Anemia of Prematurity - Portal Neonatal

Signs and symptoms of a newborn bowel obstruction may be subtle and nonspecific. Bilious gastric
aspirates or emesis suggests an obstruction distal to the ampulla of Vater, usually in the proximal
small bowel, and demands an immediate evaluation. As a rule, consider any infant or child with
bilious vomiting to have a bowel obstruction until proven otherwise; emergent assessment is
mandatory. Abdominal distention or tenderness is a less-specific finding and may indicate bowel
obstruction or bowel compromise from other causes, such as septic ileus or necrotizing enterocolitis.
An abnormal gas pattern visualized on abdominal radiography often leads to the diagnosis of bowel
obstruction.
The importance of a thorough physical examination cannot be overstated. Inspection and palpation
of the infant's abdomen and perineum often suggest a diagnosis. An incarcerated hernia, an anterior
ectopic anus, or imperforate anus can be identified with careful perineal inspection. Inability to pass
a nasogastric tube may be diagnostic of esophageal atresia. Diagnostic modalities, such as simple
abdominal radiography, radiographic contrast studies, and abdominal ultrasonography, can be
extremely helpful in identifying the cause of a neonatal bowel obstruction.
A more detailed discussion of the causes of bowel obstruction in the newborn can be divided into
proximal bowel obstruction and distal bowel obstruction. Patients with proximal obstruction often
present with different clinical scenarios than patients with distal obstruction, and different diagnostic
approaches are indicated. Understanding the causes and evolution of neonatal bowel obstruction is
enhanced by careful prenatal imaging and diagnosis.
Once a newborn presents with evidence of bowel obstruction, dividing the differential diagnoses into
categories of surgical versus nonsurgical etiologies is useful.
PRENATAL DIAGNOSIS OF BOWEL OBSTRUCTION Section 3 of 11
Prenatal imaging, especially with ultrasonography, can be extremely effective in detecting of bowel
obstruction. A fetus with proximal bowel obstruction may present with polyhydramnios that occurs
when the normally large volume of amniotic fluid swallowed by the fetus remains in the amniotic sac.
Approximately 50% of newborns with duodenal atresia have polyhydramnios. Polyhydramnios
increases the risk of premature birth.
The high resolution of fetal ultrasonography and fetal magnetic resonance imaging (MRI) frequently
enables identification of abnormal features of the bowel in the fetus. Both studies readily identify a
dilated loop of bowel and are good predictors of a proximal bowel obstruction such as atresia or
volvulus. In some situations, fetal diagnosis of a proximal bowel atresia may prompt amniocentesis
because a strong relationship exists between some types of bowel obstruction and some
chromosomal anomalies. For example, children with duodenal atresia have a higher incidence of
trisomy 21. Thus, prenatal imaging of a bowel obstruction may complement other modalities of
prenatal counseling for parents.
Ultrasonography is useful for identification of abnormal loops of bowel in the fetus. Unlike in the
newborn, the fetal bowel is gasless, without swallowed air that distorts the image. As mentioned
above, a dilated loop of small bowel may suggest an atresia or volvulus. A whirlpool appearance to
the bowel and bowel mesentery may indicate malrotation with volvulus. Echogenic bowel suggests
bowel compromise. In approximately one third of fetuses with echogenic bowel on prenatal
ultrasonography, a malformation of the GI tract is later confirmed.
Some prenatal ultrasonographic or MRI features are associated with specific abnormalities in the
fetus. A dilated proximal esophagus is often observed with esophageal atresia. Bowel within the
thoracic cavity confirms a congenital diaphragmatic hernia. More subtle signs can be observed as
well. Flecks of calcification throughout the peritoneal cavity suggest meconium peritonitis from
prenatal bowel compromise and perforation and strongly suggest cystic fibrosis. Finally, the
nonspecific finding of ascites can suggest compromised bowel in the fetus. Other nonsurgical
causes of postnatal bowel dysfunction, such as hydrocephalus or renal disease, may also be
observed on prenatal imaging studies.