Mediastinal herniation of the pleural sac: occurrence in massive pleural effusion.

In a review of 50 patients with massive pleural effusion, mediastinal herniation of the pleural sac occurred in 16 patients (32 percent). Right-to-left herniation (ten patients) was more common than left-to-right (six patients). Herniation occurred only in the posteroinferior mediastinum (D5-D11). Fourteen patients had displacement of the mediastinum away from the side of pleural effusion. Disappearance of herniated sac in every patient following thoracocentesis confirmed the diagnosis.