Major trauma: are plain radiographs more harm than good? Review Article

Sarah R Hudson, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Road, Cambridge, CB2 0SP.

Trauma is the leading cause of death in young adults in the UK with road traffic accidents being the commonest mechanism. Trauma is responsible for a burden of morbidity with socio-economic implications which are often overlooked by the media. It would seem logical to assume that the management protocol for a serious, not uncommon presentation was well established, but this is not the case: the appropriate diagnostic imaging for this patient is a contentious topic.

The formation of regional major trauma centres is currently underway in England aiming to advance the care of major trauma patients so improving outcome. Use of diagnostic imaging in the primary survey of the major trauma patient on admission to the emergency department is a point of debate: current ATLS guidance advocates plain radiographs of the chest and pelvis but practice in the UK is whole-body CT, which has evolved to become the gold standard. Issues of treatment delay, radiation exposure and low specificity for serious injury have been raised as arguments against CT. Conversely, plain x-ray is less sensitive, may waste time and cause unwarranted radiation exposure if performed in addition to whole-body CT. The best use of diagnostic imaging of the major trauma patient is currently under supported by evidence.

Introduction

A 21 year old male is brought to the emergency department having been in a road traffic accident. He has blunt trauma injuries to his chest and limbs. On examination, his pelvis is unstable. He has been intubated, is receiving fluids and is now stabilised. What imaging should you request?

Trauma is the leading cause of death in young people in the UK [1]; 36 life years are lost per trauma death on average [2]. In addition to mortality, trauma is responsible for a huge morbidity burden: for every death, two survivors suffer disability [3]. Initial management is therefore crucial as the majority of trauma deaths occur within the first hour of injury [4].

Current ATLS (Advanced Trauma Life Support) guidance advocates the use of plain radiographs of the chest and pelvis for the immediate management of the trauma patient during the primary survey [4]. The ATLS course is advised for any member of the trauma team and is renewed every 4 years: ATLS is highly influential and is implemented in the UK and world wide. Whereas guidance for the diagnostic imaging protocol for head and spinal trauma has a clear evidence-base since publication of the Canadian head CT rule and subsequent National Institute for Health and Clinical Excellence (NICE) Head Injury guideline [5-9], imaging protocol of the chest and pelvis does not.

ATLS was developed by James Styner, an orthopaedic surgeon who saw that emergency care in small American regional hospitals was inadequate and designed the ATLS course to improve this. This brings into question whether ATLS is appropriate in the setting of a busy, well equipped tertiary trauma centre and this may be reflected by the fact that the current gold standard in the UK is whole-body CT (defined as CT of the chest, abdomen and pelvis), replacing the ATLS-advised plain radiographs of the chest and pelvis [10].

Whole-body CT is more sensitive than the conventional radiograph trauma series for diagnosis of injury in trauma patients [7]. However, CT is less specific for clinically significant injury [7], exposes patients to significant doses of ionising radiation and is speculated to delay treatment [7]. Performing randomised control trials in the emergency setting is impractical due to issues of consent. However, lower quality studies have been performed aiming to address the topical issue of what form of imaging is best for the diagnosis of serious injury in major trauma patients, defines as an injury severity score (ISS) greater than 15.

Evolution of CT

Since the introduction of CT in the 1970s, helical and multislice CT has been developed making CT a rapid, accurate diagnostic tool [11]. Availability of CT in the emergency setting has increased greatly in the last decade [10]: Lee et al found that CT utilisation in trauma patients increased from 51 per 1,000 patient visits in 2001 to 106 per 1,000 in 2007 in an American emergency centre [10] and Smith et al found whole-body CT increased from 47% of eligible patients in 2007 to 76% in 2008 in a UK trauma centre after introduction of a CT protocol for trauma patients [7]. Many trauma centres in the UK have CT capabilities adjacent to the emergency department with 24 hour access to CT [1] and this applies to a rapidly increasing number of trauma centres [7]. Evidence suggests that emergency clinicians are increasingly reliant on CT in place of trauma plain radiograph series when making initial diagnoses.

Clinical judgement is essential for the diagnosis of many chest and pelvic injuries in the major trauma patient during initial assessment [12]. Imaging is an invaluable adjunct to this. Many UK trauma centres are replacing conventional plain radiograph series with whole-body CT [13] in contrast to ATLS advice. ATLS advocates Focused Assessment with Sonography in Trauma (FAST) and CT as an adjuvant to secondary assessment only and in addition to the x-ray series for suspected pelvic and chest injuries [4]. The efficacy of whole-body CT as a diagnostic aid to the physical examination during the primary survey in comparison to conventional chest and pelvic x-ray is currently undefined in the major trauma patient.

Whole-body CT should not replace clinical acumen

Studies have established the greater accuracy of CT compared to that of the physical examination [12] and also compared to plain chest and pelvic x-ray [14] but no guidelines have been published regarding use in major trauma management and whether increased sensitivity but low specificity for occult significant injury is useful for treatment planning [14]. There is evidence that the rate of missed injuries on examination increases with the ISS suggesting that the benefit of CT to this patient group is proportionately greater than to less injured patients [15].

However, CT should not be overused to the extent that it replaces the physical examination, as it has begun to in some American trauma centres [16]: though examination is less sensitive, significant injuries can be ruled out without the need for an immediate CT, particularly in patients with a low ISS. Smith et al found that clinical examination of the chest and pelvis detected injury with a sensitivity of 96.9% and 97.9% respectively [12].

