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ANSWERS
CASE 22
Conjoined (Siamese) Twins in the First
Trimester
1. B and C
2. B
3. A
4. B
References
Feldstein VA: Complications of monochorionic twins. Radiol Clin North Am
2003; 41(4):709-727.
http://www.ncbi.nlm.nih.gov/pubmed/12899487 (Accessed on June 5,
2012.)
Fong KW, Ants T, Salem S, 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 5,
2012.)
Luewan S, Sukpan K, Yanase Y, et al: Prenatal diagnosis of cephalothora-
copagus janiceps: sonographic-pathologic correlation. J Ultrasound Med
2010; 29(11):1657-1661.
http://www.ncbi.nlm.nih.gov/pubmed/20966479 (Accessed on June 5,
2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 516, 525-526.
Comment
Fraternal Twins
Most twins (80%) are fraternal, originating from two separate
fertilized ova within separate sacs (their own amniotic and
chorionic sacs), and are Di-Di twins. Ultrasound images show
either two separate sacs or a distinct, intervening membrane
(>2 mm) if the sacs impinge on each other. In the rst trimester, the accuracy of detection of a Di-Di twinning by transabdominal imaging is approximately 100%.
Identical Twins
In the remaining 20% of twin pregnancies, a single fertilized
ovum starts to develop and then splits into “identical” twins of
the same gender. If this split occurs within the rst day (20%
to 30% of cases), the twins develop in completely separate
Di-Di sacs similar to true fraternal twins.
Monochorionic-Diamniotic Twins
In the remaining cases of identical twins, the fertilized ovum
splits later and is enveloped by a single chorion (monochorionic). The twins share the same environment, either partially (monochorionic-diamniotic [Mono-Di]) or completely
(monochorionic-monoamniotic [Mono-Mono]). Mono-Di
twinning (70% to 75% of identical twins) occurs 1 to 7 days
after fertilization. The ultrasound nding of a thin intervening
diamniotic membrane is difcult to detect but is seen most
consistently in the rst trimester.
Monochorionic-Monoamniotic Twins
In the remaining 1% to 3% of cases of identical twins, with
the split occurring between days 7 and 13, the twins completely
share the same environment. This is a Mono-Mono pregnancy
without an intervening membrane. A transvaginal study is
needed in the rst trimester. The diagnosis of no interposed
membrane is accurate. Later in the pregnancy, the diagnosis of
a Mono-Mono twinning is less certain. The presence of one
yolk sac early in the rst trimester should prompt a follow-up
scan to assign amnionicity. All twin pregnancies are at risk for
perinatal morbidity and mortality; the potential for problems is
greater when the twins share the same amniotic sac.
Conjoined Twins
Rarely, in less than 1%, the fertilized ovum separates after 13 to
15 days. The twins not only share the same sac (Mono-Mono
twinning) but also cannot be separated; this is conjoined (Siamese) twinning. The twins are most commonly conjoined in the
thoracic region (thoracopagus). Conjoined twins can be joined
from the head (craniopagus) to the pelvis (ischiopagus). Delivery
must be by cesarean section because of the size of the twins.
Diagnosis of conjoined twins in the late rst trimester is
possible. It is necessary to show that the twins are inseparable
(Figure A, which suggests that the fetal heads are joined) but
also to show that they share internal structures (Figure B, which
is a scan through the fetal heads). To help dene this case of
craniopagus, a three-dimensional surface imaging reconstruction was performed (Figure C). Three-dimensional reformatting was important in this case (Figures A to C) and should be
considered whenever the fetal anatomy is difcult to image.
Currently, two-dimensional ultrasound is the primary tool.
46
CASE 23
A
History: A patient presents with a fetal scan that was
obtained at 18 weeks’ gestation and shows an echogenic mass
in the thorax.
1. What should be included in the differential diagnosis of the
echogenic left lung mass seen in Figure A? (Choose all that
apply.)
