Episode 2: Ectopic Pregnancy

Written By Learning Inthedark
 

Discover the 4 D’s of Radiology DETECT - DESCRIBE - DIFFERENTIAL - DECISION

DETECT

Epidemiology.

7 – 27% of pregnancies present with bleeding during the first trimester. Ultrasound is the workhorse imaging modality for patients to differentiate causes of bleeding in conjunction with clinical history and beta HCG Ectopic pregnancies represent 2% of pregnancies and have been increasing due to reproductive technology

Pathophysiology.

It is important to keep in mind the difference between gestational age and embryonic age.

  • Gestational age is based off the last menstrual period and embryonic age is based on the days since fertilization
  • For the purposes of this podcast we will stick to gestational age

Back to Embryology:

  • The Decidua is a transient platform within the pregnant endometrium that forms after the attachment of the blastocyst. On ultrasound you will see a thickening of the endometrium around the gestational sac. Gestational sac represents the chorionic cavity and is a hypoechoic structure embedded in the uterine endometrium
  • The gestational sac is usually evident on ultrasound at approximately week 4 of gestational age
  • The yolk sac starts to develop during the first week and is evident on ultrasound at week 5. Growth occurs through to week 10. The yolk sac appears as a round, hypoechoic structure inside the gestational sac with surrounding echogenic walls but outside the amniotic cavity. The fetal pole appears around week 6
  • In normal pregnancy this occurs in the endometrium whereas ectopic pregnancies will implant in various locations which we will get to later on in the podcast

Clinical Presentation.

Pelvice pain

Vaginal bleeding

Risk Factors.

  1. Previous ectopic pregnancy
  2. History of PID
  3. History of gynecologic surgery
  4. Infertility
  5. Use of IUD
  6. History of placenta previa
  7. Use of IVF
  8. Congenital uterine anomalies
  9. History of smoking
  10. Endometriosis
  11. Exposure to DES while in utero

Work up.

  1. History as above
  2. Lab work
    • Beta HCG
      • What: glycoprotein hormone produced primarily by syncytiotrophoblasts in the placenta to stimulate the corpus luteum to produce progesterone
      • Normal levels: normal trajectory is to follow a curvilinear growth curve with a doubling time of close to 48 hours. The levels peak at weeks 9 – 11 and begin to decline at 20 weeks
      • Abnormal Levels: Lack of doubling time in 48 hours, early plateau of Beta HCG
      • Levels of 1500 should have transvaginal presence of a pregnancy
      • Levels of around 6000 means the pregnancy should be visible on transabdominal ultrasound
    • Progesterone Levels
      • Progesterone = Pro-gestation!
      • Normal levels are typically 25 ng/mL, majority of non-viable pregnancies will have a serum progesterone < 5 ng/mL
      • Cons: Expensive, takes a while to get result from the lab

DESCRIBE

Imaging Workup

Workhorse of imaging for ectopic pregnancy is the combination of trans-abdominal and transvaginal ultrasound

MRI may be appropriate in certain clinical circumstances

CT with IV contrast is not as commonly used

Ultrasound Findings

Ultrasound Findings will be organized by location/type of ectopic pregnancy

  1. Tubal Pregnancy
    • Epidemiology: Most common type of ectopic pregnancy (approximately 95%)
    • Location: Most common is in the ampulla (70%) followed by the isthmus, and less common the fimbria
    • Findings:
      • Adnexal Findings:
        • An adnexal mass separate from the ovary is the most common finding. Specificity is 100% when the mass contains a yolk sac or live embryo
        • Tubal Ring Sign: Hypervascular hyperechoic ring surrounding an extrauterine gestational sac.
      • Endometrial findings:
        • Normal endometrium
        • Blood and fluid in the endometrial cavity and endocervical canal
        • Pseudo-gestational sac (thick decidual reaction surrounding intrauterine fluid, often located centrally within the endometrial canal as compared to eccentrically for normal gestational sacs). Other clues include a low resistance arterial flow on color Doppler
        • Trilaminar endometrium: formed during the late proliferative phase of the menstrual cycle and involves an echogenic basal layer, hypoechoic inner functional layer followed by a thin echogenic layer representing the interface to the endometrial lumen
        • Thin walled decidual cyst: thin walled cyst found at the junction between the endometrium and myometrium. The thin wall is the key to differentiating from a true gestational sac
      • Extrauterine Findings
        • Pelvic free fluid
        • Hematosalpinx
        • Hematoperitoneum
  2. Interstitial Pregnancy
    • Epidemiology: less common (2 – 3% of ectopic pregnancies)
    • Risk Factors: Prior salpingectomy, IVF
    • What: Pregnancy that implants into the intramyometrial segment of the fallopian tube. The distensibility of this segment allows for delayed presentation, sometimes up to the 16th week
    • Risks: If ruptured, the risk of life threatening hemorrhage is high because of the proximity of the uterine artery to the fallopian tube
    • Findings:
      • Eccentrically located gestational sac surrounded by a thin layer of myometrium (<5mm)
      • Make sure to assess the rest of the uterus as eccentrically located IUP’s can occur secondary to fibroids, contractions or anatomical anomalies or normal variant (“angular pregnancy”)
      • Interstitial line sign: Echogenic line extending into the uterine horn bordering the margin of the gestational sac present in the fallopian tube
  3. Cornual Pregnancy
    • What: Implantation of a blastocyst within the cornua of a bicornuate or septate uterus
    • Epidemiology: < 1% of all ectopic pregnancies
    • Risks: Rupture can lead to life threatening hemorrhage
    • Findings
      • Gestational sac surrounded by a thin rim (< 5 mm) of myometrium
      • Eccentric positioning
      • < 1 mm from the lateral wall of the endometrial cavity
  4. Ovarian Pregnancy
    • Risk factors: Use of IUD’s, may occur in relation to heterotopic pregnancies
    • Findings
      • Gestational sac, chorionic villi, atypical cyst with a hyperechoic ring within the ovary, but alongside a NORMAL fallopian tube
  5. Cervical Pregnancy
    • What: Pregnancy within the endocervical canal
    • Epidemiology: Rare accounting for less than 1% of ectopic pregnancies
    • Findings
      • Uterus may be shaped like an hour glass or figure of eight
      • Trophoblastic flow surrounding the gestational sac within the cervix
      • Cardiac activity below the internal os
      • Normal endometrial stripe
    • Differential: Ensure to watch for the sliding sign – mobility of the gestational sac to assess for a possible abortion in progress
  6. Scar Pregnancies
    • Epidemiology: Rare accounting for < 1% of ectopic pregnancies
    • Pathophysiology: During previous surgery it is suggested that a fibrous tract connects the uterine endometrium to the myometrium
    • Findings
      • Gestational sac present in the anterior wall of the inferior aspect of the uterus
      • Myometrial tissue may be thinned anteriorly due to compression
  7. Intra-abdominal Pregnancy
    • Epidemiology: Very rare cause of ectopic pregnancies
    • What: Pregnancy located within the peritoneal cavity separate from the tubes, ovaries and intraligamentous structures
    • Risks: Significant morbidity and mortality due to hemorrhage with over 7 times higher mortality compared to other causes of ectopic pregnancies
    • Findings:
      • Absence of a normal intrauterine gestational sac
      • Gestational sac within the intraperitoneal cavity
      • Abdominal or pelvic hemorrhage
  8. Heterotopic Pregnancy
    • What: intra and extrauterine pregnancy occurring at the same time
    • Risks: Assisted reproduction (in particular ovulation induction)
    • Findings:
      • Intra and extrauterine gestational sacs
      • Any of the above findings for the ectopic pregnancy may be seen depending on the location of implantation

