At the end of the qualitative and quantitative assessment of all phases summarized with the acronym ABCDE, the patient’s chance of survival is calculated according to the injury severity score (ISS), which correlates the mortality, morbidity, and hospitalization time after trauma with a number varying between 0 and 75. A major trauma (or polytrauma) is described by an ISS index greater than 15 [42]. In addition to the ISS, many trauma score systems have been developed and used. For instance, the revised trauma score (RTS) [43] is the most widely used although its calculation is too complicated for easy use in the ES [44].

According to the ATLS indications, imaging is helpful during the primary survey, but the use should neither stop nor delay life-saving maneuvers. The inherent instability of the trauma patient in this setting provides a requirement for rapid imaging and accurate, timely interpretation. It is especially relevant because evaluation by history and clinical examination alone has been shown to result in misdiagnosis in 20–50% of patients with blunt polytrauma [45]. A common concept in trauma management that early intervention leads to improved outcomes is that of the “golden hour” [36]. Since its inception, the advanced trauma life support (ATLS) program has been adopted in over 60 countries and has repeatedly undergone important changes. Throughout these revisions, the role of medical imaging has evolved. The current iteration of the program includes, after the “ABCDE” of the primary survey, descriptions of a trauma series (plain film radiographs of the cervical spine, chest, and pelvis), a focused assessment with sonography for trauma (E-FAST) examination, and the selective use of MDCT. The secondary survey is essentially a head-to-toe examination with completion of the history and reassessment of progress and vital signs.

The diagnostic procedure to be used varies according to the patient’s hemodynamic condition. An “unstable” patient is one with blood pressure < 90 mmHg and heart rate >120 bpm, with evidence of skin vasoconstriction (cool, clammy, decreased capillary refill), altered level of consciousness, and/or shortness of breath [46]. In particular, in the case of hemodynamically stable patients (blood pressure > 90 mmHg, pulse <120/min) or patients stabilized after primary resuscitation, full-body CT scan remains the gold standard in the evaluation of injured patients because it allows a detailed view of the body. In contrast, for hemodynamically unstable patients (blood pressure < 90 mmHg, pulse rate > 120/min), the time-consuming TC scan is not suggested; instead, it is suggested to use X-ray and US during the primary survey [47, 48].

X-rays and ultrasonography provide an initial diagnosis of conditions that can endanger the patient during the diagnostic phase, and in this scenario, the radiologist plays a key role at the emergency setting to provide a first effective diagnostic confirmation of potentially life-threatening clinical situations [49].

During maneuvering, resuscitators are beside the patient who is lying supine, making all the maneuvers to stabilize the patient and carrying out imaging tests such as chest X-ray (CXR) with an AP view, cervical spine X-ray with an LL view, pelvis X-ray with an AP view, and E-FAST scan (extended focused assessment with sonography for trauma). Subsequently, as mentioned above, the hemodynamically stabilized patient undergoes a TC exam that obtains a complete evaluation of all of the body parts (Fig. 1.3).

The plain anteroposterior chest radiograph remains the standard initial exam for the evaluation of the polytraumatized patient in the emergency room. Because of the inaccuracy of clinical signs, important thoracic problems that require possible intervention can be identified using a chest X-ray.

In cases of hemodynamic instability, the presence of respiratory failure (hypoxemia and dyspnea), or after pleural decompression or pleural drainage insertion, an ordinary chest X-ray is recommended. In all cases of blunt trauma, the patient must have a chest X-ray in the supine position in the resuscitation room since unstable spinal fractures have not been ruled out at this stage. In penetrating trauma (penetrating injuries), both from firearms and stab wounds, a chest X-ray should be taken preferably with the patient seated upright to increase the sensitivity for detecting small hemothorax, pneumothorax, or diaphragm injury.

Cervical spine injuries are the most dreaded among all spinal injuries because of the potential serious neurological sequelae. Significant cervical spine injury is very unlikely in the case of trauma if the patient has normal mental status without neck pain, tenderness on neck palpation, neurologic signs, or symptoms referable to the neck (such as numbness or weakness in the extremities), other distracting injuries, and history of loss of consciousness [50]. However, the radiological series for excluding a cervical spine fracture requires a posteroanterior view, a lateral view, and an odontoid view. The lateral view must include seven cervical vertebrae as well as the C7-T1 interspace, allowing visualization of the alignment of C7 and T1.

