Tag Archives: imaging

ACS Trauma Abstracts #5: Pan-scan vs Selective CT For Pediatric Patients

In major adult blunt trauma, there are still two factions: those who pan-scan for diagnosis, and those who use CT selectively. The pan-scan proponents argue that they find everything, including things that would have been missed with selective scanning. The selective scanners argue that those things are typically not clinically significant, and radiation exposure is reduced.

Who is right? We’re still not sure. But when it comes to children, most believe that less radiation is always better. The group at USC decided to look at their experience with pan-scan vs selective imaging in blunt pediatric trauma patients, defined as those < 16 years of age. They reviewed their experience over a three year period, excluding those who had low blood pressure (<90). A total of 648 children met these criteria, and an array of variables were analyzed to try to determine “superiority.”

Here are the factoids:

  • 88% of these patients had low injury severity (ISS < 15), 567 patients
  • The low severity group who were selectively scanned had a half-day decrease in length of stay*, a quarter-day decrease in ventilator days, lower morbidity (15% vs 24%)*, and radiation exposure (8 vs 18 mSv)*, with the asterisked variables being “statistically significant”
  • The high severity also showed positive differences in decreased ICU length of stay, ventilator days, morbidity*, and radiation exposure*
  • For both pan- and selective-scanning, additional imaging led to no additional interventions in 95% of cases

Bottom line: Ugh! This is not a good abstract. It shows association, but not causation with anything but the radiation exposure calculations. Yes, if you scan less in the selective arm, there better be less exposure. But the other variables are either not clinically significant, or not defined well (i.e. morbidity).

The authors conclude that selective scanning is the way to go based on this (extremely weak) data. This is why I always recommend that you read the whole paper, not just the abstract, or in this case the whole abstract and not just the conclusion. The data, as presented in this abstract, do not support this at all.

The authors don’t say how many of these patients were very young, and how many of them actually received pan-scans. But any pediatric trauma surgeon would cringe if they read this  article. Although you may be a big believer in pan-scanning, reserve it for adults only until we have some better data. Don’t irradiate kids unnecessarily!

Reference: Selective CT imaging is superior to liberal CT imaging in the hemodynamically normal pediatric blunt trauma patient. JACS 225(4S1):562, 2017.

Are You Overusing Chest CT In Kids?

Many centers have developed guidelines for ordering various imaging studies, mostly in adults. These frequently dictate indications for head, cervical spine, and abdominal CT. The use of chest CT guidelines are far less common. And for the most part, such guidelines are significantly lacking for pediatric trauma evaluation.

Oregon Health Sciences University published a study detailing the use and utility of chest CT in pediatric patients, which they defined as age less than or equal to 18. They also looked at the impact of implementation of imaging guidelines for chest CT. They pooled data on blunt injuries from two Portland children’s hospitals. They collected a historical cohort over 8 years ending in 2015. One hospital had implemented region-specific imaging guidelines in 2010, and the impact of this was observed. They pooled data from both centers to identify mechanisms predictive of significant thoracic injury.

Here are the factoids:

  • Nearly 3000 patients were reviewed for thoracic CT use across the study period.
  • 1451 had chest x-ray only, 933 had chest CT only, and 567 had both
  • Although CT use in other body regions significantly declined across the study period, thoracic CT did not.
  • Chest CT changed management on only 17 of 1500 patients (1%).  There were 2 operations, 1 stent placement, 1 medical management, and 13 changes I consider rather weak (chest tube insertion, negative workup)
  • All clinically significant findings were predicted by an abnormal chest x-ray and motor vehicle mechanism

Bottom line: Chest CT continues to be overused in pediatric blunt trauma (and adults too!). This is especially unsettling due to it’s low yield and the unclear future danger of high dose radiation received during childhood. The major issue with this study is that it mixes adults and children and calls them all children. Specifically, most patients age 13-14 or above act anatomically and physiologically more like adults. It would have been nice to separate out the lower age group, but this typically results in very low numbers for analysis. In this case, it should have been possible because the median age was 13.

I recommend that all centers adopt some kind of blunt imaging guidelines to reduce clinician variability and unneeded radiation exposure. This is particularly true for children, since they are more sensitive to it and will live long enough to potentially experience the adverse effects from it. 

For both children and adults, chest CT should be reserved for evaluation of potential aortic injury, and nothing else. Rib fractures, hemothorax, and pneumothorax are best evaluated by traditional chest x-ray, and therapeutic decisions based on this alone. Abnormal chest x-ray findings, coupled with a high-energy mechanism (MVC, crush, pedestrian struck, and fall from a real height (3+ storys) should drive the decision to obtain a chest CT.

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Reference: Limiting thoracic CT: a rule for use during initial pediatric trauma evaluation. J Ped Surg, In press, Aug 28, 2017.

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

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.

Chest CT vs Chest X-Ray After Chest Tube Insertion

Two days ago, I discussed getting the traditional chest x-ray routinely after chest tube insertion. The answer was yes, it is important even if it appears to be functioning correctly. But yesterday, I also showed you how the chest x-ray can lie.

Remember this image?

Looks perfect! But it’s a 2-D view and you don’t know where the tube is in the anterior-posterior axis. It turns out to be in the patient’s subcutaneous tissues of his back, near his scapula!

So what if this is a trauma activation patient and you are getting ready to send your patient for a chest CT shortly? Should you follow the usual dogma and still get a conventional chest x-ray prior to leaving the trauma bay?

The answer is no! Typically, your trauma activation patient should have rapid access to the CT scanner, so you won’t have to wait very long. And the additional 3-D information is very helpful in making sure the tube is placed exactly where you want it.

Bottom line: If you are planning on obtaining a chest CT anyway in your trauma patient, don’t bother with a conventional chest x-ray first to check chest tube position. But DON’T order a chest CT for this reason alone! Remember, the chest CT is only for detecting aortic injury in blunt trauma. It should not be used for diagnosing fractures, hemothorax, or pneumothorax. Or chest tube position!

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Quiz: Is This A Good Chest Tube?

A blunt trauma activation patient presents with a pneumothorax seen on the initial chest x-ray, obtained in your trauma bay. You professionally insert a large chest tube, and all appears to go well. You shoot a followup chest x-ray and this is what you get:

What do you think of the tube position? Looks great, right?

But if you look carefully, you can see the lung outline in the middle of the right side of the chest. Big-time pneumothorax despite what looks like a perfectly placed tube. There are several possible explanations, and many of you sent me your guesses:

  • The tube is in the lung. This rarely happens to normal lungs. Sure, you can probably do it to an ARDS lung, but otherwise it’s not very likely.
  • The tube is in the fissure. This does happen on occasion, but not often. And many times it works anyway.
  • The tube is occluded or kinked. A PA or AP chest x-ray will show the kink, although bent tubes frequently work anyway. If a hemothorax is present, it is possible that a clot is plugging the tube. Clearing a plugged tube will be the subject of another post.
  • It’s not really a chest tube. Hopefully, this would have been detected when it was placed, but it isn’t always. The chest x-ray above looks great, right? Unfortunately, it’s a 2 dimensional representation of a 3-D object. Where is that tube in the z-axis?

In this case the correct answer is the last one. This is one time when I would actually recommend a lateral chest x-ray. Have a look at the result. You can clearly see the tube snaking around into the soft tissues of the back.

Bottom line: Remember that a perfect x-ray doesn’t necessarily mean a perfect tube. Go through the various possibilities quickly, and make it work.

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