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ANSWERS
CASE 71
Esophageal Atresia
1. A, B, C, and D
2. C
3. B
4. B
References
de Jong EM, de Haan MA, Gischler SJ, et al: Pre- and postnatal diagnosis and
outcome of fetuses and neonates with esophageal atresia and tracheo-
esophageal stula. Prenat Diagn 2010; 30(3):274-279.
http://www.ncbi.nlm.nih.gov/pubmed/20112230 (Accessed on June 14, 2012.)
McGahan JP, Leeba JM, Lindfors KK: Prenatal sonographic diagnosis of
VATER association. J Clin Ultrasound 1988; 16(8):588-591.
http://www.ncbi.nlm.nih.gov/pubmed/3152406 (Accessed on June 14, 2012.)
Solt I, Rotmensch S, Bronshtein M: The esophageal ‘pouch sign’: a benign
transient nding. Prenat Diagn 2010; 30(9):845-848.
http://www.ncbi.nlm.nih.gov/pubmed/20582925 (Accessed on June 14, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 434-437.
Comment
Differential Diagnosis
The differential diagnosis of an absent or persistently small
stomach is quite broad. This ultrasound nding may be due
to swallowing dysfunction secondary to facial cleft lip/palate
or a central nervous system abnormality, neuromuscular disorder, neck or chest mass, or skeletal dysplasia causing a narrow
chest. In a diaphragmatic hernia, the stomach may be within
the chest or may be compressed by thoracic contents. In some
fetuses, nonvisualization of the stomach is a transient normal
nding and rescanning later during the initial examination is
recommended. If the stomach is not seen, a repeat examination later would be expected to show a uid-lled stomach
in normal cases. Oligohydramnios from any etiology leads to
nonvisualization of the stomach because no amniotic uid is
available for swallowing.
Polyhydramnios usually does not occur until later in the
second trimester in fetuses with esophageal atresia but also
is present with other types of atresia, including duodenal and
proximal small bowel atresia. There may be multiple other etiologies of polyhydramnios, including large-for-gestational-age
fetuses and fetuses with central nervous system abnormalities.
Ultrasound Findings
Ultrasound ndings in esophageal atresia include a small or
absent stomach. If a stula from the trachea to the distal
esophagus is present, the stomach is not absent but may be
very small. In some instances, there is an esophageal pouch
of the proximal atretic esophagus. Ultrasound and MRI may
identify this nding (Figure C).
Prognosis and Management
Because there is a high association with concurrent abnormalities with esophageal atresia, it is imperative to scan the
rest of the fetus carefully. Other gastrointestinal abnormalities
include duodenal atresia, intestinal malrotation, and anorectal
atresia. Cardiac abnormalities are often present with esophageal atresia. When duodenal atresia and congenital heart disease are seen, there are associated karyotypic abnormalities
such as trisomy 21. Trisomy 18 may also occur with esophageal atresia. Esophageal atresia may be part of the VACTERL
syndrome. The prognosis of infants with esophageal atresia
depends on the presence of other abnormalities and karyotypic abnormalities. Surgical repair of the esophageal atresia or
the distal esophagus is usually successful but is associated with
morbidity and mortality. For surviving infants, gastroesophageal reux may produce recurrent strictures and repeated
pneumonia.
146
CASE 72
A
History: Two asymptomatic patients present with late rst-
trimester pregnancies.
1. Which of the following syndromes are associated with
nuchal translucency? (Choose all that apply.)
A. Down syndrome
B. Trisomy 13
C. Trisomy 18
D. Turner syndrome
2. What is the normal nuchal translucency for weeks 10 to 14
of gestation?
A. >6 mm
B. >10 mm
C. >7.5 mm
D. >3 mm
3. A combination of nuchal translucency, serum markers beta–
human chorionic gonadotropin (β-hCG) and pregnancyassociated plasma protein A, and advanced maternal age
results in what sensitivity for Down syndrome?
A. 50% to 60%
B. 20% to 30%
C. 10% to 15%
D. 80% to 90%
4. What is the progression of a thickened nuchal translucency
seen at 14 weeks?
