovered on the CT scan. Occult injuries were defined as clinically important if an intervention occurred because of it. Major interventions included surgery, mechanical ventilation for pulmonary contusion, or chest tube for hemo- and pneumothoraces.

Here are the factoids:

  • Nearly six thousand patients were enrolled, and 2,048 had at least one injury identified on either study
  • A total of 1,454 of these injuries (71% of injuries, but only 25% of patients) were occult, only being seen on the CT scan
  • Chest x-ray found all injuries in only 29% of patients (not surprising)
  • When pulmonary contusion was seen by CT only, 6% were placed on ventilators; when hemo- or pneumothorax were seen, 41% and 29% respectively had chest tubes inserted (wow!)
  • The authors tallied 241 major interventions for occult injury in 202 patients, 154 chest tubes for hemo/pneumothorax and/or mechanical ventilation, 9 operations for diaphragm or aortic injury, and the remainder appear to be for other chest wall fractures

The authors concluded that occult injuries were found in 71% of their patients, with the majority of those “requiring” chest tubes. They recognized some of the shortcomings in their study and stopped short of recommending a pan-scan type approach to major chest trauma.

Bottom line: This argument always boils down to diagnostic yield vs money vs radiation. Radiologists like to find as many things as they can, so CT is great. For me, it always comes back to that old saying: “if a tree falls in the woods when no one is around, does it make a sound?” 

The corollary is “if a diagnosis is found on CT that is not clinically relevant, do we care?” But wait, you say, they did have to intervene. Or did they?

Have you ever scanned a chest and seen something that makes you intubate the patient immediately and put them on a ventilator? Probably not. It’s a clinical judgement. The scan may make you a bit more wary, but you will still wait for some clinical signs that the patient needs that extra help. 

And what about chest tube insertion? I’m sure most of you have seen a modest pneumothorax on chest x-ray (1 cm away from the chest wall, extending to the 6th intercostal space, say). Ho hum. And then you get a CT scan and your eyes widen. It always looks much larger on the scan. It always does. Yet the patient is still lying there comfortably, with normal oxygen saturations. Do you really need to put a tube in? For decades, we used only the x-ray, and patients did fine.

So I don’t buy that the CT result made them do the interventions. It was the clinician’s choice based on how they interpreted the scan, not the patient’s clinical condition. Without specific guidelines that determine when interventions are indicated, it just boils down to “I do an intervention when I think the patient needs it.” And every clinician will have their own criteria and thresholds. It’s tough to learn from things done this way.

So I stick by my guns. We know that chest x-ray is flawed. But it does provide good clinical data even without a bunch of diagnostic minutiae. A good practice guideline that helps select the patients most likely to benefit from a CT scan is paramount.

As you can probably tell, I’m a selective scan kind of guy and still have not run across a study that is clean and compelling enough to make me change. And I think I’ll be waiting for a while for one of those to pop up!

Reference: Prevalence and clinical import of thoracic injury identified by chest computed tomography but not chest radiography in blunt trauma: multicenter prospective cohort study. Ann Emerg Med 66(6):589-600, 2015.

Imaging

Is The Trauma Bay Chest X-Ray Really Necessary Or Just Dogma?

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I love challenging dogma. I spoke last week (virtually) at an excellent event at the Intermountain Medical Center in Utah. One of my talks there addressed trauma myths and dogma.

I bring this up because there is an interesting article in the Journal of Trauma this month that questions the necessity of the routine chest x-ray (CXR) in blunt trauma resuscitation. So of course, this caught my eye. Let’s dig in.

The first thing to understand is that this article is an opinion piece and is identified as such. It was written by three surgeons, including the trauma medical director, at the Stanford University Hospital trauma center.

First, what are we really looking for on the chest x-ray that is taken in the trauma bay? I call them “the three big things”.

  • Big air. The first item to be identified is a pneumothorax. The chest x-ray helps the trauma professionals decide if the pneumo needs an intervention (chest tube) and when. (Note: it could in theory identify a tension pneumothorax. But in that case, the trauma pros should be embarrassed. They should have picked that up on their clinical exam and assessment of the vitals.)
  • Big blood. The chest x-ray can also identify a hemothorax. And once again, it can help decide whether its size warrants chest tube insertion.
  • Big mediastinum. A wide mediastinum may indicate the presence of hematoma from an aortic injury. It is one of the indications for performing CT angiography of the chest to rule it out.

