Abnormal Yolk Sac

Disclosures
US Evaluation of the 1st Trimester:
Old Questions, New Answers
None relevant to this presentation
Leslie M Scoutt, MD, FACR
Professor of Diagnostic Radiology & Surgery
Chief, Ultrasound Section
Associate Program Director, Diagnostic Radiology
Yale School of Medicine
First Trimester US:
Indications
• Identify and localize the gestational sac
– distinguish an intrauterine from an ectopic pregnancy
• Assess the symptomatic patient
– embryonic demise
– predictors of poor prognosis
– miscarriage
Non-Viable 1st Trimester
Pregnancy
• Society of Radiologists in Ultrasound Consensus
Conference 2012
• Diagnostic criteria revised
Doubilet, NEJM: 2013
• Dating
Commonly Asked Questions….
1. When is it abnormal NOT to see an IUP?
2. Is an intrauterine fluid collection an IUP?
3. What are the sonographic landmarks of a
Newer Questions….
• What is a pregnancy of unknown location (PUL)?
• And how do you manage a PUL?
normally developing IUP?
4. What are the criteria for diagnosis of a failed IUP
or embryonic demise?
5. Are there predictors of poor prognosis?
1
#1: When is it abnormal NOT to
see an IUP?
• Traditionally thought the GS should be identified
#1: When is it abnormal NOT to
see an IUP?
• Traditionally thought the GS should be identified
when the serum hCG level > 1000 - 2000 mIU/ml
(IRP)
Nyberg, JUM: 1987
when the serum hCG level > 1000 - 2000 mIU/ml
(IRP)
Nyberg, JUM: 1987
Bree, AJR: 1989
Bree, AJR: 1989
• New data suggests this number is too low
– 4500 mIU/ml (anecdotal report)
– small sample size, ↑ incidence of multiple gestations
• No agreement on new discriminatory number
Doubilet, NEJM: 2013
#1: When is it abnormal NOT to
see an IUP?
What should you recommend?
• A single hCG value + empty uterus should not be
• If pt is hemodynamically stable, get follow up hCG
used as a diagnostic criterion to DEFINITIVELY
exclude a potentially normal IUP
and US
– or to discriminate btwn an IUP and EP
• However, if the uterus is empty and the hCG is
≥ 3000 mIU/ml, a normal IUP is unlikely
– most likely a nonviable IUP
Doubilet, NEJM: 2013
#2: Is an intrauterine fluid
collection an IUP?
• Intradecidual sign
– eccentric fluid collection
– echogenic rim
– subadjacent to central
linear echogenic complex
Yeh et al, Radiology: 1986
Laing et al, Radiology: 1997
Doubilet, NEJM: 2013
Intradecidual Sign
• Yeh et al, Radiology: 1986
– TA imaging
– 93% accuracy
• Laing et al, Radiology: 1997
– TVUS
– 38 - 65% accuracy
• Ddx: endometrial cyst,
pseudosac
2
Intradecidual Sign
• Obtain f/u to document presence of yolk sac
Laing et al, Radiology: 1997
SRU Consensus Conference: 2012
• An intrauterine sac-like structure w/o a YS or
embryo in a pregnant woman w/ normal adnexae
should be interpreted as follows:
– Pregnancy of unknown location (PUL) that is MOST
LIKELY an IUP
– Ectopic pregnancy, while not excluded, is less likely
• Obtain f/u to document appearance of the YS
Doubilet, NEJM: 2013
Pregnancy of Unknown Location
Pregnancy of Unknown Location
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• Common ~ 8-31%
• Depends on:
+ hCG
No IUP or EP on TVUS
No evidence of RPOC
No sign of hemoperitoneum on US
Hemodynamically stable
– how early one is asked to image
– how well one images
• Most are failing IUPs or EPs
– BUT, 1/3 = early normal IUPs
– 7-20% EPs
• Correlate with serial hCG levels
• 50-70% resolve w/o Rx
Management of PUL
• If stable → WATCH
– repeat hCG in 48 hours
– may need to follow again & get 3rd hCG
• If hCG doubles → probable IUP
– hCG ↑’s only 35-53% in some nl IUPs
• If hCG significantly drops → failed IUP > EP
– rise in hCG < 35% likely excludes viable IUP
• If hCG plateaus or has minimal ↑ or ↓
– usu EP
#2: Is an intrauterine fluid
collection an IUP?
• Double decidual sac sign
– 2 concentric echogenic rings surrounding part of GS
chorion / decidua capsularis
decidua vera
endometrial cavity in between
3
Double Decidual Sac Sign
• Should always be present if MSD > 10 mm
Bradley et al, Radiology: 1982
• Limited usefulness in today’s practice
– YS usually seen on TVUS once MSD > 8 mm
Intrauterine Gestational Sac
• Located mid to upper uterus
• Regular shape
#3: What are the Sonographic
Landmarks of NL IUP?
• Gestational sac
• Yolk sac
• Amnion
• Embryo
• Cardiac activity
Mean Sac Diameter (MSD)
• Length + height + width divided by 3
• Echogenic rim is NOT included
– round to oval
• Echogenic rim > 2 mm
• Usu seen @ 5 wks GA
• Grows ~ 1.1 mm/day
Yolk Sac
• Identification provides unequivocal dx of IUP
– look carefully!