A. It increases to term.
B. It may resolve after 14 weeks.
C. It usually leads to a cystic hygroma.
D. It usually resolves after 14 weeks.
B
C
147
ANSWERS
CASE 72
Nuchal Skin Measurement
1. A, B, C, and D
2. D
3. D
4. B
References
Fong KW, Toi A, Salem SW, et al: Detection of fetal structural abnormalities
with US during early pregnancy. Radiographics 2004; 24(1):157-174.
http://www.ncbi.nlm.nih.gov/pubmed/14730044 (Accessed on June 14, 2012.)
Spencer K, Souter V, Tul N, et al: A screening program for trisomy 21 at
10-14 weeks using fetal nuchal translucency, maternal serum free beta-
human chorionic gonadotropin and pregnancy-associated plasma protein-
A. Ultrasound Obstet Gynecol 1999; 13(4):231-237.
http://www.ncbi.nlm.nih.gov/pubmed/10341399 (Accessed on June 14, 2012.)
Wapner R, Thom E, Simpson JL, et al: First trimester screening for trisomies
21 and 18. N Engl J Med 2003; 349(15):1405-1413.
http://www.ncbi.nlm.nih.gov/pubmed/14534333 (Accessed on June 14, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 394-395.
Comment
Definition and Measurement
The nuchal region of the fetus refers to the soft tissue posterior to the cervical spine or occipital bone. In the rst trimester and early second trimester, the nuchal translucency is
usually measured in the sagittal plane, either transabdominally
or transvaginally. A translucency thickness of more than 3 mm
from 10 to 14 weeks of gestation is considered abnormal. This
measurement should include only the anechoic region between
two hyperechoic (echogenic) lines. Three-dimensional ultrasound has been useful. Figures A and B show increased nuchal
translucency in two rst-trimester fetuses with Down syndrome; Figure C shows a rst-trimester fetus with no abnormal
nuchal translucency. The nding of increased nuchal translucency may be limited to this very narrow gestational window.
Associated Chromosomal Anomalies
After 14 weeks, increased nuchal translucency may resolve, but
the risk for a chromosomal abnormality remains increased.
Increased nuchal thickening or translucency is associated
with chromosomal anomalies, most commonly Down syndrome but also trisomies 13 and 18, Turner syndrome, and
translocations.
Screening
At the present time, screening for chromosomal anomalies
is performed with a maternal serum triple screen between
15 and 20 weeks’ gestation. The triple screen includes analysis
of maternal β-hCG, estriol, and α-fetoprotein. This test
alone has only 60% sensitivity for Down syndrome (slightly
higher when maternal age is considered), with a high falsepositive rate leading to amniocentesis of normal pregnancies.
A newer screen that includes maternal serum free β-hCG
and pregnancy-associated plasma protein A, measurement of
the nuchal translucency, and consideration of maternal age
is usually conducted between 11 and 14 weeks of gestation.
Studies have shown that a combination of nuchal translucency
and serum markers results in a sensitivity of 80% to 90% for
detecting Down syndrome, with only a 5% false-positive rate.
148
CASE 73
A
C
B
History: A woman presents with right lower quadrant pain
3 days postpartum.
1. What should be included in the differential diagnosis of the
mass shown in Figure A? (Choose all that apply.)
A. Arterial aneurysm
B. Arterial pseudoaneurysm
C. Ovarian vein benign thrombosis
D. Ovarian vein tumor thrombus
2. On which side does this condition usually occur?
A. Right
B. Left
C. Thrombosis occurs with equal frequency on both sides.
D
3. Which situation does not predispose women to this
condition?
A. Full-term delivery
B. Ectopic pregnancy
C. Older maternal age
D. Abortion
4. What serious clinical situation has been linked to ovarian
vein thrombosis?
A. Pulmonary embolism
B. Ovarian torsion
C. Endometriosis
D. Cardiomyopathy
149
ANSWERS
CASE 73
Ovarian Vein Thrombosis
1. C and D
2. A
3. C
4. A
References
Brown DL: Pelvic ultrasound in the postabortion and postpartum patient.
Ultrasound Q 2005; 121(1):27-37.
http://www.ncbi.nlm.nih.gov/pubmed/15716756 (Accessed on June 14, 2012.)
Shah AA, Buckshee N, Yankelevitz DF, et al: Assessment of deep
venous thrombosis using routine pelvic CT. AJR Am J Roentgenol 1999;
173(3):659-663.
http://www.ncbi.nlm.nih.gov/pubmed/10470898 (Accessed on June 14, 2012.)
