the lower chest or upper abdomen. With penetrating trauma, the contents of the abdomen may not herniate into the chest cavity right away, but they may do so later, causing the presentation to be delayed. Since the diaphragm moves up and down during breathing, penetrating trauma to various parts of the torso may injure the diaphragm; penetrating injuries as high as the third rib and as low as the twelfth have been found to injure the diaphragm. Iatrogenic cases have occurred as a complication of medical procedures involving the thorax or abdomen. It has occurred as a complication of thoracentesis and radiofrequency ablation. Mechanism Although the mechanism is unknown, it is proposed that a blow to the abdomen may raise the pressure within the abdomen so high that the diaphragm ruptures. Blunt trauma creates a large pressure gradient between the abdominal and thoracic cavities; this gradient, in addition to causing the rupture, can also cause abdominal contents to herniate into the thoracic cavity. Abdominal contents in the pleural space interfere with heart function and lung function. High intrathoracic pressure results in an increase in right atrial pressure, disrupting the filling of the heart and venous return of blood. As venous return determines cardiac output, this results in a reduction of cardiac output. If ventilation of the lung on the side of the tear is severely inhibited, hypoxemia (low blood oxygen) results. Usually, the rupture is on the same side as an impact. A blow to the side is three times more likely to cause diaphragmatic rupture than a blow to the front. Diagnosis Physical examinations are not accurate, as there is usually no specific physical sign that can be used to diagnose this condition. Thoracoscopic and laparoscopic methods can be accurate. Chest X-ray is known to be unreliable in diagnosing diaphragmatic rupture; it has low sensitivity and specificity for the injury. Often another injury such as pulmonary contusion masks the injury on the X-ray film. Half the time, initial X-rays are normal; in most of those that are not, hemothorax or pneumothorax is present. A nasogastric tube from the stomach may appear on the film in the chest cavity; this sign is pathognomonic for diaphragmatic rupture, but it is rare. The X-ray is better able to detect the injury when taken from the back with the person upright, but this is not usually possible because the person is usually not