CHAPTER 12 • The Fetal Gastrointestinal System
INTRODUCTION
Ultrasound examination of the fetal abdomen in the first trimester includes the
assessment of abdominal organs from the diaphragm superiorly to the genitalia
inferiorly. This ultrasound examination allows for the determination of fetal abdominal
situs and for the anatomic evaluation of major organs in the gastrointestinal and
genitourinary systems. This chapter focuses on the gastrointestinal tract, whereas the
genitourinary system is discussed in the following chapter.
EMBRYOLOGY
The primitive gut is formed during the sixth menstrual week when the flat embryonic
disc folds to form a tubular structure that incorporates the dorsal part of the yolk sac
into the embryo (Fig. 12.1A–C). Ventral folding of the cranial, lateral, and caudal
sections of the primitive gut forms the foregut, midgut, and hindgut, respectively (Fig.
12.2). In this process, the yolk sac remains connected to the midgut by the vitelline
vessels (Fig 12.2). Three germ layers contribute to the formation of the gut, with the
endoderm giving rise to the mucosal and submucosal surfaces; the mesoderm to the
muscular, connective tissue and serosal surfaces; and the neural crest to the neurons and
nerves of the submucosal and myenteric plexuses. The primitive gut is initially formed
as a hollow tube, which is blocked by proliferating endoderm shortly after its formation.
Recanalization occurs over the next 2 weeks by degeneration of tissue, and a hollow
tube is formed again by the eighth menstrual week. Abnormalities of the recanalization
process result in atresia, stenosis, or duplication of the gastrointestinal tract.
The foregut, supplied by the celiac axis, gives rise to the trachea and respiratory
tract (see Chapter 10), esophagus, stomach, liver, pancreas, upper duodenum, gall
bladder, and bile ducts. The midgut, supplied by the superior mesenteric artery, gives
rise to the lower duodenum, jejunum, ileum, cecum, ascending colon, and proximal twothirds of transverse colon. The hindgut, supplied by the inferior mesenteric artery, gives
rise to the distal one-third of transverse colon, descending colon, sigmoid, rectum, andurogenital sinus. Because of lengthening of the gut and enlargement of upper abdominal
organs, an intestinal loop from the midgut protrudes through the umbilical cord insertion
into the abdomen at about the sixth week of embryogenesis (from fertilization). This
intestinal loop returns to the intraabdominal cavity by about the 10th week of
embryogenesis (from fertilization). Through the embryologic process, the midgut loop
undergoes a series of three 90-degree counterclockwise rotations around the superior
mesenteric artery.
Figure 12.1: Axial views (A–C) of the developing embryo from the fourth week
of gestation showing the formation of the primitive gut tube. Note the
incorporation of part of the yolk sac into the embryo, shown in A and B and the
primitive gut tube “gut” shown in C. See text for details.Figure 12.2: Schematic drawing of a sagittal view of the embryo at
approximately 5 to 6 menstrual weeks showing the formation of the primitive
gastrointestinal tract (foregut, midgut, and hindgut) and the liver bud. Note the
connection of the midgut to the vitelline duct. See text for details.
NORMAL SONOGRAPHIC ANATOMY
Sonographic visualization of the anatomy of the fetal abdomen is easily achieved in
early gestation by the axial, sagittal, and coronal views of the fetus. We recommend a
review of Chapter 5 on the systematic approach using the detailed first trimester
ultrasound examination.
Axial Planes
The authors recommend the systematic evaluation of abdominal organs through three
axial planes at the level of the upper abdomen (subdiaphragmatic—stomach) (Fig.
12.3), mid-abdomen (cord insertion) (Figs. 12.4 and 12.5), and the pelvis (bladder)
(Fig. 12.6). In the upper abdominal axial plane, the fluid-filled anechoic stomach is
imaged in the left upper abdomen and the slightly hypoechoic liver, as compared to the
lungs, is seen to occupy the majority of the right abdomen (Fig. 12.3). The stomach is
consistently seen at 12 weeks of gestation and beyond. This axial plane in the upper
abdomen (Fig. 12.3) is important for the assessment of the abdominal situs (see later).
In normal situs, the stomach occupies the left side of the abdomen, the liver and gall
bladder occupy the right side of the abdomen, and the inferior vena cava (IVC) is seen
anterior and to the right side of the descending aorta (Fig. 12.3B). The gall bladder isusually seen in about 50% of fetuses by the 13th week of gestation and practically in all
fetuses by the 14th week of gestation.1 The mid-abdominal axial plane is important for
the assessment of the cord insertion into the abdomen and the anterior abdominal wall
(Fig. 12.4). In the mid-abdominal axial plane, the bowel is seen with a slightly
hyperechoic sonographic appearance when compared to the liver (Fig. 12.4). Both
kidneys can be seen in cross-section in the posterior aspect of the abdomen (Fig.
12.4A). It is important to note that physiologic bowel herniation is noted up until the
12th week of gestation (Fig. 12.5). Studies have shown that the midgut herniation should
not exceed 7 mm in transverse measurements at any gestation and that the physiologic
herniation is almost never seen at crown-rump length measurements exceeding 45 mm.2,3
The axial plane at the level of the pelvis reveals the bowel surrounding a small urinary
bladder (Fig. 12.6). The two iliac crests can be seen in this plane in the posterior aspect
of the pelvis (Fig. 12.6B). A slightly oblique plane of the pelvis in color Doppler
demonstrates the two umbilical arteries surrounding the urinary bladder with an intact
abdominal wall (Fig. 12.6B).
Figure 12.3: Axial planes at the level of the upper abdomen in two fetuses at
13 weeks of gestation. The fetus in A was examined transabdominally and the
fetus in B transvaginally. Note the presence of fluid-filled stomachs (asterisks)
in the upper left abdomen in A and B. Ribs (arrows) are visualized bilaterally
along with the liver and inferior vena cava (IVC) in the right (R) abdomen. The
descending aorta (DAo) is seen posterior and to the left of the IVC. Improved
resolution is noted in fetus in B because of the transvaginal approach, thusallowing clear depiction of the IVC and DAo. L, left.
Figure 12.4: Axial plane of the middle abdomen in gray scale (A) and color
Doppler (B) at the level of the umbilical cord attachment (arrow) in a fetus at 12
weeks of gestation. Note the presence of an intact anterior abdominal wall
(arrow) and the fetal bowel appearing slightly more hyperechoic than
surrounding tissue. Both kidneys (K) are seen in the posterior abdomen in A.
Sagittal Planes
In the sagittal and coronal planes of the fetus, the chest, abdomen, and pelvic organs are
seen and are differentiated by their echogenicity. The lung and bowel are hyperechoic,
the liver is hypoechoic, and the stomach and bladder are anechoic (Fig. 12.7). Lungs
and liver are well separated by the concave-shaped diaphragm (Fig. 12.7). As in the
second trimester, the parasagittal views do not exclude a diaphragmatic hernia. In the
midsagittal view of the abdomen, the anterior abdominal wall with the umbilical cord
insertion can be demonstrated (Fig. 12.7B) either on two-dimensional (2D) color
Doppler or on three-dimensional (3D) ultrasound. This plane is ideally used in
combination with color Doppler to visualize the course of the umbilical artery, vein,
and ductus venosus (DV) (Fig. 12.8). The midsagittal plane of the abdomen is the most
optimal plane for Doppler interrogation of the DV in early gestation (see Fig. 1.4).Figure 12.5: Axial views of the fetal abdomen in gray scale (A) and color
Doppler (B) of a fetus at 10 weeks of gestation demonstrating the presence of
a physiologic midgut herniation (arrow). In the corresponding 3D ultrasound in
surface mode (C), the midgut herniation is shown as a bulge at the site of cord
insertion into the abdomen (arrow).
