US - Molar Pregnancy: Ultrasound of the Month

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THE CASE PRESENTATION…

You look at your track board and notice a new patient – a teenage female with vaginal bleeding. You start to obtain a history and she states she recently had a positive home pregnancy test. She started developing light vaginal bleeding on the day prior to presentation and is concerned given her current pregnancy. Her last menstrual period was approximately 2 months ago. She also states the she has been having some mild suprapubic abdominal cramping over the past day. She denies both presyncope and dizziness. She has not had any urinary symptoms or vaginal discharge.

The patient’s temperature is 98.6 F, heart rate is 83 beats per minute, BP 109/58 mmHg, respiratory rate 20 breaths per minute, and she has a normal oxygen saturation on room air. Her examination is unremarkable with the exception of mild suprapubic abdominal tenderness, without rebound or guarding, as well as a small amount of bleeding coming from a closed cervical os, without any appreciable discharge.

A urine pregnancy test is positive and the quantitative beta-hCG is 639,530. The remainder of the labs are notable for a mild anemia with a hemoglobin of 10 grams/deciliter and a urinalysis without evidence of infection.

Given the patient’s positive pregnancy test, you grab the ultrasound machine to evaluate for the presence of an intrauterine pregnancy.

AND NOW FOR THE ULTRASOUND IMAGES…

Watch molar pregnancy 1 GIF by @cshaw1026 on Gfycat. Discover more related GIFs on Gfycat

Watch molar pregnancy 2 GIF by @cshaw1026 on Gfycat. Discover more related GIFs on Gfycat

What do you see on ultrasound?

This is a transabdominal series demonstrating a large intrauterine collection of mixed echogenicity, with numerous well delineated hypoechoic bodies (a classic “snowstorm pattern”). These findings are concerning for a molar pregnancy.

Ultrasound pearls

Hydatiform mole, also known as a molar pregnancy, is included in a group of pathological processes known collectively as gestational trophoblastic disease. Molar pregnancies can be further subdivided into partial and complete moles, all of which are nonviable pregnancies. These result from the fertilization of an enucleated egg by a sperm. The karyotypes of these molar pregnancies can vary depending on the type of mole, but the most common is 46,XX. Other potential karyotypes include 46,XY; 69,XXX; and 69,XXY.

Molar pregnancies are rare with an estimated incidence of 60/100,000 pregnancies in North America. Specific risk factors for the development of a molar pregnancy are not exactly known, but may include the extremes of maternal age and previous molar pregnancy1. Most affected patients present with vaginal bleeding, a uterine size larger than expected based on gestational age, and a beta-hCG much higher than expected for gestational age2. Classically, patients may also report the passage of “grape-like clusters”.

Ultrasound is the diagnostic test of choice. When emergency physicians are evaluating early gestation pregnancies, molar pregnancy is likely to be a completely unexpected finding. The typical appearance of a molar pregnancy on ultrasound has been described numerous times in the literature as, “an enlarged uterus with a heterogenous dominantly echogenic mass with several hypoechoic foci”3. This has further been characterized as a “snowstorm appearance”. There are, however, subtle differences in the sonographic appearance of complete and partial moles. Complete moles are more likely to have larger gestational sacs, abnormal tissue in the uterus, and abnormalities of the placenta; partial moles frequently include yolk sacs and fetal poles and are frequently more vascular4. Despite classic sonographic appearance, the sensitivity and specificity of ultrasound for diagnosing molar pregnancies is extremely poor at 44% and 74%, respectively5,6. A hydropic failed pregnancy can take on a similar appearance on imaging and may lead to a false positive diagnosis5.

Consultation with a obstetrician/gynecologist is warranted if there is concern for molar pregnancy on bedside ultrasound in the emergency department. The treatment for molar pregnancies is dilation and curettage. While most molar pregnancies are benign, incidence of malignancy in complete moles can reach 15%. The risk is lower, approximately 0.5%, in patients diagnosed with partial moles5. Given the nonnegligible progression to malignancy, after initial treatment patients should undergo weekly beta-hCG testing to rule out previously undetected invasive disease.

Case Resolution

To conclude our case, the obstetrics team was consulted and evaluated the patient in the emergency department. They agreed with the diagnosis of molar pregnancy and the patient was taken directly to the operating room for dilation and curettage, where the diagnosis of complete molar pregnancy was confirmed.

Authored by: Andrew Golden, MD

Dr. Golden is a PGY-3 and rising chief resident at the University of Cincinnati Emergency Medicine Residency.

Peer reviewed by: Lori Stolz, MD, RDMS

Dr. Stolz is an associate professor of emergency medicine at the University of Cincinnati and fellowship trained in Ultrasound.

References

  1. Ghassemzadeh S, Kang M. Hydatidiform Mole [Internet]. StatPearls Publishing; [cited 2019 Apr 13].

  2. Soares RR, Maestá I, Colón J, Braga A, Salazar A, Charry RC, et al. Complete molar pregnancy in adolescents from North and South America: Clinical presentation and risk of gestational trophoblastic neoplasia. Gynecol Oncol. 2016 Sep 1;142(3):496–500.

  3. Shaaban AM, Rezvani M, Haroun RR, Kennedy AM, Elsayes KM, Olpin JD, et al. Gestational Trophoblastic Disease: Clinical and Imaging Features. RadioGraphics. 2017 Mar 1;37(2):681–700.

  4. Savage JL, Maturen KE, Mowers EL, Pasque KB, Wasnik AP, Dalton VK, et al. Sonographic diagnosis of partial versus complete molar pregnancy: A reappraisal. J Clin Ultrasound. 2017 Feb 1;45(2):72–8.

  5. Fowler DJ, Lindsay I, Seckl MJ, Sebire NJ. Routine pre-evacuation ultrasound diagnosis of hydatidiform mole: experience of more than 1000 cases from a regional referral center. Ultrasound Obstet Gynecol. 2006 Jan 1;27(1):56–60.

  6. Kirk E, Papageorghiou AT, Condous G, Bottomley C, Bourne T. The accuracy of first trimester ultrasound in the diagnosis of hydatidiform mole. Ultrasound Obstet Gynecol. 2007 Jan 1;29(1):70–5.