ABSTRACT
Eventration of the diaphragm refers to the radiographic finding of an abnormally elevated hemidiaphragm. The physiologic consequences of the loss of diaphragm function may result in respiratory insufficiency made worse in infants due to the mobility of the mediastinum. When the normal hemidiaphragm descends during inspiration, the mediastinum shifts to the normal side, while the eventration side paradoxically elevates. Acquired eventration (paralytic eventration) is understood on the basis of injury to the phrenic nerve, most commonly occurring at the time of intrathoracic surgery. Congenital eventration of the diaphragm is less well understood and probably includes a number of different entities. Phrenic nerve injury from birth trauma is similar to operative injury in that the diaphragm is developmentally normal. Other congenital eventrations (nonparalytic eventration) of the diaphragm are associated with anatomic abnormalities of the diaphragm. The diaphragm muscle is thinned and may be entirely absent from a portion that is normally muscular. In its most extreme forms, eventration is indistinguishable from a congenital diaphragmatic hernia with a hernia sac. Surgical treatment is based on removing the laxity of the abnormal diaphragm leaf to prevent paradoxical motion.
