A Second Look
Vasa Previa with Succenturiate Placenta. Submitted by Gavin B. Gore, MD, and Nadia J. Khati, MD.
The most popular Case in Point (CIP) submission of December 2012, as chosen by CIP users, was "Vasa Previa with Succenturiate Placenta." The month's highest-rated case explores the evaluation of a 32-year-old woman who presented with second trimester bleeding.
Readers valued the case for its "clean images," "good teaching points," and relevancy to "everyday ultrasound practice." The ACR Bulletin spoke with Nadia J. Khati, MD, associate professor of radiology at the George Washington University Hospital in Washington, D.C., about diagnosing vasa previa and submitting the case to CIP.
Q: Why did you select "Vasa Previa with Succenturiate Placenta" for submission to CIP?
A: Vasa previa is rare and can easily be overlooked in patients presenting with vaginal bleeding. As radiologists, we tend to focus on excluding the presence of a placenta previa or placental abruption in such patients. We may not realize that vessels are crossing the internal cervical os and that there may be a second, smaller placenta opposite the main one. I have found vasa previa to be confusing, particularly for residents and fellows, and I believed this was a perfect example of a type 2 vasa previa. I thought it would be a great opportunity to share this teaching case with other CIP readers.
Q: How frequently is vasa previa with succenturiate placenta encountered in routine high-volume clinical practices?
A: Only a handful of vasa previa cases have been encountered in our department. The literature suggests that the actual incidence is unknown and that many cases go undiagnosed antenatally. This underscores the need for screening patients in high-risk groups (i.e., patients with variant placental morphology, marginal and velamentous cord insertions, multiple gestations, IVF-related pregnancies, and palpable vessels on cervical examination).
Q: What is most important point on this subject that CIP readers should commit to memory?
A: Recognizing this entity is crucial to fetal well-being and survival. If undiagnosed, prenatally fetal vessels can rupture at the time of labor, potentially causing fetal exsanguination and death. For that reason, it is very important to document placental cord insertion, specifically in cases of variant placental morphology, such as low-lying or marginal placentas, and placentas with accessory lobes.
Q: In your experience, what is the most likely alternative diagnosis that might resemble this case's diagnosis?
A: There are two possible alternatives. One is an umbilical cord dangling in front of the internal cervical os. This can be easily recognized by moving the patient, which will cause shifting in the cord's position. The other diagnosis would be a marginal sinus previa, where maternal veins mimic fetal vessels. This can be confirmed by performing Doppler interrogation of the vessels at the internal os.
Q: Can you distinguish for our readers the difference between a succenturiate placenta and a bilobed placenta?
A: A succenturiate placenta refers to the presence of a smaller accessory lobe that is separate from the main larger placenta. It is important to look for the connecting vessels between the main and succenturiate placenta, as these can be associated with type 2 vasa previa when fetal vessels cross the cervical os. Succenturiate lobes can also be associated with an increased risk of postpartum hemorrhage in cases of retained accessory lobe. A bilobed placenta is composed of two lobes that are nearly equal in size and are separated by a segment of membranes. The umbilical cord can implant onto one of the lobes or on the membranes in a velamentous fashion.
Q: Why should radiologists take advantage of CIP?
A: CIP is a great learning and teaching tool for all radiologists. The cases are easily accessible online at all times, and they offer good reviews for quick study. The presentation format includes a variety of question types (multiple choice, true/false, etc.) and is very appealing to residents and fellows in addition to practicing radiologists.
"Vasa Previa with Succenturiate Placenta" was published on December 3, 2012. To view the full case, visit http://bit.ly/135QLkv.
By Anastasia Simkanin