Intestinal Obstruction in the Newborn

Obstruction of an infant's gastrointestinal (GI) tract can occur anywhere from the esophagus to the anus. For purposes of this review, the newborn infant will be defined as an infant from birth to 30 days of age. Both congenital and acquired obstructions will be addressed. In each instance, the epidemiology, pathogenesis, clinical aspects, and management of the disorder will be considered.

Esophageal Atresia

EPIDEMIOLOGY AND PATHOGENESIS
Esophageal atresia, or interruption of the esophagus, generally occurs in association with a tracheoesophageal fistula (EA -- TEF). The most common anatomic arrangement is a blind proximal esophageal pouch that has a distal tracheoesophageal fistula (Figure 1). This is seen in 85% to 90% of infants who have this anomaly. Seen less commonly is pure esophageal atresia that does not have a tracheoesophageal fistula and tracheoesophageal fistula that does not have an esophageal atresia (H-type tracheoesophageal fistula). These latter two conditions occur in approximately 10% of newborns who have these types of anomalies. Other anatomic arrangements, such as an esophageal atresia that has a fistula between the upper pouch and trachea or esophageal atresia that has a fistula to both pouches, are seen in only a tiny fraction of these infants.
EA -- TEF occurs in approximately 1 in 4000 live births. There have been numerous reports of siblings who have EA -- TEF as well as reports of the anomaly in identical twins. Also reported, however, are many instances of identical twins in which one has the anomaly and the other has been spared. It is well recognized that esophageal atresia is a frequent component of the VATER association as well as other malformations, suggesting that the anomaly also might result from a specific teratogen in the developing fetus.
It commonly is believed that interruption of the events responsible for the elongation and separation of the esophageal and tracheal tubes during the fourth week of development leads to the development of this anomaly.

PRESENTATION
Infants who have EA -- TEF commonly will present in the nursery having an excessive amount of saliva. The saliva pools in the blind proximal esophageal pouch and is either regurgitated or continuously dribbled from the infant's mouth. The infant's first feeding will not be tolerated; the formula, which is, of course, not bile-stained, will be regurgitated immediately. Because these infants most commonly have a distal tracheoesophageal fistula, air enters their GI tracts through the fistula, and the abdomen will not be scaphoid. Indeed, the infant who is ventilated may well have air forced into his or her GI tract via the fistula, causing distension. Such an infant's respiratory difficulty, thus, may be compounded by the gastric distention leading to diaphragmatic elevation. In pure esophageal atresia that has no fistula, no air will enter the GI tract, and the infant will have a scaphoid abdomen.

DIAGNOSIS
The diagnosis of esophageal atresia can be made by attempting to pass a firm catheter through the mouth and into the esophagus. Obstruction to passage of the catheter, which should not be "forced," suggests the anomaly, and a chest radiograph usually will confirm the diagnosis via the presence of the coiled catheter sitting within the proximal esophageal pouch. Air injected into the catheter provides an excellent "contrast" agent to help confirm the diagnosis. The use of a true contrast agent generally is not recommended because the infant will be at risk of aspirating the agent and acquiring a chemical pneumonitis. In the rare instance in which contrast is required, 1 mL or less of a water-soluble agent can be injected into the pouch and then withdrawn immediately once the diagnosis has been confirmed. Air in the GI tract confirms the presence of the distal tracheoesophageal fistula.

MANAGEMENT
Appropriate management of these babies begins at the time of diagnosis. A significant risk to the infants is the potential for gastric juice to pass upward in the distal esophagus and traverse the tracheoesophageal fistula where it may be aspirated, resulting in the development of chemical pneumonitis. These infants need to have a sump catheter placed immediately into the upper pouch and into the head up position at an angle of at least 45 degrees. This will help minimize the aspiration of saliva and the chance of gastric juice soiling the lungs.
As a general rule, all newborns whose GI tracts are obstructed should have intravenous fluids instituted and antibiotics begun. If the neonate is not at a surgical center, transport needs to be arranged as soon as possible.
In infants who have EA -- TEF, immediate primary repair generally is undertaken in those weighing as little as 1200 g. An infant presenting with significant pneumonia or other major congenital anomalies will require a more individualized approach; a staged repair via an initial gastrostomy may be performed in an infant who has EA -- TEF and is ill. The infant can be allowed to improve or to be evaluated for other anomalies prior to performing definitive repair.
Infants who have pure esophageal atresia generally are unable to have a primary repair performed in the newborn period because the distance between the two ends of the esophagus is too great. These infants require a gastrostomy and either exteriorization of the esophagus with a later esophageal substitution procedure (reverse gastric tube, colon interposition) or serial attempts at dilatation of the two ends of the esophagus with a later attempt at a primary anastomosis. Although conceptually more attractive, the latter option requires a prolonged initial hospitalization and has an attendant ongoing risk of aspiration.
The prognosis for most babies is excellent; only a few sick infants who have serious coexisting anomalies, are of extreme low birth weight, and have persistent pulmonary disease have a diminished chance for survival. It is not at all uncommon for the infant to develop a relative narrowing or stricturing at the anastomotic site, which does not become evident until the child is advanced to solid foods. Generally, this problem is managed easily with esophageal dilatation. The infants also may have problems with esophageal motility that mimics a stricture. This is determined easily by a contrast swallow radiograph.
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