– use harmonics/spatial compounding
– high frequency tx (7 MHz)
– magnify images
• Usu seen @ 5.5 wks GA
Yolk Sac
• Secondary yolk sac
– transfer of nutrients, hematopoesis, formation of
gut
• Grows slowly
– max diam = 5 - 6 mm
4
Yolk Sac
• Connected to midgut by vitelline duct
Yolk Sac
• Located between amnion and chorion, in
chorionic space
Amnion
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Thin
Separates amniotic cavity from chorionic cavity
Should not see amnion w/o embryo
Non-visualization of amnion is NOT abnormal
early in gestation
Amnion
• Amniotic cavity normally not much bigger than
embryo
• CRL ~ mean diameter of AC
• Fuses with chorion ~ 17 wks
– ie, can see embryo w/o amnion
Chorionic Cavity
• Contains YS
• May contain internal echoes
Embryo
• Focal thickening along YS
• CRL grows approx 1 mm/day
• Usu seen @ 6 wks GA
5
Embryo: CRL
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• Longest measurement in
straight line from top of head
to rump
+
Cardiac Activity
Usu seen as soon as see embryo
Almost always @ 3-4 mm CRL
Cardiac activity sometimes seen before embryo
Absence of cardiac activity may be normal
– if CRL < 3 mm
+
Doubilet, NEJM: 2013
Cardiac Activity
• HR varies with gestational age:
5 - 6 wks
8 wks
> 9 wks
90 - 115 bpm
144 - 159 bpm
137 - 144 bpm
• Detection of cardiac activity at
< 7 wks GA does NOT guarantee
good outcome
#4: What are the US criteria for a
Failed IUP?
• Goals have changed!
• Currently, goal = no F+ for Dx of failed IUP
– 100% specific, 100% PPV
• No F+ diagnoses of non-viable pregnancy
– 20 mm MSD w/o YS or embryo
– 6 mm CRL w/o cardiac activity
Abdallah, US Obstet & Gynecol: 2011
Discriminatory Criteria
• But, significant SD in measurement…..
– 20 mm +/- 4 mm MSD
– 6 mm +/- 0.7 mm CRL
2012 SRU Consensus
Conference: Failed IUP
• CRL ≥ 7 mm & no heartbeat
• MSD ≥ 25 mm & no embryo
• Absence of embryo w/ HB ≥ 2 wks post initial TVUS
demonstrating GS w/o YS
• Their final answer……
– 25 mm MSD w/o YS or embryo
– 7 mm CRL w/o cardiac activity
Abdallah, US Obstet & Gynecol: 2011
• Absence of embryo w/ HB ≥ 11 days post initial
TVUS demonstrating GS w/ YS
Doubilet, NEJM: 2013
6
Embryonic Demise
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Embryonic Demise
TVUS
2 observers
Look for at least 1 - 3 minutes
Absence of cardiac activity if:
– CRL ≥ 7 mm
– MSD ≥ 25 mm
#5: What US Findings are Predictive of
Poor Prognosis?
Anembryonic Gestation
• MSD ≥ 25 mm, no YS or embryo
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CRL < 7 mm & no heartbeat
MSD 16-24 mm & no embryo
No embryo w/ HB 7-13 days after a scan showing a GS w/o YS
No embryo w/ HB 7-10 days after a scan showing a GS w/ YS
No embryo 6 wks post LMP
Empty amnion
Large YS (> 7 mm)
Small sac size (MSD – CRL < 5 mm)
Doubilet, NEJM: 2013
Abnormal Amnion
• Significantly larger than embryo
• Thick
• Empty
Abnormal Yolk Sac
• Too big, > 7 mm
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Abnormal Yolk Sac
• MSD - CRL < 5 mm
• Calcified, echogenic
– 94% had SAB
Abnl Gestational Sac
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Small Sac Size
Bromley, Radiology: 1991
Abnl Gestational Sac
Lower uterine segment
Distorted
Echogenic rim < 2 mm
Hypoechoic, edematous rim
Growth < 0.6 mm/day
Nyberg, AJR: 1987
Abnl Gestational Sac
Abnl Gestational Sac
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Abnormal Embryo
• Slow growth
– should grow ~ 1 mm/day
– growth < 0.6 mm/day considered abnormal
• New reports question if normal growth rate can even
be slower than this…..
Bradycardia
• Depends on GA
– at 6.2 weeks GA
HR 80 - 90 bpm; px poor
HR < 80 bpm; px dismal
Doubliet, JUM: 1995
HR = 50 bpm
Subchorionic Hemorrhage
Subchorionic Hemorrhage
• Surrounds GS within endometrial cavity
– echogenicity variable
• Common
• Clinical significance controversial
– ? related to: size
location
gestational age (< 8 wks)
older maternal age (> 35 yrs)
Subchorionic Hemorrhage
Subchorionic Hemorrhage
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Chorionic Bump
Chorionic Bump
• Irregular, convex bulge from choriodecidual
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surface into the 1st trimester sac
Assoc with poor px, low birth weight
Px not related to size
Most pts had been treated for infertility
What is it?
– ? hematoma
Harris, J Ultrasound Med: 2006
Spontaneous Abortion
• Threatened AB
– symptoms
– use US to look for poor prognostic signs
Impending Abortion
• Open cervix
• Impending/inevitable AB
– open cervical OS
• Incomplete AB
– positive serum hCG level
– use US to look for RPOC, trophoblastic flow
– may guide pt management
• Complete AB
Impending Abortion
• Open cervix
• GS in cervix
Incomplete Abortion
• Most specific US findings:
– retained GS
– trophoblastic flow
– thickened, heterogeneous endometrium (> 10 mm)
• US findings often non-specific, F+ & F– endometrium can look normal
– Ddx: hemorrhage, endometritis
• Clinical correlation key
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Incomplete Abortion
Incomplete Abortion
Complete Abortion
• Endometrial stripe may be NL
• Fluid, debris, hemorrhage w/in endo cavity
• No trophoblastic flow
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