Ultrasound Findings Flashcards
What is an absent nasal bone
no bony part of the nasal bridge can be identified
What is an absent nasal bone most commonly associated with
T21
What is the likelihood ratio for absent nasal bone in African American, Asian, Chinese/Japanese, and Caucasian populations
AA=8.8
Asians= 14.2
Chinese/Japanese= 15.3
Caucasians= 31.3
What is a likelihood ratio
Used to assess the value of a diagnostic test by comparing the likelihood that a patient with a disease has a particular test result compared to someone without the disease.
The higher the LR, the more likely it is that the ultrasound finding is consistent with a genetic etiology
What are anterior clefts
Can extend through the lip and into the primary/hard palate
What are posterior clefts
CANNOT be visualized on u/s bc they include clefts of the secondary/soft palate
When is the susceptible period for clefting
4th-12th embryonic weeks (6-14 weeks GA)
Unilateral clefts account for ___% of CL+/- CP while bilateral clefts account for the remaining ___%
90; 10
Clefts extend into the palate in ___% of cases that are unilateral and in ___% of bilateral cases
70; 85
What is the order of the most common clefting patterns
(L unilateral, Bilateral, R unilateral)
- L unilateral
- R unilateral
- Bilateral
Ratio is 6:3:1
What is the incidence of CL +/- CP? Which gender is more likely to have CL +/- CP?
1 in 700; Males
Male to Female ratio is 2:1
What populations have the highest frequency of CL+/- CP
Native American and Asian populations
What are potential candidate genes for CL +/- CP
IRF6, MSX1, SATB2, FGFR1
What are the teratogenic associations that can result in CL +/- CP
Alchohol, hyperthermia (fever), methotrexate, maternal PKU, hydantoin, trimethadone, aminopterin, retinoic acid, valproic acid, smoking (odds ratio 1/3)
What is the detection of CL +/- CP on u/s
65-70% depending on the abnormality present
What are the testing recommendations for CL +/- CP identified on u/s
chroms, microarray (specifically for 22q11.2), comprehensive fetal u/s and echo should be offered to detect other defects and monitor for polyhydramnios second to swallowing issues
Parental exams for lip pits, craniofacial abnormalities, single central incisor, hypotelorism, and olfactory issues to r/o conditions like Van der Woude and AD holoprosencephaly
What is the recommended treatment for CL +/- CP
sx correction for CL usually occurs shortly after birth and CP between 6-18mo
Complications prior to sx may include poor feeding that could result in poor weight gain, poor dentition, and hearing problems
What is the general population risk for isolated CL +/- CP
0.1%
What is the empiric risk for a first degree relative with CL +/- CP
4-8%
Bilateral CL+CP=8.0%
Bilateral CL only= 6.7%
Unilateral CL+CP= 4.9%
Unilateral CL alone= 4%
What is talipes equinovarus
Clubfoot; foot brought downward and inward which cannot be brought to a neutral position
Half are bilateral; if it is unilateral, R side is usually affected
What is talipes calcaneovalgus
Foot is bent backward at the ankle and turned out with the foot bones in normal position relative to each other
Unlikely to be syndromic or the result of neurological impairment/syndromes
What is metatarsus varsus
forefront of the foot is turned inward and bent backward while heel and ankle remain in normal position. Usually mild and does not require sx
Unlikely to be syndromic or the result of neurological impairment/syndromes
What is the incidence of clubfoot? Which gender is more likely to have clubfoot?
