Flashcards in Ultrasound Deck (80)
What's the lemon sign on fetal ultrasound? Significance?
indentation in the bilat frontal bones
(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:
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 =
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?
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?
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
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?
fetal cardiac activity
Yolk sac: sac diameter >10mm
Embryo: sac diameter 15-18mm
Cardiac activity: fetal pole >5mm