A. Congenital cystic adenomatoid malformation (CCAM)
B. Congenital pulmonary airway malformation (CPAM)
C. Bronchogenic cyst
D. Neuroenteric or duplication cyst
E. Bronchopulmonary sequestration
2. Which of the following statements concerning CCAM/
CPAM is not true?
A. These lesions are often bilateral.
B. These lesions may be cystic, solid, or mixed.
C. The pulmonary artery supplies the mass.
D. In unilateral cases, they may be either right sided or left
sided.
B
Used with permission from Anderson Publishing Ltd. from Victoria T,
et al: Fetal MRI of common non-CNS abnormalities: a review. Appl
Radiol 2011;40(6)8-17. © Anderson Publishing Ltd.
3. Which of the following statements concerning CCAM/
CPAM is not true?
A. Hydrops fetalis occurs in most cases of CCAM/CPAM.
B. Most fetuses that do not develop fetal hydrops have a
fairly good outcome.
C. Fetuses that develop fetal hydrops often have an omi-
nous outcome.
D. Some CCAM/CPAM lesions are noted to decrease in
size during gestation.
4. Which of the following statements concerning therapeutic
options for cases of CCAM/CPAM is false?
A. A lung mass in an asymptomatic newborn should be
resected.
B. A thoracoamniotic shunt can be performed successfully
in the cystic component of CCAM/CPAM.
C. In utero surgery should not be considered in most cases
of CCAM/CPAM.
D. In high-risk fetuses, ex utero intrapartum therapy
(EXIT) is the treatment of choice.
47
ANSWERS
CASE 23
Congenital Cystic Adenomatoid Malformation
(CCAM)/Congenital Pulmonary Airway
Malformation (CPAM)
1. A, B, and E
2. A
3. A
4. D
References
Curren PF, Jelin EB, Rand L, et al: Prenatal steroids for microcystic congeni-
tal cystic adenomatoid malformations. J Pediatr Surg 2010; 45(1):145-150.
http://www.ncbi.nlm.nih.gov/pubmed/20105595 (Accessed on June 5,
2012.)
Thorpe-Beeston JG, Nicolaides KH: Cystic adenomatoid malforma-
tion of the lungs: prenatal diagnosis and outcome. Prenat Diagn 1994;
14(8):677-688.
http://www.ncbi.nlm.nih.gov/pubmed/7991510 (Accessed on June 5, 2012.)
Tsao K, Hawgood S, Vu L, et al: Resolution of hydrops fetalis in congenital
cystic adenomatoid malformation after prenatal steroid therapy. J Pediatr
Surg 2003; 38(3):508-510.
http://www.ncbi.nlm.nih.gov/pubmed/12632377 (Accessed on June 5,
2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 419-426.
Comment
Differential Diagnosis
The differential diagnosis of an echogenic lung mass includes
CCAM/CPAM. Bronchopulmonary sequestration should also
be included in the differential diagnosis. In some cases, CCAM/
CPAM may be combined with other entities such as bronchial
atresia and lobar emphysema. Congenital diaphragmatic hernia
also may be considered within the differential diagnosis. Congenital diaphragmatic hernia may appear cystic, solid, or mixed.
The solid component is due to multiple loops of small bowel
that are herniated in the thorax. Isolated bronchial obstruction
may be unilateral with the appearance of an enlarged echogenic mass. If congenital high airway obstruction syndrome is
present, it appears as bilateral enlarged echogenic lungs.
