Paediatric ImagingGas, portal vein
Gas may enter the portal venous system from bowel wall through mesenteric veins and become temporarily trapped in the liver. Any cause of pneumatosis (gas within bowel wall) may lead to portal venous gas. Common causes include necrotizing enterocolitis (NEC) and neutropenic colitis (typhlitis) but any cause of bowel wall ischaemia or necrosis may lead to it.
Radiographically, small branching lucencies are seen in a peripheral distribution over the liver (Fig.1). They may be transient and alter configuration between successive radiographs. Ultrasonography will demonstrate static and mobile echogenic foci within the portal vein branches. CT may also demonstrate portal venous gas.
The presence of portal venous gas indicates severe but not necessarily fatal disease in premature neonates with NEC.
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Supine radiograph of a neonate with necrotizing enterocolitis. The branching lucencies over the liver are the typical appearances of portal vein gas.
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Gas, portal vein, Fig.1 | |