A 79-year-old man presented with symptoms and signs of upper respiratory tract infection; he had a history of permanent pacemaker implantation. An upright postero-anterior chest radiograph showed a raised right hemidiaphragm delineated by subdiaphragmatic air. Unlike free air, which forms an uninterrupted crescent-shaped subdiaphragmatic radiolucency, this radiograph showed a haustral pattern of subdiaphragmatic lucency, overlapping the upper border of the liver shadow. On examination, clinical findings suggesting acute abdomen from rupture of a hollow viscus were absent and there was no recent history of abdominal surgery to account for the presence of subdiaphragmatic air.
The visualisation of a gas filled transverse colon lumen interpositioned between the right hemidiaphragm and the liver on a chest film is called Chilaiditi’s sign. A CT scan may confirm these anatomical relations. In our patient’s radiograph, the haustral pattern of air was indicative of colonic origin, and the continuity of the subdiaphragmatic air was broken up by the shadow of the vertical plicae semilunares of the colon. Chilaiditi’s sign was first described in 1910 by Demetrious Chilaiditi and it is an incidental radiographic finding. This sign can be mistaken for pneumoperitoneum and can lead to needless surgical intervention. Our patient was treated only for his upper respiratory tract infection.