Portal vein pneumatosis is an imaging sign formed by abnormal accumulation of gas in the portal vein and its intrahepatic portal vein branches due to various causes, and is usually diagnosed by abdominal radiographs. It is commonly seen in neonates with necrotizing small bowel colitis. Neonatal necrotizing small bowel colitis is a serious disease with abdominal distension, vomiting and blood in the stool as the main clinical manifestations, and cystic intestinal wall pneumoperitoneum as the X-ray features. 90% of the cases occur in preterm infants, and the mortality rate is as high as 86% in the case of the simultaneous accumulation of intestinal wall pneumoperitoneum and portal vein pneumoperitoneum. So, what are the tests needed for patients with portal venous effusion? The following is a list of tests for portal vein pneumoperitoneum. Abdominal X-ray film is important for the diagnosis of this disease. Early main manifestation of paralytic intestinal obstruction: small bowel arrangement disorder, inflation obvious, intestinal lumen can be seen in multiple liquid flat, in the form of a step. If the disease progresses and the intestinal gas enters the intestinal wall, then there is a cystic pneumatosis of the intestinal wall. Interstitial widening of the intestinal wall, localized vesicular or bead-like translucent areas of the intestinal wall, subplasma pneumoperitoneum can show lines, arcs or rings of translucent areas, the more severe cases due to the entry of intestinal gas into the portal vein can be seen as portal venous insufflation sign: the liver can be seen from the hepatic portal to the intrahepatic along the portal venous route of the strip or dendrite translucent shadows, the severe cases can be seen as the intestinal collaterals of the fixation (intestinal necrosis) pneumoperitoneum (intestinal perforation), and peritoneal fluid accumulation (peritonitis). Cystic pneumatosis of the intestinal wall and signs of portal vein insufflation characterize the disease. In severe cases, the disease is often accompanied by severe infections, metabolic and/or respiratory acidosis, thrombocytopenia and neutropenia, and DIC, etc. Therefore, blood gas analysis, fecal occult blood and culture, blood count and culture, as well as DIC screening and diagnostic laboratories are very important for the determination of the disease. The diagnosis can be confirmed if the following three items are present at the same time: 1. Abdominal X-ray manifestations: intestinal obstruction and intestinal wall pneumatization. 2. Gastrointestinal manifestations: gastric retention, vomiting, bloody stools, abdominal distension and loss of bowel sounds. 3.Systemic toxicity manifestations: such as unstable body temperature, pallor, irregular respiration and bradycardia.