A 28-year-old woman presents with 6 weeks of amenorrhea, unilateral lower abdominal pain, and scanty dark vaginal bleeding. Transvaginal ultrasound shows an empty uterine cavity, and the structure marked **A** (hyperechoic adnexal tubal ring) is identified separate from the ipsilateral ovary. Serum β-hCG is 2800 mIU/mL. Which of the following is the MOST appropriate next step in management for this hemodynamically stable patient with no fetal cardiac activity and an ectopic mass measuring 2.8 cm?

Explanation

## Why Single-dose methotrexate 50 mg/m² IM is correct The tubal ring sign (**A**) — a hyperechoic ring around a hypoechoic gestational sac separate from the ovary — is the classic sonographic hallmark of ectopic pregnancy. This patient meets ALL criteria for medical management with methotrexate: hemodynamically stable, hCG 2800 mIU/mL (well below the 5000 mIU/mL threshold), ectopic mass <4 cm (2.8 cm), no fetal cardiac activity, and no rupture. Methotrexate is a folate antagonist that kills rapidly dividing trophoblast cells and has an 80–95% success rate in appropriately selected cases. Per Williams Obstetrics 26e and Rumack Diagnostic Ultrasound 6e, medical management preserves tubal integrity and fertility potential in stable, compliant patients and is preferred over surgery in this clinical scenario. ## Why each distractor is wrong - **Expectant management with serial β-hCG monitoring**: While expectant management is an option for hCG <1000 mIU/mL and falling, this patient's hCG of 2800 mIU/mL is above that threshold. Expectant management carries a higher risk of rupture and is reserved for smaller, slower-rising ectopics; methotrexate is more appropriate here. - **Immediate laparoscopic salpingectomy**: Salpingectomy (tube removal) is reserved for ruptured ectopic, severely damaged tubes, or patients with completed families. This patient is young, hemodynamically stable, and desires fertility preservation — salpingostomy or medical management is preferred. Salpingectomy unnecessarily sacrifices reproductive potential. - **Transabdominal ultrasound to confirm and assess for free fluid**: Transvaginal ultrasound is the gold standard for ectopic diagnosis and has already been performed. Repeating with transabdominal ultrasound adds no diagnostic value and delays definitive management. The tubal ring sign is already diagnostic. **High-Yield:** Tubal ring/bagel sign + empty uterus + hCG 1500–5000 mIU/mL + no fetal cardiac activity + stable patient = methotrexate eligibility; salpingectomy reserved for rupture or completed family. [cite: Williams Obstetrics 26e Ch 12; Rumack Diagnostic Ultrasound 6e Ch 30]