ETIOLOGY In urban centers, diaphragmatic injuries are caused most frequently by penetrating trauma, particularly gunshot wounds of the lower chest or upper abdomen. Rupture due to blunt trauma is much less frequent and occurs in only 4 to 5 percent of patients hospitalized with chest trauma. If there is a fracture of the pelvis, the incidence increases to about 8 to 10 percent.
Because of the protective effect of the liver on the right and the possible increased weakness of the left posterolateral diaphragm, most series report that 80 to 90 percent of the diaphragmatic injuries following blunt trauma occur in that area. However, in the series of Brown and Richardson, 17 the incidence of right- and left-sided diaphragmatic rupture was almost equal.
NATURAL HISTORY Since 60 to 70 percent of normal ventilation depends on proper function of the diaphragm, trauma to this structure can cause serious ventilatory problems. However, the initial signs and symptoms are often masked by other injuries. Unless the diaphragmatic lesion is large, symptoms due to abdominal viscera in the thoracic cavity usually occur rather late. Over time, sometimes even years, a large amount of viscera can gradually work up into the chest through small diaphragmatic tears. The intrathoracic bowel may then become obstructed or strangulated or cause severe compression of the adjacent lung, a phenomenon we have referred to as tension enterothorax.
DIAGNOSIS With penetrating trauma, the diagnosis of diaphragmatic injury is often made only intraoperatively. However, if the entrance wound is in the abdomen and there is evidence of an intrathoracic injury or foreign body, one can assume that the missile or knife has traversed the diaphragm. In the series just mentioned, 59 percent of the patients with diaphragmatic injuries had diagnostic chest x-rays. However, eight of nine peritoneal lavages done in these patients were negative. In the only positive lavage, the lavage fluid drained out through a previously placed chest tube.
With blunt trauma, any abnormality of the diaphragm or lower lung fields on chest x-ray should arouse suspicion of a diaphragmatic tear. Occasionally a nasogastric tube is seen to go into the abdomen and then back up into the chest because the stomach has passed through a diaphragmatic tear.
Techniques for diagnosing the less obvious diaphragmatic injuries include (1) peritoneal lavage with a chest tube in place; (2) upper gastrointestinal (GI) series, looking for displacement of viscera into the chest; (3) pneumoperitoneum with carbon dioxide; (4) CT scan with contrast; and (5) intraperitoneal technetium sulfur colloid. However, up to 50 percent of diaphragmatic injuries are diagnosed only during a thoracotomy or laparotomy.
Subtle diaphragmetic injuries can be difficult to diagnose, particularly on the right. Axial CT scans that are virtually tangent to areas at risk are difficult to interpret unless there is herniation of abdominal contents through the defect. The advent of laparoscopy has provided a new, useful tool for identifying the smaller injuries, and this may well be the diagnostic mode of choice for patients who have no other indications for laparotomy. Caution should be exercised, since insufflated gas can leak from the abdomen across a violated diaphragm and cause acute cardiorespiratory embarassment.
THERAPY Laparotomy is necessary to repair the diaphragm. Thoracotomy may be necessary for associated chest injury, resuscitation, delayed repair of the diaphragm, or management of thoracic complications. Recently there have been several reports of repair using thoracoscopy techniques.
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