Category: Radiology

When Is An Extremity CTA Necessary?

Here’s another piece regarding low-value testing in trauma, focusing on another topic: the use of CT angiograms for evaluation of extremity vascular injury.

This single-center, retrospective series looks at use of the extremity computed tomography angiogram in the setting of orthopedic and multi-system trauma. For what it’s worth, at least, there were only 275 scans identified during their 10-year study period. However, the bad news, of course: only 16 (6%) of those scans identified an injury requiring treatment.

Of greatest interest to those trying to eradicate low-value care comes the entirely unsurprising observation that 109 (40%) of patients received CTAs despite the absence of hard or soft signs of vascular injury – and all were normal. Additionally, all 16 cases requiring treatment had diminished or absent distal pulses on presentation.

I do anedcotally see the clinical examination being devalued, especially in trauma – it shouldn’t be!

“When are CT angiograms indicated for patients with lower extremity fractures? A review of 275 extremities”
http://journals.lww.com/jtrauma/Abstract/publishahead/When_are_CT_angiograms_indicated_for_patients_with.99386.aspx

All Glory to the Triple-Rule-Out

The conclusions of this study are either ludicrous, or rather significant; the authors are either daft, or prescient. It depends fundamentally on your position regarding the utility of CT coronary angiograms.

This article describes a retrospective review of all the “Triple-Rule-Out” angiograms performed at a single center, Thomas Jefferson University Hospital, between 2006 and 2015. There were no specific circumstances under which the TRO were performed, but, grossly, the intended population were those who were otherwise being evaluated for an acute coronary syndrome but “was suspected of having additional noncoronary causes of chest pain”.

This “ACS-but-maybe-not” cohort totaled 1,192 patients over their 10 year study period. There were 970 (81.4%) with normal coronary arteries and no significant alternative diagnosis identified. The remaining, apparently to these authors, had “either a coronary or noncoronary diagnosis that could explain their presentation”, including 139 (11.7%) with moderate or severe coronary artery disease. In a mostly low-risk, troponin-negative population, it may be a stretch to attribute their symptoms to the coronary artery disease – but I digress.

The non-coronary diagnoses, the 106 (8.6%) with other findings, range from “important” to “not at all”. There were, at least, a handful of aortic dissections and pulmonary emboli picked up – though we can debate the likelihood of true positives based on pretest odds. However, these authors also credit the TRO with a range of sporadic findings as diverse as endocarditis, to diastasis of the sternum, and 24 cases of “aortic aneurysm” which were deemed important mostly because there were no priors for comparison.

The authors finally then promote TRO scans based on these noncoronary findings – stating that, if a traditional CTCA were performed, many of these diagnosis would likely be missed. Thus, the paradox. If you are already descending the circles of hell, and are using CTCA in the Emergency Department – then, yes, it is reasonable to suggest the TRO is a valid extension of the CTCA. Then again, if CTCA in the acute setting is already outside the scope of practice, and TRO is an abomination – carry on as if this study never existed.

“Diagnostic Yield of Triple-Rule-Out CT in an Emergency Setting”
http://www.ncbi.nlm.nih.gov/pubmed/27186867

The Extra Head CTs in Trauma, Estimated

In the world of academia and residency training, the spirited debate in trauma is usually regarding the merits of the “pan-scan” – and whether we can all agree it is probably safe to reduce costs and resource utilization by selective scanning. In community practice, it’s about picking up the needle in a haystack – and, hence, preventing the innumerable unnecessary CTs.

This is a retrospective review using electronic health record data to estimate the number of potentially unnecessary head CTs in the setting of trauma. These authors pulled records for all patients for whom a head CT was obtained, and for whom recorded EHR values suggested an encounter for trauma. This cohort was then evaluated for appropriateness of a CT by retrospectively determining the presence of high-risk or exclusion criteria for the Canadian CT Head Rule.

Among 27,240 patients extracted, 11,432 (42.0%) were “discordant” with the CCHR by structured EHR content. However, upon manual review of the chart narrative, the structured EHR content misclassified the CCHR recommendation 12.2% (95% CI 5.6-18.8%) of the time. Thus, the authors then estimate approximately 36.8% (95% CI 34.1-39.6%) of CT head for trauma in a community setting is inappropriate.

This is probably a reasonable research strategy, warts and all. Due to EHR limitations, they actually only filtered for 3 of the 5 high-risk criteria – basilar skull fracture and open skull fracture are such rare findings in their cohort the impact on overall results would be negligible. Then, Kaiser is probably more aggressive at minimizing CT use than the general community ED population, as routine quality improvement monitors individual and group rates of CT usage.

Bottom line: at least a third of head CTs for trauma in the community can probably be obviated by use of validated criteria.

