The pendulum has swung one way with CT for trauma, but has it gone too far? Liberal use of CT raises concerns over resource utilization, cost, and the consequences of radiation exposure [1,2]. No-one can seem to agree, including trauma surgeons, on guidelines for a more selective use of imaging studies [3-6].
“CT pan scan” is the term, source unclear, which describes the whole body CT (WBCT) imaging strategy used in blunt trauma management. It consists of the following CT studies:
We know it is thorough, fast, and convenient— very seductive. Yet, here are my top ten reasons NOT to order a pan-CT scan on your next stable blunt trauma patient.
1. There is no definitive proof that WBCT has a DIRECT positive effect on outcomes.
Surendran, et al. conducted a systematic review of the literature for all outcomes measured in comparing WBCT with selective CT in trauma patients. The goal of the review was to (1) determine the benefits and harms of one approach compared to the other, and (2) assess the degree to which research had given attention to all relevant considerations of this complex topic .
Eight retrospective cohort studies and two systematic reviews were identified. The methods and data were heterogeneous between studies, but WBCT imaging seemed to be associated with reduced times to in-hospital events (diagnoses and treatment decisions) following traumatic injury. There was an association towards decreased short-term mortality with WBCT, but not seen in all studies.
The Surendran review discusses whether WBCT or unknown confounders deserved credit for the effect on mortality. It may be that quicker diagnoses or avoiding ‘missed’ diagnoses led to a management change (e.g. rapid control of bleeding) that improved outcomes. The most critically injured patients may be too unstable to be sent for a CT scan. With this reasoning, the patients with the highest mortality are likely to be in the non-WBCT cohort, confounding the mortality results. Another possible confounder is that centers with high WBCT utilization are also trauma centers with high volume and experience with the severely injured and with better quality of care. The improved outcomes may be institutionally based rather than the direct management effects of WBCT in and of itself.
2. CT chest is usually overkill in blunt trauma.
Over a 7-year period at LAC/USC trauma a study showed a 10-fold increase (2.7% to 28.7%) in chest CT (CCT) utilization. Of these, 80% of CCT were done after a negative initial chest x-ray .
Although there was an increased diagnostic rate of many blunt chest injuries, the authors argue that the vast majority of these additional findings led to no meaningful change in management. Of the 102 occult pneumothoraces and hemothoraces (diagnosed on CT and not seen on CXR), only 12 patients (0.1% of the study population) were intervened upon.
The authors also argue that a selective CCT strategy should be deployed, focusing on the highest risk presentations for blunt aortic injury (BAI), such as high velocity deceleration injury. With a flat diagnosis rate over the study period, despite much higher CCT use, it is unlikely that a meaningful additional clinical impact was made for BAI over the study period.
3. A quality CXR and/or ultrasound are good enough for pneumothorax assessment.
A supine CXR has notoriously poor sensitivities for detecting pneumothoraces (50%). This improves to 92% with a technically sound, upright CXR . Chest ultrasound (US) can overcome any sensitivity concerns with CXR. As a supplement to the Focused Assessment with Sonography for Trauma (FAST) examination, a chest US detects 92–100% of all pneumothoraces . It is a quick and simple extension of the trauma primary survey.
4. Screen for the patients who won’t need an abdominal CT.
Holmes derived and validated a low risk prediction rule with 100% sensitivity for the need of a therapeutic intervention in blunt abdominal trauma . Patients are low risk for an adverse outcome if the following are absent:
- Abdominal tenderness
- Altered mental status
- Costal margin tenderness
- Abnormal chest radiograph
- Hematocrit 30%
- Hematuria (≥25 RBCs/HPF)
5. Don’t throw away the FAST just yet in the hemodynamically stable trauma patient.
Are we asking the right question of the FAST exam? Does it need to find all pathology, or simply risk-stratify for patients in need of an intervention? In unstable patients, the FAST tells you if the patient needs an immediate laparotomy. In stable low risk patients, the FAST can tell you whether the patient may need a downstream intervention.
Smith published a retrospective cohort analysis of consecutive normotensive blunt trauma patients presenting to two trauma centers. The outcome was therapeutic laparotomy (2% rate overall). Of the 1636 patients studied, a negative FAST missed 3% of findings discovered on subsequent CT. The negative predictive value for the requirement of a therapeutic laparotomy within 2 days was very high. Only 8 of the 1569 (0.5%) stable patients with a negative FAST went on to a laparotomy .
