Doge cap sign (pneumoperitoneum)

The doge cap sign, also referred to as Morison pouch sign, is a radiographic sign of pneumoperitoneum. It presents as a triangular-shaped gas lucency or can be crescent shaped, or semicircular is usually bound by the 11th rib in the right upper quadrant on abdominal radiographs due to air in the Morison pouch, which resembles the medieval caps worn by Italian doges.