A 25 y.o. patient complains of body temperature rise up to 37°C, pain at the bottom of her abdomen and vaginal discharges. Three days ago, when she was in her 11th week of pregnancy, she had an artificial abortion. Objectibely: cervix of uterus is clean, uterus is a little bit enlarged in size, painful. Appendages cannot be determined. Fornixes are deep, painless. Vaginal discharges are sanguinopurulent. What is the most probable diagnosis?