Figure 12.6: Axial oblique plane of the lower abdomen at 13 weeks ofgestation in gray scale (A) and color Doppler (B) demonstrating the fluid-filled
urinary bladder (asterisk), surrounded by the left and right umbilical arteries
(UA). This view is best visualized with color Doppler (B), which can also confirm
the intact abdominal wall (arrow). Note the posterior location of the iliac crests
in B.
Coronal Planes
A coronal view is rarely necessary in the first trimester, but it has been our experience
that the coronal view is best suited to evaluate the position of the stomach when the
diagnosis of diaphragmatic hernia is suspected (see Chapter 10) . Transvaginal
ultrasound examination of the abdomen in the first trimester provides high-resolution
display of organs, which is helpful when abnormalities are suspected. It is important to
note, however, that the fetal bowel appears more echogenic on transvaginal imaging,
and differentiating normal bowel from hyperechogenic bowel because of pathologic
conditions is difficult in early gestation. This is discussed later in this chapter.
Figure 12.7: Parasagittal plane in two fetuses at 13 (A) and 12 (B) weeks of
gestation demonstrating the thorax and abdomen. The filled stomach (asterisk)
is seen under the diaphragm (arrows). Fetus A is presenting in a dorsoposterior position and fetus B in a dorso-anterior position. Note the hyperechoic
lungs and bowel, the hypoechoic liver, and anechoic stomach and bladder (not
shown).Figure 12.8: Midsagittal view of a fetus at 13 weeks of gestation in color
Doppler demonstrating the cord arising from the abdomen (arrow) with the
umbilical artery (UA) and vein (UV). Ao, descending aorta.
Three-Dimensional Ultrasound of the Fetal Abdomen
Similar to the use of 3D ultrasound in surface mode in the second and third trimester of
pregnancy, 3D ultrasound in the first trimester provides additional information to the 2D
ultrasound views.4 Surface mode is especially helpful for the demonstration of a normal
and abnormal abdominal wall (Fig. 12.9), as illustrated in this chapter. For the
assessment of the intraabdominal organs, 3D ultrasound can also be used in multiplanar
display, with reconstruction of planes for the specific evaluation of target anatomic
regions displayed in tomographic view of axial (Fig. 12.10) or coronal (Fig. 12.11)
planes. For more details on the use of 3D ultrasound in the first trimester, refer to
Chapter 3 in this book and a recent book on the clinical use of 3D in prenatal medicine.4
Figures 12.5C and 12.9 show surface mode of the fetal anterior abdominal wall and
Figures 12.10 and 12.11 show the use of multiplanar mode with plane reconstruction of
axial and coronal views. In our experience, multiplanar mode can be of help especially
in the transvaginal approach where transducer manipulation is limited (Figs. 12.10 and
12.11).Figure 12.9: Schematic drawing (A) and corresponding 3D ultrasound image in
surface mode of a fetus at 12 weeks of gestation. Note the normal insertion of
the umbilical cord in the abdomen in A and B (arrows).Figure 12.10: Tomographic axial views of the abdomen in a fetus at 12 weeks
of gestation showing the upper, mid, and lower abdomen. Note the presence of
the stomach (asterisk) and liver in the upper abdomen, kidneys (Kid.) and
abdominal cord insertion (arrow) in the mid-abdomen, and the urinary bladder
(Bl.) in the lower abdomen. L, left.
VENTRAL WALL DEFECTS
Defects of the abdominal wall are common anomalies in the fetus, and large defects are
often detected in the first trimester.5 These anomalies include omphalocele,
gastroschisis, Pentalogy of Cantrell, and body stalk anomaly (Table 12.1) . Bladder
exstrophy and cloacal exstrophy are often listed as abdominal wall defects, but are
discussed in Chapter 13 as part of the urogenital anomalies.
Omphalocele
Definition
Omphalocele, also known as exomphalos, is a congenital defect of the anterior midline
abdominal wall with herniation of abdominal viscera, such as bowel and/or liver into
the base of the umbilical cord. Embryologically, omphalocele results from failure of
fusion of the lateral folds of the primitive gut. Omphalocele has a covering sac made of
peritoneum on the inner surface, Wharton’s jelly in the middle, and amnion on the outersurface. The typical location of an omphalocele is in the middle of the abdominal wall
at the level of the umbilical cord attachment, and the umbilical cord typically inserts on
the dome of the herniated sac. On rare occasions, the covering membrane can rupture
prenatally. When this occurs, differentiating an omphalocele from gastroschisis on
prenatal ultrasound is difficult. The size of the omphalocele differs based upon its
content, which may include bowel alone or bowel with liver and other organs.
Omphaloceles are commonly associated with fetal genetic and structural abnormalities.
Birth prevalence of omphalocele is reported around 1.92 per 10,000 live births.6
Figure 12.11: Tomographic coronal views of the fetal chest and abdomen at
13 weeks of gestation. In this view, the diaphragm, liver, stomach (asterisk),
bowel, kidneys, and urinary bladder can be seen. Note that the bowel appears
echogenic because of the transvaginal approach.
Table 12.1 • First Trimester Ultrasound and Ventral Wall Defects
Physiologic midgut
herniation
Herniation of small bowel in a small midline sac,
measuring less than 7 mm and physiologically seen until
the 12th week of gestationOmphalocele
Midline defect with viscera covered by a membrane.
Umbilical cord arises from the dome of the sac. Content
can be small with bowel, but can also be large including
bowel, liver, stomach, and other organs
Gastroschisis
Paraumbilical defect typically to the right of the umbilical
cord insertion with evisceration of bowel. No covering
membrane
Pentalogy of
Cantrell
Five features: Abdominal defect similar to omphalocele
but higher on abdomen (1), anterior defect of
diaphragm (2), distal sternal defect (3), pericardial
defect (4), cardiac abnormalities with partial or
complete ectopia cordis (5)
Ectopia cordis Sternal defect with the heart partly or completely
exteriorized, with or without cardiac abnormalities
Body stalk
anomaly (limbbody wall
complex)
Complex large anterior wall defect with the fetus fixed
to the placenta because of a short or absent umbilical
cord. Deformities of body, spine, and limbs. Body stalk
anomaly can also result from an amniotic band
syndrome with a normal umbilical cord. See also in
OEIS
Bladder exstrophy
Defect in the abdominal wall below the attachment of
the umbilical cord. The insertion of the cord is low and
below it bladder tissue is exteriorized. Urinary bladder is
not visible. Female and male genitalia malformed. Can
be part of cloacal exstrophy
Cloacal exstrophy,
(OEIS complex)
In addition to bladder exstrophy, a low omphalocele is
present in association with rectal and anorectal
malformations and distal spine anomaly. Anomaly of
genitalia is part of complex.
OEIS complex is rare and stands for omphalocele,
exstrophy of bladder, imperforate anus, and spinal
defect. A body stalk anomaly of the lower body can
present as OEIS complex, usually legs are completely
or partly absent.
Ultrasound Findings
The physiologic midgut herniation (Fig. 12.5) is present between the 6th and 11th weekof gestation and at crown-rump length of less than 45 mm.2 Therefore, the diagnosis of a
small omphalocele cannot be performed reliably before the 12th week of gestation. The
omphalocele is seen as a protrusion at the level of the cord insertion into the abdomen.
The omphalocele-covering sac is seen as clear borders on ultrasound. Omphaloceles
can be easily demonstrated on sagittal or axial views obtained at mid-abdomen (Figs.
