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SON 2122
Obstetrical Sonography II
Chapter 15
The Fetal Abdominal Wall and GI
Harry H. Holdorf PhD, MPA, RDMS, RVT, LRT
 GASTROSCHISIS – Abdominal Wall
 OMPHALOCELE – Abdominal Wall
 Bladder Extrophy – Abdominal Wall
 Congenital Diaphragmatic Hernia – Abdominal Wall
 Abdominal Ascites – Abdominal Wall
 Persistent right umbilical vein – Abdominal Wall
 Diaphragm – Abdominal wall
 Esophageal atresia
 Duodenal Atresia
 Intestinal Atresia
 Meconium Peritonitis
 Teratomas
 Meconium Ileus
 Volvulus
The Gastro-Intestinal System
 Difficult to image unless fetus is swallowing
 On transverse view, seen ovoid or round fluid collection
in upper left abdomen
 Muscular layer may be thickened in hypertrophic pyloric
Normal fetal esophagus
The fetal Stomach
 Protrusion of intestines into the amniotic cavity through
an open defect in the anterior abdominal wall.
Gastroschisis occurs adjacent to the cord insertion,
usually on the right.
 It is not covered by a membrane.
 It results from a muscular defect, possibly related to
vascular disruption.
 Gastroschisis is not associated with an increased risk of
chromosomal abnormalities.
Sonographic findings.
 Loops of bowel seen extending into the amniotic cavity
 Cord is seen adjacent to the defect
 No membranous sac covers the hernia
 Results from a failure of the intestines to return to the
abdomen during the second stage of intestinal rotation.
 They may contain a single loop of bowel, or most of the
abdominal contents, depending on the severity. The
defect is covered by a layer of amniotic epithelium, and
is seen at the level of the umbilical cord insertion.
 Rupture of the sac during vaginal delivery may cause
 There is a high association between omphalocele and
other congenital anomalies (65-90% of fetuses seen
have a cardiac defect or chromosomal abnormities, most
commonly Trisomies 13 and 18), patients should receive
genetic counseling.
Sonographic findings
 Extra-abdominal mass, consisting of a combination of
fluid-filled bowel loops, mesentery, omentum, liver, and
sometimes pancreas and spleen
 Mass contiguous with umbilical cord
 Membranous sac covers the herniated organs
Bladder Extrophy
 This midline defect involves the lower abdominal wall as
well as the anterior wall of the urinary bladder.
Generally, bladder extrophy is an isolated defect, but can
possibly be associated with genital anomalies such as
cleft clitoris, epispadias, and the wide separation of
pubic bones.
 Midline defect involves the lower abdominal wall as well
as the anterior wall of the urinary bladder.
 Isolated defect
 Protrusion of the urinary bladder
 Possibly associated with genial anomalies – cleft clitoris,
or wide separation of public bones
 Bladder not ID over 30 minutes of scanning, but normal
 Possible soft tissue protrusion form lower abdominal wall
 Separation of pubic bones
 Epispadias is a rare defect that is present at birth
(congenital). It is located at the opening of the urethra.
In this condition, the urethra does not develop into a full
tube. The urine exits the body from the wrong place.
Epispadias can occur with bladder exstrophy. In this rare
birth defect, the bladder is inside out and sticks through
the abdomen wall. Epispadias can also occur with other
birth defects.
Epispadias occurs in 1 out of every
117,000 newborn boys and 1 in 484,000 newborn girls.
The condition is usually diagnosed at birth or soon
afterward. Patients who have more than a mild case of
epispadias will need surgery. Some people with this
condition may continue to have urinary incontinence,
even after surgery. Ureter and kidney damage and
infertility may occur.
Sonographic findings
 Bladder not identified over 30 minutes of scanning but
normal AFV
 Possible soft tissue protrusion from lower abdominal wall
 Separation of pubic bones (diastasis)
 Micorphallus in male fetus
Bladder Extrophy-The
cord insertion is visualized
above the protruding mass that contains bladder and bowel
Congenital Diaphragmatic
 CDH is the most common developmental abnormality of
the diaphragm. The small bowel, stomach, spleen, colon
and liver may herniated into the chest.