Twickler DM, Setiawan AT, Evans RS, et al: Imaging of puerperal septic
thrombophlebitis: prospective comparison of MR imaging, CT and sonog-
raphy. AJR Am J Roentgenol 1997; 169(4):1039-1043.
http://www.ncbi.nlm.nih.gov/pubmed/9308461 (Accessed on June 14, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, p 237.
Comment
Etiology and Clinical Presentation
Ovarian vein thrombosis is caused by an ascending infection
after an ectopic pregnancy, abortion, vaginal delivery, or cesarean section. Patients are usually seen in the rst week postpartum with fever, lower abdominal pain, or a tender mass.
Ovarian vein thrombosis occurs in less than 2% of postpartum patients. The right ovarian vein is thrombosed in most
cases (80%) (Figure A). Both veins are thrombosed in 15% of
cases; the left ovarian vein is thrombosed in only 6% of cases
(Figures B to D).
Differential Diagnosis
The differential diagnosis of ovarian vein thrombosis includes
other right lower quadrant pathologies, such as appendicitis, tuboovarian abscess, pyelonephritis, ovarian torsion,
endometritis, and hematoma of the broad ligament. Ovarian
vein thrombosis is also classically associated with inammatory disease and gynecologic surgery.
Evaluation with CT and MRI
Cross-sectional imaging modalities can often conrm the diagnosis. CT usually shows well-dened tubular intraperitoneal
masses and the dilated gonadal vein with central low attenuation of thrombus extending from the pelvis to the infrarenal
inferior vena cava. CT and MRI have been found to be comparable in the evaluation of ovarian vein thrombosis (Figure D).
MRI has been shown to differentiate acute from subacute
thrombus using the signal intensity of the clot.
Evaluation with Ultrasound
Because the ovarian vein cannot be consistently identied by
ultrasound, it is the least reliable imaging modality. However,
when detected, a thrombus of the ovarian vein has the typical appearance of a thrombus elsewhere (Figures A to C).
The signs include a hypoechoic or heterogeneous thrombus
(depending on its age) distending the vein, with pain occurring directly over the region. The distended vein can appear
masslike. The two tubular spaces behind the thrombosed vein
(Figure A) are the normal, more deeply and laterally positioned internal iliac artery and vein. Knowledge of the anatomic position of the right ovarian vein, its oblique course
adjacent and lateral to the psoas muscle, and its insertion into
the inferior vena cava 4 cm below the right renal vein origin helps to improve identication. Color Doppler imaging
has been found to be helpful in evaluating the ovarian vein,
inferior vena cava, and renal vein for thrombus propagation.
Enlargement of the ipsilateral ovary is an important secondary nding.
Complications
Complications of ovarian vein thrombosis include right-sided
hydronephrosis, pulmonary or septic emboli, Budd-Chiari
syndrome, hepatic infarction, and renal or inferior vena cava
thrombosis.
150
CASE 74
A
History: A patient undergoes follow-up ultrasound for a
third-trimester fetus with large bowel obstruction.
1. What should be included in the differential diagnosis of a
dilated fetal colon? (Choose all that apply.)
A. Meconium plug syndrome
B. Hirschsprung disease
C. Cancer of the colon
D. Anorectal atresia
2. How is sacral agenesis related to the etiologies of bowel
obstruction?
A. It is part of the caudal regression syndrome.
B. It causes an aganglionic segment of distal colon.
C. It causes meconium buildup.
D. It causes bowel infarct.
B
H = heart.
3. At what gestational age is colon dilation from anorectal
atresia likely to be diagnosed on ultrasound?
A. After 22 weeks
B. After 16 weeks
C. After 12 weeks
D. After 21 weeks
4. Which of the following bowel dilation pathologies or syndromes is not related to maternal diabetes mellitus?
A. Anorectal atresia
B. Caudal regression syndrome
C. Hirschsprung disease
D. Meconium plug syndrome
151
ANSWERS
CASE 74
Large Bowel (Anorectal) Atresia
1. A, B, and D
2. A
3. A
4. C
References
Harris RD, Nyberg DA, Mack LA, et al: Anorectal atresia: prenatal sono-
graphic diagnosis. AJR Am J Roentgenol 1987; 149(2):395-400.
http://www.ncbi.nlm.nih.gov/pubmed/3300224 (Accessed on June 14, 2012.)
