Abnormal Sac Contents



Abnormal Sac Contents


Anne Kennedy, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Anembryonic Pregnancy


  • Abnormal Yolk Sac


  • Embryonic Demise


  • Pseudosac in Ectopic Pregnancy


Less Common



  • Retained Products of Conception


  • Gestational Trophoblastic Disease



    • Complete Hydatidiform Mole


    • Partial Mole


    • Invasive Mole


  • Chorionic Bump


  • Endometrial Polyp in Pregnancy


Rare but Important



  • Abnormal Fetus


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Be familiar with normal appearances of early pregnancy (i.e., normal sac contents)



    • Intradecidual sac sign (IDSS)



      • Earliest described sign of intrauterine pregnancy (IUP)


      • Cystic structure within endometrium, eccentric in relation to cavity


    • Double decidual sac sign (DDSS)



      • Earliest transabdominal finding of IUP


    • Double bleb sign



      • Seen for short period in early pregnancy


      • Double bleb = yolk sac + amnion on either side of embryonic disc


  • Extra-embryonic coelom (chorionic cavity) = space between amnion and chorion



    • Normally echogenic compared to anechoic fluid inside amnion


  • Normal IUP growth/milestones



    • Normal gestational sac grows ∽ 1 mm per day


    • When mean sac diameter (MSD) ≥ 10 mm yolk sac should be visible


    • When MSD ≥ 18 mm embryo should be visible


    • “Five alive” rule: Embryo with crown rump length ≥ 5 mm must have cardiac activity


Helpful Clues for Common Diagnoses



  • Anembryonic Pregnancy



    • Empty amnion sign


    • Gestational sac with MSD > 18 mm, visible amnion ± yolk sac but no embryo



      • Failure of embryo to develop


      • Early embryonic demise and resorption


  • Abnormal Yolk Sac



    • Flattened


    • Calcified


    • > 6mm diameter


  • Yolk sac supports pregnancy prior to placental development



    • Normally ≤ 6 mm in diameter, spherical in shape


  • Embryonic Demise



    • Absence of cardiac activity in an embryo with crown rump length > 5 mm



      • Use endovaginal sonography


      • Two independent observers


    • Beware of confusing maternal pulse with embryonic cardiac activity



      • Embryonic heart rate is usually faster than maternal (120-160 vs. 80 beats per minute)


      • If possible embryonic bradycardia feel maternal pulse while watching embryonic heart rate


  • Pseudosac in Ectopic Pregnancy



    • Oval or flat shape


    • Central in cavity


    • Not surrounded by double, echogenic, chorionic ring


    • Possible pseudosac merits careful search for ectopic pregnancy


    • Tubal ectopic most common association with pseudosac



      • Cornual, cervical, C-section ectopics should be evident


Helpful Clues for Less Common Diagnoses



  • Retained Products of Conception



    • RPOC: Irregular collapsed sac or echogenic chorionic remnants


    • Blood flow on color Doppler implies RPOC rather than blood clot


  • Complete Hydatidiform Mole



    • Typical clinical presentation



      • Hyperemesis, hypertension, size > dates, vaginal bleeding


    • Cavity distended by mass with multiple “cysts” → “bunch of grapes” or “snowstorm” appearance


    • May be associated with ovarian theca lutein cysts



  • Partial Mole



    • First trimester: Unusual looking sac/chorionic bump


    • Second trimester presentation depends on source of third set of chromosomes



      • Large, cystic placenta if paternal


      • Small placenta if maternal


  • Invasive Mole



    • No embryo


    • Complex intrauterine vascular mass


    • Loss of endometrial myometrial interface due to invasion into myometrium


  • Chorionic Bump



    • Focal protuberance from chorionic surface


    • First described among in vitro fertilization (IVF) population but also seen with spontaneous conception


    • 50% loss rate documented in IVF patients


    • Etiology unknown; possible early bleed


    • Strong association with partial mole


  • Endometrial Polyp in Pregnancy



    • < 2 cm unlikely to impact pregnancy rate/success in IVF population


    • Modern approach to IVF patients indicates polypectomy justifiable if polyp discovered in work-up


Helpful Clues for Rare Diagnoses

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Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Abnormal Sac Contents

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