 Hernias usually occur on the left side 80% of the time
and are associated with pulmonary hypoplasia if large.
 Cardiomedastinal shift is the most recognizable
sonographic feature. The Sonographer should be aware
of CDH associations with other anomalies, frequently
cardiac and brain.
 CDH is common
 Small bowl, stomach, spleen colon and liver may
herniate into the chest.
 Usually occur on the left side (80%) and associated with
pulmonary hypoplasia if large
 Cardio-mediastinal shift can occur
 Associated with other anomalies
 ID of fluid-filled bowel and stomach within the thoracic
cavity at level of 4 chamber view of heart
 Heart displaced from the left chest toward the right
 Associated Polyhydramnios
Sonographic findings
 ID of fluid-filled bowel and especially stomach within the
thoracic cavity at the level of the four chamber view of
the heart
 Heart displaced from the left chest toward the right
 Associated Polyhydramnios
CDH (Congenital Diaphragmatic
Abdominal Ascites
 Ascites in the fetal abdomen is most commonly
associated with a condition called Hydrops Fetalis.
Abdominal Ascites
Persistent right umbilical vein
 When the umbilical vein courses toward the left side of
the fetal abdomen, this is called persistent right
umbilical vein.
 The umbilical vein is actually entering the right portal
vein of the liver rather than the left portal vein.
 This variation itself is not pathogenic, but can be seen
with some anomalous conditions, and therefore warrants
a detailed investigation for other fetal anomalies.
PRUV-Transverse color Doppler scan of the
abdomen demonstrating the right umbilical
vein (pointing towards the stomach).
 Appears as a hypoechoic curved line separating the
more echogenic fetal lungs from the liver and the
Esophageal atresia
 This is the discontinuation of the esophagus. 90% are
accompanied by a distal trachoesophageal fistula.
 There is a 30-70% association with other congenital
malformations, including cardiovascular, gastrointestinal,
genitourinary, and musculoskeletal anomalies.
 Discontinuation of the esophagus.
 70% have other malformations
 Small or absent fluid-filled stomach
 Failure to demonstrate the stomach on serial sonograms
 Polyhydramnios
Esophogeal Atresia
Sonographic Findings
 Small to absent fluid-filled stomach
 Failure to demonstrate stomach on serial sonograms
 Associated Polyhydramnios
 Not always detectable with ultrasound
 Esophageal atresia is a congenital medical condition
which affects the alimentary tract. It causes the
esophagus to end in a blind-ended pouch rather than
connecting normally to the stomach. It occurs in
approximately 1 in 4425 live births.
 Congenital esophageal atresia (EA) represents a failure
of the esophagus to develop as a continuous passage.
Instead, it ends as a blind pouch. Tracheoesophageal
fistula (TEF) represents an abnormal opening between
the trachea and esophagus. EA and TEF can occur
separately or together. EA and TEF are diagnosed in the
ICU at birth and treated immediately.
 This condition takes several different forms, often
involving one or more fistulas connecting the trachea to
the esophagus (tracheoesophageal fistula).
 This birth defect arises in the fourth fetal week, when
the trachea and esophagus should begin to separate
from each other.
 Other birth defects may co-exist, particularly in the heart,
but sometimes also in the anus, spinal column, or kidneys.
This is known as VACTERL syndrome because of the
involvement of Vertebral column, Anorectal, Cardiac,
Tracheal, Esophageal, Renal, and Limbs. It is associated
with polyhydramnios in the third trimester.