12.12 to 12.16). Figure 12.12 shows a schematic drawing of an omphalocele along
with its corresponding 3D ultrasound in surface mode. In the first trimester, the
omphalocele sac is either relatively small containing bowel loops (Fig. 12.13A) or
large containing liver and bowel (Fig. 12.13B). Figure 12.14 shows parasagittal and
axial views of a fetus with a large omphalocele, containing liver at 12 weeks of
gestation, and Figure 12.15 shows a large omphalocele in two fetuses at 12 and 13
weeks of gestation containing bowel, liver, and stomach. The size of the omphalocele
sac has an inverse relationship with chromosomal abnormalities. The presence of a
small omphalocele in the first trimester with a thickened nuchal translucency should
raise suspicion for the presence of associated fetal malformations and chromosomal
aneuploidy (Figs. 12.13A and 12.16). Color Doppler helps in the demonstration of the
umbilical cord attachment at the dome of the omphalocele, which can differentiate it
from gastroschisis (Fig . 12.17). 3D ultrasound helps in the demonstration and
documentation of the size of the omphalocele (Fig. 12.12). Transvaginal ultrasound
provides detailed information of the omphalocele content and additional anomalies of
the heart, brain, kidneys, and spine. On occasion, the omphalocele can be as large or
even larger than the abdominal circumference (Fig. 12.15). Follow-up of a first
trimester isolated small omphalocele with a normal karyotype and nuchal translucency
into the late second trimester is important because resolution of such cases has been
documented in about 58% of fetuses.7 The presence of the liver in the omphalocele
precludes resolution.
Figure 12.12: Schematic drawing (A) and corresponding 3D ultrasound image
in surface mode of a fetus at 12 weeks of gestation with an omphalocele
(arrows). Note in A the presence of an omphalocele sac covering the protruding
intraabdominal organs (bowel, with or without liver), with the umbilical cordattached to the top of the omphalocele. The umbilical cord is not seen in B, as
the lower extremities obscure it.
Figure 12.13: Midline sagittal plane in two fetuses with small (A) and large (B)
omphalocele (arrows) at 12 weeks of gestation. In fetus A, the omphalocele is
small and contains bowel only, whereas in fetus B, the omphalocele is relatively
large and contains liver and bowel. Note the presence of an enlarged nuchal
translucency (asterisk) in fetus A and workup revealed trisomy 18 in this fetus.Figure 12.14: Parasagittal (A) and axial (B) view of a fetus at 12 weeks of
gestation with a large omphalocele (arrows). Note the presence of liver and
bowel within the omphalocele.
Figure 12.15: Axial view of the abdominal wall at the level of the cord insertion
in two fetuses at 12 (A) and 13 (B) weeks of gestation. Note the presence of a
large omphalocele (asterisks) with liver and bowel content in both fetuses. In
fetus A the stomach is partly in the omphalocele, whereas in fetus B the
stomach has completely protruded into the omphalocele. Sp, spine.Figure 12.16: Axial view of the abdominal wall at the level of the cord insertion
in two fetuses at 12 (A) and 13 (B) weeks of gestation. Note the presence of a
small omphalocele (arrows) in fetus A and B, with only bowel content. Trisomy
18 was diagnosed in both fetuses.
Figure 12.17: Sagittal (A) and axial (B) planes of the mid-abdomen in color
Doppler in a fetus at 12 weeks of gestation with trisomy 18. Note the presence
of a small omphalocele (asterisk) in A and B and a thickened nuchal
translucency (double headed arrow) in A. The use of color Doppler is helpful
because it shows the umbilical cord arising from the top of the omphalocele in
A (arrow) (compare with Fig. 12.12A) and a single umbilical artery in B (arrow).
Associated MalformationsAssociated anomalies are common and are present in the majority of omphaloceles.6
Cardiac malformations are the most common associated structural abnormalities, and
detailed cardiac imaging is thus recommended when an omphalocele is diagnosed in the
first trimester6,8 (see Chapter 11). Chromosomal abnormalities, commonly trisomies 18,
13, and 21, are seen in about 50% of cases diagnosed in the first trimester.8
Omphaloceles associated with chromosomal abnormalities are typically small, with
thickened nuchal translucency and other fetal structural abnormalities. Trisomy 18
represents the most common chromosomal abnormality in fetuses with omphaloceles.
Large omphaloceles containing liver were assumed not to be commonly associated with
aneuploidy,9 but recent studies do not support this observation. In a recently published
large study on 108,982 fetuses including 870 fetuses with abnormal karyotypes,
omphalocele was found in 260 fetuses for a prevalence of 1:419.10 The majority of
omphaloceles (227/260 [87.3%]) had bowel as the only content, with only 33/260
(12.7%) containing liver. In this study, the rate of aneuploidy in association with an
omphalocele was 40% (106/260), and this rate was independent from the omphalocele
content. The most common aneuploidy was trisomy 18 (55%), followed by trisomy 13
(24%), whereas trisomy 21, triploidy, and others were found in 6%, 5%, and 7%,
respectively.10 The presence of a genetic syndrome should be considered in the
presence of an isolated omphalocele with a normal karyotype. Beckwith–Wiedemann
syndrome, reported to be present in about 20% of isolated omphaloceles, should be
considered especially if first trimester biochemical markers of aneuploidy, such as β-
human chorionic gonadotropin and pregnancy-associated plasma protein-A values, are
elevated11 (Fig. 12.18). The diagnosis of Beckwith–Wiedemann syndrome is typically
suspected in the second and third trimester when an omphalocele is seen in association
with macroglossia, polyhydramnios, renal and liver enlargements, and a thickened
placenta called mesenchymal dysplasia of the placenta. Associated ultrasound findings
that suggest the presence of a genetic syndrome in omphaloceles are rarely seen in the
first trimester. Differential diagnosis of ventral wall defects is summarized in Table
12.1.
Gastroschisis
Definition
Gastroschisis is a full-thickness, paraumbilical defect of the anterior abdominal wall
with herniation of the fetal bowel into the amniotic cavity (Figs. 12.19 and 12.20). The
defect is typically located to the right side of the umbilical cord insertion (Fig. 12.21).
The herniated bowel is without a covering membrane and is freely exposed to the
amniotic fluid. Gastroschisis has traditionally been regarded as a vascular lesion
resulting from compromise of the right umbilical vein (UV) or the omphalomesenteric
artery, with resultant ischemic injury of the abdominal wall. Recent theories challenge
this pathogenesis and propose that gastroschisis results from faulty embryogenesis withfailure of incorporation of the yolk sac and vitelline structures into the umbilical stalk,
resulting in an abdominal wall defect, through which the midgut egresses into the
amniotic cavity.12 Gastroschisis is more common in pregnant women of young age.13
Unlike omphalocele, gastroschisis is rarely associated with chromosomal or structural
abnormalities. There has been an increase in the prevalence of gastroschisis
worldwide.13
Figure 12.18: Fetus with Beckwith–Wiedemann syndrome. At 13 weeks of
gestation a small omphalocele with bowel content was detected, as shown in a
midsagittal plane of the fetus in A. In addition, free β human chorionic
gonadotropin (hCG) and pregnancy-associated plasma protein-A were
elevated. Chorionic villous sampling revealed a normal karyotype. At 22 weeks
of gestation, no omphalocele was found but macroglossia was noted as shown
in a midsagittal and coronal planes of the face in B (arrows). The placenta also
appeared thickened at 22 weeks of gestation, suggesting mesenchymal
dysplasia (C). Sonographic signs were suggestive of Beckwith–Wiedemann
syndrome, which was confirmed postnatally with molecular genetics.Figure 12.19: Schematic drawing (A) and corresponding 3D ultrasound image
in surface mode of a fetus at 13 weeks of gestation with gastroschisis. Note in
A and B the presence of bowel loops anterior to the abdominal wall (arrows).
