A 58-year-old man presented with acute onset of epigastric pain that lasted for 2 h. Physical examination showed generalised abdominal tenderness and a positive peritoneal sign. Plain abdominal radiography disclosed a double-wall sign, indicating pneumoperitoneum. A subsequent computed tomography scan confirmed the diaphragm outlined by the pleural cavity and pneumoperitoneum, resembling the silhouette of Mount Fuji, the large volcano in Japan (fig 1). Exploratory laparotomy showed a small perforation of the gastric body. Suture of the ulcer and drainage was performed, leading to an uneventful recovery.

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Figure 1

Computed tomography of the abdomen showing the Mount Fuji sign of the pneumoperitoneum.

When the patient is in the supine position, pneumoperitoneum preferentially accumulates in the anterior portion of the peritoneal cavity, beneath the central tendon of the diaphragm and within the median subphrenic space. The Mount Fuji sign originally indicates tension pneumocephalus with subdural air collection compressing the frontal lobes.1 We highlight that this sign is another indicator of emergency conditions, such as pneumoperitoneum, as shown here.