Ultrasound Findings
CCAM/CPAM may appear as cystic, solid, or mixed (Figure
A). In one series, 60% were mainly macrocystic, and 40% were
microcystic with multiple small cysts that appeared solid on
ultrasound. CCAM/CPAM can be distinguished from bronchopulmonary sequestration by identifying pulmonary arteries
supplying the mass. In bronchopulmonary sequestration, an
artery from the thoracic aorta supplies the extra lobar sequestration. However, these lesions have been resected and found
to have components of both CCAM/CPAM and bronchopulmonary sequestration in the same mass, and the term hybrid
lesions has been used for these cases. There may be mass effect
from CCAM/CPAM, which can cause obstruction of venous
ow to the heart and resultant fetal hydrops. For larger masses,
frequent scanning is needed to aid early detection of fetal
hydrops, which has a poor prognosis. In some cases, CCAM/
CPAM lesions have been noted to regress. On follow-up chest
x-rays these lesions are not seen; however, when CT is performed, there are always some residual elements of CCAM/
CPAM present in the neonate. In utero MRI may identify the
lesion, the effect on surrounding structures, and resultant
hydrops (Figure B).
Prognosis and Management
The prognosis for CCAM/CPAM is usually good. Although
these lesions may be associated with other abnormalities such
as chromosomal abnormalities or renal abnormalities, this incidence is fairly small. However, the incidence is large enough
that when these lesions are detected, chromosomal analysis
may be warranted. In most series, the survival rate for CCAM/
CPAM is in the range of 75%. However, if cases that do
not have fetal hydrops are separated from cases that develop
hydrops, there are two distinct fetal outcomes. The outcome
is very good in cases that do not develop fetal hydrops. The
outcome is poor in cases that develop hydrops, with a reported
fetal or neonatal death rate of 90%. Treatment options in
high-risk fetuses include close follow-up, early delivery, and a
course of steroids such as betamethasone. In addition, if there
is a large cyst and there is impending hydrops, the cyst may
be aspirated or shunting to the amniotic uid has been advocated. Another possible complication is the development of
the maternal “mirror syndrome,” which occurs when the fetus
develops hydrops and the mother “mirrors” the sick fetus by
developing swelling and high blood pressure. When this complication occurs, immediate delivery of the fetus is required
because the mirror syndrome is potentially life threatening to
the mother.
48
CASE 24
L
R
A
Arrows = associated fused thalami; L = left; R = right.
C
History: A patient presents with an ultrasound scan that
was obtained at an outside institution and that shows a cystic
brain mass.
1. What should be included in the differential diagnosis?
(Choose all that apply.)
A. Hydranencephaly
B. Semilobar holoprosencephaly
C. Massive hydrocephalus
D. Alobar holoprosencephaly
E. Lobar holoprosencephaly
2. Which of the following is not a common facial nding in a
fetus with alobar holoprosencephaly?
A. Cyclopia
B. Ethmocephaly
C. Cebocephaly
D. Lateral cleft lip
3. What is the most common chromosomal abnormality asso-
ciated with alobar holoprosencephaly?
A. Trisomy 13
B. Trisomy 18
C. Trisomy 21
D. XO (Turner syndrome)
4. Survival of infants with alobar holoprosencephaly is closest
to what percentage?
B
A. 10%
B. 30%
C. 55%
D. 85%
49
ANSWERS
CASE 24
Holoprosencephaly
1. B and D
2. D
3. A
4. A
References
Dill P, Poretti A, Boltshauser E, et al: Fetal magnetic resonance imaging in
midline malformations of the central nervous system and review of the
literature. J Neuroradiol 2009; 36(3):138-146.
http://www.ncbi.nlm.nih.gov/pubmed/19157551 (Accessed on June 5,
2012.)
McGahan JP, Nyberg DA, Mack LA: Sonography of facial features of
alobar and semilobar holoprosencephaly. AJR Am J Roentgenol 1990;
154(1):143-148.
http://www.ncbi.nlm.nih.gov/pubmed/2104699 (Accessed on June 5, 2012.)
McGahan JP, Pilu G, Nyberg DA: Cerebral malformation. In Nyberg DA,
McGahan JP, Pretorius DH, et al. (eds): Diagnostic Imaging of Fetal
Anomalies. Philadelphia: Lippincott Williams & Wilkins, 2003, pp 221-290.
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 383-387, 389.
