Ectopic Pregnancy Part 5

I want you to be aware of the large ectopic pregnancy in ultrasound.

If you look at a case and start to measure the biparietal diameter of this fetus, you’re in trouble, because the actual uterus is here and the endometrial cavity is here. So large size is something that doesn’t necessarily mean that pregnancy must be in the uterus.

Also very important is that there is no mass and no fluids. So you might have a patient at risk, you look and you are unable to demonstrate an interuterine pregnancy, and that brought her risk to greater than 50/50.

If in that same patient you cannot find a mass or any fluid, you have to remember that she still carries a modest risk for ectopic pregnancy ranging from 7% to 33%.

So the inability to see adnexal findings did reduce her risk, but it didn’t reduce her risk to a level that is acceptable. The patient is still at risk for ectopic pregnancy.

So when you see no intrauterine pregnancy and no adnexal mass or fluid, you cannot exclude ectopic pregnancy.

So remember, if the patient is clinically suspected of harboring an ectopic pregnancy and has a positive pregnancy test, her risk is about 15%, about 10% higher than the average woman in the U.S. population who is pregnant.

If you do a sonogram and are able to demonstrate an intrauterine pregnancy, you effectively take the woman out of the group at risk for ectopic pregnancy.

If you show no intrauterine pregnancy, you increase her risk to over 50/50.

From that point you can subsequently increase her risk anywhere from 75% to 100% by demonstrating fluid, mass or an embryo in her adnexa, but at no point subsequently can you bring her risk down to 0, because a significant number of these patients still have an ectopic pregnancy.

Author: Roy A. Filly, MD
Excerpted from:
Diagnostic Imaging Review: For Residents, Fellows and Radiologists
Female Pelvis Section