Despite its technical limitations, which include the supine positioning, the use of portable radiography, and the limited patient’s cooperation, a CXR remains valuable as first radiological examination in the acute phase for the detection of a TDI [4]. It is generally performed only in the supine position and frequently it is acquired on the long spine board (LSB) in the shock room. For these reasons, the CXR has a relatively poor sensitivity and specificity, resulting normal or nonspecific in 20–50% of cases of a traumatic TDI, due to the high range of initially unrecognized injuries. Generally, the diagnosis or the suspicion of a left-sided injuries is easier (with detection sensitivity up to 60% of patients) than for right-sided injuries (18–33%) [8, 26, 28]. Indeed, a right TDI is more difficult to detect on CXR, as the liver blocks herniation of abdominal contents into the lower right side of the chest. Moreover, herniation of the liver is often overlooked and differentiation of a herniated liver through a TDI, from other causes of elevated diaphragm, such as atelectasis, pleural effusion, or pulmonary contusion or laceration, remains difficult [4].

The following two are the main radiographic findings that are specific of TDI:

Other common and suggestive, but nonspecific findings of TDI on CXR are:

It is important to underline how concurrent pulmonary abnormalities, related to the trauma, such as hemothorax, pulmonary contusion or laceration, atelectasis, and phrenic nerve palsy may mimic or mask a TDI on CXR. In addition, the positive pressure of ventilatory support may delay herniation of abdominal contents through a torn diaphragm. Therefore, the rate of a missed TDI on CXR ranges from 12 to 66%, with the potential risk of a late visceral herniation through the diaphragmatic defect. Anyway, in the presence of both specific and nonspecific CXR findings a MDCT examination is warranted in hemodynamically stable patients to confirm a TDI to assess potential associated injuries and to guide clinical management [1, 4].

The MDCT is nowadays considered the gold standard imaging study for the assessment of a TDI, with a specificity of 76–99% and a sensitivity of 61–100%, considerably higher if compared with the single-layer CT era [8, 10, 20, 32]. Indeed, the improvement of the MDCT technology, such as the use of multilayer scanners, with higher spatial resolution and speed, reduces artifacts and produces high quality MPR images, which are fundamental for diagnosis [33]. If a TDI is suspected, on a clinical and/or a radiographic basis, the hemodynamically stable patients should undergo a whole-body MDCT examination, whereas hemodynamically unstable patients (or patients with signs of acute peritonitis) must be directed to a surgical exploration as soon as possible [6, 20, 34]. The MDCT protocols vary depending upon the type of scanner available, the institution, and the patient’s clinical conditions. Usually, a whole-body MDCT, with intravenous (IV) contrast is performed. In our emergency department, the MDCT examination is composed by three phases: a first non-enhanced phase, from the thoracic inlet through the symphysis pubis to appreciate hyperdense features (such as calcification or blood), an arterial phase (for which it is advisable to use high-flow IV contrast, by means of a power injector) to detect arterial lesion and a venous phase for visualization of parenchymal injuries. The arterial and portal venous scan can be acquired using, respectively, delays of 30 and 70 s, but, for the arterial phase, a bolus tracking or a smart prep technique is preferred. The images should have a thin collimation (2.5–3 mm) and they might afterwards be reconstructed at 0.625–1 mm for the interpretation and post-processing.

Several MDCT findings have been described over the years, which have been classified into three groups [10]: direct and indirect evidence of rupture; uncertain-controversial signs; and associated signs, according to Table 12.1. These signs are highly specific but the sensibility is lower because, in the setting of penetrating trauma, the herniation might be of small size and it might be overshadowed by more critical and severe traumatic injuries. The fundamental role of MDCT is to establish the best therapeutic management for patients with TDI giving clear indications to the emergency clinician and surgeon. As summarized in Table 12.2, the findings specific for a diaphragmatic rupture directly refer the patient to the operating room, while nonspecific findings need a radiological follow-up [8].

Discontinuity of the diaphragmatic profile. It is the most frequent and important sign of a TDI since it represents the direct evidence of the tear of the musculotendinous component, which can be located both centrally and peripherally (Fig. 12.7). This sign is observed in almost 96% of all traumatic diaphragmatic hernia, and it is considered to be very significant since its sensitivity has been reported to be 58–82.7% and its specificity 88–95%. The free edges of the ruptured diaphragm are usually thickened by post-traumatic edema, hemorrhage, or muscle retraction [10, 20].

Segmental non-visualization of diaphragm. It is an isolated absence of a part of the diaphragm in the site of the injury. This sign has a sensitivity of 86% and a specificity of 68% since it may be falsely positive in elderly patients, in whom the non-visualization of a section of diaphragm might be a normal variant, or when the outline of the diaphragm is blurred due to retroperitoneal hematoma, hemothorax, pulmonary contusion, or atelectasis of pulmonary bases [20].