Comment
Differential Diagnosis
The differential diagnosis of midline intracranial abnormality
is quite large. However, the differential diagnosis of a massive
cystic midline abnormality is relatively small and includes massive hydrocephalus, hydranencephaly, and either alobar or semilobar holoprosencephaly. With massive hydrocephalus, there
are cerebral tissue, midline structures, and separate thalami.
Choroid plexus can be seen dangling in the lateral ventricles.
Hydranencephaly is usually characterized by lack of cerebral
tissue, the presence of a midline falx, and nonfused thalami.
Ultrasound Findings
The most common form of holoprosencephaly detected
prenatally is the alobar form. In this form, there is a
monoventricular cavity (Figure A) that may protrude posteriorly with a dorsal sac. Other midline structures are lacking with fused thalami and midline facial abnormalities. In
one series, 90% of prenatally diagnosed cases of holoprosencephaly had associated facial anomalies. The most severe
anomaly is cyclopia (fused orbits, with a proboscis above the
orbits) (Figures B and C). Other midline abnormalities include
various degrees of hypotelorism, nasal abnormalities, and a
median cleft lip. In semilobar holoprosencephaly, the frontal
horns of the lateral ventricles are fused but the occipital horns
are separate.
Prognosis and Management
The prognosis of alobar holoprosencephaly and the rarer
form of semilobar holoprosencephaly is nearly uniformly
fatal. When this condition is recognized in utero, many fetuses
die spontaneously, others are terminated, and a few are born
but die soon after birth. In a series by McGahan et al., of 27
cases of prenatally diagnosed alobar or semilobar holoprosencephaly, 24 had pathologically conrmed facial anomalies,
including cyclopia (n = 5), ethmocephaly (n = 3), cebocephaly
(n = 3), midline cleft lip (n = 8), lateral cleft lip (n = 2), and
hypotelorism (n = 3). Not all facial anomalies were noted on
ultrasound.
Alobar holoprosencephaly is often associated with non–
central nervous system malformations. These may not always
be recognized because of the focus on the severity of the brain
and face abnormalities. Renal dysplasia, omphalocele, bowel
atresia, and cardiac anomalies may be present.
Trisomy 13 is the most common chromosomal abnormality
associated with lobar holoprosencephaly, although trisomy 18,
triploidy, trisomy 22, and partial chromosomal defects may be
seen. In the series by McGahan et al., of 27 cases diagnosed
prematurely, 13 fetuses died in utero or were terminated, 13
newborns died shortly after birth, and only 3 infants left the
hospital.
50
CASE 25
DD
A
History: A 29-year-old woman presents with infertility.
Images of the right ovary are provided; the left ovary has a
similar appearance.
1
1. What is the diagnosis for this patient based on the appear-
ance of the ovaries?
A. Dermoid cysts
B. Polycystic ovaries
C. Corpus luteum cyst
D. Endometriosis
2. What is an alternative to surgery to treat this patient?
A. Progesterone treatment
B. Estrogen treatment
C. Fertility medication
D. Gonadotropin-releasing hormone agonist
3. What is the associated syndrome for this entity?
B
A. Curtis-Fitzhugh syndrome
B. Stein-Leventhal syndrome
2
1
C. Marfan syndrome
D. Lynch syndrome
4. What are the typical ndings in this syndrome (Figures A
to D)?
A. Atrophic ovaries with dystrophic calcications
B. Large shadowing calcications
C. Volume greater than 10 mL, 12 or more follicles 2 to 9
mm in diameter in the periphery, and alopecia
D. Volume greater than 10 mL, 12 or more follicles 2 to 9
mm in diameter in the periphery, and hirsutism
C
51
ANSWERS
CASE 25
Polycystic Ovarian Disease
1. B
2. C
3. B
4. D
References
Balen AH, Laven JS, Tan SL, et al: Ultrasound assessment of the polycys-
tic ovary: international consensus denitions. Hum Reprod Update 2003;
9(6):505-514.
http://www.ncbi.nlm.nih.gov/pubmed/14714587 (Accessed on June 5,
2012.)