There is no covering sac around the bowel and the surface of herniated bowel
appears irregular.Figure 12.20: Axial (A) and sagittal (B) views of a fetus with a gastroschisis at
12 weeks of gestation. Note in A and B the presence of fetal bowel outside of
the abdominal cavity (arrows). Also note that the herniated bowel loops appear
irregular (arrow).Figure 12.21: Axial view in color Doppler of the fetal abdomen in a fetus at 12
weeks of gestation with gastroschisis. Note the normally inserted umbilical cord
into the abdomen to the left of the gastroschisis defect. L, left; R, right.
Ultrasound Findings
Prenatal diagnosis on ultrasound can be achieved after 11 weeks of gestation and is
based on the visualization of the herniated, free-floating, bowel loops in the amniotic
cavity with no covering sac (Figs. 12.19 to 12.23). The superior surface (dome) of the
herniated bowel in gastroschisis appears irregular on ultrasound examination (like a
cauliflower), an important differentiating feature from omphalocele, which typically has
a smooth surface (compare Fig. 12.12 with 12.19). Color Doppler helps in identifying
the normally inserting umbilical cord into the fetal abdomen, commonly to the left of the
herniated bowel (Fig. 12.21). 3D and transvaginal ultrasound are helpful in the
demonstration and documentation of detailed anatomic findings in gastroschisis (Figs.
12.19, 12.22, 12.23).
Associated Malformations
Large series of fetal gastroschisis have shown additional unrelated fetal malformations
and chromosomal aneuploidy in 12% and 1.2%, respectively.14 The presence of
hyperechoic bowel loops in the first trimester may represent bowel underperfusion, and
follow-up of such cases into the second and third trimester is recommended to assess
for the presence of bowel atresia.15 Follow-up ultrasound examination in later gestationis also recommended given the association of gastroschisis with fetal growth restriction
and oligohydramnios.
Pentalogy of Cantrell and Ectopia Cordis
Definition
Pentalogy of Cantrell is a syndrome encompassing five anomalies: midline
supraumbilical abdominal defect, defect of the lower sternum, defect in the
diaphragmatic pericardium, deficiency of the anterior diaphragm, and intracardiac
abnormalities. The presence of an omphalocele and displacement of the heart partially
or completely outside the chest (ectopia cordis) are hallmarks of this syndrome (Fig.
12.24). The structural abnormalities in Pentalogy of Cantrell show a wide spectrum, but
the outcome primarily depends on the size of the chest and abdominal wall defects and
the type of cardiac malformations. The location of the omphalocele on the abdominal
wall is important, and close attention should be given to that during the ultrasound
examination. Typically, omphaloceles are located in the mid-abdominal wall region at
the level of the umbilical cord insertions. A higher position of an omphalocele on the
abdominal wall can be suggestive for the presence of a supraumbilical abdominal
defect, which is likely to be part of Pentalogy of Cantrell even in the absence of ectopia
cordis.
Figure 12.22: Axial (A), sagittal (B) views in two-dimensional ultrasound and
corresponding three-dimensional ultrasound surface mode (C) of a fetus at 13weeks of gestation with gastroschisis. Note the irregular surface appearance of
the herniated bowel loops (arrows), which is typical for gastroschisis.
Ectopia cordis is an anomaly where the heart is partially or completely located
outside the thorax. It is often found together with a Pentalogy of Cantrell, with body
stalk anomaly,16 but can be isolated as well, in the presence of a split sternum with
closed abdominal wall or in the presence of amniotic band syndrome.
Ultrasound Findings
The prenatal diagnosis of Pentalogy of Cantrell is easily made in the first trimester by
the demonstration of the omphalocele and ectopia cordis (Figs. 12.24 and 12.25). The
midsagittal view of the chest and abdomen is optimal because it demonstrates the
abdominal wall defect and the ectopia cordis in one plane (Figs. 12.26 to 12.28).
Typically, the omphalocele is large, is positioned high on the abdominal wall, and
contains liver (Figs. 12.24 to 12.28). The lower part of the abdomen appears normal. In
a sagittal or axial view, the heart appears to be partly or completely protruding toward
the omphalocele (Figs. 12.24 and 12.25). 3D ultrasound in surface mode can show the
high position of the omphalocele and demonstrate ectopia cordis (Fig. 12.24). Once the
diagnosis of Pentalogy of Cantrell is made, identifying the associated cardiac
malformation is important for patient counseling. This can be challenging in the first
trimester given the presence of ectopia cordis and cardiac malrotation. A follow-up
ultrasound at around 14 to 15 weeks of gestation is helpful in confirming the associated
type of cardiac abnormality. One study noted that the degree of cardiac protrusion tends
to regress with advancing gestation (Fig. 12.28).17Figure 12.23: Parasagittal (A) and axial (B) views in two-dimensional
ultrasound and corresponding three-dimensional (3D) ultrasound in surface
mode (C) of a fetus at 13 weeks of gestation with gastroschisis. Note that the
herniated bowel (arrows) is echogenic in A and B. C: Free bowel loops on 3D
ultrasound. Bowel dilation in gastroschisis is first evident in the second trimester
of pregnancy.Figure 12.24: Schematic drawing (A) and corresponding 3D ultrasound image
in surface mode (B) and glass-body mode (C) in a fetus at 11 weeks of
gestation with Pentalogy of Cantrell. Note the presence of a high omphalocele
with ectopia cordis (arrows). Ectopia cordis could be partial or complete
(complete in this case). Pentalogy of Cantrell is often associated with a cardiac
anomaly (see text for details).Figure 12.25: Axial views at the level of the thorax in gray scale (A) and color
Doppler (B) in a fetus at 11 weeks of gestation with Pentalogy of Cantrell. Note
the presence of an omphalocele (asterisks) with ectopia cordis (arrows).
Figure 12.26: Sagittal views at the level of the thorax and abdomen in gray
scale (A) and color Doppler (B) in a fetus at 13 weeks of gestation with a mild
form of Pentalogy of Cantrell with partial ectopia cordis. Note the presence of a
high omphalocele (asterisks), inferiorly displaced heart, pericardial defect, and
an anterior defect in the chest (arrow).
The diagnosis of an isolated ectopia cordis has been reported in the first trimester aswell. In general, it is rather rare, however. In a series of seven cases of ectopia cordis,
Sepulveda et al. noted only one isolated case, whereas in the remaining cases Pentalogy
of Cantrell and body stalk anomaly were associated findings.16 The diagnosis of a heart
outside of the thoracic cavity can be performed even earlier than 11 weeks of gestation.
Associated intracardiac and extracardiac anomalies are common.18
Associated Abnormalities
Enlarged nuchal translucency and cystic hygroma have been reported in association with
Pentalogy of Cantrell.16 Many associated fetal malformations have also been reported to
include neural tube defects, encephalocele, craniofacial defects, and limb defects among
others. Chromosomal anomalies can be present, and invasive procedure should be
offered.16 When the full spectrum of Pentalogy of Cantrell is present, the prognosis is
typically poor, with neonatal mortality reported in the range of 60% to 90%. In fetuses
with variants of the syndrome, prognosis is improved.
