Air or gas may be seen in the liver or portal vein on imaging studies or may be encountered during surgery. The significance depends on identifying the cause.
The first issue is to localize where the air or gas is:
(1) liver parenchyma
(2) portal vein
(3) biliary system (see pneumobilia, above)
Sources of air or gas may include:
(1) infection with a gas forming bacteria (Clostridium or other bacteria)
(2) entry of air or bowel gas into the portal vein
(3) iatrogenic
The highest mortality is associated with:
(1) infection of the liver parenchyma with gas-forming bacteria (may be primary or may secondarily infect a tumor or parasitic abscess)
(2) small and/or large bowel necrosis secondary to mesenteric vessel occlusion
Conditions associated with air or gas entering the portal venous system include:
(1) peptic ulcer disease
(2) intra-abdominal cancer
(3) inflammatory bowel disease (Crohn's disease, ulcerative colitis)
(4) parasitic disease involving the intestines (typically amebiasis)
(5) trauma
(6) abdominal surgery or endoscopic procedure, especially if there is gas insufflation
