The causes of sudden abdominal enlargement are the following: 1. intestinal obstruction, this is a relatively common cause, most will be accompanied by pain, vomiting, distension, closure, that is, abdominal pain, abdominal distension, stop defecation and exhaustion, while abdominal plain film can be seen in the plane of gas and liquid. 2. constipation, constipation is mostly due to poor bowel discharge, which leads to excessive accumulation of intestinal tract, causing abdominal distension and causing sudden enlargement of the abdomen. 3, The abdominal cavity fluid, this is often due to cirrhosis portal hypertension, resulting in the increase in intra-abdominal pressure caused by hypoproteinemia, and cause an increase in the amount of fluid in the abdominal cavity, especially within a short period of time the intra-abdominal fluid more than 2000ml, there will be a very obvious abdominal bulge, abdominal suddenly become large. 4, abdominal perforation, and this suddenly become large, often accompanied by obvious abdominal pain, plate abdomen, accompanied by high fever convulsions. accompanied by high fever convulsions.