Page 3 of 3Pearls & Pitfalls for Ultrasound Evaluation for an Ectopic Pregnancy
1. Assess Stability: Do not send an unstable patient to radiology. If you have the skills, perform a bedside ultrasound yourself and call your surgeon early. If not, have your ultrasound tech scan at the bedside. For unstable patient’s, call your surgeon early, even before all of your diagnostic tests come back.
2. Start at Morison’s Pouch: Begin by scanning the hepatorenal recess (Morison’s Pouch). This is the most dependent position when the patient is lying supine and free fluid may be noted here first. Unfortunately, your hospital ultrasound tech may not include this area in a pelvic ultrasound, but you won’t make that mistake. If you see fluid here, call for help ASAP. Any patient with a positive pregnancy test and free fluid visible on bedside ultrasound should be suspected of having a RUPTURED ectopic pregnancy until proven otherwise. In many ectopic pregnancies, free fluid is the only sonographic abnormality appreciated. Even if the pregnancy test is not resulted yet, free fluid here is reason enough to call OB and prep your patient for the OR. Of all of the causes of non-traumatic intraperitoneal free fluid in an otherwise healthy patient, a ruptured ectopic pregnancy or a ruptured hemorrhagic ovarian cyst are the two most likely diagnoses.
3. Transabdominal Scan: If Morrison’s Pouch is clean, evaluate the pelvis via a transabdominal approach. To get the best views, the patient should ideally have a full bladder to serve as an acoustic window. Look for hypoechoic free fluid in the vesicouterine and rectouterine spaces, and assess the uterus for the presence or absence of an intrauterine pregnancy. In a ruptured ectopic, all you may see is a confusing mess of heterogeneous clotted blood that can even make it hard to delineate the uterus. If you have done plenty of scans of the normal pelvis, you will be able to tell that “something just looks wrong” though you may have a hard time accurately determining what exactly you are looking at.
4. Transvaginal Scan: If adequate images are not obtainable via the transabdominal approach, a transvaginal ultrasound can be performed at the bedside. Cover the endovaginal transducer with a gel filled sheath and apply a copious amount of clear gel to the outside of the sheath. Insert and advance the transducer with the indicator marker pointing anteriorly towards the patient’s pubic symphysis. Alternatively, you may let the patient insert the probe herself as this method is often less uncomfortable. Scan through the uterus in this sagital plane, noting the presence or absence of an intrauterine pregnancy. Note if you see any free fluid in the anterior or posterior cul-de-sac.
5. Optional - Look for the Ectopic: It is often possible to visualize the ectopic pregnancy during a quick transvaginal bedside scan. Rotate the probe 90° counter-clockwise and point the indicator marker towards the patient’s right side. Trace the broad ligament of the uterus out toward the ovaries, which lie just medial to the iliac vessels. Look for any complex adnexal masses or tubal rings.
6. Don’t Delay: You do not need to see the ectopic to diagnose it. If you see free fluid, get on the phone to OB, and don’t delay patient care.
7. Scan Normal Pelvises: Whenever you scan for alternate indications, practice looking at the pelvis with trans-abdominal approach. The more normal studies you look at, the more likely you are to recognize when something isn’t right.
Brady Pregerson manages a free on-line EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more information visit EMresource.ORG.
Teresa S. Wu is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa Emergency Medicine Program in Phoenix, Arizona. She is an Associate Professor in Emergency Medicine at the University of Arizona, School of Medicine-Phoenix.