Consider the scenario of a low clinical pretest probability for needing a laparotomy combined with a high negative predictive value from a negative FAST examination. This combination may reduce the post-test likelihood for needing a laparotomy below acceptable standards. At the very least it provides a viable argument for observation rather than a universal CT default choice.
6. Low dose CT: the next best thing to no-dose CT
Eftekhari et al. have cited success with the application of low-dose CT algorithms in blunt liver injury. At a 50% reduction in dose, no significant loss in sensitivity was found . Wherever low-dose CT performs similarly to full-dose, should this not be our standard practice? What is lacking is the more universal adoption of this radiation mitigation strategy beyond the level of a research novelty.
7. Whole body CT = a lot of irradiation = cancer risk
An individual CT scan is incredibly safe with a favorable risk-benefit balance in the sick patient. A WBCT is a sum of multiple CT scans, enough to raise the cancer risk in a 25-year-old male by 1 in 275 (www.xrayrisk.com). With trauma being largely a disease of the young, and radiation exposure risk being inversely proportional to age, clinicians often struggle with the dilemmas of ordering the WBCT over a more selective CT approach.
Berrington de Gonzalez’s study estimates that 1-3% of worldwide cancers can be attributed to medical imaging . The baseline lifetime incidence for invasive cancer is roughly 40%, with a 21% average lifetime risk of dying from cancer .
8. Avoid making your patient ‘VOMIT’.
Beyond radiation concerns with CT are the risks of false positive results or ‘incidentalomas.’ The subsequent cascade testing can lead to increased morbidity, anxiety, and downstream costs after that initial CT .
VOMIT (Victims of Modern Imaging Technology), describes patients who experience adverse outcomes as a result of the flood of information from modern technology and downstream cascade testing. This can lead to unnecessary procedures, anxiety, and complications .
9. Use clinical decision rules to determine need for head CT.
Children: CT utilization rates have been high despite a very low rate of clinically important findings in low risk patients. One likely reason is the unreliable nature of a clinical exam in patients under 2 years of age, even more so in the less than 1 year of age cohort .
This has started to change in 2009 when Kupperman et al. derived and validated age-specific prediction rules for clinically important traumatic brain injury (ciTBI). Their Pediatric Emergency Care Applied Research Network (PECARN) study enrolled an impressive 42,412 pediatric patients with a ciTBI rate of 0.9%. Children with zero medium and high risk criteria had a <0.1% risk of intracranial injury requiring prompt intervention . Use the PECARN Head Injury criteria [MDCalc] to determine whether a patient warrants CT or ED observation.
Adults: Multiple reasonable head CT rules exist for ciTBI. Two often cited decision rules, New Orleans Criteria [MDCalc] and Canadian CT-Head Rules [MDCalc], are both highly sensitive (100%). The Canadian study is more specific (76% vs 12%) for predicting a need for neurosurgical intervention .
10. Use clinical decision rules to determine need for c-spine CT.
Obtaining a c-spine CT in high-risk patients is not controversial. You should do it. The idea of ‘high risk’, however, seemingly has expanded over time.
Both the NEXUS low-risk criteria [MDCalc] and Canadian C-Spine Rule [MDCalc] are safe and effective decision rules. Their use is to clinically ‘clear’ a patient of significant cervical spine injury, without the use of any imaging. They also allow the option of using a 3-view series c-spine x-ray as the first imaging test in a low risk patient who fails either of these rules .
Of note in younger patients, especially, intoxication and/or associated mild head injury does not mandate a CT c-spine, reflexively coupled to a CT head. If the clinician expects the mental status changes to normalize in a reasonable time frame, the c-spine can often be cleared clinically in a delayed fashion.
There is no question that sicker patients benefit more from WBCT than the less sick, hemodynamically stable trauma patient. Recent trends in the management of blunt trauma, however, have demonstrated a sort of “imaging creep” whereby more WBCT’s are more aggressively ordered for sick AND non-sick patients, despite the fact that trauma outcomes have not shown net benefit with this strategy to date [21-25].
For hemodynamically stable patients, highly consider a more selective CT imaging strategy, especially when the patient is clinically evaluable through the use of observation, ultrasonography, and clinical decision rules.
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Edited by Scott Kobner, ALiEM-EMRA fellow.