According to current evidence, CT imaging of the cervical spine in polytrauma patients has replaced plain film imaging due to its greater sensitivity.

Pelvic fractures resulting from motor vehicle accidents and also from falls from heights are very complex, as they imply high-energy trauma that disrupt the solid pelvic ring. These fractures are rarely isolated and are often associated with life-threatening complications such as bleeding (arterial, venous, and cancellous bone).

Up to 60% of mortality rates likely related to significant differences in fracture types have been reported [51]. Hemodynamic instability and multiple organ failure as direct consequences of pelvic hemorrhage have been identified as the primary causes of death following pelvic fracture [52]. In the prehospital exam, signs and symptoms of pelvic injury include deformity, bruising, or swelling over the bony prominences, pubis, perineum, and/or scrotum. Leg-length discrepancy or rotational deformity of a lower limb (without fracture in that extremity) may also appear. Wounds over the pelvis or bleeding from the patient’s rectum, vagina, or urethra may indicate an open pelvic fracture. Neurological abnormalities may also rarely be present in the lower limbs after a pelvic fracture [53]. Screening radiographs of the pelvis are recommended when the mechanism of injury or the degree of hemodynamic instability indicates the possibility of a pelvic fracture. According to the mechanism and severity, pelvic fractures are classified into three main patterns of injuries: anteroposterior compression, lateral compression, and vertical shear [54].

Anterior posterior compression is secondary to a direct or indirect force in an AP direction leading to diastasis of the symphysis pubis with or without obvious diastasis of the sacroiliac joint or fracture of the iliac bone. AP compression injuries cause an increased pelvic volume with any resulting hemorrhage that is unlikely to spontaneously tamponade. Pelvic wrapping therefore should be a priority in early management [55]. The AP projection, recommended by the ATLS program performed during the primary survey provides a large amount of information about the mechanism of injury. In the anterior, the AP projection can identify the presence and extent of the diastasis of symphysis pubis and/or the fracture of the obturator ring. In the posterior, the AP projection recognizes the presence and extent of dislocation of the injured side of the pelvis, dislocations of the sacroiliac joint, or fractures of L5 transverse apophysis. However, this type of projection does not help to evaluate the real dimension of the injury, especially its posterior component [56].

Lateral compression is a lateral compression force that causes rotation of the pelvis inwards, leading to fractures in the sacroiliac region and pubic rami. The lateral fractures are the most common type of pelvic fractures that are mainly associated (88% of cases) to the sacral fractures [54]. In lateral fractures, there is a reduction of the pelvic volume with hemorrhage that is more likely to spontaneously tamponade.

Vertical shear is an axial shear force that disrupts the iliac or sacroiliac junction and is combined with cephalic displacement of the fracture component from the main pelvis. In vertical shear injuries, the hemipelvis is shifted cranially, and fractures are vertically and rotationally unstable. There is a high rate of associated injuries to the torso and spine and a high rate of hemodynamic instability [55].

Other projections that can add more information are the following: the oblique outlet view, performed with patient in supine position; caudal-cranial inclination of 30° of the incidental beam centering on the pubis is useful in quantifying the cranial dislocation of the injured hemipelvis; and the oblique inlet view, which is performed with patient in supine position, caudal-cranial inclination of 30° of the incidental beam centering on the umbilicus is useful in documenting the posterior sacroiliac joint dislocation or pubic branches dislocation on AP view or the inward/outward rotation of the pelvis [56].

Ultrasound (US) is an important adjunct to the primary survey of polytraumatized patients and has replaced diagnostic peritoneal washing or sometimes laparotomy in the resuscitation room because it is noninvasive, repeatable, safe, non-irradiating, inexpensive, and quick to perform [57]. There are no absolute contraindications against its use except in cases where the patient may require immediate surgery. However, before transferring the patient to the operating room for emergency laparotomy, it may be necessary to exclude pericardial tamponade or pneumothorax.

In the trauma setting, the FAST and E-FAST examinations are usually performed in hypotensive and hemodynamically unstable patients because they help to determine whether immediate surgery is needed before the patient undergoes a CT evaluation [58] (Fig. 1.5).

