Survey radiographs a.
Abdominal fat is responsible for intra-abdominal serosal detail. Without fat, intra-abdominal viscera are not discernible. On the other hand, increased abdominal serosal detail is due to pneumoperitoneum. Left side down horizontal beam is indicated to identify a small volume of free abdominal gas. Gas in the retroperitoneal space may be secondary to pneumomediastinum.