Here are their authors’ arguments:

  • There are other imaging modalities available to us that are very accurate. FAST ultrasound has been used routinely for abdominal and cardiac evaluation for over a decade. The extended FAST (eFAST) involves evaluation of the pleural interface to identify pneumothorax. A study published last year pitted CXR vs eFAST. It found that the eFAST outperformed with a sensitivity of 94% and specificity of nearly 100%.
    But what about hemothorax? Ultrasound is less helpful here. But the CT scanner is. It is far more accurate at identifying and quantifying hemothorax than the CXR.
  • Evaluation of the aorta can either wait, or it can’t wait at all. If the patient loses vital signs in the trauma bay the decision to open the chest or insert a REBOA catheter must be made. In the latter case, a chest x-ray must be obtained to exclude a thoracic source of bleeding that the cathether is of no use for. But if the patient truly is bleeding out from a blunt aortic injury, it is nearly certain that he or she is not leaving the trauma bay alive.
    What about using the wide mediastinum as an indication or order the chest CT angiogram? The authors argue that there will probably be a history of deceleration or other associated injuries (femur fracture is a very common one).

Bottom line: The authors argue that the chest x-ray should go the way of the lateral cervical spine x-ray used at the turn of the 21st century and before. They claim that judicious use of the extended FAST and CT angiography can identify the significant injuries we need to know about in a timely manner.

My own opinion is more nuanced. I buy their arguments that the extended FAST will identify all significant pneumothoraces. However, we have typically answered the question “how big is too big” using the chest x-ray. That is the most helpful tool in deciding whether a chest tube is warranted or not.

As for hemothorax, I don’t believe that a CT is the best tool for evaluating this, either. Are the authors members of the “pan-scan” school? What about those of us that use the “selective scan” philosophy. True, the abdominal scan will identify both hemothorax and pneumthorax on the lower cuts of the chest. But as in the previous paragraph, we are better trained to judge when a chest tube is indicated by the appearance of the chest x-ray. Hemothorax (or pneumothorax) is not an indication to get a chest CT.

I don’t buy argument that there will be other indications of potential aortic injury. Deceleration is in the eye of the beholder. How do we know how fast the vehicle was actually moving? What is the magic velocity that will break this patient’s aorta? This particular patient may not have any of the other potential indicators that increase suspicion for aortic injury. That wide mediastinum may be the only clue. Yes, the numbers of affected patients are small, but the consequences of missing one could be deadly.

And what about patients who might not get scanned at all? And those who need a study to confirm tube or line placement? They must absolutely get a chest x-ray before they leave the trauma bay.

At this point, I can’t see a way to dispense with the chest x-ray completely. It should still be used to:

  • Confirm pneumothorax from eFAST to help decide if a chest tube is needed
  • Identify potential pathology (hemothorax, wide mediastinum) in patients who don’t otherwise meet criteria for chest CT
  • Verify endotracheal tube position after intubation

What do you think? Please leave your comments or Tweets about this topic.

References:

  • Extended-FAST plus MDCT in pneumothorax diagnosis of major trauma: time to revisit ATLS imaging approach? J Ultrasound. 2019;22(4):461–469.
  • Necessity of routine chest radiograph in blunt trauma resuscitation: Time to evaluate dogma with evidence. J Trauma 2020;89(3):e69-70.
Imaging

Do You Really Need To Repeat That Trauma Bay Xray?

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It happens all the time. You get that initial chest and/or pelvic xray in the resuscitation room while evaluating a blunt trauma patient. A few minutes later the tech returns with another armful of xray plates to repeat them. Why? The patient was not centered properly and part of the image is clipped.

Where is the left side of the chest, and do we care?

Do you really need to go through the process of setting up again, moving the xray unit in, watching people run out of the room (if they are not wearing lead, and see my post below about how much radiation they are really exposed to), and shooting another image? The answer to the question lies in what you are looking for. Let’s address the two most common (and really the only necessary) images needed during early resuscitation of blunt trauma.

First, the chest xray. You are really looking for 3 things:

  • Big air (pneumothorax)
  • Big blood (hemothorax)
  • Big mediastinum (hinting at aortic injury)

Look at the clipped xray above. A portion of the left chest wall is off the image. If there were a large pneumothorax on the left, would you be able to see it? What about a large hemothorax? And the mediastinum is fully included, so no problem there. So in this case, no need to repeat immediately.