Vijayaraghavan SB, Prema AS, Saganyadevi P: Sonographic depiction of the
fetal anus and its utility in the diagnosis of anorectal malformations.
J Ultrasound Med 2011; 30(1):37-45.
http://www.ncbi.nlm.nih.gov/pubmed/21193703 (Accessed on June 14, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 436-439.
Comment
Fetal Large Bowel Dilation
The fetal bowel normally becomes more dilated with increasing gestational age. Normal fetuses have a mean colon
diameter of 15 to 16 mm at term, and the upper limits of
normal approach 20 mm. A dilated colon is often peripheral in location (Figures A and B); however, some cases of
small bowel dilation can appear peripheral. Tracing the dilation to the rectosigmoid colon in the pelvis (Figure B) aids
in conrming that the obstructed bowel is colon. Peristalsis
has been described in dilated large bowel loops but would
be considered unusual (dilated small bowel loops more commonly show peristalsis). The differential diagnosis of dilated
colon includes Hirschsprung disease, anorectal atresia, and
meconium plug syndrome; the latter two are associated with
maternal diabetes.
Anorectal Atresia
Anorectal atresia is often one manifestation of a spectrum of
anomalies as part of the VACTERL syndrome, which includes
vertebral, anorectal, cardiovascular, tracheoesophageal, renal,
and limb anomalies. Almost 75% of affected neonates have
such associated malformations. In anorectal atresia, the bowel
dilation is often greater than 2 standard deviations above the
mean for any given gestational age. Anorectal atresia can also
be seen as part of caudal regression syndrome. A careful search
for associated anomalies is imperative because one ultrasound
series showed other VACTERL anomalies in more than 90%
of the fetuses with anorectal atresia.
Ultrasound Imaging of Large Bowel Obstruction
One series showed that prenatal ultrasound detects less than
10% of cases of large bowel obstruction. The presence of
dilated bowel in anorectal atresia correlates with the gestational
age. The bowel does not dilate before 22 weeks of gestation,
but progressive dilation is often present and can be detected
after 27 weeks. Failure to visualize the fetal anus on ultrasound
is diagnostic of an anorectal malformation. The presence of
a perineal stula does not correlate with degree of bowel dilation. Oligohydramnios and occasionally polyhydramnios have
been reported, both probably related to the commonly present
additional abnormalities.
152
CASE 75
A
B
History: A pregnant woman known to be carrying twins
presents for a routine assessment.
1. What should be included in the differential diagnosis of
a twin pregnancy without a clear membrane between two
fetuses with one placenta? (Choose all that apply.)
A. Monochorionic diamniotic
B. Dichorionic monoamniotic
C. Monochorionic monoamniotic
D. Dichorionic diamniotic
2. What type of twin pregnancy is represented in Figures A
and B?
A. Monochorionic diamniotic
B. Dichorionic monoamniotic
C. Monochorionic monoamniotic
D. Dichorionic diamniotic
C
D
3. In what percentage of twin pregnancies are the twins in
separate amniotic cavities?
A. 20%
B. 99%
C. 80%
D. 10%
4. What is the Spalding sign?
A. The vanishing twin
B. Decreased amniotic uid
C. Absence of a fetal heart rate
D. Overlapping of calvarial sutures after fetal death
153
ANSWERS
CASE 75
Second-Trimester Twin Gestation and Fetal
Demise
1. A and C
2. A
3. C
4. D
References
Bromley B, Benacerraf B: Using the number of yolk sacs to determine
amnionicity in early rst trimester monochorionic twins. J Ultrasound Med
1995; 14(6):415-419.
http://www.ncbi.nlm.nih.gov/pubmed/7658507 (Accessed on June 14, 2012.)
Crow HC: Trouble with twins. Appl Radiol 1996; 25:19-24.
Feldstein VA, Filly RA: Complications of monochorionic twins. Radiol Clin
North Am 2003; 41(4):709-727.
http://www.ncbi.nlm.nih.gov/pubmed/12899487 (Accessed on June 14, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 375, 516-521, 523-527.
Comment
Types of Twin Gestations
In 80% of cases, twin gestations occur in their own separate sacs
(dichorionic-diamniotic [Di-Di]) and have separate environments. In the other 20% of twin gestations, the twins develop
within the same monochorionic environment, either partially
or completely. They partially share the same environment and
are diamniotic (monochorionic-diamniotic [Mono-Di]) or
completely share the same environment and are monoamniotic
(Mono-Mono), both with intermingled placental circulations.
