Traumatic diaphragmatic injury: a review of CT signs and the difference between blunt and penetrating injury

PURPOSE

We aimed to present the frequency of computed tomography (CT) signs of diaphragmatic rupture and the differences between blunt and penetrating trauma.

MATERIALS AND METHODS

The CT scans of 23 patients with surgically proven diaphragmatic tears (both blunt and penetrating) were retrospectively reviewed for previously described CT signs of diaphragmatic injuries. The overall frequency of CT signs was reported; frequency of signs in right- and left-sided injuries and blunt and penetrating trauma were separately tabulated and statistically compared.

RESULTS

The discontinuous diaphragm sign was the most common sign, observed in 95.7% of patients, followed by diaphragmatic thickening (69.6%). While the dependent viscera sign and collar sign were exclusively observed in blunt-trauma patients, organ herniation (P = 0.05) and dangling diaphragm (P = 0.0086) signs were observed significantly more often in blunt trauma than in penetrating trauma. Contiguous injury on either side of the diaphragm was observed more often in penetrating trauma (83.3%) than in blunt trauma (17.7%).

CONCLUSION

Knowledge of the mechanism of injury and familiarity with all CT signs of diaphragmatic injury are necessary to avoid a missed diagnosis because there is variability in the overall occurrence of these signs, with significant differences between blunt and penetrating trauma.Traumatic diaphragmatic injury has been found in 3%–8% of patients undergoing surgical exploration after blunt trauma and in 10% of patients with penetrating trauma (1, 2). The rate of initially missed diagnoses on computed tomography (CT) ranges from 12% to 63%. A missed diagnosis can later present as intrathoracic visceral herniation and strangulation with a mortality rate of 30%–60% (2, 3). In this era of increasing nonoperative management for most cases of blunt abdominal trauma, it becomes essential to diagnose diaphragmatic rupture on imaging to ensure early and timely operative repair of the rupture. The reasons for missed early diagnoses include potentially distracting and more severe thoracic and abdominal visceral injuries and lack of familiarity with all the imaging appearances and signs of diaphragmatic rupture (2, 4).Various imaging modalities including chest radiographs, ultrasonography, CT, and magnetic resonance imaging have been used in the diagnosis of diaphragmatic rupture (1). Currently, multidetector CT (MDCT) is the modality of choice for the detection of diaphragmatic injury. MDCT has increased the accuracy of diagnosis of diaphragmatic rupture. MDCT has inherent technical advantages, such as rapid, volumetric data acquisition for the chest and abdomen within a single breath hold, minimization of motion artifacts, thin-section reconstruction and sagittal and coronal reformat-reducing partial-volume effects that assist in diagnosing subtle defects (1). MDCT also aids in detecting the associated chest, abdomen, ribs, and bony injuries in these polytrauma patients. Various studies have revealed CT to have a variable sensitivity and specificity of 61%–87% and 72%–100%, respectively, for the diagnosis of diaphragmatic rupture (1, 5–7). Killeen et al. (6) demonstrated that the sensitivity for detecting left-sided ruptures (78%) is higher than for right-sided ruptures (50%). This finding has been attributed to the better soft tissue-fat contrast on the left side and the difficulty in diagnosing subtle liver herniation on the right side.Various signs of diaphragmatic rupture have been described on CT. These signs have been divided into direct and indirect signs and signs of uncertain/controversial origin, according to Desir and Ghaye (8), and have been tabulated in 2, 3).

Table 1.

CT signs of diaphragmatic injury^a

Direct signs Direct discontinuity of the diaphragm Dangling diaphragm sign

Indirect signs Collar sign Intrathoracic herniation of viscera Dependent viscera sign Contiguous injury on either side of the diaphragm Sinus cut-off sign

Signs of uncertain origin Thickening of the diaphragm Hypoattenuated diaphragm Fractured rib Diaphragmatic/peridiaphragmatic contrast extravasation

Open in a separate window^aModified from Bodanapally et al. (7) and Desir and Ghaye (8).Because the biomechanics of blunt and penetrating diaphragmatic ruptures are different, a variation in the frequency of individual signs should also be expected. Although the dependent viscera sign is a good sign of blunt diaphragmatic injury, it is an unreliable indicator for penetrating trauma (9). Penetrating traumatic diaphragm injuries are more easily diagnosed by following the trajectory of the weapon and looking for contiguous injury on either side of diaphragm (1, 7). Thus, it becomes imperative to be familiar with the signs of diaphragmatic rupture to avoid a missed diagnosis. Recently, Desser et al. (10) have reported a new sign, called the dangling diaphragm sign, in patients with blunt diaphragmatic injuries.Most of the studies about the individual CT signs of diaphragmatic injury have focused only on blunt trauma (2–6, 11–13). Moreover, to our knowledge, no analysis of the dangling diaphragm sign has been conducted in both blunt and penetrating trauma patients (5). Therefore, the purpose of our study was to present the frequency of CT signs in patients with diaphragmatic injury and to describe the differences between blunt and penetrating trauma.