There are several reasons why the stomach suddenly becomes big: the first point is that there is too much water in the stomach, that is, there is too much edema, and it is more common that edema caused by various reasons causes the stomach to become big, for example, nephrogenic edema, cardiogenic edema, and hepatic edema are the most common ones. The second point is the sudden enlargement of the stomach due to intestinal inflation, which is mostly seen in the gastrointestinal tract dysfunction caused by some emotional disorders and anger, and there is a large amount of flatulence, and a lot of gases in the intestines can not be discharged, causing the stomach to become bigger. The third point, a large amount of fat accumulation and lead to a bigger stomach, generally more common in men, especially prone to fatty liver, intestinal fat excess, subcutaneous fat excess, and lead to a big belly. The fourth point, the possibility of female pregnancy also exists. The fifth point, pathological causes, such as splenomegaly caused by cirrhosis, and splenomegaly caused by leukemia and so on, can also cause a sudden enlargement of the stomach.