The reason for this symptom may be that the abdominal muscles are flabby when the person is lying down, especially when there is inflammation in the abdominal organs, which does not stimulate the peritoneum and thus the patient does not feel the pain. When standing up the inflammation of the organs can stimulate the peritoneum and belly pain can occur, or the belly pain can be caused by the prolapse of the organs. Common diseases include pelvic inflammatory disease, chronic appendicitis, chronic cholecystitis or mesenteric lymphadenitis, and intestinal cramps. Diseases with organ prolapse, such as gastric prolapse, rectal prolapse, and gastric mucosal prolapse. Common clinical hernias, such as inguinal hernia, inguinal hernia, and pelvic floor hernia, may present with this symptom. Therefore, it is recommended to seek medical attention when such clinical symptoms appear and treat them promptly after clear diagnosis.