“Computed Tomography Use for Adults with Head Injury: Describing Likely Avoidable ED Imaging based on the Canadian CT Head Rule”

http://www.ncbi.nlm.nih.gov/pubmed/27473552

An Oddly Dire Look at CIN after CTPA

This is an abstract that sucked me in – not because of the concept of the study – but because of its quoted incidence of adverse outcomes.  23.7% incidence of contrast-induced nephropathy following a CT pulmonary angiogram!  12.5% incidence of renal failure!  12.8% in-hospital mortality!

But, no.

The study itself is a comparison between three different prophylaxis methods for the prevention of CIN after CTPA – N-acetylcysteine plus normal saline, bicarbonate plus NS, or NS alone.  The simple summary: no difference between groups.

But, getting back to those dire numbers – roughly double the typically reported incidence of CIN.  They’re a mirage.  In reality, they assigned the primary outcome to all 26 (9.3%) of patients lost to follow-up.  Therefore, the starting point for their outcomes of interest are in a more reasonable range: 15.2% CIN, 2.6% renal failure, and 3.0% in-hospital mortality.

This, again, leads us back to the question: how much renal impairment is attributable to the CTPA, and how much to the underlying disease processes leading patients to require a CTPA in the first place?  Yield for PE on their CTPA cohort was 31.9%, which, in itself, elevates the comorbid burden of the population and could contribute to heart failure and renal injury.  There is no control group not receiving CTPA – for obvious clinical reasons – so it is hard to estimate the additive injury resulting directly from the CTPA.

But, at least, the big numbers displayed in their abstract a little misleading.

“The high risk of contrast induced nephropathy in patients with suspected pulmonary embolism despite three different prophylaxis: A randomized controlled trial”
http://onlinelibrary.wiley.com/doi/10.1111/acem.13051/abstract

Pan-Scans Don’t Save Lives

Humans are fallible.  We don’t always make good choices, and our patients – bless their hearts – can sometimes be time bombs wrapped in meat.  Logically, then, as many trauma services have concluded, the solution is to eliminate the weak link: don’t let the human chose which parts of the body to scan – just scan it all.

This is REACT-2, a randomised [sic] trial evaluating precisely the limits to human judgment in a resource-utilization versus immediacy context.  In this multi-center trial, adult trauma patients wth suspected serious injury were randomized to either imaging guided by clinical evaluation or total-body CT.  The primary outcome was in-hospital mortality, with secondary outcomes relating to timeliness of diagnosis, to mortality in other time frames, morbidity, and costs.

This was a massive undertaking, with 1,403 patients randomly assigned to one of the arms, with ~540 in each arm successfully allocated and included in their primary analysis.  Each cohort was well-matched on baseline characteristics, including all physiologic markers, although the Triage Revised Trauma Score was slightly lower (worse) for the total-body CT group.  The results, in most concise form, weakly favor selective scanning.  There was no difference in mortality nor complications nor length-of-stay nor virtually any reliable secondary outcome.  Costs, as measured in European terms, were no different, despite the few scans obviated.  Time-to-diagnosis was slightly faster in the total-body CT group, owing to skipping initial conventional radiography, while radiation exposure was slightly lower in the selective scanning group.

In some respects, it is not surprising there were no differences found – as CT was still frequently utilized in the selective CT cohort, including nearly half that ultimately underwent total-body CT.  There were some differences noted in in-hospital Injury Severity Score between groups, and I agree with Rory Spiegel’s assertion this is probably an artifact of the routine total-body CT.  This study can be used to justify either strategy, however – with selective CT proponents focusing on the lack of differences in patient-oriented outcomes, and total-body CT proponents noting minimal resource and radiation savings at the expense of timeliness.

“Immediate total-body CT scanning versus conventional imaging and selective CT scanning in patients with severe trauma (REACT-2): a randomised controlled trial”
http://www.ncbi.nlm.nih.gov/pubmed/27371185

tPA – For Minor Strokes, With Many Caveats

It is well-established many patients with minor or rapidly improving stroke fail to thrive.  The NIHSS is a crude tool, and its correlation with infarct size and ultimate disability is limited.  It is not inconceivable some patients with minor stroke could be candidates for intervention.  However, these patients would need to fit our critical requirements: 1) there must be substantial at-risk territory preserved by collateral perfusion, and 2) the occluded vessel must be reliably opened at a greater rate and timelier fashion than the body’s natural recanalization process.

This brief report is an interesting stepping stone on the pathway towards the practical realization of some of these issues.  These authors present a retrospective review of patients with minor stroke (NIHSS ≤ 3) evaluated at their institution.  Their institution routinely performs CT imaging with perfusion (RAPID software) on most stroke evaluations.  They further trim out 73 of these patients for whom the CT perfusion demonstrated substantial volumetric deficits.  Generally, these were patients with small (<5 mL) core infarcts surrounded by 20-40 mL of delayed perfusion, as would be reasonably expected for patients with minimal clinical symptoms.

