Diaphragmatic eventration is an abnormal contour of the diaphragmatic dome. It typically affects only a segment of the hemidiaphragm, in contrast to paralysis/weakness where the entire hemidiaphragm is typically affected. 

It is congenital in nature affecting commonly the anteromedial part of the right hemidiaphragm but other parts and side may be affected. It is due to incomplete muscularisation of the diaphragm with a thin membrane replacing normal diaphragmatic muscle. Over time this region stretches and on inspiration does not contract normally. 

Treatment

In contrast to the large thoracotomy incisions required by standard surgical techniques for repair of diaphragmatic eventration, the procedure can be performed by video-assisted thoracoscopy, thus offering patients the advantages of a minimally invasive operation. Various methods have been described. Plication can be performed by two superposed series of transverse back-and-forth continuous non absorbable sutures, the diaphragm is invaginated, then the sutures tightened. Sometimes the excess redundant portion can be excised and muscular part approximated like diaphragmatic hernia. A Endo GIA stapler can be fired after bunching up the redundant excess thinned out diaphragm and firing a stapler across.