Detection of pneumoperitoneum: optimum body position and respiratory phase.

Experimental studies of pneumoperitoneum in left lateral decubitus and erect positions were made in various phases of respiration to evaluate the visibility of small amounts of free intraperitonel air. Films were also made with various positions of the central ray of the x-ray beam. The expiratory left lateral decubitus film nd the mid-inspiratory chest film demonstrated the small pneumoperitoneums best. Both inspiration and expiration chest films are recommended inm the refilming and expiration chest films are recommended in the refilming sequence if a clinically suspected pneumoperitoneum is not visualized initially. In all cases the central ray of the x-ray beam should be at the highest level fo the peritoneal cavity.