Saber sign (pneumobilia)

The saber sign refers to a pattern of gas distribution seen in supine abdominal radiographs of patients with pneumobilia.  A sword-shaped lucency is apparent in the right paraspinal region of the upper abdomen representing arching gas extending from the common bile duct into the left hepatic duct.  This is present in ~50% of patients with pneumobilia .  It can be a helpful sign when differentiating between biliary and portal venous gas and is an important 'review area' on abdominal films.