Category Archives: Imaging

Imaging

The Role Of Postop CT Scan In Penetrating Trauma

CT scans are commonly used to aid the workup of patients with blunt trauma. They are occasionally useful in penetrating trauma, specifically when penetration into a body cavity is uncertain and the patient has no hard signs that would send him or her immediately to the operating room.

Is there any role in operative penetrating trauma, after the patient has already been to the OR? The dogma has always been that the eyeballs of the surgeon in the OR are better than any other imaging modality. Really? The surgical group at San Francisco General addressed this question by retrospectively reviewing 6 years of their operative penetrating injury registry data. They were interested in finding how many occult injuries (seen with CT but not by the surgeon) were found on a postop CT. A total of 225 patients who underwent operative management of penetrating abdomen or chest injury were included. Here are the factoids:

  • Only 110 patients had a postop CT scan; 73 had scans within the first 24 hours, the other 37 were scanned later
  • Rationale for early scan was to investigate retroperitoneal injury in half of patients, but frequently no indication was given (41%)
  • Rationale for late scan was for workup of ileus in one third, or for evaluation of new or unexpected clinical problems
  • Occult injuries were found in about half of early CT patients (52%), and 22% of late CT patients
  • The most common occult injuries were fractures, GU issues, regraded solid organ injury, and unrecognized vascular injuries
  • Ten patients had management changes, including:
    • Interventional radiology for four injuries with extravasation
    • Operation for orthopedic or GU injury in seven patients
    • One patient underwent surgery for an unstable spine fracture

Bottom line: There appears to be a significant benefit to sending some penetrating injury patients to CT in the early postop period. Specifically, those with injury to the retroperitoneum, deep into the liver, near the spine, or with multiple and complicated injuries would benefit. Simple stabs and gunshots that stay away from these areas/structures probably do not need followup imaging. 

Reference: Routine computed tomography after recent operative exploration for penetrating trauma: What injuries do we miss? J Trauma 83(4):575-578, 2017.

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Imaging

The Value Of Reinterpreting Outside CT Scans

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Okay, one of your referring hospitals has just transferred a patient to you. They diligently filled out the transfer checklist and made sure to either push the images to your PACS system or include a CD containing the imaging that they performed. For good measure, they also included a copy of the radiology report for those images.

Now what do you do?

  • Read the report and consider the results
  • Look at the images yourself and make decisions
  • Have your friendly neighborhood radiologist re-read the images and produce a new report

Correct answer: all of the above. But why? First, you can get a quick idea of what another professional thought about the images, which may help you think about the decisions you need to make.

And one of the few dogmas that I preach is: “read the images yourself!” You have the benefit of knowing the clinical details of your patient, which the outside radiologist did not. This may allow you to see things that they didn’t because they don’t have the same clinical suspicion. Besides, read the images often enough and you will get fairly good at it!

But why trouble your own radiologist to take a look? Isn’t it a waste of their time? Boston Children’s Hospital examined this practice in the context of taking care of pediatric trauma patients. This hospital accepts children from six hospitals in the New England states. In 2010, they made a policy change that mandated all outside images be reinterpreted once the patient arrived. They were interested in determining how often there were new or changed diagnoses, and what the clinical impact was to the patient. They focused their attention only on CT scans of the abdomen and pelvis performed at the referring hospital.

Here are the factoids:

  • 168 patients were identified over a 2-year period. 70 were excluded because there was no report from the outside hospital (!), and 2 did not include the pelvis.
  • Reinterpretation in 28% of studies differed from the original report (!!)
  • Newly identified injuries were noted in 12 patients, and included 7 solid organ injuries, 3 fractures, an adrenal hematoma, and a bowel injury. Three solid organ injuries had been undergraded.
  • Four patients with images interpreted as showing injury were re-read as normal
  • Twenty of the changed interpretations would have changed management

Bottom line: Reinterpretation of images obtained at the outside hospital is essential. Although this study was couched as pediatric research, the average age was 12 with an upper limit of 17. Many were teens with adult physiology and anatomy. There will be logistical hurdles that must be addressed in order to get buy-in from your radiologists, such as how they can get paid. But the critical additional clinical information obtained may change therapy in a significant number of cases.

Reference: The value of official reinterpretation of trauma computed tomography scans from referring hospitals. J Ped Surg 51:486-489, 2016.

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Head, Imaging

Best Of EAST #9: Routine Repeat Head CT For TBI Patients On Antithrombotic Agents

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The data we use as guidance for repeat head CT in elderly patients who sustain mild TBI while taking antithrombotic therapy remains limited. There is a slowly growing consensus that the need is limited, but there is still a very wide variation in practice patterns.

