The vague pain in the left lower abdomen after menstruation is due to: i. colitis; ii. adnexitis; iii. enteritis caused by unclean diet or cold. The main organs of the left lower abdomen are the sigmoid colon, fallopian tubes and ovaries. Digestive disorders can occur during menstruation when the resistance is low, the abdomen is cold and improper diet. If the stool is accompanied by bloody discharge, the symptoms of urgency, do not exclude colitis or colon polyps, as soon as possible to the hospital for examination, the left side of the abdominal pain with increased secretions consider the possibility of adnexitis, pelvic inflammatory disease. The menstrual period may cause pelvic effusion caused by the backflow of menstrual blood, stimulating the surrounding tissue vague pain, abdominal hot compresses, do not eat cold, spicy stimulating food, according to the symptoms of complications to take examination or treatment.