<unk>  is the presence of air in the retroperitoneum. It is always a pathological condition and can be caused by a perforation of a retroperitoneal hollow organ such as the duodenum, colon or rectum.<unk>  can best be identified by CT scan.
Pneumoretroperitoneum
Pneumoperitoneum
Diaphragmatic rupture
Pulmonary laceration
Hemoperitoneum
Pneumopericardium
Urinothorax
Hemopericardium