Diagnostic ultrasound ( PDFDrive )

CHAPTER 38 The Fetal Gastrointestinal Tract and Abdominal Wall 1307
St
L
Dia
St
A
B
C
FIG. 38.3 Normal Stomach. (A) In irst trimester the fetal stomach
(St) is an echolucent structure below the diaphragm. (B) In second trimester
in sagittal view, the stomach (St) is seen below the diaphragm
(Dia), and the liver (L) extends anteriorly to the abdominal wall. (C) In
second trimester in transverse view of abdominal circumference with
the spine to the left, the stomach is superior.
Dilated Fetal Stomach
In the second or third trimester a prominent or transiently dilated
fetal stomach may be seen on ultrasound. Use of a nomogram
can aid in identifying true outliers. 17 However, there is a considerable
variation in the normal size of the stomach, and given the
asymmetrical shape of the stomach, standardization of the
measurement of the stomach dimensions is diicult. 15 In addition,
because of the considerable normal luctuations in stomach size,
the diagnosis of a dilated fetal stomach requires that the stomach
be persistently dilated throughout a 30-minute assessment as
well as on successive examinations. he diferential diagnosis of
a dilated fetal stomach includes normal variation in stomach
size and GI atresia (e.g., duodenal atresia, pyloric atresia) as
well as pyloric stenosis (Fig. 38.4).
Pyloric atresia is a rare form of intestinal atresia. 18-20 he
underlying cause is thought to be diferent than that of atresia
of other parts of the GI tract, and a familial form with an
autosomal recessive transmission is well documented. 21 A unique
aspect of pyloric atresia is the association with epidermolysis
bullosa, an oten fatal skin disorder characterized by blisters in
the skin and mucosal membranes which is inherited in an
autosomal recessive pattern. he main sonographic indings in
cases of pyloric atresia include gastric dilatation (which can be
massive), esophageal dilatation caused by gastroesophageal relux,
and severe polyhydramnios. he co-presence of epidermolysis
bullosa may be suggested by elevated levels of maternal serum
alpha-fetoprotein and snowlake appearance of the amniotic
luid 22 and can be conirmed by molecular analysis of fetal skin
biopsy. 21,23
Midline or Right-Sided Stomach
An abnormal position of the stomach is an important clue for
the presence of a severe abnormality and therefore requires
detailed anatomic assessment. A right-sided stomach (Fig. 38.5B)
should raise the possibility of heterotaxy syndrome, which is
characterized by an abnormal symmetry of the viscera and veins
and is associated with complex cardiac anomalies, intestinal
malrotation, and splenic (asplenia or polysplenia) (Fig. 38.6)
and hepatic abnormalities. 24,25 he incidence of heterotaxy
syndrome with asplenia or polysplenia is 0.45 per 10,000 pregnancies.
26 Because of the combined cardiovascular and GI abnormalities,
infant mortality is high, with the 1-year mortality rate
reaching 32%. 27 A midline stomach can represent intestinal
malrotation. 28