What is the appearance of portal gas on abdominal radiography in necrotizing enterocolitis (NEC)?

Updated: Dec 27, 2017
  • Author: Shelley C Springer, JD, MD, MSc, MBA, FAAP; Chief Editor: Muhammad Aslam, MD  more...
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Portal gas appears as linear, branching areas of decreased density over the liver shadow and represents air present in the portal venous system. Its presence is considered to be a poor prognostic sign. Portal gas is much more dramatically observed on ultrasonography.

Although once heralded as an ominous sign in NEC, portal gas is now believed to be less so. It is caused by gas produced by bacteria in the portal veins or by the transmigration of gas from the bowel wall to mesenteric veins and into the portal vein. It is frequently a transient finding; the pattern is demonstrated in only 9-20% of infants with NEC.

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