Ectopic pregnancy

Epidemiology

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Etiology

• Risk Factors (High-Yield)
  • Prior ectopic pregnancy (strongest risk factor)
  • Pelvic Inflammatory Disease (PID): Causes tubal scarring (esp. from Chlamydia trachomatis)
  • History of tubal surgery (e.g., tubal ligation)
  • Infertility and use of assisted reproductive technology (e.g., IVF)
  • Intrauterine device (IUD) in situ (prevents uterine implantation but not ectopic)
  • Smoking

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Pathophysiology

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Clinical features

• Lower abdominal pain and guarding (ectopic pregnancy is often mistaken for appendicitis due to the similarity of symptoms)
• Possibly, vaginal bleeding
• Signs of pregnancy
  • Amenorrhea
  • Nausea
  • Breast tenderness
  • Frequent urination
• Tenderness in the area of the ectopic pregnancy
• Cervical motion tenderness, closed cervix
• Enlarged uterus

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Diagnostics

• Initial / Screening Test:
  • Urine β-hCG (rapid screen) + Serum quantitative β-hCG.
  • Transvaginal Ultrasound (TVUS).
• Diagnostic Algorithm & Discriminatory Zone:
  • Discriminatory Zone (β-hCG 1,500–3,500 mIU/mL): Level at which an intrauterine pregnancy (IUP) must be visible on TVUS.
    • If β-hCG > discriminatory zone + empty uterus on TVUS $\to$ Ectopic pregnancy presumed.
    • If β-hCG < discriminatory zone + indeterminate TVUS (Pregnancy of Unknown Location) $\to$ Repeat β-hCG and TVUS in 48 hours. c
      • Normal IUP: $\beta$-hCG increases by $\ge 35\text{–}50\%$ in 48 hrs.
      • Ectopic Pregnancy: $\beta$-hCG plateaus, shows a subnormal rise (<35%), or subnormal decline.
      • Spontaneous Abortion / Failing Pregnancy: $\beta$-hCG decreases by $\ge 35\text{–}50\%$ in 48 hrs.
• TVUS Findings:
  • Extrauterine gestational sac with yolk sac/fetal pole (“tubal ring sign”).
  • Complex adnexal mass.
  • Free peritoneal fluid / echogenic fluid in the pouch of Douglas (indicates rupture).
• Key Labs:
  • Type & Screen / Rh status (critical for RhoGAM administration).
  • Baseline CBC (anemia, blood loss).
  • Baseline LFTs, BUN/Cr (prior to methotrexate).
• Confirmatory / Gold Standard: Direct visualization via Diagnostic Laparoscopy or surgical histopathology.

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Treatment

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