On erect plain abdominal X-ray, which of the following indicates free intraperitoneal gas MOST reliably?

• A Rigler's sign — gas on both sides of the bowel wall
• B Football sign — elliptical radiolucency over the abdomen
• C Lucency over the liver (hepatic gas)
• D Air under the right hemidiaphragm in the erect position ✓

Explanation

Air under the right hemidiaphragm on an erect chest/abdominal X-ray is the most commonly used and reliable sign of free intraperitoneal gas (pneumoperitoneum). Rigler's sign (double-wall sign) indicates large volumes of free gas and is seen on supine films. The football sign is also seen on supine films in neonates with massive pneumoperitoneum. Hepatic gas (portal venous or biliary) is seen within the liver parenchyma and indicates different pathologies.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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