Figure 12.27: Sagittal views at the level of the thorax and abdomen in gray
scale (A) and color Doppler (B) in a fetus at 11 weeks of gestation with
Pentalogy of Cantrell. Note the presence of a high omphalocele (asterisks) with
ectopia cordis (arrows).Figure 12.28: Sagittal view of the fetal chest and abdomen in a fetus at 12
weeks of gestation with a high omphalocele and ectopia cordis (heart) as part
of Pentalogy of Cantrell. This fetus was also found to have tetralogy of Fallot.
Upon follow-up ultrasound examinations in the late second and third trimesters,
the fetal heart retracted into the chest. The newborn underwent corrective
surgery and is currently alive and well.
Body Stalk Anomaly
Definition
Body stalk anomaly is a severe abnormality resulting from failure of formation of the
body stalk and involves a combination of multiple malformations to include the
thoracoabdominal wall (Figs. 12.29 and 12.30), craniofacial structures, spine, and
extremities.19 The umbilical cord is either very short or absent (Fig. 12.31). Typically,
the abdominal organs lie in a sac outside the abdominal cavity and are covered by
amnion and placental tissue (Figs. 12.29 and 12.30). In a study involving 17 cases of
body stalk anomalies diagnosed at a median gestational age of 12 + 3 weeks, liver and
bowel herniation into the coelomic cavity, along with an intact amniotic sac containing
the rest of the fetus and normal amount of amniotic fluid, was noted in all fetuses.20
Additionally, absent or short umbilical cord and severe kyphoscoliosis and positional
abnormalities of the lower limbs were common associated findings.20 The authors noted
that examination of the amniotic membrane continuity, content of both the amniotic sac
and coelomic cavity, and short or absent umbilical cord help in differentiating thiscondition from other abdominal wall defects.20
Although body stalk anomaly is not primarily related to the gastrointestinal
anomalies, the associated abdominal/chest wall defect is quite large, which typically
leads to the initial suspicion of the defect. The embryogenesis of this anomaly is
primarily related to defective development of the germinal disc, probably because of a
vascular insult, resulting in amnion rupture with amniotic band-type defects.19,21 Three
main types of malformations in body stalk anomaly include body wall defects, limb
deformities/amputations, and craniofacial defects. The conditions affecting the spine
such as sacral agenesis or interrupted spine are discussed separately in Chapter 14.
Figure 12.29: Schematic drawing (A) and corresponding 3D ultrasound image
in surface mode (B) in a fetus at 11 weeks of gestation with a body stalk
anomaly. Note the presence of a large anterior wall defect, with a nearly
absent umbilical cord. The fetus is stuck to the placenta, and the whole body is
severely deformed (see also Fig. 12.30). Also note that the fetal liver and
bowel (asterisks) are outside of the amniotic cavity. Arrows point to the
amniotic membrane.Figure 12.30: Two-dimensional ultrasound in gray scale (A) and color Doppler
(B) along with the corresponding three-dimensional ultrasound in surface mode
(C) in a fetus at 11 weeks of gestation with a body stalk anomaly. Note that the
liver is outside the amniotic cavity (asterisks in A and B). The yellow arrow
points to the amniotic membrane in A. There is also ectopia cordis noted in B
on color Doppler (long white arrow). Body deformity is noted on the threedimensional ultrasound in C.
Ultrasound Findings
The ultrasound diagnosis of body stalk anomaly is generally straightforward, and the
anomaly can be detected even before 11 weeks of gestation. A large chest and
abdominal wall defect with massive evisceration of organs is seen on ultrasound along
with spinal abnormalities such as kyphoscoliosis (Figs. 12.29 and 12.30). Because of
severe anatomic distortion, a midsagittal plane of the fetus is typically not possible (Fig.
12.30). The presence of a very short or absent cord and the proximity of the fetus to the
placenta help to confirm the diagnosis (Fig. 12.31). 3D ultrasound in surface mode and
in multiplanar display of the whole fetus is ideal in order to demonstrate the complete
picture of this severe anomaly (Figs. 12.29 and 12.30). On many occasions, body stalk
anomaly is easier to diagnose in the first trimester. In the second and third trimesters,the associated presence of oligohydramnios and fetal crowding makes the diagnosis of
body stalk anomaly more challenging. Occasionally, a body stalk anomaly is associated
with amniotic bands, which can be visualized on transvaginal ultrasound by the
demonstration of reflective membranes connected to the wall defect.
Figure 12.31: Axial view in color Doppler of the fetal abdomen in a fetus with
body stalk anomaly at 12 weeks of gestation. Note the presence of a short
cord (arrow). The fetus also had multiple complex malformations.
Associated Malformations
Associated malformations are many, include all organ systems, and are features of body
stalk anomaly. Neural defects, facial deformities, and skeletal abnormalities are
common. On occasion, a lower extremity is partly or completely absent. Anomalies of
the chest and abdominal walls are nearly always present. In addition, a thickened nuchal
translucency is found in most cases. Fetal karyotype is usually normal, and body stalk
anomaly is uniformly fatal.
Cloacal Exstrophy and OEIS Syndrome
Cloacal exstrophy is a spectrum of malformations with its severity related to the time of
embryologic disruption in the development of the genitourinary system. Epispadia
represents the milder form and bladder/cloacal exstrophy represents the severe form of
cloacal exstrophy spectrum. The association of cloacal exstrophy with imperforate anus,
omphalocele, and vertebral defects has often been referred to as OEIS complex. OEIS
therefore represents the combination of omphalocele, exstrophy of the bladder,
imperforate anus, and spinal defects (Figs. 12.32 and 12.33). Often, the appearance can
be suggestive of a body stalk anomaly, severe sacral agenesis with spinal defects or acloaca, and the first trimester diagnosis can therefore be technically difficult.
Figure 12.32: Ultrasound images of a fetus at 12 weeks of gestation with
OEIS. OEIS includes the presence of an Omphalocele, Exstrophy of the
bladder, Imperforate anus, and Spinal defect. OEIS is the most severe form of
body stalk anomaly with parts of the body missing and others outside of the
amniotic cavity. Note the presence of severe body deformity and a significant
part of the embryo outside of the amniotic cavity in A and B. Arrows point to
the amniotic membrane.
In a series involving 12 cases of OEIS reported in the literature, all had exstrophy of
the bladder.22 Neural tube defects, omphalocele, and anal atresia were found in 10/12,
9/12, and 9/12 cases, respectively.22 Vertebral defects, along with lower extremityabnormalities, were found in less than half of cases.22 Additional malformations
involved central nervous system, cardiac, and renal organs. All fetuses in this series had
normal karyotype.22 OEIS complex is rare, with an incidence ranging from 1/200,000 to
1/400,000.23,24 Almost all cases of OEIS occur sporadically.25
GASTROINTESTINAL OBSTRUCTIONS
The following gastrointestinal obstructions are commonly diagnosed in the second
trimester of pregnancy, and their sonographic features are rarely identified before the
14th week of gestation. We are hereby listing them for completion sake. Despite
reported cases of gastrointestinal obstruction diagnosed in the first trimester, the authors
believe that these represent the exception rather than the rule because most cases of
gastrointestinal obstruction are associated with normal first trimester ultrasound.
Detailed presentation of ultrasound findings, associated malformations, and outcome is
beyond the scope of this chapter.
Figure 12.33: Sagittal views in gray scale (A) and the corresponding threedimensional ultrasound in surface mode in B in a fetus with OEIS complex (see
Fig. 12.32 for explanation) at 13 weeks of gestation. Note the presence of
major body deformities with absence of the majority of the lower body. A large
abdominal wall defect (arrow) is noted with liver (L) and bladder (B) stuck to
the uterine wall.
