If there is small abdominal distension and pain in daily life, accompanied by low back pain, it is common to see: 1. The greatest clinical possibility is caused by chronic inflammation of the pelvis, because chronic inflammation of the pelvis will cause local tissue exudation, so there will be lower abdominal distension and pain in the lumbosacral area, often during menstruation, after exertion or after intercourse may aggravate the symptoms of this pain. 2. Endometriosis can cause small abdominal distension and lumbar pain, it is recommended to do ultrasound examination or combine with medical history, such as lower abdominal pain or infertility during menstruation, which may be caused by endometriosis. 3. caused by pelvic tumors, such as uterine fibroids, ovarian tumors or other tumors may cause small abdominal distension and lumbar pain. And there is back pain, which can be diagnosed by ultrasound.