So you have a patient who is pregnant and has abdominal pain. You, as the astute provider you are, decide to do an ultrasound to rule out an ectopic, and low and behold! You see a gestational sac and a yolk sac within the uterus! You show your patient, you both breathe a sigh of relief, and you discharge them…
But they return two weeks later, now hypotensive, excruciating pain, and extremely pale. On an emergent bedside ultrasound, you see copious amounts of free fluid, and OBGYN tells you, after they rush your patient to the OR, that it was an ectopic - but how? The pregnancy was in the uterus!
Welcome everyone to the world of interstitial and angular pregnancies, pregnancies that are much closer to the endometrium than normal ectopic pregnancies and therefore have a much higher chance of progressing further before they rupture, meaning that when they do, they are devastating!
To evaluate for these ectopics, make sure that you get a mantle distance on every pregnancy ultrasound you do looking for an ectopic. Mantle distance is measured from the end of the gestational sac to the outer edge of the thinnest side of endometrium. If your value is >0.8cm, you should be okay. If it's less than <0.5cm, you most likely have an ectopic. Between 0.5cm and 0.8cm, consult OB urgently or have extremely close follow up for your patient.
Doane B, Perera P. Emergency ultrasound identification of a cornual ectopic pregnancy. West J Emerg Med. 2012;13(4):315. doi:10.5811/westjem.2011.10.6912
https://radiopaedia.org/articles/interstitial-ectopic-pregnancy?lang=us
