Suspected ectopic pregnancy
NICE NG126; ACR AC Acute Pelvic Pain in the Reproductive Age Group (2023 rev)Localisation of a pregnancy in a woman with a positive test and pain or bleeding. Transvaginal ultrasound is the whole first line; the vetting work is protecting its urgency and making sure a non-diagnostic scan is not read as reassurance.
Positive pregnancy test with pelvic pain, bleeding or shoulder-tip pain, typically in the first trimester and often via an early pregnancy assessment unit or the emergency department.
Referenced decision support — confirm against your local protocol.
Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.
Accept as requested
Pelvic ultrasound — transabdominal and transvaginal
Ultrasound pelvis (transabdominal ± transvaginal)
What we'd amend, and why
- Transvaginal ultrasound is the only test that answers the actual question — where the pregnancy is. It resolves the intrauterine sac, the adnexal mass moving separately from the ovary, and free fluid, none of which a transabdominal view or a blood test can do reliably at the gestations that matter. The transabdominal component is added for a large or high-lying uterus and for free fluid in the upper abdomen.
Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.
How was this decided?
- pathwayany — Any woman with a positive pregnancy test
Decision support only. Local protocol takes precedence.
Worth asking the referrer (2)
None of these hold the request up. They sharpen the protocol or the plan that follows.
- What is the serum hCG, is it rising or falling, and what is the gestation by dates?It sets the expectation for what should be visible and decides whether a non-diagnostic scan needs repeating in days or hours.
- Is the woman haemodynamically stable?Instability moves the decision from imaging to resuscitation and theatre; the scan should then follow the patient rather than the patient the scan.
Pathways
Big forks are separate pathways; the first whose conditions match is the one used.
Haemodynamically unstable — resuscitation and theatre, not the scan room
| Role | Study & protocol | Why this answers the question |
|---|---|---|
| First line | Ultrasound pelvis (transabdominal ± transvaginal) Pelvic ultrasound — transabdominal and transvaginal usually not appropriate | A shocked woman with a positive pregnancy test has a ruptured ectopic pregnancy until theatre shows otherwise, and the operation is both the diagnosis and the treatment. Booking a departmental transvaginal scan at this point does not change what happens next and costs the minutes that decide the outcome — this card says in its own notes that imaging must not become the reason theatre is delayed. Where ultrasound is used at all it is a bedside look for free fluid taken alongside resuscitation, not a transfer to the ultrasound department, and a scan that shows no free fluid does not make a shocked patient stable. Nothing here withholds imaging from a woman who is stabilised: once she is, the standard pathway resumes and transvaginal ultrasound is the study. |
- This is a verdict about sequence, not about whether the woman deserves a scan. The surgical team and the anaesthetist are the call to make now; radiology helps most by saying so quickly.
- The same reasoning retires the radiation conversation: if CT is ever contemplated for suspected haemoperitoneum here, it proceeds on clinical grounds and must not delay resuscitation.
Any woman with a positive pregnancy test
Matches your inputsDefault| Role | Study & protocol | Why this answers the question |
|---|---|---|
| First line | Ultrasound pelvis (transabdominal ± transvaginal) Pelvic ultrasound — transabdominal and transvaginal usually appropriate | Transvaginal ultrasound is the only test that answers the actual question — where the pregnancy is. It resolves the intrauterine sac, the adnexal mass moving separately from the ovary, and free fluid, none of which a transabdominal view or a blood test can do reliably at the gestations that matter. The transabdominal component is added for a large or high-lying uterus and for free fluid in the upper abdomen. |
| Problem solving | MRI Pelvis (Gynaecological) MRI Pelvis — general gynaecological | Reserved for an implantation site that ultrasound has found but not fully characterised — caesarean scar, interstitial or cervical — where the operation planned depends on the depth of myometrial involvement and the relationship to the bladder. It is a surgical planning study, never a delay to treatment in a woman who is bleeding. |
- A pregnancy of unknown location is a recognised interim state, not a failed scan. It is managed with serial hCG and a repeat scan, and the report should say so rather than describing a "normal pelvis".
Pitfalls
- Treating "no intrauterine pregnancy seen" as a negative study. It is a pregnancy of unknown location and needs a defined follow-up plan, not discharge.
- Booking a transabdominal-only scan because the request said "pelvic ultrasound" — for this question the transvaginal component is the examination.
- Mistaking a pseudo-sac of intracavitary fluid for an early gestational sac, and reassuring on that basis.
- Deferring the scan to the next working day in a woman with pain and free fluid. This is one of the few gynaecological questions where hours matter.
- Assuming an intrauterine sac excludes an ectopic after IVF, where heterotopic pregnancy is uncommon but real.
- Using a serum hCG below a "discriminatory level" to postpone or downgrade the scan. That level was derived to decide whether an intrauterine sac SHOULD be visible by now, not to decide who gets scanned — ectopic pregnancies present across the whole range of hCG values, including very low and falling ones, and a symptomatic woman is scanned whatever the number.
- Missing the non-tubal implantations. An interstitial, cornual, cervical or caesarean-scar pregnancy sits within or against the uterus and is easily reported as intrauterine; the findings are an eccentric sac with a thin myometrial mantle, a sac below the level of the internal os, or a sac embedded in the hysterotomy scar. These are the ones that bleed catastrophically, and they are the reason the interstitial line and the myometrial thickness are measured rather than eyeballed.
Priors — what to pull first
- Look for a previous scan in this pregnancy: a documented intrauterine pregnancy changes the question entirely, though it does not exclude a heterotopic pregnancy after assisted conception.
- Previous ectopic pregnancy, tubal surgery and an in-situ intrauterine device all raise the pre-test probability and are worth retrieving before reporting.
What makes a good request
- The serum hCG level and whether it is rising, static or falling changes what the scan means, so it belongs on the request. It does not change which study to do.
- A haemodynamically unstable woman with a positive pregnancy test is a surgical problem first. Imaging must not become the reason theatre is delayed.
Scoring this once it is done
The classification and risk tools this question ends in.
How these studies are acquired
Contrast, phases and timing for every study on the pathways above.
Confirm locally
- Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
- Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.
References
- NICE NG126 — Ectopic pregnancy and miscarriage: diagnosis and initial management · NICE
- ACR Appropriateness Criteria — Acute Pelvic Pain in the Reproductive Age Group: 2023 Update · ACR Appropriateness Criteria
- Pregnancy of unknown location — definitions and management · Primary literature
- NICE NG126 — Ectopic pregnancy and miscarriage: diagnosis of viable intrauterine pregnancy and of tubal ectopic pregnancy · NICE
- ACR Appropriateness Criteria — Acute Pelvic Pain in the Reproductive Age Group (2023 update) · ACR Appropriateness Criteria
Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.