Pregnancy Ultrasound Potpourri
A little pregnancy potpourri today.
Utility of POCUS for First Trimester Vaginal Bleeding in the ED
Your primary goal with first trimester POCUS is simple. Confirm an intrauterine pregnancy. If you see an IUP, you have essentially excluded ectopic pregnancy unless the patient has risk factors for heterotopic pregnancy.
Transabdominal POCUS should be your first look. It is fast, widely available, and usually gets you the answer you need. If you confirm an IUP, most patients can be discharged with outpatient OB follow up.
If you cannot confirm an IUP on transabdominal scan, move to transvaginal ultrasound. You can perform this yourself at the bedside or request a radiology study. In these cases, sending labs is reasonable since the patient may be undifferentiated for longer.
Emergency physicians have repeatedly been shown to accurately and rapidly diagnose IUPs using POCUS with specificity approaching 100 percent. Studies also show that using POCUS up front expedites ectopic management and shortens ED length of stay.
Definition reminder for an IUP on ultrasound: a yolk sac or fetal pole within an intrauterine gestational sac that is clearly located within the endometrial cavity.
Great summary here from The Land of EM that pulls together many of these points: https://www.thelandofem.com/blog/2022/10/30/iusotm-pocus-for-1st-trimester-bleeding-in-the-ed
Here is the basic algorithm I trained with. Not what you must do, just one reasonable approach:
First trimester vaginal bleeding or abdominal pain? Do a POCUS ultrasound.
If you see an IUP (gestational sac with live fetal pole or yolk sac), you are done. Discharge home with OB follow up. No labs needed.
If the scan is indeterminate, perform a transvaginal US (your own or formal radiology) and send labs.
*This algorithm needs revision since the ACOG RhoGam Update
See that here: https://pubmed.ncbi.nlm.nih.gov/39255498/
Transvaginal Ultrasound
Short, older but still very solid video on TVUS: https://www.youtube.com/watch?v=0CqicUl0hw8
If you want to practice this scan, grab the probe sometime and find someone at your institution who is comfortable walking you through it.
Simple diagram from UMEM Pearls here: https://em.umaryland.edu/educational_pearls/4392/
For probe cleaning, follow your local sterilization procedure. At my institution, this means giving it to the charge nurse.
Having a hard time with positioning for TVUS or a pelvic exam? Consider this alternative approach using a chair with armrests published in Annals of EM.
Early Pregnancy Loss on Ultrasound
Practical EM definitions (see more on Radiopaedia):
CRL ≥ 7 mm with no heartbeat on TVUS.
MSD ≥ 25 mm with no embryo on TVUS.
When you see these findings, it is best to confirm with a radiology-performed ultrasound, because OB typically wants a radiologist’s formal interpretation before determining management.
Additional References
Stein JC, Wang R, Adler N, et al. Emergency physician ultrasonography for evaluating first trimester pregnancy. Ann Emerg Med. 2010;56(4):456 to 466. [pubmed]
Woo J, Lyon M, Kramer N, et al. Effect of first trimester pregnancy ultrasound performed by emergency physicians on length of stay in the ED. Am J Emerg Med. 2005;23(3):338 to 343. [pubmed]
Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med. 2013;369:1443 to 1451. [pubmed]
