An inconspicuous penetrating injury of the diaphragm

A 22-year-old male without any significant medical or surgical history presented to the emergency department with multiple stab wounds involving the left arm and anterior chest wall below the nipple (Figure 1). The patient was haemodynamically stable on arrival and only reported pain at the sites of lacerations. Contrast-enhanced computed tomography (CECT) of the chest, abdomen, and pelvis was obtained to evaluate the extent of penetrating injury.

The patient’s chest CECT demonstrated soft tissue lacerations of the chest wall and a trace left haemothorax, but no other injuries were initially identified (Figures 2a and 2b). Upon later review, a focal defect was identified in the left anterior diaphragm adjacent to the site of the left anterior chest wall stab wound, with herniation of intra-abdominal fat into the thoracic cavity (Figures 3a, 3b, 3c, 4a and 4b). There were no significant traumatic injuries in the abdomen or pelvis.

Acquired diaphragmatic hernias can occur from penetrating or blunt traumatic mechanisms [1]. The most common cause of blunt diaphragmatic injury is motor vehicular accidents, while the mechanism of penetrating diaphragmatic injuries is typically gunshot or stabbing. Traumatic diaphragmatic injuries may not be recognised at the time of the traumatic event as they often present in combination with other more severe injuries or can be difficult to detect [2].

Most traumatic diaphragmatic hernias tend to involve the left hemidiaphragm, at its posterolateral aspect. Blunt diaphragmatic injuries tend to be ruptures measuring greater than 10 cm in length; while penetrating traumas can often cause smaller defects, which if gone unrecognised, can increase in size over months to years [3].

Traumatic diaphragmatic injuries occur more commonly in younger adults, with a higher incidence in males as these populations are more likely to be injured in the setting of motor vehicle collisions and penetrating injury [4]. The true incidence of traumatic diaphragmatic hernias is unknown as they can be frequently missed on initial imaging [5].

There is evidence in the literature of higher mortality in patients with diaphragmatic injuries due to other severe concurrent injuries. Prognosis is improved with earlier diagnosis and repair. Diaphragmatic injuries may not heal spontaneously, given continuous diaphragmatic motion and differences in the pressure gradient across the diaphragm. In the setting of delayed diaphragmatic injury diagnosis, the injuries can enlarge, and abdominal viscera may herniate into the chest [6]. Due to the high probability of eventual abdominal herniation through a diaphragm injury, surgical repair is recommended [7]. The complications of traumatic diaphragmatic hernia include bowel obstruction and strangulation, central venous obstruction or respiratory failure due to mass effect from the herniated structures.

Due to the relative ease of acquisition and low cost offered by plain radiographs, they are often acquired as the initial imaging examination. Radiographic technique, patient cooperation and positioning can affect imaging outcomes and small or focal diaphragmatic injuries can be missed on initial radiographs [8]. The diagnostic accuracy of penetrating diaphragmatic injuries on radiographs has not been well-established in the literature. Signs of diaphragmatic rupture on plain radiographs include discontinuity of the normal hemidiaphragm contour, intrathoracic herniation of abdominal contents, or an elevated left hemidiaphragm relative to the right.

Multidetector CT is considered the preferred modality of choice for evaluating diaphragmatic injury. In the setting of trauma, rapid volumetric data acquisition with thin-section multi-planar reconstructions allows for rapid detection of life-threatening injuries. The reported sensitivity and specificity of CT for the detection of diaphragmatic ruptures in the literature are between 61–87% and 72–100%, respectively [9]. On CT, diaphragm injuries are characterised by a segmental diaphragmatic defect, with or without protrusion of abdominal contents into the thorax. Secondary signs on CT include: focal thickening of the diaphragm; the presence of pneumothorax and pneumoperitoneum or haemothorax and haemoperitoneum, indicating injuries on both sides of the diaphragm; active contrast extravasation near the diaphragm on angiographic imaging; and; generally injury near the diaphragm with possible associated fat stranding [2,10].

In our case, a secondary review of imaging by the trauma surgery team prompted a question of possible discontinuity of the diaphragm. A diagnostic laparoscopy was performed and revealed a 1–2 cm diaphragmatic defect with herniation of intra-abdominal fat into the thorax. The fat was reduced back into the peritoneum, and the diaphragmatic defect was repaired. The patient recovered well and was eventually discharged.

Informed patient consent for publication has been obtained.