Barbieri RL: Metformin for the treatment of polycystic ovary syndrome.
Obstet Gynecol 2003; 101(4):785-793.
http://www.ncbi.nlm.nih.gov/pubmed/12681887 (Accessed on June 5,
2012.)
Hopkinson ZEC, Satter N, Fleming R, et al: Polycystic ovarian syndrome: the
metabolic syndrome comes to gynaecology. BMJ 1998; 317(7154):329-333.
http://www.ncbi.nlm.nih.gov/pubmed/9685283 (Accessed on June 5, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 566-567, 569.
Comment
Ultrasound Imaging of Polycystic Ovarian Disease
PCOD has a spectrum of ultrasound and clinical ndings. The
full-blown clinical syndrome of PCOD comprises hirsutism,
infertility, and oligomenorrhea; this is called Stein- Leventhal
syndrome. In these cases, there are frequently abnormal serum
antigens or an increased ratio of luteinizing hormone to follicle-stimulating hormone. Stein-Leventhal syndrome is the most
common form of anovulatory infertility. Ultrasound ndings
do not always correlate with clinical and biochemical ndings.
The most common ovarian feature is multiple small follicles
5 to 8 mm, typically peripherally located (Figures A to D).
The classic appearance of PCOD is rounded enlarged ovaries,
commonly at least greater than 10 mL in volume (length ×
width × height ÷ 2) (Figures B and C). However, polycystic
ovaries may be normal in size, ovoid instead of round, and
not enlarged. Polycystic ovaries are more vascular than normal
(Figure D). A more recent international joint consensus meeting concluded that the denition of polycystic ovaries should
have at least one of the following: either 12 or more follicles
measuring 2 to 9 mm in diameter or increased ovarian volume
greater than 10 mL. Under these new criteria, a description
of the stroma is not required for the diagnosis. A recent publication suggests 3D sonography as better than 2D sonography for assessing and studying ovarian morphology because it
facilitates measurements of the follicular count, total ovarian
and stromal echogenicity, and ovarian volume and blood ow.
Polycystic ovaries can be detected incidentally in normally fertile women who do not have additional problems. The clinical
signicance of polycystic ovaries is based on clinical symptoms and laboratory ndings.
Treatment of Polycystic Ovary Disease
Polycystic ovaries are known pathologically to have brous
capsules. The capsules cannot be appreciated by ultrasound,
but their presence has been thought to be the cause of infertility because the follicles could not rupture and release their
ova. As a result, past treatment was surgical wedge resection
of the ovary to disrupt this capsule. The actual etiology of
the condition is unknown. However, with the advent of fertility medicines, in particular, clomiphene citrate, the treatment
has become hormonal. Gonadotropins have often been used.
More recent evidence suggests that the underlying disorder is
insulin resistance. The resulting hyperinsulinemia stimulates
excess ovarian androgen production. Metformin is now used
to treat PCOD.
52
CASE 26
History: An asymptomatic pregnant patient with a second-
trimester pregnancy undergoes ultrasound.
1. What is the diagnosis for the appearance of the atrium of
the lateral ventricles?
A. Hydrocephalus
B. Porencephaly
C. Dandy-Walker cyst
D. Choroid plexus cyst
2. Which of the following entities is not a cause of
hydrocephalus?
A. Aqueductal stenosis
B. Mass in ventricular system
C. Arnold-Chiari malformation
D. Dangling choroid plexus
3. What is the normal range in size of the atrium of the lateral
ventricle?
A. 4 to 10 mm
B. 2 to 4 mm
C. 10 to 22 mm
D. Less than 1 mm
4. Which of the following statements is true?
A. Asymmetric hydrocephalus has fewer associated anom-
alies than symmetric hydrocephalus.
B. Hydrocephalus is rarely associated with anomalies.
C. Prenatal shunt placement benets a communicating
hydrocephalus.
