Ultrasound Flashcards
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:
Associations?
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
ascites
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
micrognathia
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 =
associations?
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
embryo
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
Findings of trisomy 18 on fetal ultrasound
clenched fist with overriding index finger heart defect (VSD) strawberry skull CP cyst single umbilical artery clubfoot micrognathia hypoplastic nasal bone
fetal long bone fracture
OI
Placenta accreta, percreta, increta:
accreta: villia attached to myometrium but no invasion
increta: partially invade
percreta: invade through and outside serosa
What lab value is useful to check for neural tube defects?
AFP (elevated in neural tube defects)
Name the three neural tube defects
Anencephaly 47%
myelomeningocele 47%
encephalocele 5%
Where are encephaloceles located?
posterior midline most common
next most common nasal/frontal
Vein of Galen malformation - what do you want to check for?
Heart failure/hydrops
Causes of antenatal ventriculomegaly:
TORCH infection, aqueductal stenosis, Chiari II, Dandy-Walker, trisomy 21
What’s a porencephalic cyst? Caused by?
focal cystic area of encephalomalacia that communicates with the ventricular system and/or the subarachnoid space
typically lined with white matter
Caused by perinatal cerebral ischaemia, trauma, infection, antenatal intraparenchymal hemorrhage
Holoprosencephaly is associated with what genetics? What are the features of alobar holoprocensephaly?
Trisomy 13
Fused thalami, absent falx and CC, monoventricle. Assoc with cyclopia and cleft lip.
What’s the term for isolated enlargement of the occipital horns of the lateral ventricles? What does this indicate?
Colpocephaly
Agenesis of the corpus callosum
If the falx is present but there’s no or very little brain tissue, what is it?
Hydranencephaly.
Ischemic insult early, no genetic component
Cleft lip (unilateral) - what are the chances of other problems? Cleft palate - now what chance of abnormalities?
lip: 20% chance
palate: 50% chance (assoc with trisomy 13)
micrognathia - what associations?
trisomy 18, Treacher-Collins (others, but forget about them)
macroglossia - what associations
trisomy 21, Beckwith-Wiedeman, maternal DM, omphalocele
fetal pericardial effusion - what syndrome comes to mind?
trisomy 21
isolated pleural effusions - associated with:
trisomy 21, Turner’s
cystic hygroma - associated with
Turner’s, trisomy 21, 18, 13
definition of fetal hydrops:
What are the 4 compartments?
Fluid in two or more compartments
pericardium, pleural, abdomen, body (anasarca, cystic hygroma)
Dilated bowel in a fetus - ddx
ileal atresia, volvulus, ileal obstruction (meconium ileus)
Colon problems don’t cause dilated bowel in a fetus!!
Ddx of echogenic bowel in fetus
Can be normal
trisomy 21, CF, TORCH infxn
25% chance of future IUGR
2 most common causes of hydronephrosis
1: UPJ obstruction
2: Reflux
Causes of dilated ureter
Primary megaureter, reflux, posterior urethral valves (if bilateral)
What’s the Spalding sign and what does it mean?
Overlap of the skull bones on fetal ultrasound, means fetal demise
What’s a low lying placenta?
Within 2 cm of internal cervical os
associations with club foot?
Many, including Trisomy 18
Placental mass - looks cystic but is highly vascular = ?
Associations?
Concern?
Chorioangioma
Beckwith-Wiedemann (others)
anemia, heart failure
What is choriocarcinoma?
Aggressive, highly vascular tumor
Sometimes in gestational trophoblastic dz
sometimes in non-pregnant (ovary) or men (testes)
Causes high b-HCG
a fetus appears to have a cardiac abnormality on ultrasound. Do you offer amnio?
Yes - for all congenital heart disease!
Findings of trisomy 21 / Downs on ultrasound:
thickened nuchal translucency (>3mm) short femur and humerus small/absent nasal bone echogenic bowel cardiac - ECD, ASD, VSD, echogenic focus duodenal atresia sandal gap toes
findings in trisomy 13
CNS - holoprosencephaly and others, spina bifida cardiac - HLHS, VSD cleft lip and palate micrognathia polydactyly, rockerbottom feet clenched hands
Internal carotid artery - what velocity indicates normal to 70%?
Peak systolic of up to 125 is normal
Above 230 is >70% stenosis
But always ask to see contralateral side - velocities increase to compensate if other side is occluded.
What causes the wild color of a color doppler of a carotid stenosis?
Aliasing - the inability to detect the true peak velocity because the Doppler sampling rate is too slow
You see a diaphragmatic hernia in a fetus. What now?
Determine side (usually L), look for other problems. Mention concern regarding pulmonary hypoplasia, including other lung from compression. CDH is associated with abnormal karyotype.
What’s a complete placenta previa? Marginal? Low-lying?
Complete: covers internal cervical os
Marginal: partly covers
Low: less than 2 cm
What counts as endometrial thickening in a postmenopausal woman? What are the causes?
> 4mm unless on hormones, so ask
Hyperplasia, polyps, cancer
Gestational trophoblastic disease - types, what to do about it. What else to look for/confirm?
Complete mole - sperm + empty egg hyperechoic/heterogeneous tissue, no fetal parts. 85% noninvasive, but the rest invade and 2% met as choriocharcinoma
Partial mole: 2 sperm + egg
may see fetal parts, especially early
Ovaries: theca lutein cysts from high b-HCG
Thyroid ultrasound - see a hypoechoic mass just behind the thyroid - what is it? What do you say?
Probably parathyroid adenoma. You would check for hypercalcemia.
What’s a target lesion in the liver on ultrasound? What might it be?
Hyperechoic center and hyopechoic periphery. Most likely malignancy - mets or HCC. Less likely adenoma or FNH or hemangioma (more typically reverse target). Also lymphoma, fungal microabscesses.
What is an echogenic intracardiac focus? What do you do if you see one?
Must be as bright as bone - calcification of a papillary muscle.
May be normal variant, but look for Down’s syndrome
Renal artery doppler - what’s the normal peak velocity max?
Max 200cm/s - but must be careful of angle
Also check for parvus tardus post stenosis
Discuss transplant renal vein thrombosis
Usually within 1st week
Enlarged kidney, absent flow in vein, reversal of flow in diastole in artery.
Adrenal lesion in fetus or neonate
Hemorrhage
Neuroblastoma (met)
Hyperechoic (calcified) renal pyramids in an infant
Lasix is most common
causes of oligohydramnios
AFI less than 8, often just obvious Fetal demise bilateral renal abnormalities PROM postmaturity
Ddx for echogenic kidneys
In general, renal parenchymal disease
If small: diabetic nephropathy, chronic glomerulonephritis, interstitial nephritis
If large: HIV nephropathy
Incompetant cervix - findings? How diagnosed?
V or U shaped cervical funneling. US with EMPTY bladder. Don’t press too hard (may artificially lengthen cervix)
Fluid collection around kidney - what do you need to ask? What’s the ddx for early postop?
Time since transplant and is the patient infected
Early postop: hematoma (document size, monitor for decrease, concern for page kidney)
Seroma
Urinoma (w/in 1st 1-2 weeks. check fluid for creatinine, requires surgery)
Abscess (may have gas)
Lymphocele (usually not for at least 3 weeks postop)
Intracardiac mass in utero
Most likely cardiac rhabdomyoma in TS
What causes gallbladder adenomyomatosis?
Cholesterol crystals in dilated Rokitansky-Aschoff sinuses
