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DIAPHRAGMATIC INJURIES

DIAPHRAGMATIC INJURIES

The diaphragm is an arched muscle dividing the thorax and the abdomen and is interrupted by three major openings: the vena cava, esophagus, and aorta. The diaphragm is the main respiratory muscle, with inspiratory and expiratory functions. Diaphragmatic injuries may be caused by penetrating or blunt trauma; the mechanism influences the site and extent of injury. With gunshot wounds, the chances of right versus left side are roughly equal, and the wound from most hand- guns is small, usually smaller than 1 cm. In contrast, stab wounds involve the left side of the diaphragm more commonly because the right-handed assailant holds the weapon in the right hand and confronts the victim at close range. Knife wounds are also typically small, usually smaller than 2 cm. The left hemidiaphragm is injured two to three times more frequently than the right after blunt trauma. The difference is attributed to the protective effect of the liver that distributes a sudden increase in intraabdominal pressure more evenly across the right hemidiaphragm. Blunt diaphragm injuries are considerably larger than penetrating wounds and are usually larger than 5 cm in length and in many cases exceed 10 cm. During quiet respiration, the normal intraperitoneal pressures ranges from+2 to +10 cm H2O, and the corresponding intrapleural pressure fluctuates from -5 to -10 cm; thus, a gradient exists varying from +7 to +20 cm H2O. But with maximal inspiration, this gradient may exceed 100 cm H2O. Consequently, there is high risk for abdominal viscera to herniate into the thorax. The risk is higher on the left side because the liver provides a barrier on the right, and herniation increases with the extent of the diaphragmatic defect. Ambroise Paré, in 1579, is credited with describing the first case of visceral herniation in a French artillery captain who sustained a gunshot wound to the left chest 8 months before a lethal colonic obstruction.

DIAPHRAGMATIC INJURIES
Plate 4-142


The diagnosis of diaphragmatic injury depends on the size of the diaphragm lesion. With larger defects, the presenting symptoms are usually pulmonary because of the volume of the pleural cavity occupied by the displaced intraabdominal viscera. On the other side, incarcerated stomach, colon, or small bowel may produce peritoneal signs. The most common finding on chest radiography is an apparent elevated hemidiaphragm and, when the left diaphragm is torn, a nasogastric tube is frequently seen in the thorax. Smaller defects produced by penetrating wounds, however, are frequently asymptomatic initially, and the chest radiographs are often normal. The most definitive diagnostic adjunct is laparoscopy or thoracoscopy, but multidetector computed tomography scanning and magnetic resonance imaging are becoming more accurate.

The operative management of patients with diaphragm injuries is largely dictated by the risk of associated abdominal injuries. In the acute phase, more than 50% of blunt trauma and more than 75% of penetrating trauma involve abdominal viscera. Thus, the operative approach is via the abdomen early after injury. In hemodynamically stable patients, laparoscopy may be used to evaluate the abdominal organs and, in the event of no hollow visceral injury, may suffice for definitive repair of the diaphragm. In the chronic phase with delayed visceral herniation, a thoracotomy is generally recommended to free the lung from adhesions and provide access to the diaphragm injury.