There were 34 patients in this cohort who received tPA and 39 who were admitted without.  Patients were generally similar, although the tPA cohort had twice the prevalence of prior stroke (29.4% vs. 16.7%) and – most importantly – double the area of delayed perfusion (41.3 mL vs. 25.1 mL with wide standard deviation).  Despite these poorer prognostic features, 90-day mRS 0-1 were 91.2% in the tPA cohort and 71.8% in the standard care.

This is hardly practice changing in its crude, non-randomized, retrospective form.  It does, however, have face validity for informing future study.  It also fits with the paradigm of stroke care I’ve been promoting on this blog for years – the inanity of unselected tPA – and the requirements as above – to maximize potential benefit by ensuring those offered tPA have salvageable tissue (read: small core, large mismatch) and likely to recanalize (read: small vessel).  There’s virtually no question CTP or its equivalent needs to become part of the treatment decision-making process, rather than simple non-contrast CT or even CTA without evaluation of collateral flow.

“Utility of Computed Tomographic Perfusion in Thrombolysis for Minor Stroke”
http://stroke.ahajournals.org/content/early/2016/05/19/STROKEAHA.116.013021.abstract

Trauma is Still Trauma the Next Day

Acute closed head trauma is easy enough – and challenging enough.  There are validated decision instruments and guidelines, yet still plenty of CTs performed absent sound indications.  However, the question this study addresses is slightly different: what to do with those who present in a delayed fashion following minor head trauma?

The authors probably sum it up best in a reasonably concise fashion:

“Patients presenting after 24h of injury are a potentially distinct subpopulation. They could be at lower risk, as there is evidence that patients with mild/minor head injury who have injuries requiring neurosurgery will deteriorate within 24h. Alternatively, they could be a self-selecting higher-risk group attending due to the worsening or persistence of symptoms.”

These authors reviewed 2,240 patient encounters resulting in a CT scan of the head, with a goal of winnowing it down to just those performed for a traumatic indication.  Of those, 549 were performed within 24 hours of injury and 101 were delayed presentations.  There were 46 (8.4%) CTs positive for traumatic injury in the acute presentations and 10 (9.9%) in delayed, while 5 and 3 patients each underwent neurosurgical intervention, respectively.  So, the answer to their research question, at least in pragmatic terms, may be that the two forces balance each other out.

These authors also present “sensitivity” statistics regarding the utility of guidelines at predicting the presence of an important TBI, and quote a sensitivity of 70% based on chart review.  The denominator for sensitivity would more appropriately the entire population of presentations for trauma, not simply those who underwent CT scanning.  It is also probably more likely, given these patients had important TBI on CT, there may have been undocumented, guideline-compliant, indications not abstracted by chart review.

While our decision instruments for closed head injury were derived in typically an acute population, I would not yet draw any conclusions refuting their generalizability to delayed presentations.

“CT head imaging in patients with head injury who present after 24 h of injury: a retrospective cohort study”
https://www.ncbi.nlm.nih.gov/pubmed/27076439

Putting Children to the Flame

Many readers here are students, trainees, or otherwise academic-affiliated, and have limited exposure to the world of community practice.  In these settings, frequently, our pediatric exposure is supervised by clinician-educator sub-specialists in Pediatric Emergency Medicine.  We see the very best evidence translated into acute care of children in the Emergency Department.

The real world is a little different.

These two articles describe the shortcomings of advanced imaging practice in community pediatric settings – in the diagnosis of appendicitis, and in the evaluation of closed head injury.

In the appendicitis article, the authors compare two settings both staffed by PEM physicians – an academic medical center with in-house pediatric surgical coverage, and a community center with consultation available only by phone.  Each site had similar rates of appendicitis diagnoses – 4.7% vs. 4.0% at the academic and community site, respectively.  The academic site, however, evaluated fewer patients with abdominal pain with blood work, and then fewer still of those went on to advanced imaging.  Then, of those receiving advanced imaging, the rates were 10.8% CT at the academic center vs. 28.1% CT at the community center.  Ultrasound however, was employed in 16.6% of cases at the academic center versus 6.5% at the community practice.  Nearly all this difference, however, seemed to be made up of patients admitted to the hospital without any operative intervention.  The obvious reality, then:  radiation in lieu of observation.

The second article here describes the neuroimaging (CT or MRI) of patients evaluated following trauma, along with their ultimate disposition.  Of 2,679 patients reviewed, there were 94 patients with important non-surgical, trauma-related diagnoses, and an additional 16 patients who required neurosurgical intervention.  These authors, however, based on GCS estimates recorded and the distribution of outcomes in the PECARN study, estimate the prevalence of entry criteria into appropriate scanning would have obviated >2000 of these scans.  While I believe they are probably mis-applying the evidence and overstating the inappropriateness of CT, the rarity of serious diagnoses suggests at least a majority of these CTs probably could have been avoided.

