A 28-year-old woman has been hospitalized with complaints of dizziness, bloody discharge from her genital tract, and pain that suddenly appeared in her lower abdomen and radiates into the anal region. According to the patient's medical history, the delay of menstruation is 4 weeks. Signs of peritoneal irritation are positive. During bimanual examination, the uterus and its appendages are sharply painful and cannot be clearly outlined. "Fluctuating uterus sign" and protrusion and tenderness of the posterior fornix are observed. Body temperature 36.7°C. Blood test results: hemoglobin 82 g/L, erythrocytes 2.8-1012/L. What is the most likely diagnosis in this case?