D. The natural progression of hydrocephalus is clear.
53
ANSWERS
CASE 26
Hydrocephalus
1. A
2. D
3. A
4. A
References
D’Addario V: The role of ultrasonography in recognizing the cause of fetal
cerebral ventriculomegaly. J Perinat Med 2004; 32(1):5-12.
http://www.ncbi.nlm.nih.gov/pubmed/15008380 (Accessed on June 5,
2012.)
Davis GH: Fetal hydrocephalus. Clin Perinatol 2003; 30(3):531-539.
http://www.ncbi.nlm.nih.gov/pubmed/14533894 (Accessed on June 5,
2012.)
Durfee SM, Kim FM, Benson CB: Postnatal outcome of fetuses with the
prenatal diagnosis of asymmetric hydrocephalus. J Ultrasound Med 2001;
20(3):263-268.
http://www.ncbi.nlm.nih.gov/pubmed/11270531 (Accessed on June 5,
2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 376, 379, 381-383, 404-406.
Comment
Ultrasound Imaging of Hydrocephalus
Fetal hydrocephalus can be diagnosed with prenatal ultrasound
by detecting an enlarged atrium of the lateral ventricle. The
upper limits of normal are 8 mm before 25 weeks’ gestation
and 10 mm later in the gestation period. The normal choroid plexus should ll 50% to 60% of the lateral ventricle. In
the setting of hydrocephalus, choroid is surrounded by uid
within the dilated ventricle and appears to dangle—an important secondary sign.
Care must be taken to obtain an accurate measurement of the lateral ventricle. The atrium must be measured
perpendicularly at the edge of the choroid plexus. False
enlargement can be diagnosed if the interface with the subarachnoid space is misinterpreted as the lateral border of the
ventricle; in addition, the medial boundary of the cerebral
hemisphere must not be mistaken for the medial border of
the lateral ventricle. Typically, the lateral ventricle farther
from the transducer is better seen, whereas the closer ventricle is obscured by reverberation artifact from the overlying
calvaria (see Figure).
Etiology and Progression of Hydrocephalus
The etiology of hydrocephalus may be difcult to determine
in utero. Its natural progression is not entirely understood. It
is almost always associated with other intracranial and extracranial anomalies. Aqueductal stenosis manifests with enlarged
third and lateral ventricles but a small fourth ventricle. ArnoldChiari malformation consists of a myelomeningocele, a small
posterior fossa, and associated ventriculomegaly and a lemonshaped skull early in the gestation. An obstructing mass is an
uncommon cause of fetal hydrocephalus. Asymmetric hydrocephalus has fewer associated anomalies compared with symmetric hydrocephalus, and the asymmetric type has a better
prognosis.
54
CASE 27
A
B
History: A 30-year-old patient with a second-trimester
pregnancy is referred because of an abnormal ultrasound scan.
1. What should be included in the differential diagnosis?
(Choose all that apply.)
A. Congenital cystic adenomatoid malformation or con-
genital pulmonary airway malformation
B. Neuroblastoma
C. Congenital diaphragmatic hernia
D. Subdiaphragmatic sequestration
E. Duodenal atresia
C
Used with permission from Anderson Publishing Ltd., from Victoria
T, et al: Fetal MRI of common non-CNS abnormalities: a review. Appl
Radiol 40(6):8-17, 2011. © Anderson Publishing Ltd.
2. Color Doppler imaging can help in making the diagnosis by
identifying what body part?
A. Urinary tract
B. Tracheobronchial tree
C. Pulmonary artery
D. Systemic artery
3. Which of the following entities is not associated with
sequestration?
A. Tracheoesophageal stula
B. Hydrothorax
C. Congestive heart failure
D. Cystic hygroma
4. What is the least likely location of extralobar sequestration?
A. Left upper lobe
B. Left lower lobe
C. Under the diaphragm
D. Right lower lobe
55