In patients with major trauma, the first-line abdominal US examination is generally performed with a FAST protocol (i.e., focused assessment with sonography for trauma), which aims to identify a free-fluid effusion within the peritoneal cavity or pericardial sac through the ultrasound exploration of four regions (subxiphoid region, right and left hypochondriac regions, pelvic cavity). The FAST scan is performed at bedside in the ER; it is usually performed with a portable machine using a lower frequency transducer, such as a 3.5–5 MHz convex array [59]. Although the effectiveness of the FAST scan to detect free intra-peritoneal fluid has been reported by many studies, the sensitivity of the FAST examination as a diagnostic test for therapeutic laparotomy accounts for only 75% (while confounded by multiple variables); similarly, its positive predictive value was only 37.3% [59]. In another review, a positive FAST exam was found to vary in the 24.2–56.3% range for penetrating trauma, while the diagnostic modality was highly specific (94.1–100.0%) but not very sensitive (28.1–100%) [60]. If the free abdominal effusion is considered as the only diagnostic finding, the rate of false negatives may further increase, since too-early scans might miss significant releases of intra-peritoneal fluid, requiring more time to accumulate [61]. Even if it is claimed that ultrasound can detect as little as 100 mL of free intra-peritoneal fluid, for a negative response it is necessary to observe the patient for at least 4–6 h and, if indicated, repeat the FAST scan or conduct a CT scan [62]. Some clinicians incorporate inferior vena cava (IVC) evaluation into the FAST examination to help determine the patient’s volume status and fluid responsiveness [63].

Ultrasound may also be technically limited in the traumatized patient due to bowel gas, obesity, subcutaneous emphysema, or patient positioning. Other limitations to FAST assessments include its poor sensitivity in detecting the hemoretroperitoneum, parenchymal traumatic injuries, and almost bowel and mesenteric injuries detection; the latter two are both diagnosable with a CT scan.

Although FAST has a high specificity, false-positive results can be encountered in patients with a history of ascites or inflammatory processes in the abdomen or pelvis or even ovarian cyst rupture.

The Consensus Conference recommends that hemodynamically unstable patients with positive FAST examination should generally be followed by a laparotomy, while a search for extra-abdominal sources of hemorrhage should follow a negative exam [64].

In hemodynamically stable patients, a positive FAST result should be followed by a TC exam to better define the nature of the injuries. For negative FAST scan cases, a period of monitoring for at least 6 h, serial FAST scans, or further investigations (e.g., CT scan or peritoneal lavage) are recommended.

In many trauma centers, the use of the FAST technique is extended to the thorax (Extended-FAST) for the detection of hemothorax and pneumothorax, including the presence of hemopericardium (whose evaluation is already performed with a FAST scan) through the execution of some standard scanning with a convex and linear probe (transducer) [58]. Thoracic ultrasound (e-FAST) is defined as a rapid and accurate first-line bedside diagnostic modality for the diagnosis of pneumothorax in unstable patients with major chest trauma during the primary survey in the emergency room [58].

The diagnostic performance of ultrasound is high (i.e., 77% sensitivity, 99.8% specificity, 98.5% positive predictive value, 97% negative predictive value, and 97.2% accuracy). This sensitivity value is statistically significantly higher than that of supine chest radiograph (approximately 50%, as reported in the literature). According to anti-gravity laws, PNX air in the pleural space tends to accumulate in the least-dependent part of the chest [65, 66]. When the patient lies in the supine position, the area of interest corresponds to the anterior and inferior part of the chest on both sides of the thorax, which is approximately the third–fourth intercostal space between the parasternal and the mid-clavicle lines [67, 68]. The probe should be placed in the intercostal acoustic window of the located area.

The parietal pleura appears as a thin echogenic horizontal line located between and below two adjacent ribs. Sometimes, it is necessary to scan more intercostal spaces by moving the probe laterally and inferiorly in order to evaluate the extension of PNX or to confirm the diagnosis. Sonographic signs that can help in the diagnosis of a pneumothorax are the absence of lung sliding (the visualization of lung sliding has a 100% negative predictive value), lung pulse, loss of B lines, and identification of the lung point (100% specificity) [69].

Patients in physiologic extremis and suspected of having PTXs on physical examination should undergo immediate tube or needle thoracostomy without awaiting imaging studies [70] (Fig. 1.6). The limitations in the evaluation for pneumothorax include main-stem bronchus intubation, severe chronic obstructive pulmonary disease, or other lung pathology that inhibit adequate visualization of lung sliding, and small apical or localized pneumothoraces may not be visualized [63].