 This condition is visible, after about 26 weeks or it may be
detected soon after birth as the affected infant will be
unable to swallow its own saliva. Also, the newborn can
present with gastric distention, cough, apnea, and cyanosis
 Any attempt at feeding could cause aspiration pneumonia
as the milk collects in the blind pouch and overflows into
the trachea and lungs. Furthermore, a fistula between the
lower esophagus and trachea may allow stomach acid to
flow into the lungs and cause damage. Because of these
dangers, the condition must be treated as soon as possible
after birth.
Esophageal Atresia
Duodenal Atresia
 This is the most common perinatal intestinal obstruction.
development, choledochal cysts, superior mesenteric
artery defect, and extrinsic pressure.
 65% of fetuses with duodenal atresia have a karyotype
abnormality or an associated malformation at birth,
most commonly cardiac and vertebral anomalies. 30% of
infants with DA have Down syndrome.
 Duodenal atresia is the congenital absence or
complete closure of a portion of the lumen of the
 Approximately 20-40% of all infants with duodenal
atresia have Down syndrome Approximately 8% all
infants with Down syndrome have duodenal atresia.
 It is also associated with polyhydramnios.
 The diagnosis of duodenal atresia is usually be
ultrasound of the abdomen, which shows two large air
filled spaces, the so-called "double bubble" sign The air
is trapped in the stomach and duodenum. Since the
closure of the duodenum is complete in duodenal
atresia, no air is seen distal to the duodenum.
Duodenal Atresia
 Most common perinatal intestinal obstruction
 30% have Down’s syndrome
 Double bubble sign- distention of the stomach and first
portion of the duodenum
 Polyhydramnios
 Sonographic Findings
 “Double bubble sign” due to simultaneous distention of
stomach and first portion of the duodenum
 Polyhydramnios
Duodenal Atresia
Duodenal Atresia
 Normally mixed echogenicity to cystic in appearance.
Peristalsis should be seen by late second trimester.
Meconium – a mixture of bile and swallowed vernix,
epithelium, and fetal hair, becomes packed in the large
bowel and may appear as highly echogenic areas within
the bowel.
Intestinal Atresia
 Obstruction of the intestine, with subsequent distention
of bowel loops, may occur anywhere along the intestinal
tract or at the level of the anus. The precise site is
frequently indeterminate.
Intestinal Atresia
 Obstruction of the intestine
 Distention of bowel loops
 Multiple fluid-filled bowel loops
 Increased bowel peristalsis
 Possible perforation – indicated by abdominal
calcifications and ascites
 Polyhydramnios
Intestinal atresia is a malformation where there is a
narrowing or absence of a portion of the intestine. This
defect can either occur in the small or large intestine.
 The different types of intestinal atresia are named after
their location:
 Duodenal atresia - malformation of the duodenum, part of
the intestine that empties from the stomach
 Jejunal atresia - malformation of the jejunum, the second
part of the intestine extending from the duodenum to the
 Ileal atresia - malformation of the ileum, the lower part of
the small intestine
 Colon atresia - malformation of the colon
 Intestinal atresias are often discovered before birth:
either by ultrasounds show a dilated intestinal segment
due to the blockage, or by the development of
polyhydramnios These abnormalities are indications that
the fetus may have a bowel obstruction
 Some fetuses with bowel obstruction have abnormal
chromosomes. An amniocentesis is recommended
because it can determine not only the sex of the baby,
but whether or not there is a problem with the
 Fetal and neonatal intestinal atresia treated with using
laparotomy after birth. If the area affected is small, the
surgeon may be able to remove the damaged portion
and join the intestine back together. In instances where
the narrowing is longer, or the area is damaged and
cannot be used for period of time, a temporary stoma
may be placed.
 Sonographic findings
 Multiple fluid-filled bowel loops
 Small bowel internal diameter >7mm
 Increased bowel peristalsis
 Possible perforation, indicated by abdominal
calcifications and ascites
 Polyhydramnios
 Often difficult to determine exact site of obstruction
Intestinal Atresia
Intestinal Atresia
Meconium Peritonitis
 Peritoneal inflammatory reaction occurs following an
intrauterine bowel perforation.
