The patient lies on his back on the x-ray table. The film is beneath the patient, and the x-ray tube is positioned overhead (vertical beam).

Patient is positioned erect for several minutes to allow air to rise. The film should include the diaphragms, abdomen and pelvis. An erect chest film is often included in an acute abdomen series to detect small quantities of free air.

If patient cannot tolerate erect positioning, he is positioned with left side down. The film should include both the right diaphragm and abdomen to the iliac crest to exclude free air at either site.

Prone film: Patient lays face down on the table, allowing gas in the more proximal colon to rise to the highest point in the pelvis, which is the rectum. Prone film is used to exclude distal colonic obstruction in patients with dilated, gas filled bowel and no gas in the rectum on supine film.

Supine film shows: ·distribution of bowel gas ·caliber of bowel ·bowel wall thickening ·solid organ enlargement ·abnormal gas collections ·calcifications ·tube placement ·osseous structures

Erect and left decubitus views are films which show: ·air/fluid levels in bowel ·free air     -under diaphragm     -along iliac crest