Abdomen on both sides of the navel is not the same size may be caused by abdominal tumor, abdominal fluid, body position, intestinal distension and other reasons. 1. Abdominal tumor: Abdominal tumor is mostly related to long-term smoking, heredity, infection and other factors, patients usually have no obvious symptoms in the early stage, with the increase of the tumor, the abdomen on the affected side of the patient will be inconsistent and bigger, i.e., there may be different size of abdomen on both sides of the navel. 2. Abdominal fluid accumulation: abdominal fluid accumulation is usually caused by liver disease, infection, nutritional deficiency, trauma and so on. During physical examination, the fluid in the abdominal cavity can move with the body position, resulting in the abdomen on both sides of the navel is not the same size. 3. Body position: when in the side position, the gravity of the navel will be converged on one side, which will cause the two sides of the abdomen are not the same size. 4. Intestinal flatulence: Intestinal flatulence is generally caused by intestinal emptying obstacles, swallowing too much air and other reasons, the patient’s gas will accumulate in the gastrointestinal tract on one side, which will make the affected side of the abdominal bias, appearing on both sides of the abdomen is not the same size of the performance. If the belly button on both sides of the abdomen is not the same size of the situation, to rule out the cause of changes in body position, you need to consult a doctor in a timely manner, improve the examination, a clear diagnosis, and then follow the doctor’s instructions for treatment.