Volume 1, Case 6 Answers

This CXR demonstrates a pacemaker wire and air in the left chest with a tracheal shift to the right. This was not felt to be a pneumothorax, but rather an intrapulmonary pneumatocele. An upper GI series was performed, which showed the stomach to be in the normal position below the left hemidiaphragm. There was also paradoxical motion of her left hemidiaphragm noted. This was felt to be due to phrenic nerve injury during her pacemaker implantation. She developed worsening abdominal pain that night. Early the next morning, abdominal distention and worsening tenderness were noted. She was thought to have an acute abdomen. A follow-up abdominal series showed a bowel obstruction pattern and a barium filled colon in the left side of the chest, indicating a diaphragmatic hernia. She was taken to surgery where a left diaphragmatic hernia was noted. Colon and spleen were noted to be in the left hemithorax. A small volvulus was noted. A successful repair was performed.

Teaching Points and Discussion

Large pockets of air in the chest do not always represent a pneumothorax. This can be extremely deceiving at times since large air pockets will often have signs and symptoms similar to a tension pneumothorax. Respiratory distress, diminished breath sounds, and a mediastinal shift may all be present. A classic example of this is a diaphragmatic rupture following trauma to the chest or abdomen. Crying, hyperventilation, or mask ventilation may increase the degree of air in the bowel, distending it further, resulting in expanding air pockets in the chest. The bowel may be so distended at times, that an initial chest radiograph may have difficulty distinguishing this from a pneumothorax. It is often taught that thoracentesis or chest tube thoracostomy should not wait for a CXR if a tension pneumothorax is suspected. If a tension pneumothorax is present, air evacuation would result in immediate improvement in the patient's status; however, with a ruptured diaphragm, such a procedure would not result in any improvement.

Diaphragmatic hernia is usually a diagnosis made at birth; however, the diaphragmatic defect can be small such that the herniation of abdominal contents occurs later in life similar to an inguinal hernia. Although an upper GI series will usually show the stomach to be in the left chest, less frequently, the stomach will remain in the abdomen while distal bowel is found in the chest instead.

Congenital lobar emphysema can also present with findings mimicking a tension pneumothorax. The emphysematous lobe may be so distended that appreciating any lung markings may be difficult.

Cystic malformations of the lung or pneumatoceles may also resemble air leak syndromes.

It is possible that thoracentesis or chest tube thoracostomy will result in complications if performed in any of the above conditions. In addition, such procedures are not helpful in these conditions. Although a metal trochar is included with most chest tubes, it is not advisable to use these. The trochar is more likely to cause injury to lung and bowel, if one of the above conditions is present instead of a pneumothorax. In all conditions, the trochar is more likely to injure one of the great vessels. It is preferable to insert the chest tube without the trochar, thereby substantially reducing the risk of complications.

References

Templeton JM. Thoracic Emergencies. In: Fleisher GR, Ludwig S. Textbook of Pediatric Emergencies, third edition. Baltimore, Williams & Wilkins, 1993, pp. 1336-1362.

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 Loren Yamamoto, 
      MD, MPH Associate Professor of Pediatrics University of Hawaii John A. Burns 
      School of Medicine loreny@hawaii.edu