Classification

  • Definite ectopic pregnancy:
    • Extrauterine gestational and yolk sacs, +/- embryo
  • Probable ectopic pregnancy:
    • Extrauterine/adnexal mass
  • Pregnancy of unknown location:
    • No GS, YS, or fetal pole; but also no suspicious extrauterine/adnexal findings
    • Diagnostic possibilities – early IUP, occult ectopic, or completed spontaneous abortion
  • Probable intrauterine gestation:
    • Intrauterine fluid sac-like structure. No yolk sac or embryo
  • Definite intrauterine gestation:
    • Intrauterine gestational and yolk sacs, +/- embryo

DIFFERENTIAL

Abdominal and pelvic pain in pregnancy has a broad differential, in the context of a mass within the possible common locations as described above be sure to think about the following

  1. Appendicitis
    • Please check back for our appendicitis episode for further details of common findings and our tips and tricks
  2. Ruptured corpus luteum
    • US Findings:
      • Complex adnexal mass
      • Thick walled cystic lesions with lace like strands
      • Adnexal thick walled cystic lesion with low level echoes
      • Peripheral vascularity termed the “ring of fire sign” – be careful to distinguish this from peripheral hypervascularity of a tubal ectopic pregnancy
  3. Intrauterine pregnancy
  4. Incidental adnexal mass
  5. Miscarriage
  6. Early pregnancy not detected on ultrasound
  7. Pregnancy of unknown location

DECISION

Treatment options are very patient dependent and prompt referral and notification to the managing clinician should occur as delayed diagnosis and treatment can warrant poor outcomes

  1. Expectant management
    • May be considered in the context of early, asymptomatic patients with low or declining Beta HCG levels
    • Beta HCG levels will be followed to a level of 0
    • Follow up ultrasounds may also be recommended
  2. Medical Management
    • Medical management in the form of Methotrexate may be considered in the context of hemodynamically stable patients with an unruptured ectopic pregnancy and who have no contraindications to methotrexate
  3. Surgical Management
    • Usually a laparoscopic approach with removal of the ectopic pregnancy
    • Approach differs depending on the location of the ectopic pregnancy
 
 

References

Nalaboff, K. M., Pellerito, J. S., & Ben-Levi, E. (2001). Imaging the endometrium: disease and normal variants. Radiographics, 21(6), 1409-1424.

Swire, M. N., Castro-Aragon, I., & Levine, D. (2004). Various sonographic appearances of the hemorrhagic corpus luteum cyst. Ultrasound quarterly, 20(2), 45-58.

Lane, B. F., Wong-You-Cheong, J. J., Javitt, M. C., Glanc, P., Brown, D. L., Dubinsky, T., ... & Zelop, C. M. (2013). ACR appropriateness criteria® first trimester bleeding. Ultrasound quarterly, 29(2), 91-96.

Po, L., Thomas, J., Mills, K., Zakhari, A., Tulandi, T., Shuman, M., & Page, A. (2021). Guideline No. 414: Management of Pregnancy of Unknown Location and Tubal and Nontubal Ectopic Pregnancies. Journal of Obstetrics and Gynaecology Canada, 43(5), 614-630.

Donovan, M. F., & Cascella, M. (2020). Embryology, Weeks 6-8. StatPearls [Internet].

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