In infants, what is intrahepatic portal vein gas primarily due to?

Intrahepatic portal vein gas in infants is primarily associated with necrotizing enterocolitis (NEC). This condition is characterized by the inflammation and necrosis of the intestinal wall, which can lead to various complications, including the formation of gas within the portal venous system. When the bowel becomes ischemic or necrotic, bacteria can invade the vascular structures, resulting in gas production that can be seen on imaging studies like ultrasound.

Necrotizing enterocolitis typically occurs in premature infants or those with low birth weight, and it is crucial to recognize the radiographic findings associated with this condition early in order to manage it effectively. Intrahepatic portal vein gas serves as an important marker for the severity of NEC and often correlates with a poor prognosis, requiring prompt medical or surgical intervention.

The other options listed are less commonly associated with intrahepatic portal vein gas. For instance, hepatitis A mainly leads to liver inflammation without significant portal vein gas, while intestinal obstruction and congenital hypertrophic pyloric stenosis are not directly linked to the presence of gas in the portal venous system.