Hepatic Portal Venous Gas: Review of Ultrasonographic Findings and the Use of the "Meteor Shower" Sign to Diagnose It.

Ultrasonography (US) is believed to be the most available method of detecting hepatic portal venous gas (HPVG) with real-time imaging capability. Hepatic portal venous gas has characteristic image appearances in various ultrasound modes such as bright mode, Doppler mode, and even motion (M) mode. In this article, we give a comprehensive review of the image appearances of HPVG among different modes of US with a special focus on the M mode US. Hepatic portal venous gas was recognized as linear echogenicities in various oblique directions (the meteor shower sign) on the M mode US. This specific sign may expand some potential of HPVG detection by US.