Spontaneous Loss of a Fetus
The rate of spontaneous abortion (miscarriage) in singleton
pregnancies is approximately 20% to 25%. This rate is slightly
higher in twin gestations. In a monochorionic twin gestation,
because of the shared circulation, the dead twin may adversely
affect the living twin. In the second and third trimesters, a
spontaneous loss of one of the twins is uncommon. However,
even in Di-Di twin pregnancies, the loss rate is slightly higher
than in singleton pregnancies, partly because of the higher incidence of growth restriction. With monochorionic pregnancies,
there are additional problems because of the shared placental
circulation, which could lead to a twin-twin transfusion. Late in
a Mono-Mono pregnancy, there is also the potential complication of fetal demise caused by entangled umbilical cords.
Types of Twin Gestations, Ultrasound Imaging,
and Fetal Loss
The diagnosis of diamniotic twins in a monochorionic pregnancy can be made early in the rst trimester with ultrasound
identication of two yolk sacs, before the amniotic membrane can be seen; an abnormal empty sac; a sac containing
an embryo without heart motion; or an abnormal yolk sac. In
a Di-Di pregnancy, a rst-trimester loss of one of the twins
may not be noticed. If incidentally detected by ultrasound, the
dead twin is shown by an abnormal empty sac, a sac containing an embryo without heart motion, or an abnormal yolk sac.
In these cases, if the pregnancies are followed, the dead twin
“vanishes,” leaving one developing gestational sac. In a monochorionic twin gestation, because of the shared circulation, the
dead twin may adversely affect the living twin.
When there is a loss of a twin in a Di-Di pregnancy in
the second or third trimester, the demise should not adversely
affect the living fetus. The dead fetus has no detectable heart
motion. Because autolysis occurs within the rst week, the
dead fetus loses its internal anatomy and begins to collapse.
The head of the dead fetus B (Figure D) shows no demonstrable internal anatomy and overlapping of calvarial sutures
(arrow); this is called the Spalding sign. In addition, there
appears to be a decrease in the amount of amniotic uid in the
sac surrounding fetus B (Figures A and B), a nding also noted
in fetal demise. The increased echogenicity of the uid is of
uncertain signicance.
The diagnosis of a dichorionic pregnancy is important
because it helps predict the risk to the remaining fetus. This
risk can be determined by the following: different fetal genders, separate placentas, or a thick (1 to 2 mm) and well-dened
membrane. The membrane is better dened in the rst trimester, but when clearly seen in the second or third trimester it is
indicative of a diamniotic pregnancy (Figures A and B).
The dead twin in the second and third trimesters does not
“vanish.” Instead, in a Di-Di pregnancy, the fetus may atten
and be pushed to one side but may still be visible even at term.
This is called a fetus papyraceus (“paper fetus”). This fetus,
although not directly impinging on the other fetus, may cause
spontaneous labor or, at term, may block the exit of the normal fetus. If the pregnancy is monochorionic, the shared placental circulation may create signicant problems for the living
remaining fetus, most likely owing to disseminated intravascular coagulopathy; this can cause in utero demise or destructive
(embolic) changes in the surviving fetus.
154
CASE 76
A
Courtesy of Beryl Benacerraf, MD.
B
Courtesy of Beryl Benacerraf, MD.
History: Several asymptomatic patients present for prenatal
ultrasound imaging.
1. What should be included in the differential diagnosis of the
bony abnormalities including the skull demineralization in
Figure C? (Choose all that apply.)
A. Osteogenesis imperfecta
B. Congenital hypophosphatasia
C. Achondrogenesis
D. Down syndrome
2. What is the underlying biochemical abnormality in osteogenesis imperfecta?
A. Defective type I collagen
B. Elevated glucose
C. Elevated triglycerides
D. Low phosphate
C
B = bladder; H = fetal head; P = placenta.
3. What is the general outcome of fetuses with osteogenesis
imperfecta?
A. Early neonatal death
B. Mild afiction, osteoporosis
C. Early fetal death
D. Range from mild afiction to early neonatal death
4. What is the basis of the classication system for osteogenesis imperfecta (types I through IV)?
A. Genetic criteria only
B. Ultrasound criteria only
C. Clinical criteria only
D. Genetic, ultrasound, and clinical criteria
155