Ultrasonography has in recent years found new application areas through the use of contrast enhancement based on microbubbles [48]. This method has many advantages mainly due to the fact that avoiding ionizing radiation represents a safe tool—particularly in selected series, including pediatric patients and females of reproductive age [71].

Its application for children is still considered off-label, and it is allowed only after the parents (or legal guardians) have been adequately informed and given their specific consent. CEUS also exhibits an advantage compared to contrast-enhanced MRI and CT because it can be used in patients with renal failure or allergy [72]. The CEUS technique can be carried out in a variety of scenarios, including bedside, operating room, and trauma suite [71]. Also, compared to other techniques, it is not expensive. There is still debate for how to integrate CEUS in the trauma patient workup [73, 74].

Although it is considered to be more sensitive and accurate than baseline US and almost as sensitive as CT in the identification and characterization of solid-organ lesions in blunt abdominal trauma, the CEUS use in the primary survey is limited by several factors such as the lack of panoramic view, typical of CT, and, like conventional US imaging, insensitivity in depicting diaphragmatic rupture, bowel, or mesenteric traumatic injuries [75]. Moreover, CEUS is strongly operator dependent, requiring dedicated contrast agent-specific software, and it takes a long time to be performed [76]. An excellent correlation was found between the size of the traumatic injury (as shown at CT) and the related CEUS findings with respect to hepatic traumatic injuries, advocating its employment as a first-line examination in mild blunt abdominal trauma and in pediatric patients and leaving CT as the gold standard for polytrauma and major trauma [74].

Nowadays, contrast-enhanced ultrasound (CEUS) has an important role in the follow-up of conservatively treated traumatic injuries of the abdominal parenchymal organs (liver, spleen, and kidneys) or as a first-line examination in low-energy or mild isolated abdominal trauma [76, 77]. It can integrate conventional US imaging in the triage of hemodynamically stable patients, in particular with low-energy abdominal trauma; also, it can be routinely used as a completion of a US FAST examination to scan severe trauma patients in the assessment of solid-organ injuries [78]. This happens especially when the use of CT exposes patients to excessive radiation dose. In some departments, protocols for the follow-up of blunt abdominal trauma that are conservatively treated include a CEUS at 24 and 72 h after trauma as well as CEUS and MRI after 1 month [79].

CEUS cannot replace abdominal CT, but it represents a noninvasive and repeatable imaging tool that is capable of providing a reliable assessment of trauma severity and expediting the patient’s treatment [71].

Current scanners are capable of rendering submillimeter resolution images of the entire body in a matter of seconds [80]. Among the long list of advantages derived from MSCT technology for obtaining useful imaging information, we enucleate three: (a) shorter scan time, (b) extended scan range, and (c) improved longitudinal resolution, particularly when 3D post-processing is part of the clinical protocol. The ability to acquire volume data also paved the way for the development of three-dimensional (3D) image processing techniques, such as multiplanar reformation (MPR), maximum intensity projection, surface-shaded display, and volume-rendering techniques, which have become a vital component of medical imaging today. CT has become an especially vital component of patient evaluation in the ED and is helped by the increased diffuse use of picture archiving and communication systems (PACSs), teleradiology, and voice recognition software, which facilitate all the rapid image dissemination and interpretation [80–83]. CT is well suited for the ED: it provides rapid, minimally invasive, high-resolution imaging that can quickly direct patients toward further treatment. Factors that might limit the growth of CT use include cost-containment efforts [84], intervention to improve evidence-based guideline adherence [85], and concerns regarding radiation exposure [86].

WBCT is a sensitive and comprehensive tool for the diagnosis of a wide range of traumatic injuries, especially in the severely injured patient [87–91].

Contrary to selectively performing CT scans on one or more body regions, a WBCT scan comprises a CT of the head without intravenous contrast, cervical spine (acquired before, or following, intravenous contrast), and chest, abdomen, and pelvis following intravenous contrast. In the largest systematic review and meta-analysis that determined the odds of mortality in trauma patients, patients who underwent a WBCT scan were less likely to have a fatal outcome compared to those who received selective CT.