A 30-year-old man presents with sudden onset severe central abdominal pain. Plain X-ray shows free intraperitoneal gas (pneumoperitoneum) as a thin crescent of air under the right hemidiaphragm. He is haemodynamically stable. Which plain film sign confirms the presence of extraluminal free air on a supine film when erect views are not obtainable?
- A Rigler's sign (double wall sign) ✓
- B Cupola sign
- C Football sign
- D Falciform ligament sign
Explanation
Rigler's sign (double wall sign) is seen on supine films when free peritoneal gas outlines both the inner mucosal and outer serosal surfaces of the bowel wall simultaneously, making the bowel wall appear as a visible thin white line with gas on both sides. Normally only the mucosal surface is seen. The football sign describes a large oval lucency over the abdomen in massive pneumoperitoneum (common in neonates). The cupola sign is air beneath the central tendon of the diaphragm. The falciform ligament sign shows the ligament outlined by free gas as a vertical density in the right upper abdomen.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.