 Perforation may occur after the fetal bowel obstruction
caused by intestinal atresia, volvulus, or Meconium ileus.
Cystic fibrosis is considered to be the etiology in 30-40%
of all patients because of thick, sticky Meconium.
Meconium Peritonitis
 Peritoneal inflammatory reaction following an
intrauterine bowel perforation.
 Cystic fibrosis is a likely etiology because of thick, sticky
 Brightly echogenic, intra-abdominal foci
 Meconium peritonitis refers to rupture of the bowel
prior to birth, resulting in fetal stool (meconium)
escaping into the surrounding space (peritoneum)
leading to inflammation (peritonitis). Despite the bowel
rupture, many infants born after meconium peritonitis in
utero have normal bowels and have no further issues.
Twenty percent of infants born with meconium peritonitis
will have vomiting and dilated bowels on x-rays which
necessitates surgery. Meconium peritonitis is often
diagnosed on prenatal ultrasound where it appears as
calcifications within the peritoneum. Infants with cystic
fibrosis are at increased risk for meconium peritonitis.
 Sonographic findings
 Brightly echogenic, intra-abdominal foci which cast an
acoustic shadow
 Fetal ascites and Polyhydramnios
Meconium Peritonitis
Meconium Peritonitis-Calcifications are
seen throughout the abdomen in this 17
week fetus with meconium peritonitis
 Usually arises from the sacral area. Three pathologic
types exist: Mature, immature and malignant.
 They frequently are hypervascular and consists of solid
and calcified components
 They are described by the site of origin:
 Pre-sacral
 Sacrococcygeal
 Germ cell tumors usually arising from the sacral area
 Complex, large mass seen in the fetal pelvis or arising
from the fetal rump.
 May contain cystic, solid, and calcified components
Sonographic findings
 A complex, large mass seen in the fetal pelvis of arising
from the fetal rump
 May contain cystic, solid, and calcific components
 Possible differential diagnosis includes Myelomeningocele
Meconium ileus
 Sometimes the meconium becomes thickened and
congested in the ileum, a condition known as meconium
ileus. Meconium ileus is often the first symptom of cystic
fibrosis. In cystic fibrosis, the meconium can form a blackgreen mechanical obstruction in a segment of the ileum.
Beyond this there may be a few separate grey-white
globular pellets. Below this level, the bowel is a narrow and
empty micro-colon. Above the level of the obstruction, there
are several loops of hypertrophied bowel distended with
fluid. No meconium is passed, and abdominal distension and
vomiting appear soon after birth.
 About 20% of cases of cystic fibrosis present with
meconium ileus, while approximately 20% of one series of
cases of meconium ileus did not have cystic fibrosis. The
presence of meconium ileus is not related to the severity of
the cystic fibrosis. The obstruction can be relieved.
Meconium ileus
A volvulus is a loop of the bowel whose nose has twisted on itself. The
American Heritage Stedman's Medical Dictionary defines volvulus
slightly differently as "abnormal twisting of the intestine causing
obstruction," which adds obstruction in the definition, and would be
the more clinically significant term.
 Midgut volvulus occurs in patients (usually in infants) that are
predisposed because of congenital intestinal malrotation Segmental
volvulus occurs in patients of any age, usually with a predisposition
because of abnormal intestinal contents (e.g. meconium ileus) or
adhesions. Volvulus of the cecum, transverse colon, or sigmoid
colon occurs, usually in adults, with only minor predisposing factors
such as redundant (excess, inadequately supported) intestinal
tissue and constipation.
 Regardless of cause, volvulus causes symptoms by two
mechanisms. One is bowel obstruction, manifested as abdominal
distension and vomiting. The other is ischemia (loss of blood flow)
to the affected portion of intestine. This causes severe pain and
progressive injury to the intestinal wall, with accumulation of gas
and fluid in the portion of the bowel obstructed. Ultimately, this can
result in necrosis of the affected intestinal wall, acidosis, and death.