1 in 1000; more common in males (2:1)
What populations have the highest frequency of clubfoot
High incidence in Polynesian population (6.5-7 in 1000)
What is the general population risk for clubfoot
0.1%
What is the empiric recurrence risk in a first degree relative with clubfoot
2-7%
~2% risk to sibs of a male with clubfoot; ~5% risk to sibs of a female with clubfoot
metatarsus varsus and talipes calcaneovalgus appear to run separately from equinovarus and may have an increased rr of 4-5% to sibs
False positives up to ___% in the 3rd tri using u/s for clubfoot. __% of cases do not develop/present until the 3rd trimester
40; 10
What are some causative factors in the intrauterine environment that can cause clubfoot
Twins. oligohydramnios, amnion rupture sequence, fetal positioning, placental insufficiency, maternal infection, maternal toxin exposure
What are testing recommendations for suspected clubfoot
amnio with karyotype and CMA
can consider genetic testing if specific condition is suspected (ex: distal arthrogryposis type 1- bilateral equinovarus)
comprehensive u/s to r/o additional anomalies
fetal MRI and echo may be indicated in complex cases
What is the recommended treatment for clubfoot
sx occurs in 20-80% of cases; most commonly, Ponseti technique is used (4-6wks long leg plaster casts, more casting, abduction brace worn during sleep until ~4yo)
Where should patients with clubfoot be referred
Orthopedic surgeon, postnatal genetics eval with pediatric geneticist
What fraction of clubfoot cases are isolated and syndromic
2/3 are isolated
1/3 are complex (other systems involved; 10-30% are associated with T13/T18)
What is a choroid plexus cyst
trapped cerebrospinal fluid within a fold of the primitive neuro tissue with subsequent accumulation of cellular debris
When can a choroid plexus cyst be visualized on u/s
as early as 9wks GA, but often seen between 16-25wks GA
What is the incidence of choroid plexus cyst
0.5-4% of routine mid-gestation u/s exams
What does the presence of a choroid plexus cyst indicate and what percentage of these case have a choroid plexus cyst
T18; 40-50%
What are the recommendations from ACOG concerning the identification of a choroid plexus cyst
amnio if serum screening is abnormal or the person is 32yo or older at delivery. CMA may also be considered but data is limited on the detection of microdel/dup syndromes in presence of CPCs
How many choroid plexus cysts disappear
> 95% disappear before 26wks (even those with an abnormal karyotype)
What should the follow up be following identification of choroid plexus cysts
Consider fetal echo; f/u u/s for growth can be considered since T18 is associated with IUGR
What is nuchal translucency and when is it measured
accumulation of fluid in the fetal neck ; measured between 11-14 weeks
What are the 95th and 99th percentile cutoffs for NT
3.0mm and 3.5mm respectively
What are some explanations for an increased NT
- cardiac failure secondary to abnormalities of heart/great arteries
- venous congestion of head + neck
- failure of lymphatic drainage bc of impaired fetal movement
- delayed/abnormal development of lymphatic system
- altered composition of ECM
- Chromosome abnormalities
- Microdel/dup syndromes
- Single gene disorders
What are the structural defects associated with increased NTs
CHDs, orofacial clefts, diaphragmatic hernia, omphalocele, body stalk anomalies
What are the testing recommendations following increased NT
fetal karyotyping by CVS/amnio; CMA and testing for Noonan should be discussed; A detailed level II u/s w fetal echo is recommended
What are adverse pregnancy outcomes associated with increased NT
Progression to fetal hydrops, fetal death, major cardiac/structural anomalies
What is hydronephrosis/pyelectasis
dilation of the fetal pelvis
What is the cutoff for a dilated renal pelvis in patients with hydronephrosis/pyelectasis
greater than or equal to 4mm at <33wks; greater than 7mm at >33wks
What is the incidence of hydronephrosis/pyelectasis and which gender is more likely to have the finding
found in ~2-3% of fetuses; more commonly seen in males (2:1 ratio)
What are alternative explanations (non-genetic) for hydronephrosis/pyelectasis finding on u/s
Ureteropelvic junction obstruction (makes up ~44-65% of cases, most of which are unilateral)
Posterior urethral valves (PUVs)- the most common cause of bladder obstruction, may present prenatally with oligohydramnios, bilateral hydronephrosis, and subcortical renal cyst formation