In short, we’re still doing too many CTs on children.  Some of the contributing issues are systems based, and some are related to practice re-education.  More ultrasound and more observation, please – and less nuking of children.

“Imaging for Suspected Appendicitis: Variation Between Academic and Private Practice Models”
https://www.ncbi.nlm.nih.gov/pubmed/27050738

“Neuroimaging Rates for Closed Head Trauma in a Community Hospital”

Hello, Have You Heard of NEXUS/CCR?

In the same vein as my previous post inappropriate imaging despite the presence of PERC, this next article takes our evaluation of minor trauma to task.

This brief retrospective series looked only at presentations to the Emergency Department following “ground level fall” leading to a CT of the cervical spine.  These authors defined a “ground level fall” as fall of fewer than 3 feet or 5 stairs.  These authors then reviewed the documentation associated with each case for criteria specifically excluding the case from NEXUS or CCR and appropriate for CT imaging.

Of the 760 patients with ground-level falls included in this study, there were 7 cervical spine fractures – 6 stable, and 1 unstable.  All patients with a cervical spine fracture had documented criteria supporting appropriate CT imaging.  However, based on their retrospective review, 22.0% and 20.7% of encounters specifically documented criteria meeting NEXUS and CCR, and should not have led to CT imaging.  An additional 9.3% and 29.9% of patients had insufficient documentation of NEXUS or CCR criteria needed to determine appropriateness.

These authors posit there may be substantial cost savings to the healthcare system if these decision instruments are appropriately applied.  I tend to agree – although, there are obvious limitations to this sort of retrospective review.  It does, at least, back up my own anecdotal experience witnessing clinically questionable use of advanced imaging in minor trauma.

“Utility of computed tomography imaging of the cervical spine in trauma evaluation of ground level fall”
https://www.ncbi.nlm.nih.gov/pubmed/27032009

Let’s Get Inappropriate With AHA Guidelines

How do you hide bad science?  With meta-analyses, systematic reviews, and, the granddaddy of the them all, guidelines.  Guidelines have become so twisted over the recent history of medicine the Institute of Medicine had to release a statement on how to properly create them, and a handful of folks have even gone so far as to imply guidelines have become so untrustworthy a checklist is required for evaluation in order to protect patients.

Regardless, despite this new modern era, we have yet another guideline – this time from the American Heart Association – that deviates from our dignified ideals.  This guideline is meant to rate appropriate use of advanced imaging in all patients presenting to the Emergency Department with chest pain.  This includes, for their purposes, imaging to evaluate nSTEMI/ACS, suspected PE, suspected syndromes of the aorta, and “patients for whom a leading diagnosis is problematic or not possible”.

My irritation, as you might expect, comes at the expense of ACS and “leading diagnosis is problematic or not possible”.  The guidelines weighing the pros and cons of the various options for imaging PE and the aorta are inoffensive.  However, their evaluation of chest pain has one big winner: coronary CT angiograms.  The only time this test is not appropriate in a patient with potential ACS is when the patient has a STEMI.  They provide a wide range of broad clinical scenarios to assist the dutiful reader – all of which are CCTA territory – including as every low/intermediate risk nonischemic EKG and troponin-negative syndrome, explicitly even TIMI 0 patients.

Their justification of such includes citation of the big three – ACRIN-PA, ROMICAT II, and CT-STAT – showing the excellent negative predictive value of the test.  Indeed, the issues with the test – middling specificity inflicted upon low disease prevalence, increased downstream invasive angiography and revascularization of questionable value – are basically muttered under the breath of the authors.  Such dismissive treatment of the downsides of the test are of no surprise, considering Harold Litt, of ACRIN-PA and Siemens, is part of the writing panel for the guideline.  I will, again, point you to Rita Redberg’s excellent editorial in the New England Journal of Medicine, refuting the foundation of such wanton use of CCTA in the emergency evaluation of low-risk chest pain.

The “leading diagnosis is problematic or not possible” category is just baffling.  Are we really trying to enable clinicians to be so helpless as to say, “I don’t know!  Why think when I can scan?”  The so-called “triple rule-out” is endorsed in this document for this exact scenario – so you can use a test whose characteristics for detection of each entity under consideration are just as degraded as your clinical acumen.

Fantastically, both the Society of Academic Emergency Medicine and the American College of Emergency Physicians are somehow co-signatories to this document.  How can we possibly endorse such fragrant literature?

“2015 ACR/ACC/AHA/AATS/ACEP/ ASNC/NASCI/SAEM/SCCT/SCMR/ SCPC/SNMMI/STR/STS Appropriate Utilization of Cardiovascular Imaging in Emergency Department Patients With Chest Pain”
http://www.ncbi.nlm.nih.gov/pubmed/26809772