Pelvic inflammatory disease manifests as lower abdominal pain and needs to be differentiated from the following diseases: 1. ectopic pregnancy with a history of menopause, positive urine pregnancy test with pain in one side of the lower abdomen and may have vaginal bleeding; pelvic inflammatory disease with negative urine HCG and no pregnancy symptoms; 2. ovarian cysts with torsion B ultrasound examination may reveal ovarian cysts in the adnexal area and position change may show cyst rupture and torsion; pelvic inflammatory disease B ultrasound does not show this; 3. acute appendicitis with metastatic right lower abdominal pain and chronic pelvic inflammatory disease with lower abdominal pain.