Hidden pain in the middle of the lower abdomen may be caused by endometriosis or pelvic inflammatory disease. 1. endometriosis: female patients appear in the lower abdomen in the middle of the hidden pain, is likely to be the performance of endometriosis, ectopic endometrial growth in the uterus outside the parts of the location, such as the bladder, ovaries, peritoneum and other locations, cyclic bleeding rupture formation of adhesions, the patient will appear in the lower abdomen in the middle of the hidden pain. 2. Pelvic inflammatory disease: patients with pain in the lower abdomen, may also be some pelvic organ infections, such as vaginitis, cervicitis, as well as urinary tract infections caused by pelvic tissue adhesions and pelvic effusion results. The cause of the pain in the lower abdomen cannot be accurately determined solely by the woman, but also needs to be combined with the characteristics of the medical history and other test results to make an accurate judgment, it is recommended to clarify the cause of the disease under the guidance of a doctor.