Esophageal Atresia
The classic sonographic features of esophageal atresia in the second and third trimester
of pregnancy, such as an empty stomach and polyhydramnios, are not seen in the first
trimester. The stomach in the first trimester of pregnancy is primarily filled because of
gastric secretions, and polyhydramnios is seen in the late second and third trimester ofpregnancy. A normally filled stomach in the upper left abdomen therefore does not
exclude esophageal atresia in the first trimester. Indeed, the authors have observed
normal sonographic anatomy of the gastrointestinal tract in the first trimester in fetuses
that were later diagnosed with esophageal atresia in the second trimester of pregnancy.
In pregnancies at high risk for esophageal atresia because of a prior family history or in
the presence of associated anomalies, we recommend direct visualization of the
esophagus as a continuous hyperechogenic structure (Fig. 12.34), rather than looking for
indirect signs such as stomach filling. The two reported cases of first trimester
diagnosis of esophageal atresia were associated with duodenal atresia.26,27
Duodenal Atresia
The prenatal diagnosis of duodenal atresia is occasionally possible in the first trimester,
and few case reports have described the appearance of the classic double bubble sign
(dilated stomach and proximal duodenum) in the first and early second trimester of
pregnancy.28 An associated esophageal atresia was present in few reported cases in the
literature.26,27 The authors are cautious about making the diagnosis of duodenal atresia
in the first trimester given the scarcity of follow-up data on this subject. When duodenal
atresia is suspected in the first trimester (Fig. 12.35), risk assessment for aneuploidy
should be performed and follow-up ultrasound examinations into the second trimester
are recommended before a final diagnosis is attained. In our experience, most cases of
duodenal atresia are evident after the 23rd week of gestation.
Anorectal Atresia
The prenatal diagnosis of anorectal atresia is a challenge in the second and third
trimester of pregnancy because several cases escape prenatal identification.
Interestingly, sonographic markers of anorectal atresia in the first trimester have been
reported.29–32 The detection of an anechoic sausage-shaped structure in the lower
abdomen in the first trimester, representing a dilated colon or rectum (Fig. 12.36), can
be a clue to the presence of anorectal atresia.29–31,33 Commonly, this marker resolves in
the second trimester and often reappears in the third trimester of pregnancy. The
presence of other fetal abnormalities increases the risk for an associated anorectal
atresia, especially when a VATER (Vertebral anomaly, Anorectal atresia, TracheaEsophageal fistula, and Renal anomaly) association is suspected33 (Fig. 12.36). The risk
for associated gastrointestinal obstruction is increased when single umbilical artery,
absent kidney, hemivertebra, and/or other malformations are noted (Fig. 12.36). In a
metaanalysis of 33 fetuses with intraabdominal cysts in the first trimester of pregnancy,
four had anorectal malformations at birth.33Figure 12.34: Transabdominal (A) and transvaginal (B) parasagittal ultrasound
images of the chest and upper abdomen in two fetuses at 13 weeks of
gestation demonstrating echogenic esophagus (arrows). High-resolution
ultrasound transducers enable imaging of the esophagus in early gestation.Figure 12.35: Axial views of the abdomen in a fetus at 13 weeks of gestation
demonstrating a “double bubble” (arrows). A and B: Two phases of stomach
peristalsis. Follow-up ultrasound examination at 17 weeks of gestation noted
absence of the double bubble and workup revealed normal karyotypic analysis.
Note in A and B that the “double bubble” does not cross the midline of the
abdomen.Figure 12.36: Ultrasound images of a fetus with a VATER association, first
suspected at 13 weeks of gestation. A: The presence of hemivertebra
(asterisk) at 13 weeks of gestation. B: A cystic structure in the lower abdomen
(arrows) at 13 weeks of gestation. C: A sagittal view of the abdomen and
pelvis showing the cystic structure as a dilated rectum with echogenic borders
(arrows). D: A sagittal view of the pelvis at 18 weeks of gestation
demonstrating the rectum and colon with increased echogenic borders
(arrows), suggesting the presence of anal atresia. The bowel echogenicity
disappeared on follow-up ultrasound with advancing gestation. Postnatally,
VATER association and anal atresia were confirmed.
OTHER GASTROINTESTINAL SYSTEM
ABNORMALITIES
Abnormal Abdominal Situs
An accurate comprehensive examination of the abdominal situs is recommended during
the ultrasound examination in the first trimester (Fig. 12.37). The presence of abnormal
abdominal situs is an important aspect of fetal anatomy survey because it can be a clueto the presence of heterotaxy and complex congenital heart disease (Fig. 12.38).
Abdominal situs abnormality is first suspected when the stomach is not located in the
left abdominal cavity (Fig. 12.38) or in the presence of abnormal venous connections
(Fig. 12.39).
Echogenic Bowel
The diagnosis of echogenic bowel in the first trimester is similar to that in the second
trimester and is based on bowel echogenicity equal to bone (Fig. 12.40). This is a
subjective assessment that is tricky in the first trimester, especially when transvaginal
ultrasound is used, because enhanced tissue resolution provides for increased bowel
echogenicity under normal conditions (Fig. 12.41). In order to avoid false-positive
diagnosis, the authors recommend that the diagnosis of echogenic bowel in the first
trimester be reserved for bowel that is unequivocally as bright as bone and a follow-up
ultrasound examination is performed. Workup includes risk assessment and/or
diagnostic testing for genetic abnormalities, screening for infectious etiologies, and
detailed anatomic survey.
Figure 12.37: Axial view of the upper abdomen in a normal fetus at 12 weeks
of gestation, imaged by high-resolution transvaginal ultrasound. The stomach
(asterisk) and the descending aorta (DAO) are left sided, whereas the inferior
vena cava (IVC) and liver are right sided. This plane is visualized routinely in
order to exclude situs anomalies, especially if a cardiac defect has been
suspected. L, left; R, right.Figure 12.38: Axial view of the upper abdomen showing abnormal abdominal
situs in a fetus with right isomerism suspected because of a complex cardiac
anomaly at 13 weeks of gestation. Note the presence of a right-sided stomach
(St), whereas the descending aorta (DAO), inferior vena cava (IVC), and liver
are left sided. L, left; R, right.Figure 12.39: Axial view of the upper abdomen, obtained with high-resolution
transvaginal scanning, showing abnormal abdominal situs in a fetus with left
isomerism suspected because of a complex cardiac anomaly at 14 weeks of
gestation. Note the presence of a left-sided stomach (St), an interrupted
inferior vena cava, and a hemiazygos vein continuation shown to the left of the
descending aorta (DAO). L, left; R, right.Figure 12.40: Axial view (A) at 12 weeks of gestation and parasagittal view
(B) at 13 weeks of gestation in two fetuses with echogenic bowel (circle) and
trisomy 21. Note that the bowel is as bright as bone and the presence of
hydropic skin (arrows) in both fetuses. Echogenic bowel in trisomy 21 is rarely
an isolated finding.Figure 12.41: Axial view of the fetal abdomen at 13 weeks of gestation
obtained with transvaginal ultrasound. Note that the bowel is echogenic
because of the high resolution of the ultrasound transducer. Differentiating
echogenic bowel from normal bright bowel in early gestation can be
challenging, especially when high-resolution transducers are used in
transvaginal scanning.
Intraabdominal Cysts
The presence of intraabdominal cysts in the fetus can be detected by ultrasound in the
first trimester34–36 as anechoic structures in the fetal abdomen that are distinct from the
stomach and bladder (Fig. 12.42). The shape, location, size, and content of the cyst(s)
reveal its possible etiology. Abdominal cysts that are present in the liver are typically
circular and tend to resolve spontaneously by the second trimester (Fig. 12.43).
