Abdomen X-Ray Erect

Air–fluid levels and pneumoperitoneum (free subdiaphragmatic air).

Patient standing with back against the detector.
Field centred to include both diaphragmatic domes to mid-abdomen.
Expiration at the moment of exposure.
Central ray: perpendicular to the IR.

T10 (approximately 6 cm above the iliac crest), to include both diaphragmatic domes

Diaphragmatic domes included.
Air–fluid levels visible if present.
Free subdiaphragmatic air demonstrable.

Patient must stand for at least 10 minutes before exposure to allow free air to collect in the subdiaphragmatic space.
If unable to stand: perform in left lateral decubitus (left side down) — wait at least 5–10 minutes so that air migrates to the right side overlying the liver.