Acute volvulus therefore requires immediate surgical intervention to
untwist the affected segment of bowel and possibly resect any
unsalvageable portion.
 List all abnormalities and conditions with which
Oligohydramnios is associated.
 Polyhydramnios is associated with many conditions. List
as many as you can.
 Define premature rupture of membranes (PROM)
 What are the sonographic fetal findings in a patient with
 What are three distinctive features of gastroschisis?
 What are three distinctive features of omphalocele?
 What is bladder Exstrophy?
 What sonographic findings might suggest bladder
 What is the most recognizable sonographic feature of a
congenital diaphragmatic hernia (CDH)?
 List other sonographic findings of CDH, as well as
possible associated anomalies.
 True or false: Esophageal atresia is very commonly
accompanied by a distal trachoesophageal (T-E) atresia.
 List the sonographic findings of esophageal atresia.
 Describe how duodenal atresia may appear
 What other anomalies are associated with duodenal
 Intestinal atresia may occur anywhere along the
intestinal tract, and often the site of obstruction is
indeterminate. What are the sonographic findings of an
intestinal atresia (other than duodenal atresia??
 What is Meconium peritonitis?
 What findings might raise suspicion for Meconium
peritonitis in a fetus?
Take home test
1. In the late gestation, the hypoechoic contents of the
fetal colon typically represent
 Normal muscle of the bowel
 Meconium
 A distal obstruction, such as anal atresia
 An inflammatory reaction to bowel perforation
2. With endovaginal scanning, a small soft tissue mass is
seen anterior to the abdominal wall of an 11 week
embryo, at the location of the umbilical cord insertion.
What is the probable explanation for this finding?
 Early diagnosis of an omphalocele
 Early diagnosis of a gastroschisis
 Normal herniated bowel in the umbilical cord
 Amniotic band syndrome causing evisceration
3. The fetal urinary bladder is not observed at the
beginning of the obstetrical sonogram. The Sonographer
 Consider a diagnosis of bilateral renal agenesis
 Search carefully for associated cardiac anomalies
 Continue with the rest of the exam, and re-check for
bladder filling after 20-30 minutes
 Try a higher frequency transducer for better image
4. Which of the following statements regarding
diaphragmatic hernias is not true?
 Most diaphragmatic hernias occur on the right side
 A differential diagnosis for a fluid-filled mass on the lung is
CCAM type I
 Severe diaphragmatic hernias include bowel and even liver
 There is associated Polyhydramnios with a diaphragmatic
5. An omphalocele defect, in addition to ectopic cordis, is
associated with
 Meckel-Gruber syndrome
 Pentalogy of Cantrell
 Fetal alcohol syndrome
 Edward’s syndrome
6. Duodenal atresia is characterized by which of the
following sonographic findings?
 Oligohydramnios
 Multiple fluid-filled structures in the fetal abdomen
 Failure to demonstrate the stomach on two consecutive
 Polyhydramnios
More Homework From Callen
1. What are the consequences of the failure to visualize the
fetal stomach?
2. What are the consequences of an Esophageal Atresia?
3. Why would you, as a sonographer, be concerned that
your fetal exam patient demonstrated echogenic small
4. What sign would be expected in a fetus with duodenal
atresia? Explain your answer- what do the findings
5. Define and give the ramifications of Meconium
 What are the causes?
 What is the prognosis of the fetus diagnosed with this?
 What is the US finding?
6. Explain the anomaly of Persistent Right Umbilical Vein.
7. Define Umbilical Vein Varix
8. List the causes of fetal splenomegaly
9. Is the differential diagnosis for cystic abdominal mass
different between the male and female fetus? Explain
10. Explain the embryonic development of the fetal
gastrointestinal tract (the fetal gut).
11. Define Cloacal Exstrophy
12. Define Limb-Body Complex
13. Explain the importance of the relationship of the cord
insertion to an abdominal wall defect.
14. Define Uterine Synechia