The diaphragm, in its role as a musculoaponeurotic structure separating the thoracic and abdominal domains, is subject to injury following blunt or penetrating trauma. Historical accounts documenting diaphragmatic injury date from 1541, when Sennertus described the postmortem finding of delayed herniation of the stomach through a diaphragmatic defect in a patient who had previously suffered a penetrating chest wound. Detailed postmortem findings related to both blunt and penetrating diaphragmatic injuries were reported by Ambroise Pare in the sixteenth century. The first antemortem diagnosis of a traumatic diaphragmatic injury was published by H. I. Bowditch in 1853, who also set forth physical criteria for the diagnosis of traumatic diaphragmatic hernias: (1) prominence and immobility of the left thorax; (2) displacement to the right of the area of cardiac dullness; (3) absent breath sounds over the left thorax; (4) audible bowel sounds in the left chest; and (5) tympany to percussion over the left chest. Riolfi, in 1886, subsequently performed the first successful repair of a diaphragmatic laceration secondary to penetrating trauma. Hedblom, in 1925, reviewed 378 cases of diaphragmatic hernias in the surgical literature, providing a contemporary overview of diagnosis and surgical treatment.

The diaphragm (dia: across, phragm: fence) is the musculotendinous, dome-shaped structure separating the negative-pressure thoracic cavity and the positive-pressure peritoneal cavity. Embryologically, the diaphragm is derived from the fusion of four distinct structures: the septum transversum, the pleuroperitoneal membranes, the dorsal mesentery of the esophagus, and the body wall musculature. After development is complete, the diaphragm is composed of two distinct muscle groups, costal and crural. The costal muscle group is composed of peripherally located skeletal muscle fibers, whose contraction results in flattening of the diaphragm and lowering of the ribs. The crural muscle group, by contrast, does not contribute significantly to diaphragmatic excursion. The left crus arises from the upper two lumbar vertebrae and the right crus arises from the lateral aspect of the upper three lumbar vertebrae. The interdigitation of the medial tendinous crural fibers anterior to the aortic hiatus forms the median arcuate ligament, and the fibers of the right crus encircle the esophagus. Both costal and crural muscle fibers converge to insert into the aponeurotic central tendon, whose central aspect lies immediately beneath the pericardium (Fig. 154-1). Thoracoabdominal structures traverse the diaphragm through three major openings: the vena cava aperture (T8 vertebral level, containing the vena cava), the esophageal aperture (T10 vertebral level, containing the esophagus and the left and right vagal nerves), and the aortic aperture (T12 vertebral level, containing the aorta, thoracic duct, and the azygos vein (Fig. 154-2).

The diaphragm attaches to the xiphisternum anteriorly, the first three lumbar vertebrae posteriorly, and laterally attaches to the internal surface of the lower ribs, spanning the sixth rib anteriorly to the twelfth rib posteriorly. The phrenic nerves, arising from the anterior rami of the third through fifth cervical nerve roots, supply motor innervation to the diaphragm and sensory innervation to the central tendon and parietal pleura. In addition, the outer portion of the diaphragmatic musculature is innervated by the lower intercostal nerves (T7–T12) secondary to derivation from the somatopleuric mesenchyme during embryologic development. The rich arterial blood supply includes the pericardiophrenic arteries on the superior aspect and branches from the abdominal aorta and intercostal arteries on the inferior surface (Fig. 154-3).

As the chief respiratory muscle of the body, the diaphragm is a dynamic structure.

With normal respiration, a 3- to 5-cm diaphragmatic excursion is produced in both directions, providing 75% to 80% of tidal volume. On deep exhalation, the right hemidiaphragm rises anteriorly to the fourth intercostal space, and the left hemidiaphragm to the fifth intercostal space. Both hemidiaphragms ascend to the seventh or eighth intercostal space posteriorly. Clinically useful landmarks for the cephalad extent of diaphragmatic excursion are the nipple line anteriorly and tip of scapula posteriorly.

Diaphragmatic injury may occur secondary to either penetrating or blunt mechanisms. Retrospective reviews have demonstrated the incidence of diaphragmatic injuries to range from 0.8% to 5.8%. Penetrating injuries remain the most common cause of diaphragmatic injuries, outnumbering blunt injury twofold.¹ Penetrating injuries associated with stab wounds, the left hemidiaphragm is more frequently injured due to the preponderance of right-handed assailants. The principal mechanism involved in blunt injury is a sudden and abrupt increase in the pleuroperitoneal pressure gradient, which normally ranges from +7 to +20 cm H₂O. The resulting burst-type diaphragmatic injury results from the transmission of force through the abdominal viscera to the diaphragm.

Injury to the left hemidiaphragm occurs more frequently than that to the right, secondary to the protection afforded the right hemidiaphragm by the liver. Most left-sided diaphragmatic tears are greater than 10 cm long, and rupture typically occurs in the posterolateral aspect due to congenital weakness of the fusion between the costal and lumbar diaphragmatic muscular attachments. Lateral impact motor vehicle collisions are associated with a higher incidence of diaphragmatic ruptures compared to frontal collisions.²

Associated injuries are commonly encountered with acute diaphragmatic rupture, secondary to the dynamic nature of the diaphragm and its proximity to multiple intra-abdominal organs, including the liver, spleen, stomach, and kidneys. These are dictated to a certain extent by the mechanism of injury. Blunt trauma is associated with significant orthopedic injuries. Rodriguez-Morales et al.³ reported a 55% incidence of associated pelvic fractures in their series of blunt diaphragmatic injuries.

Demetriades et al.⁴ reported associated intra-abdominal injuries in 75% of patients sustaining penetrating injuries to the diaphragm.

The ability to diagnose an injury to the diaphragm requires a high index of suspicion, and is in part related to the extent of the diaphragmatic defect and the associated intra-abdominal organ injury. The diagnosis of traumatic diaphragmatic injury is rarely obvious, and can infrequently be missed even when patients undergo surgical exploration for penetrating injuries. Feliciano et al.⁵ reported three patients during a 9-year period in whom the diaphragmatic injury was missed at operation. Aronoff et al.⁶ reported normal physical findings in 55% of blunt injuries and 44% of penetrating injuries.