Ectopic pregnancy (suspected)

• TVUS is the primary imaging test for suspected ectopic pregnancy (EP) in stable patients 1, 2
• Complementary TAUS is performed to provide a pelvic overview (uterine position and high adnexa), to help assess larger adnexal masses, and to evaluate for large-volume free fluid; images of the right upper quadrant (Morison’s pouch) are included when symptoms raise concern for significant haemoperitoneum 3
• A complete examination documents: the uterus (sagittal/transverse), endometrium, cervix, both ovaries and adnexa (confirm whether any mass is extra-ovarian), and the pouch of Douglas/cul-de-sac, +/- significant free fluid or clot
• Minimum reporting items include: 
  • Category (definite/probable Intrauterine Pregnancy (IUP); definite/probable EP; PUL*) 
  • Site (tubal vs non-tubal suspected) 
  • Adnexal mass size (max. diameter, mm) and relationship to ovary
  • Contents (sac/yolk sac/embryo; cardiac activity) 
  • Free fluid amount/character (simple vs complex)

*PUL= Pregnancy of unknown location (a positive pregnancy test with no definite/probable IUP or EP on TVUS)

• A probable tubal ectopic is suspected when TVUS shows an extra-ovarian adnexal abnormality typical of EP but without diagnostic contents (yolk sac/embryo) 4

• Classic appearances are:

• Blob sign - inhomogeneous extra-ovarian adnexal mass
• Bagel/tubal ring sign - echogenic ring with central lucency (tubal ring)

• These signs have very high specificity and positive predictive value (>95%) for tubal EP in published series/meta-analysis; the recommendation is for expedited clinical review and safety-netting regardless of β-hCG trend. Doppler may show peripheral flow, but it is not diagnostic by itself. Mass size, relationship to the ovary (movement independent of the ovary), and any free fluid (complex or anechoic) should be documented.

• Corpus Luteum Pitfall: The ectopic pregnancy is usually located on the same side as the corpus luteum. Gentle transducer pressure should be applied to slide the mass away from the ovary to differentiate an ectopic mass from an exophytic corpus luteum cyst.

• The earliest gestational sac is usually a round or oval fluid collection with a hyperechoic trophoblastic rim. A yolk sac within that collection makes the diagnosis of a definite IUP. Without a yolk sac or embryo, an empty round/oval sac-like collection is better regarded as a probable gestational sac/probable IUP, not a definite IUP. The intradecidual sign and double decidual sac sign as well as the sac lying eccentric to the cavity centre increase confidence when present, but are not required and are not sensitive. 
• Avoid the terms “pseudosac” and “pseudogestational sac”. Suspicious non-sac uterine fluid should be described as “intracavitary fluid” or “fluid in the endometrial cavity,” especially when it has pointed/non-curved margins or variable internal echoes and/or is mobile with probe pressure or position change. 
• Intracavitary uterine fluid does not exclude ectopic pregnancy, but it makes ectopic much less likely. In a study conducted by Lee et al., only 8/162 ectopics (4.9%) had an intrauterine fluid collection, compared with 363/789 intrauterine pregnancies (46.0%). Among women with an intrauterine fluid collection, the ectopic rate was 2.2% and the IUP rate was 97.8% 7. 
• Sac size does not reliably distinguish an early gestational sac from intracavitary fluid associated with ectopic pregnancy. Lee et al. found substantial overlap and no useful discriminatory threshold; several ectopics with intrauterine fluid also had other suspicious findings, especially an adnexal mass 7. 
• Practical message: assess the whole scan, not just the uterine cavity - adnexal mass, free fluid, symptoms, and interval change still matter.

• PUL means a positive pregnancy test with no definite/probable Intrauterine Pregnancy (IUP) or ectopic pregnancy (EP) on TVUS 8
• Serial β-hCG measurements are used to guide follow-up but β-hCG should not be used to determine location 9, 10. Two β-hCG values are obtained as near as possible to 48 hrs apart (not earlier) 
• Interpretation of change of β-hCG over 48 hrs 11:
  • Rise >63% → likely developing IUP (ectopic not excluded) - 
    • Management recommended: TVUS 7–14 days, consider earlier if β-hCG ≥1500 IU/L
  • Fall >50% → pregnancy unlikely to continue -
    • Management recommended: urine pregnancy test 14 days after second β-hCG (return within 24h if positive)
  • Between 50% fall and 63% rise → higher risk ectopic/persistent PUL - 
    • Management recommended: clinical review within 24 hrs, further tests only after senior review. Provide written return advice to the patient, with emphasis that symptoms trump β-hCG.

• A definite IUP usually makes an ectopic unlikely, but does not completely exclude heterotopic pregnancy, especially in higher-risk settings e.g. IVF/Assisted Reproductive Technology (ART) or when symptoms are disproportionate (severe unilateral pain, significant adnexal tenderness, or unexplained free fluid) 12, 13
• In these situations, the adnexa should be carefully assessed even when an IUP is confirmed and any extra-ovarian adnexal mass, free fluid characteristics, and any site suspicious for non-tubal implantation isreported. 
• If a suspicious adnexal mass is present, urgent clinical review is recommended rather than reassurance based on the intrauterine finding alone.

• For suspected/confirmed ectopic pregnancy (EP), moderate or large complex free fluid should be treated as haemoperitoneum until proven otherwise, especially if echogenic/clotted predominantly in one adnexa, or free fluid present in the right upper quadrant
• Imaging should not delay escalation
• It is important to note that some non-tubal ectopics (e.g. cervical/Caesarian Scar Pregnancy) may bleed predominantly vaginally/uterine, so ‘no free fluid’ does not exclude danger - clinical instability, peritonism, syncope, or heavy bleeding overrides laboratory trends
• If features of rupture are present, recommend immediate senior O&G/surgical review and communicate directly (phone) per escalation policy.

• Non-tubal ectopics require clear reporting and same-day specialist pathway (often consultant-level O&G ± tertiary centre referral) 14, 15
• Non-tubal ectopic pregnancy (EP) should be considered when features suggest:
  • Caesarean Section scar implantation: Sac in anterior lower uterine segment scar region; thin/absent myometrium between sac and bladder; often hypervascular 16
  • Cervical implantation: Sac in the cervix; caution miscarriage-in-progress is a mimic, it will be mobile with US probe pressure 17
  • Interstitial implantation: Eccentric high cornual sac; myometrial mantle <5 mm, lies external to the endometrial cavity. If partially exophytic to the myometrium, moves with the uterus on probe pressure 18. 
• Reporting should include: the exact site, the relationship to the cervix/scar/uterine cavity, a myometrial mantle where relevant, vascularity, and any features of haemorrhage.

Unstable patients should be resuscitated, escalated urgently for O&G/surgical opinion and point-of-care US performed of the abdomen (including the RUQ) and pelvis to identify haemoperitoneum/free fluid.