Figure 1. Posterior-anterior chest radiograph.
Figure 2. Lateral chest radiograph.
Eventration is defined as an abnormal elevation of an intact hemidiaphragm. It was first described by Jean Louis Petit in 1774 during a postmortem examination.1 In true eventration, all or part of the elevated hemidiaphragm retains its attachments to the abdominal wall, and the peripheral musculature is normal. Eventration is uncommon, with a reported incidence of one in 1400 cases.2 Bochdalek hernia and eventration are thought to arise from a congenital abnormality of the pleuroperitoneal membrane.3 Both conditions occur more frequently in males and on the left side; however, Bochdalek hernia represents a true posterolateral defect.
Diaphragmatic elevation due to phrenic nerve paralysis is an acquired lesion. Disorders of the phrenic nerve are classified as posttraumatic, infectious, neoplastic, neuromuscular, or idiopathic. Trauma occurs most commonly after surgery for congenital cardiovascular disorders. Herpes zoster, influenza, and subphrenic abscess are infectious causes. Poliomyelitis is a neurogenic cause. Neoplastic involvement of the phrenic nerve is often secondary to mediastinal tumors and bronchogenic carcinoma with mediastinal involvement.
Newborns with eventration may have respiratory distress requiring mechanical ventilation. Rotation of the gastric fundus underneath the elevated diaphragm can cause frequent regurgitation, epigastric pain, or progress to gastric volvulus. In adults, the primary physiological abnormality is a restrictive respiratory defect characterized by moderate hypoxia and decreased vital capacity and expiratory reserve volume. Hoover's sign—the marked outward excursion of the costal margin from the midline on inspiration—is considered to be a sensitive sign of eventration that results from the unopposed action of intercostal muscles.3
In adults, the diagnosis of eventration is usually made with posterior-anterior and lateral radiographs. Eventration is distinguished from acquired phrenic nerve disorders by the absence of paradoxical motion during fluoroscopic examination. Computed tomography scans and ultrasonography do not reliably differentiate eventration from a diaphragmatic hernia.
Surgery for diaphragmatic eventration is indicated in newborns and infants who have severe respiratory distress, require prolonged ventilatory support, or fail nonoperative management. Adults with disabling respiratory symptoms and a marked restrictive ventilatory defect are also surgical candidates. Asymptomatic adults are managed without surgery.
When surgery is indicated, the diaphragm is usually approached through a posterolateral thoracotomy. When the eventration is bilateral or has an infracardiac component, an abdominal approach is recommended. In both cases, the surgical goal is to immobilize the diaphragm in a flattened position 1 to 2 intercostal spaces inferiorly. Simple plication of the diaphragm involves mobilizing the muscle in a radial direction while creating pleats in the anteromedial and posteromedial direction using full-thickness nonabsorbable horizontal mattress sutures. This approach is favored in children because of its speed and minimal blood loss. An alternative approach is resection of the redundant aponeurotic section of the diaphragm, followed by an overlapping reapproximation of normal muscle. This approach is associated with better functional recovery of the diaphragm. A third alternative uses video-assisted thoracic surgery to plicate the diaphragm through a mini thoracotomy made over the ninth intercostal space. Because this approach is minimally invasive, it can reduce pain and disability and result in shorter hospital stays.4
Corresponding author: Cynthia L. Leslie, MD, Critical Care Unit, Yale–New Haven Hospital, 333 Cedar St LH118, PO Box 208062, New Haven, CT 06520.
Image of the Month. Arch Surg. 2001;136(10):1211-1212. doi: