The absence of a belly button can be caused by a long umbilical cord, umbilical hernia and surgical removal. 1. Long umbilical cord: Normally, the navel of a normal person will be more or less concave, but if the umbilical cord is left in the stomach when it is cut, it may cover the navel after the umbilical cord shrinks. 2. Umbilical hernia: When the patient has the symptom of umbilical hernia, because the organs and tissues in the abdominal cavity will protrude into the body surface around the navel, therefore, the phenomenon of the navel similarly disappearing may occur. 3. Surgical excision: In addition, there are some patients may be due to abdominal surgery, cosmetic surgery and other reasons, resulting in the navel was surgically removed. Therefore, patients are advised to undergo a detailed examination in a timely manner in the hospital to clarify the cause of the disease and treat it as early as possible.