The same thing goes for the pelvis. You are looking for gross disruption of the pelvic ring, especially posteriorly because this will cause you to intervene in the ED (order blood, consider wrapping the pelvis). So if parts of the edges or top and bottom are clipped, no big deal.

Bottom line: Don’t let the xray tech disrupt the team again by reflexively repeating images that are not technically perfect. See if you can use what you already have.  And how do you decide if you need to repeat it later, if at all? Consider the mechanism of injury and the physical exam. Then ask yourself if there is anything you could possibly see that was not imaged the first time that would change your management in any way. If not, you don’t need it. But it certainly will irritate the radiologists!

Imaging, Tips

Best Of: Finding Rib Fractures On Chest X-Ray

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A lot of people have been viewing and requesting this post recently.

Here’s a neat trick for finding hard to see rib fractures on standard chest xrays.

First, this is not for use with CT scans. Although chest CT is the “gold standard” for finding every possible rib fracture present, it should never be used for this. Rib fractures are generally diagnosed clinically, and they are managed clinically. There is little difference in the management principles of 1 vs 7 rib fractures. Pain management and pulmonary toilet are the mainstays, and having an exact count doesn’t matter. That’s why we don’t get rib detail xrays any more. We really don’t care. Would you deny these treatments in someone with focal chest wall pain and tenderness with no fractures seen on imaging studies? No. It’s still a fracture, even if you can’t see it.

So most rib fractures are identified using plain old chest xray. Sometimes they are obvious, as in the image of a flail chest below.

But sometimes, there are only a few and they are hard to distinguish, especially if the are located laterally. Have a look at this image:

There are rib fractures on the left side side on the posterolateral aspects of the 4th and 5th ribs. Unfortunately, these can get lost with all the other ribs, scapula, lung markings, etc.

Here’s the trick. Our eyes follow arches (think McDonald’s) better than all these crazy lines and curves on the standard chest xray. So tip the xray on its side and make those curves into nice arches, then let your eyes follow them naturally:

Much more obvious! In the old days, we could just manually flip the film to either side. Now you have to use the rotate buttons to properly position the digital image.

Final exam: click here to view a large digital image of a nearly normal chest xray. There is one subtle rib fracture. See if you can pick it out with this trick. You’ll have to save it so you can manipulate it with your own jpg viewer. 

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Imaging

Chest X-Ray After Chest Tube Insertion: Why Do We Do It?

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More dogma, or is it actually useful? Any time a chest tube (tube thoracostomy) is inserted, we automatically order a chest x-ray. Even the ATLS course recommends obtaining an image after placement. But anything we do “automatically” is grounds for critical analysis to see if there is a valid reason for doing it.

A South African group looked at the utility of this practice retrospectively in 1004 of their patients. They place 1042 tubes. Here are the factoids:

  • Patients were included if they had at least one chest x-ray obtained after insertion
  • Patients were grouped as follows: Group A (10%) had the tube inserted on clinical grounds with no pre-insertion x-ray (e.g. tension pneumothorax). Group B (19%) had a chest x-ray before and had ongoing clinical concerns after insertion. Group C (71%) had a chest-xray before and no ongoing concerns.
  • 75% of injuries were penetrating (75% stab, 25% GSW), 25% were blunt
  • Group A (insertion with pre-x-ray): 9% had post-insertion findings that prompted a management change (kinked, not inserted far enough)
  • Group B (ongoing clinical concerns): 58% required a management change based on the post-x-ray. 33% were subcutaneous or not inserted far enough (!!)
  • Group C (no ongoing clinical concerns): 32 of 710 (5%) required a management change, usually because the tube was too deep

The authors concluded that if there are no clinical concerns (tube functioning, no clinical symptoms) after insertion, then a chest x-ray is not necessary.

Bottom line: But I disagree with the authors! Even with no obvious clinical concerns, the tube may not be functioning for a variety of reasons. Hopefully, this fact would then be discovered the next day when another x-ray is obtained. But this delays the usual progression toward removing the tube promptly by at least one day. It increases hospital stay, as well as the likelihood of infection or other hospital-associated complication. A chest x-ray is cheap compared to a day in the hospital, which would potentially happen in 5% of these patients. I recommend that we continue to obtain a simple one-view chest x-ray after tube insertion.

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Reference: What is the yield of routine chest radiography following tube thoracostomy for trauma?  Injury 46(1):45-48, 2015.