Mortality and morbidity

Huber-Wagner et al found that whole-body CT significantly reduced the mortality rate of major trauma patients compared to predictions by Trauma and ISS (TRISS) and Revised Injury Severity Classification (RISC) scores with an absolute risk reduction of 5.9% and 3.1% respectively [17]. Smith et al found that CT detected injuries that were occult on conventional radiographs, although only 18% of these injuries required immediate intervention [12]. This raises the question as to whether the increased sensitivity of CT is useful when specificity for serious injury is low. Hilty et al found that x-ray gave a false negative in 4% cases when compared to CT. However, the missed injuries did not require immediate attention [18].

The National Confidential Enquiry into Patient Outcome and Deaths (NCEPOD) has advised the use of CT for imaging the major trauma patient [1].

Ionising radiation exposure

50% of all CT scans are requested by the emergency department in America [19]. This trend is likely to apply to the UK. The benefit to the patient must outweigh the risk associated with increased exposure to ionising radiation from CT compared to conventional radiography. One CT of the chest, abdomen and pelvis emits approximately fifteen times the ionising radiation of one chest x-ray [20]. High doses of radiation are particularly worrisome as major trauma is the leading cause of death in young people3 so lifetime potential cancer risk to survivors may be significant [21]. Tien et al found that trauma patients receive a mean effective radiation dose of 22.7mSv and estimate that this would lead to 190 extra cancer deaths per 100 000 individuals [21].

Trauma patients often require repeat or multiple imaging studies so the cumulative effect may be great. Griffey et al found that over a 7.7 year study period in an American trauma centre, the median number of CT scans per person was 10; the median lifetime attributable cancer risk was 1 in 110; and 72% of studies were repeated CTs [19]. Brenner suggests that 20-40% of CT scans could be avoided if decision guidelines are in place and followed, particularly in trauma centres [22]. The American College of Radiology has issued a white paper suggesting surveillance of patients who have had repeat or multiple CT [23].

Where unnecessary plain chest and pelvic trauma radiographs are performed in addition to whole-body CT, it can be argued that plain radiography is the source of unnecessary radiation exposure as no additional injuries are likely to be found from them. It has been suggested that where CT is readily available in the emergency setting, plain radiography does not add to the primary survey or initial diagnosis and is an unwarranted radiation exposure [11].

Time delay to treatment

Other disadvantages of whole-body CT may include increased time taken for transfer to CT relative to conventional radiography which is often portable and requires no transfer24. However, plain x-ray itself may cause delay. In addition to this, if there is evidence that sensitivity of plain x-ray is low for chest and pelvic injuries leading to CT being performed consistently in addition to plain x-ray, plain x-ray may be increasing delay.

In fact, Huber-Wagner et al found that the mean time from trauma-room admission to whole-body CT was shorter than for non-whole-body CT [17]. This requires verification by future studies.

Unanswered questions

There are important issues which must be addressed to facilitate a switch from conventional radiograph series to whole-body CT in the management of major trauma patients.

1. Timing

Portable radiography can be carried out in the resuscitation room whereas CT demands transportation of the patient to the radiology CT suite. CT is not adjacent to the emergency department in all trauma centres and CT may not therefore be appropriate in these settings. With the current evolution of regional major trauma centres underway, these specifications may be easier to implement as part of the changes. Another question is whether haemodynamically unstable patients should go straight to the operating theatre or have imaging first. This is likely to remain a contentious debate and be decided on an individual basis until evidence is available.

Another issue is that if CT is going to be performed for a trauma patient, it could be argued that performing plain radiography in addition to this is wasting time [17]. Timing is imperative when managing a trauma patient; more research into the best use of it is required.

2. Ionising radiation exposure

A central question is whether the benefit of diagnostic accuracy of whole-body CT is worth the potential cancer risk. This is dependant on several factors: patient ISS and likelihood of occult serious injury, age and previous ionising radiation exposure and likely future exposure. This point could be extended to question the benefit of chest and pelvic x-ray if whole-body CT is to be performed regardless of plain radiograph findings.

It is known that radiation exposure to the abdomen and pelvis is most significant when calculating whole-body effective radiation dose and that exposure of thyroid, breast and gonads carries a relatively high potential cancer risk [21]. Tien et al found that American trauma patients receive a mean effective dose of 22.7mSv but the thyroid receives a mean dose of 58.5mSv meaning 11.7 additional deaths from thyroid cancer per 100 000 [21]. Therefore, consideration of the need for whole-body CT is essential to prevent unnecessary harm.

Future

It is clear that guidance is needed to determine the most accurate and rapid form of diagnostic imaging during the primary survey of major trauma patients in order to reduce mortality and morbidity of this highly prevalent problem. The evidence-base is currently lacking. From the small amount of evidence available thus far, it seems likely that in the emergency setting the diagnostic benefit of whole-body CT outweighs the radiation exposure and potential cancer risk in major trauma patients with a high ISS. Patients with a lower ISS may not benefit significantly from CT. However, there should be a high threshold for performing CT scanning in other settings and recording individual patient radiation exposure, as recently proposed in America, may be a useful tool to monitor exposure and guide clinical decision making.

It seems unlikely that transfer to CT causes a delay to treatment but this is difficult to conclude definitively based on the available evidence. Where there is an indication for whole-body CT in the primary survey of the trauma patient, pelvic and chest plain radiographs are not warranted as they are likely to cause delay to treatment and exposure to radiation without adding to the diagnosis. The impact of radiation exposure in young adults will not be realised for many years: the potential burden of our current practice should not be underestimated.

Management of major trauma patients is on the point of overhaul with the creation of regional major trauma centres as a National strategy. This would be the opportune time to implement evidence-based clinical guidance for diagnostic imaging and potentiate the reduction in mortality and morbidity of major trauma patients.

References: 

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