Occasionally, a remnant echogenic intrahepatic focus can be seen following resolution
(Fig. 12.43). Intraabdominal cysts in the lower abdomen, especially with abnormal
shape and echogenic content, are commonly bowel in origin and may be related to an
abnormal genitourinary system such as a cloaca (Figs. 12.44 to 12.46) or an anorectal
atresia33 (Fig. 12.36). Often, upon follow-up of lower abdominal cysts that are
suspected to be related to abnormal genitourinary system, echogenic debris are found as
evidence for enterolithiasis (Fi g . 12.46). The presence of peristalsis in an
intraabdominal cyst suggests a gastrointestinal origin. A large dilated cystic structure inthe lower abdomen may represent a dilated bladder related to an obstructed urethra (see
Chapter 13). Omphalomesenteric cysts can originate in the abdomen and migrate into the
umbilical cord (see Chapter 15).35 Fetal intraabdominal cysts are rare in the first
trimester, and in the majority of cases they represent an isolated finding.33 When
isolated, intraabdominal cysts are usually associated with a good prognosis and tend to
resolve on follow-up ultrasound in about 80% of cases33 (Figs. 12.42 and 12.43).
Follow-up ultrasound in the second and third trimester is recommended even when
resolution of the cysts occurs, given a reported association with anorectal and other
gastrointestinal malformations.33,36
INTRAABDOMINAL ARTERIAL AND VENOUS
ABNORMALITIES
Normal Sonographic Anatomy
The fetal vascular anatomy of the umbilical, hepatic, and portal venous systems along
with the IVC is complex, because of small vasculature, the presence of normal anatomic
variations, and the close spatial relationship of the vessels.
Figure 12.42: Sagittal (A) and axial (B) views of a fetus at 13 weeks of
gestation with a large intrahepatic cyst (arrows). The stomach is seen in B
(asterisk). Expectant management and follow-up ultrasound at 16 weeks of
gestation (Fig. 12.43) showed resolution of cyst. L, left; R, right.Figure 12.43: Sagittal (A) and axial (B) views of the same fetus in Figure
12.42, now at 16 weeks of gestation. Note the resolution of the large
intrahepatic cyst within 3 weeks. An echogenic focus (arrow) is now present
within the liver. L, left; R, right.
Figure 12.44: Sagittal (A) and axial (B) views of a fetus at 12 weeks of
gestation with a large bladder (asterisk) and adjacent dilated bowel loops withechogenic walls. These findings are suspicious for bowel obstruction with a
fistula into a cloaca. See Figures 12.45 and 12.46.
Figure 12.45: Three-dimensional ultrasound in tomographic display of a fetus
at 12 weeks of gestation with a large bladder (asterisk) and dilated bowel
loops (same fetus as in Fig. 12.44). Note the presence of multiple dilated bowel
loops with echogenic borders.
The umbilical vein (UV) enters the fetal abdomen in the midline and has a short
extrahepatic course before entering into the liver with a slight right tilt (Fig. 12.47). The
UV drains into a confluence called the portal sinus. The ductus venosus (DV) is a thin
hourglass-shaped fetal vessel that connects the UV to the heart. The DV arises from the
region of the portal sinus and joins the IVC at the level of the subdiaphragmatic
vestibulum (Fig. 12.47). The hepatic veins are the intrinsic veins of the liver; they
converge into three main hepatic veins and join the inferior vena cava (IVC) and DV at
the subdiaphragmatic vestibulum, which drains into the right atrium. The IVC in the
abdomen courses on the right side of the spine and assumes a more ventral position
along the posterior liver surface as it enters the subdiaphragmatic vestibulum.Figure 12.46: Axial views (A and B) of the same fetus as in Figures 12.44 and
12.45, now at 17 weeks of gestation. Note the presence of a dilated cloaca
(asterisks) with echogenic wall. B: The presence of enterolithiasis with
echogenic debris within the cyst (arrow).Figure 12.47: Sagittal view of the thorax and abdomen in color Doppler (A) and
in 3D glass-body mode (B) in a normal fetus at 13 weeks of gestation,
demonstrating the main intraabdominal vasculature. Note that the ductus
venosus (DV), the inferior vena cava (IVC), and the left hepatic vein (HV)
merge together to enter the heart. From the descending aorta (AO) arise the
celiac trunk (1) and the superior mesenteric artery (2). UV, umbilical vein.The descending aorta gives rise to several branches in the abdomen to include,
among others, four main ones: the celiac trunk at level of T12 (Fig. 12.47), the superior
mesenteric artery at level L1 (Fig. 12.47), the renal arteries at level L1 to L2, and the
inferior mesenteric artery at level L3. Three branches arise from the celiac trunk
including the common hepatic, splenic, and left gastric artery. The superior mesenteric
artery provides several branches to the small bowel and part of large bowel.
Most reports in the literature on the sonographic imaging of the abdominal
vasculature are from the second and third trimester of pregnancy. Because of the small
size of abdominal vasculature in early gestation, the sonographic imaging in the first
trimester is quite difficult and is only achieved with color Doppler and in optimal
imaging conditions. A slightly oblique plane of the abdomen at the level of the liver,
pointing toward the left shoulder, is best for the visualization of the three hepatic veins.
The DV can be visualized in an axial plane of the upper abdomen, but imaging of the DV
in the first trimester is best seen in a midsagittal longitudinal view of the abdomen (Fig.
12.47). In this approach, the junction between the DV and the UV is seen, and the
narrow size of the DV is appreciated (Fig. 12.47). Because of its narrow and short size,
visualization of the DV is facilitated by the use of color Doppler, which reveals the
presence of color aliasing, an important feature that helps in the identification of DV
(Figs. 12.47 and 3.11). The IVC is visualized by an oblique insonation of the abdomen
in a midsagittal view as shown in Figure 3.12. The celiac trunk with its hepatic artery
branch along with the superior mesenteric artery is best seen when the fetus is in a
dorsoposterior position and the aorta is in a horizontal orientation (Figs. 12.8 and
12.47). This fetal orientation allows for flow in the celiac trunk and mesenteric arteries
to be parallel to the ultrasound beam, which optimizes visualization (Fig. 12.47). In our
experience, the midsagittal plane of the abdomen in low-velocity color Doppler is the
most optimal view for the visualization of the main abdominal vasculature to include the
UV, DV, IVC, and hepatic artery. For a more detailed discussion on the sonographic
anatomy of the intraabdominal venous system, we recommend our two review articles
on this subject.37,38
Intraabdominal Venous and Arterial Anomalies
Prenatal reports on anomalies of the abdominal venous system in the first trimester are
scarce. In general, there are two groups of abnormalities, one related to anomalies
affecting the DV, such as agenesis or the anomalous connections of the DV, and the other
related to interruption of the IVC with azygos continuity. These conditions are briefly
discussed in the following sections.