The group at HCA Healthcare Nashville collected data from 24 system hospitals on this very specific cohort of patients: elderly (age > 55), head trauma with GCS 14-15, an initial head CT, and no other injuries with AIS > 2. They divided these patients into two groups based on whether they were currently taking antithrombotic (AT) therapy. Rate of delayed intracranial hemorrhage (ICH), need for neurosurgical intervention, and mortality were compared.

Here are the factoids:

  • About 3,000 patients were enrolled and only 10% had a repeat head CT
  • Of those who were rescanned, 10% of patients on meds had a new ICH vs 6% in those not taking meds (not statistically significant)
  • Extrapolating those numbers to all patients, the rate of delayed ICH would be 0.7% in patients not taking AT vs 1.0% for those who were (also not significant)
  • Mortality attributable to a head bleed occurred in only one patient who was made comfort care
  • There were no neurosurgical procedures performed in either group

The authors concluded that this specific subset of patients has a very low rate of delayed ICH, and that there are minimal clinical consequences in those that do. They do not support repeat head CT.

Bottom line: This abstract adds to the growing body of literature that shows little benefit to repeat head CT scan after a negative initial study, even if the patient is on blood thinners. Many previous studies involve only a single center and/or have smaller numbers. This one is larger because of the size of the HCA trauma system, and answers a simple set of questions on a limited subgroup of patients: elderly, mild TBI, with limited other injuries.

My back of the envelope power calculations show the authors may be a little short of the number of subjects to be able to show that the difference in the number of delayed ICH (0.7% vs 1.0%) is statistically significant. But the numbers are close enough and the p value so large (0.3) that they are probably right. This is completely offset by the absence of necessary neurosurgical interventions and the single attributable death.

Many trauma centers, including my own, have adopted a “no repeat scan” policy after a negative initial scan, even on thinners. In fact, unless the patient has some other injury that requires admission, they are discharged home with a responsible adult.

Here are my questions for the authors and presenter:

  • Did you do any type of power analysis to determine if the large number of patients included was actually large enough?
  • The term “antithrombotic therapy” is used broadly; which agents were considered in this category? Traditional warfarin therapy? Aspirin and other antiplatelet agents? DOACS?
  • Have you changed your system guidelines to reflect your work?

This is important and practical work! I’m looking forward to hearing all the details.

Reference: ROUTINE REPEAT BRAIN CT SCANNING IS UNNECESSARY IN OLDER PATIENTS WITH GCS 14-15 AND A NORMAL INITIAL BRAIN CT SCAN REGARDLESS OF PREINJURY ANTITHROMBOTIC USE: A MULTICENTER STUDY OF 3033 PATIENTS. EAST 35th ASA, oral abstract #31.

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Complications, Imaging

Best Of EAST #8: Timing Of Reimaging For BCVI

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There are still many questions regarding optimal management of blunt carotid and vertebral arterial injury (BCVI). We know that they may ultimately result in a stroke. And we kind of know how to manage them to try to avoid this. We also know that the grade may change over time, and many vascular surgeons recommend re-imaging at some point.

But when? There are still many questions. A multi-center trial has been collecting observational data on this issue since 2018. The group reviewed three years of data to examine imaging characteristics and stroke rate during the study period.

Here are the factoids:

  • A total of 739 cases were identified at 16 trauma centers
  • The median number of imaging studies was 2, with a range of 1-9 (!). Two thirds received only one study.
  • Injury grade distribution was as follows:
    • Grade 1 – 42%
    • Grade 2 – 30%
    • Grade 3 – 10%
    • Grade 4 – 18%
    • Grade 5 – <1%
  • About 30% changed in grade during the hospitalization, with 7% increasing and 24% decreasing.
  • Average time to change in grade was 7 days
  • Nearly 75% of those that decreased actually resolved. All of the grade 1 lesions resolved.
  • Stroke tended to occur after about one day after admission, although the grade 1 lesions took longer at 4 days
  • Strokes occurred much earlier than grade change

The authors concluded that there should be further investigation about the utility of serial imaging for stroke prevention.

Bottom line: This is basically a “how we did it” study to tease out data on imaging and stroke after BCVI. It’s clear that there is no consensus across trauma centers regarding if and when repeat imaging is done. And it’s not really possible to make any recommendations about repeat imaging based on this study.

However, it does uncover one important fact. It takes a week for the injury grade on CT to change, but strokes occur much earlier and usually within 24 hours! This is important because it makes it clear that it’s crucial to actually make the diagnosis early. Average stroke occurrence was 9% overall. Grade 1 injuries had only a 3% rate, but grades 2-4 were in the 12-15% range. Grade 5 had a 50% stroke rate!

