The cause of small belly refers to a large small abdomen, which may be caused by physiological factors or diseases, such as abdominal fluid accumulation, gastroptosis and so on. 1. Physiological reasons: If the intake of food is too much, and the patient is sedentary after intake without exercise, it is easy to lead to the accumulation of abdominal fat, which leads to the phenomenon of small belly big. Or due to women after giving birth, abdominal rectus abdominis muscle separation, no repair leads to small abdominal skin elasticity is weakened, skin laxity caused by the phenomenon of small abdominal large. 2. Pathological causes (1) abdominal fluid: due to patients suffering from abdominal fluid (such as pelvic inflammatory disease, etc.), the increase in ascites in the abdominal cavity, and the fluid can not be effectively discharged, will also make the patient look small belly abdomen. (2) Gastric prolapse: for some thin and weak patients who have been sick for a long time, the stomach may prolapse into the pelvis, and this patient is usually accompanied by indigestion and other symptoms, as indigestion is usually accompanied by abdominal distension, so it looks like a small belly. (3) Abdominal and pelvic tumors are also common causes. For patients with a small belly, but also seen in other causes, should be timely medical treatment, targeted treatment.