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Flashcards in Ultrasound Deck (80)
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What's the lemon sign on fetal ultrasound? Significance?

indentation in the bilat frontal bones
Chiari II
(others include Dandy-Walker, encephalocele, cystic hygroma, etc.)
Say you'd look at the spine for meningocele, prognosis involves brainstem (get decompressed) and LE paralysis.


What's the banana sign of fetal head imaging? Significance?

the way the cerebellum is wrapped tightly around the brain stem as a result of spinal cord tethering and downward migration of posterior fossa contents
Chiari II and spina bifida


Large midline posterior fossa cyst:

Dandy Walker: absent cerebellar vermis, associated with other problems in 70-90% (cortical dysplasia, dysplasia of corpus callosum, lipoma of CC, scizencephaly)


What's a Blake pouch cyst?

posterior ballooning of the superior medullary velum into the cisterna magna, below and posterior to the vermis. It is thought to be secondary to failure of perforation of the foramen of Magendie
In ddx for Dandy Walker


Joubert syndrome is what?

(aka vermian aplasia or molar tooth midbrain-hindbrain malformation) is an autosomal recessive disorder where there is a variable degree of cerebellar vermis agenesis


How do you diagnose fetal hydrops?

accumulation of fluid + / - edema involving at least two fetal components. This may manifest as:
pleural effusion
pericardial effusion
generalised body edema - fetal anasarca / nuchal edema / cystic hygroma


Causes of fetal hydrops:

fetal anemia (alloimmunization, Rx is fetal blood transfusion, parvovirus), genetic (Trisomy 21, Turner causing lymphatic obstruction), circulatory failure (AVM, vascular tumor), heart defect, infection (CMV, syphilis)


Multicystic dysplastic kidney - what associations?

80% are unilateral
bilateral is lethal from pulmonary hypoplasia
other kidney has an anomaly in 40%


Ddx for polyhydramnios

Duodenal or esophageal atresia, facial abnormalities (Pierre Robin), trisomy 18, holoprosencephaly, anencephaly, myotonic dystrophy, arthrogryposis


Describe Pierre Robin syndrome

glossoptosis (retracted tongue)
posterior cleft palate or arched palate
Not genetic, associated with polyhydramnios from impaired swallowing


What's a normal cervical length?

2.5 cm or greater


What's double bubble? Associations?

Duodenal atresia (look for polyhydramnios), only 30% have Downs


communication between atria and ventricles =

AV canal
50% have Downs


What's a normal lateral ventricle measurement in a fetus?

10mm or less


What's an omphalocele? What's gastroschisis?
When does bowel normally herniate?

Omphalocele: membrane covered defect, cord inserts into sac. Associated abnormalities (80%) - esp. cardiac, including chromosomal
Gastroschisis: free-floating bowel, cord inserts to the left (it's on the right). 5% chance of other anomalies (usually don't offer amnio)
Normal herniation is before 12 weeks


vessels run through membranes across the internal cervical os =
When especially should you look for this?

vasa previa
Often seen in: low-lying placenta, vellamentous cord insertion, succenturiate lobe


High resistance/reversal in umbilical artery - what's the problem?

IUGR, placental insufficiency. Deliver if near term.


What does "monochorionic" mean? "Monozygotic"? What are the types of twins?

Chorion Contains it All (Chorion outside Amnion)
Chorion encloses fetus and amnion. Can have two amnions in one chorion
Monochorionic monoamniotic: no membrane (always identical twins)
Monochorionic, diamniotic: thin membrane, usually single placenta
Dichorionic, diamniotic: twin peak, thicker membrane, usually two placentas, but can be fused


What type of twins are at risk for twin-twin transfusion?

Monochorionic -15% Also at risk for IUGR, villamentous cord insertion.
Does not occur in dichorionic
Rx laser coag the connecting vessels


small left ventricle prenatally. Called?

Hypoplastic left heart (requires a lot of surgery postnatally)


What's the normal thickness of a nuchal translucency? When can it be measured?

3.0mm or less. 11-14 weeks only. After this, can measure nuchal fold/thickening (<6mm).


what's blood between the placenta and uterus called?

Placental abruption


What are normal renal pelvis measurements in a fetus?

<7mm after ~30 weeks


Two vessel cord - what's missing? Significance?

Single umbilical artery (check by bladder)
20% have other malformations eg trisomy 13,18, cardiac and renal malformations
Risk of IUGR and prematurity


Fetal ehogenic bowel - what's it from?

Must be bright as bone! Often normal variant, but could be:
CMV, CF, trisomy 21, bowel ischemia


Fetal tumor arising from sacrum/coccyx

Sacrococcygeal teratoma
AV shunting may lead to hydrops
must know before delivery!


What's a cystic hygroma? Significance?

congenital lymphovascular malformation. Associated with turner and trisomy 21. Commonly have hydrops.


Keyhole bladder in male fetus =

posterior urethral valves. Causes oligohydramnios and pulmonary hypoplasia


Early pregnancy: when should you see the following?
Yolk sac
fetal cardiac activity

Yolk sac: sac diameter >10mm
Embryo: sac diameter 15-18mm
Cardiac activity: fetal pole >5mm


Significance of clenched fist in fetus:

Trisomy 18
(trisomy 13)