These facts reinforce the importance of identifying as many of these BCVI as possible during the initial evaluation. The abstract I reviewed yesterday confirmed that the existing screening criteria (Memphis, Denver) will miss too many. More liberal imaging is probably indicated. If you missed the post, click here to view it in a new window.

Here are my comments for the authors and presenter:

  • The “change in BCVI grade over time” charts in the abstract are not readable. Please provide clear images during your presentation and explain what they mean. I was confused!
  • Based on your data, do you have any recommendations regarding the utility of re-imaging? Is it necessary in the same hospitalization at all? These patients will receive treatment anyway, and it doesn’t appear to have any impact on stroke rate.
  • Do you have any recommendations regarding the (f)utility of existing screening systems given the early occurrences of stroke in the study? Are you a fan of using energy / mechanism rather than a bullet list of criteria?

This is important work and I can’t wait to look at the data up close.

Reference: BLUNT CEREBROVASCULAR INJURIES: TIMING OF CHANGES TO INJURY GRADE AND STROKE FORMATION ON SERIAL IMAGING FROM AN EAST MULTI-INSTITUTIONAL TRIAL. EAST 35th ASA, oral abstract #34.

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Complications, Imaging

Best Of EAST #7: Routine Screening vs Denver Criteria For BCVI

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Currently, blunt carotid and vertebral artery injury (BCVI) is diagnosed using CT angiography of the great vessels and neck. This study is typically ordered when there is some degree of clinical suspicion based on the application of an established screening system. There are currently two such systems in use, Denver and Memphis.

I dedicated a week to BCVI earlier in the year. If you’d like to read the series, click here.

Both screening systems have been updated over the years. There is now a modified Memphis and an expanded Denver system. The reason for the modifications is simple: some patients were not flagged as at risk by the original versions of the systems. Does this mean we should screen more, or even screen everybody?

To answer this question, it’s important to have an idea of the number of patients who actually sustain the injury. This means having a liberal screening policy in place in the first place. The trauma group at Ascension St. Vincent Hospital in Indianapolis liberalized their criteria in 2012 and first published their experience in 2015. In this abstract, they examined their experience in screening all high-energy patients and reviewing how many patients would have been screened using the expanded Denver criteria.

Here are the factoids:

  • This is a single-center, retrospective study carried out over 5.5 years
  • A total of about 17,000 blunt trauma patients were seen, and about 30% underwent CTA neck for BCVI screening
  • About 1% of total patients screened were found to have BCVI, which was about 3% of those who underwent CTA
  • Sixteen percent of patients who actually had BCVI did NOT meet any of the expanded Denver criteria
  • Ten percent of patients with grades III-V injury did not meet any of the criteria

The authors concluded that using the expanded Denver criteria alone will result in missed injuries and that liberalized screen should be considered to decrease risk.

Bottom line: Once again, this is a paper that conforms to my own bias and experience, so I have to work to be critical of it. We have seen delayed diagnoses of this injury at our center using the standard criteria. For that reason, we recently implemented a guideline to add CTA neck on any patient with a mechanism sufficient to warrant CTA chest (we are not automatic pan-scanners).

This is a straightforward descriptive study at a center that has had a liberal BCVI screening guideline for nearly a decade. The only opportunity for bias lies in the specifics of the screening criteria. In St. Vincent’s case, it is simple: any patient with a mechanism sufficient to require CT cervical spine or chest received CTA neck as well.

I would argue that this might be a bit too liberal. There are many elderly patients who fall that require cervical spine CT, but the mechanism should be insufficient to sustain a BCVI. It can be an add-on study if fracture patterns are seen that fall within the Denver or Memphis criteria.

Here are my questions for the authors and presenter:

  • Why choose the Denver criteria? Why not look at Memphis, too? I’m sure you will find similar issues.
  • Did you analyze your elderly falls patients who got their CTA based on your cervical CT criterion? It seems like this could result in substantial overtriage. Did you actually detect any BCVI in this group if they didn’t have one of the classic fracture patterns?

This is an important abstract, and I’m looking forward to hearing all the specifics! It looks like it may be time to seriously consider the energy of the mechanism, if not ditch the criteria altogether.

Reference: ROUTINE CT SCREENING FOR BLUNT CEREBROVASCULAR INJURY IDENTIFIES INJURIES MISSED BY CLINICAL RISK FACTORS. EAST 35th ASA, oral abstract #35.

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