Ectopic pregnancy is the leading cause of death in the 1st trimester of pregnancy. The prevalence in the general population is 1.5-2% of pregnancies, but if you talk to any ED doc or resident, they have seen at least 1 or 2. Mortality is 6-9%, so it’s easy to say, this is a can’t miss diagnosis. By using a linear probe on POCUS in the ED, IUP can be more quickly identified in some patients by the ED physician, without having to send the pt for a formal transvaginal US. This could lead to quicker dispositions and lower cost to the patients. So why not try and identify the IUP yourself?

Tabbut, M., Harper, D., Gramer, D. and Jones, R., 2015. High-frequency Linear Transducer Improved Detection of an Intrauterine Pregnancy in First-trimester Ultrasonography. American Journal of Emergency Medicine, [online] (34), pp.288-291. Available at: <http://dx.doi.org/10.1016/j.ajem.2015.11.001> [Accessed 14 April 2020].

• Single center prospective study

  • Large (100,000 pt/year), urban,  academic ED

  • Established US fellowship program

• Inclusion: + pregnancy test, no prior imaging for this pregnancy

• Images obtained by US fellow or EM residents supervised by an US educator

• IUP identified as a yolk sac and/or fetal pole in a gestational sac

• 88 patients enrolled

• 7 patients excluded for “incomplete data obtained”

• IUP seen in 54 patients using curvilinear transabdominal probe (CTA)

  • Presumably if you see it with the CTA you can see it with the LTA and TV probes because they have higher resolution, so they stopped here

  • Linear transabdominal (LTA) probe - IUP in 9 patients (33.3%, 0.95 CI, 15.5%-51.1% )

  • Transvaginal (TV) probe - IUP in 3 patients (16.7%, 0.95 CI, 0%-33.9%)

• CTA - No IUP in 27 (33.3%, 0.95 CI, 23%-44.6%)

  • Failure rate of CTA = 33.3% (compared to previous studies where failure rate was 20% for CTA and/or TV)

• LTA - No IUP in 18 (66.7%, 0.95 CI, 48.9%-84.5%)

  • Failure rate for CTA + LTA = 22.2%

• TV - No IUP in 15 (83.3%, 0.95 CI, 66.1%-100%)

• 33.3% of cases that previously would have needed TV approach had an IUP identified by LTA, so decreased the need of TV by 33.3% 

• 83.3% of cases who had TV US had concordant results w/ LTA 

• NNT = 3

• Average depth from the IUP to the CTA transducer was 5.3cm and to the LTA transducer was 3.9cm

• Using this technique can reduce ED stay time and cost for a clinically significant amount of patients

• Using POCUS, specifically the linear transducer, on patients in their first trimester can more quickly identify an IUP than sending the patient for a formal transvaginal US, which has its own discomfort associated

• It cannot definitely r/o ectopic pregnancy, but it can expedite the typical work up for vaginal bleeding in the first trimester, if an IUP is confidently identified at bedside

I will definitely try and use this technique on my patients who are pregnant in their 1st trimester. I will bring the US with me when I do my initial exam. If I can confidently identify an IUP, I can save the patient the time and discomfort of a transvaginal US, and have them follow up in two days for a repeat beta quant and in a week for a repeat US. If I can’t confidently identify an IUP or they have risk factors for heterotopic pregnancy, then I will just treat as usual.

1. Up to date - https://www.uptodate.com/contents/ectopic-pregnancy-epidemiology-risk-factors-and-anatomic-sites?search=ectopic%20pregnancy&topicRef=5487&source=see_link

2. Taming the SRU - http://www.tamingthesru.com/early-pregnancy-ultrasound