## Investigation of Choice in Suspected Ectopic Pregnancy ### Clinical Context The patient presents with classic features of ectopic pregnancy: amenorrhea, positive β-hCG, abdominal pain with adnexal tenderness, and an empty uterus on transabdominal ultrasound. The next step is to localize the pregnancy. ### Why Transvaginal Ultrasound is the Gold Standard **Key Point:** Transvaginal ultrasound (TVS) is the investigation of choice for confirming ectopic pregnancy because it has superior resolution (7–10 MHz probe) compared to transabdominal ultrasound (3–5 MHz), allowing visualization of the adnexa and fallopian tubes with 95–100% sensitivity and specificity. **High-Yield:** TVS can detect: - Gestational sac in the fallopian tube (most common site, 95% of cases) - Adnexal mass or "pseudosac" (fluid collection in uterus mimicking early intrauterine pregnancy) - Free fluid (blood) in the pouch of Douglas - Fetal pole with cardiac activity in tubal pregnancy ### Diagnostic Criteria on TVS | Finding | Interpretation | |---------|----------------| | Gestational sac outside uterus with yolk sac | Definitive ectopic pregnancy | | Adnexal mass + positive β-hCG + empty uterus | Probable ectopic pregnancy | | Fetal pole with cardiac activity outside uterus | Confirmed ectopic pregnancy | | Free fluid in POD + no IUP | Suggestive of rupture | **Clinical Pearl:** TVS can be performed immediately in the outpatient or emergency setting, is non-invasive, has no radiation, and guides management (medical vs. surgical) without delay. ### Why TVS Supersedes Other Modalities - **vs. Diagnostic laparoscopy:** TVS is less invasive, first-line, and avoids unnecessary surgery in stable patients. - **vs. Serum progesterone:** Progesterone is supportive but not diagnostic; cannot localize the pregnancy. - **vs. Culdocentesis:** Outdated; TVS has replaced it (culdocentesis only shows presence of blood, not location). [cite:Park 26e Ch 18]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.