Agenesis or Abnormal Connection of the Ductus Venosus
As known from reports in the second trimester, anomalies of the DV include its
complete agenesis (Fig. 12.48) or its anomalous connection to the IVC, hepatic system,
other abdominal vasculature, or directly to the right atrium and other sites.37,38 Ingeneral, abnormalities of DV are suspected when the examiner is looking for the DV in
a midsagittal plane in color Doppler in order to perform pulse Doppler sampling. There
are no large series on the clinical relevance of DV anomalies in the first trimester, but
such abnormalities are known to be associated with cardiac defects, aneuploidies such
as trisomy 21, 13, 18, Turner syndrome, and syndromic conditions as in Noonan
syndrome and others (Figs. 12.49 and 12.50). The risk for aneuploidy is higher when
the DV connects at an abnormal level on the IVC (intrahepatic portion) rather than in its
normal location at the subdiaphragmatic vestibulum (Figs. 12.49 and 12.50).39
Abnormal direct connection of the UV to the IVC is also associated with increased risk
of aneuploidy.39 In one study on 37 fetuses with trisomy 21, it was shown that 11% of
cases had a direct connection of the DV to the intrahepatic portion of the IVC.39 This
observation has also mirrored our clinical experience as we have found similar
associations with aneuploidies and Noonan syndrome (Figs. 12.49 and 12.50). Because
anomalies of the DV can also be associated with cardiac anomalies, as well as other
anomalies of the umbilicoportal system when seen in the first trimester (Fig. 12.51), a
careful examination of these two anatomic regions should be performed and follow-up
ultrasound in the second trimester is recommended. We propose a workup of DV or UV
abnormalities diagnosed in the first trimester in Table 12.2.
Figure 12.48: Sagittal view of the thorax and abdomen in color Doppler (A) and
in 3D glass-body mode (B), in a fetus at 12 weeks of gestation with agenesis
of the ductus venosus (asterisk). Compare with the normal abdominal
vasculature in Figure 12.47. IVC, inferior vena cava; HV, left hepatic vein; UV,
umbilical vein.Interruption of the Inferior Vena Cava
Interruption of the IVC with azygos continuation is an anomaly that is commonly seen in
the presence of heterotaxy syndrome mainly in left atrial isomerism, but can also occur
in isolation.40 Its detection in the first trimester is very difficult because of the small
size of the azygos vein. When suspected in the first trimester by the presence of complex
cardiac defects or abnormal situs, color Doppler can reveal the absence of the IVC and
the presence of a dilated azygos vein with a course side-by-side to the descending aorta,
thus confirming the diagnosis (Fig. 12.52). The authors have also noticed that in the
presence of azygos continuation of an interrupted IVC in the first trimester, increased
blood flow in the superior vena cava (SVC) or a persistent left SVC (possible site of
drainage of azygos second to SVC) can be demonstrated on color Doppler in the threevessel trachea view (Fig. 12.52).
Figure 12.49: Sagittal view of the thorax and abdomen in color Doppler (A) and
3D glass-body mode (B) in a fetus at 12 weeks of gestation with trisomy 21.
Note the direct connection (asterisk) of the ductus venosus (DV) with the
inferior vena cava (IVC) and the separate attachment of the hepatic vein (HV)
to the IVC. The fetus also had thickened nuchal translucency (not shown).Figure 12.50: Sagittal views of the abdomen in color Doppler in four fetuses
with trisomy 18 (A), trisomy 13 (B), monosomy X (C), and Noonan syndrome
(D), respectively, obtained between 12 and 13 weeks of gestation. Note that all
four fetuses (A–D) show the direct connection (asterisks) of the ductus venosus
(DV) or umbilical vein (UV) to the inferior vena cava (IVC). Additional markers
of aneuploidy were found in all fetuses.Figure 12.51: Sagittal views of the abdomen in color Doppler in the same fetus
at 13 weeks of gestation (A) and at 22 weeks of gestation (B) demonstrating
the direct connection (asterisks) of the umbilical vein (UV) to the inferior vena
cava (IVC). No additional anomalies were found and fetal karyotype was
normal. This finding was confirmed at 22 weeks of gestation (B). The portal
system was normally developed and abdominal ultrasound after birth showed a
closure of the connection and no signs of portosystemic shunt.
Table 12.2 • Workup of Ductus Venosus and/or Umbilical Vein
Abnormalities
Assess the connecting site of the ductus venosus (if present) or umbilical
vein (intrahepatic, extrahepatic, iliac, right atrium, etc.)
Check for aneuploidies such as trisomy 21, 13, 18, monosomy X, triploidy,
and others
Check for the presence of syndromic sonographic markers (heterotaxy,
Noonan syndrome, etc.)
Perform fetal echocardiography to rule out cardiac defects, including
venous anomalies
Look for anomalies in other organs (renal, gastrointestinal, skeletal, centralnervous system)
Check for the presence of early hydrops, and perform follow-up ultrasound
for hydrops development
Assess in the second trimester for the presence of portal venous system
abnormalities
Prognosis is good if none of the above additional conditions is present, but
postnatal ultrasound of liver vasculature is recommended
Adapted from Chaoui, R, Heling, KS, Karl K. Ultrasound of the fetal veins.
Part 1: The intrahepatic venous system. Ultrasound in Med. 2014;35:208–
238, with permission, Copyright by Thieme Publishers.
Intraabdominal Arterial Abnormalities
With the exception of the single umbilical artery, further information on anomalies of the
other intraabdominal arteries in the first trimester is currently almost nonexistent in the
literature. Abnormalities involving the hepatic artery and celiac trunk are probably the
easiest to demonstrate in the first trimester. Doppler assessment of the hepatic artery in
the first trimester has been described41 (see Chapter 6). A fistula between the hepatic
artery and the UV in a fetus with trisomy 21 presenting with hydrops in early gestation
has been described by our group.42 In addition, we observed three cases with the
presence of an additional accessory hepatic artery arising from the aorta, superior to the
celiac trunk, coursing along the diaphragm, and entering the liver cranially (Figs. 12.53
and 12.54). In one of the three fetuses, the diagnosis of trisomy 21 was made and in the
other two, the finding disappeared likely because of spontaneous closure of the
accessory artery. Conditions associated with a single umbilical artery are discussed in
Chapter 15.Figure 12.52: Three-vessel trachea view (A) and sagittal view (B) in color
Doppler of a fetus at 12 weeks of gestation with a hemiazygos continuation.
The fetal heart and stomach are left sided but the four-chamber view (not
shown) revealed a cardiac anomaly. The three-vessel trachea view (A) shows
an atypical vessel to the left of the pulmonary artery (PA), which was found to
be the connection of a dilated hemiazygos vein into a persistent left superior
vena cava. In the sagittal view (B), the aorta (Ao) and hemiazygos vein are
seen side-by-side and the IVC is absent (asterisk). The clue to the diagnosis of
a hemiazygos (or azygos) is facilitated by color Doppler showing opposite
direction of blood flow in the aorta and hemiazygos (blue and red arrows,
respectively). This fetus had left atrial isomerism.Figure 12.53: A: A sagittal view of the fetal abdomen in color Doppler in a
fetus at 14 weeks of gestation with an aberrant liver artery (arrow) arising from
the descending aorta (Ao) with a course toward the surface of the liver. B: A
cross-section at the level of the diaphragm in the same fetus showing the
course of the aberrant liver artery (arrow) on the top of the liver (L). C: The
pulsed Doppler of the aberrant vessel with high arterial velocity. We have seen
this condition in fetuses with trisomy 21. On occasions, the aberrant artery
obliterates on follow-up ultrasound examination into the second trimester as in
this case. See Figure 12.54.1.
2.
3.
4.
5.
6.
7.
8.
Figure 12.54: A: A sagittal view of the fetal abdomen in color Doppler in a
fetus at 13 weeks of gestation with an aberrant liver artery (arrow) arising from
the descending aorta (Ao) with a course toward the surface of the liver. The
stomach is well seen (asterisk). B: A follow-up ultrasound examination at 17
weeks showing the aberrant liver artery (arrow). In this case, it persisted unt
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