GASTROINTESTINAL & ABDOMINAL SURGICAL CONDITIONS IN THE NEWBORN INFANT

ESOPHAGEAL ATRESIA & TRACHEOESOPHAGEAL FISTULA

• Essentials of Diagnosis & Typical Features
• Polyhydramnios.
• Baby with excessive drooling and secretions, choking with attempted feeding.
• Unable to pass an orogastric tube to the stomach.

General Considerations
These associated conditions are characterized by a blind esophageal pouch and a fistulous connection between the proximal or distal esophagus (or both) and the airway. In 85% of affected infants, the fistula is between the distal esophagus and the airway. Polyhydramnios is common because of the high level of gastrointestinal obstruction.

Clinical Findings
Infants present in the first hours of life with copious secretions, choking, cyanosis, and respiratory distress. Diagnosis can be confirmed with chest x-ray after careful placement of a nasogastric tube to the point at which resistance is met. On chest x-ray, the tube will be seen in the blind pouch. If a tracheoesophageal fistula is present to the distal esophagus, gas will be present in the bowel. In cases of esophageal atresia without tracheoesophageal fistula, there is no gas in the bowel.

Treatment
The tube in the proximal pouch should be placed on continuous suction to drain secretions and prevent aspiration. The head of the bed should be elevated to prevent reflux of gastric contents through the distal fistula into the lungs. Intravenous glucose and fluids should be provided and oxygen administered as needed. Definitive treatment is by operation and depends on the distance between the segments of esophagus. If the distance is not too great, the fistula can be ligated and the ends of the esophagus anastomosed. In instances in which the ends of the esophagus cannot be brought together, the initial surgery entails fistula ligation and a gastrostomy for feeding. Echocardiography should be performed prior to surgery to rule out a right-sided aortic arch. In those cases, a left-sided thoracotomy would be preferred.

Prognosis
Prognosis is determined primarily by the presence or absence of associated anomalies. Vertebral, anal, cardiac, renal, and limb anomalies are the most likely anomalies to be observed (VACTERL association). Evaluation for associated anomalies should be done early.

INTESTINAL OBSTRUCTION

• Essentials of Diagnosis & Typical Features
• Infants with high intestinal obstruction present soon after birth with emesis.
• Bilious emesis represents a malrotation with midgut volvulus until proved otherwise.
• Low intestinal obstruction is characterized by abdominal distention and late onset of emesis.

General Considerations
A history of polyhydramnios is common and the fluid, if bile-stained, can easily be confused with thin meconium staining. The higher the obstruction in the intestine, the earlier the infant will present with vomiting and the less prominent the distention will be. The opposite is true for lower intestinal obstructions. Most obstructions are bowel atresias, believed to be caused by an ischemic event during development. Approximately 30% of cases of duodenal atresia are associated with Down syndrome. Meconium ileus is a distal small bowel obstruction caused by the exceptionally viscous meconium produced by fetuses with cystic fibrosis. Hirschsprung disease is caused by a failure of neuronal migration to the myenteric plexus of the distal bowel so that the distal bowel lacks ganglion cells, causing a lack of peristalsis in that region with a functional obstruction.
Malrotation with midgut volvulus is a surgical emergency that appears in the first days to weeks as bilious vomiting without distention or tenderness. If malrotation is not treated promptly, torsion of the intestine around the superior mesenteric artery will lead to necrosis of the entire small bowel. For this reason, bilious vomiting in the neonate always demands immediate attention and evaluation.

Clinical Findings
Diagnosis of intestinal obstructions depends on plain abdominal radiographs with either upper GI series (high obstruction suspected) or contrast enema (lower obstruction apparent) to define the area of obstruction. Table 1–21 summarizes the findings expected.

All infants with meconium ileus are presumed to have cystic fibrosis. Infants with pancolonic Hirschsprung disease, colon pseudo-obstruction syndrome, or colonic dysgenesis or atresia may also present with meconium impacted in the distal ileum. Definitive diagnosis of cystic fibrosis is by the sweat chloride test (Na+ and Cl{–} concentration > 60 mEq/L) or by genetic testing. Approximately 10– 20% of infants with cystic fibrosis present with meconium ileus. Infants with cystic fibrosis and meconium ileus generally have a normal immunoreactive trypsinogen test because of the associated severe exocrine pancreatic insufficiency in utero.
Any in utero perforation results in meconium peritonitis with residual intra-abdominal calcifications. Many of these are completely healed at birth. If the infant has no signs of obstruction, no further immediate evaluation is needed. A sweat test to rule out cystic fibrosis should be done at a later date.
Low intestinal obstruction may present with delayed stooling (> 24 hours in term infants is abnormal) with mild distention. X-ray findings of gaseous distention should prompt contrast enema to diagnose (and treat) meconium plug syndrome. If no plug is found, the diagnosis may be small left colon syndrome (occurring in IDMs) or Hirschsprung disease. Rectal biopsy will be required to make this diagnosis. Imperforate anus should be apparent on physical examination, although a rectovaginal fistula with a mildly abnormal-appearing anus can occasionally be confused with normal.

Treatment
Nasogastric suction to decompress the bowel, intravenous glucose, fluid and electrolyte replacement, and respiratory support as necessary should be instituted. Antibiotics are usually indicated. The definitive treatment for most of these conditions (with the exception of meconium plug syndrome, small left colon syndrome, and some cases of meconium ileus) is surgery.

Prognosis
Up to 10% of infants with meconium plug syndrome are subsequently found to have cystic fibrosis or Hirschsprung disease. For this reason, some surgeons advocate performance of a sweat chloride test and rectal biopsy in all of these infants before discharge. The infant with meconium plug syndrome who is still symptomatic after contrast enema should have a rectal biopsy.
In cases of duodenal atresia associated with Down syndrome, the prognosis will depend on associated anomalies (eg, heart defects) and the severity of prestenotic duodenal dilation. Otherwise, these conditions usually carry an excellent prognosis after surgical repair.


ABDOMINAL WALL DEFECTS

1. OMPHALOCELE
Omphalocele is a membrane-covered herniation of abdominal contents into the base of the umbilical cord. There is a high incidence of associated anomalies (cardiac, gastrointestinal, chromosomal—eg, trisomy 13). The sac may contain liver and spleen as well as intestine.
Acute management of omphalocele involves covering the defect with a sterile dressing soaked with warm saline to prevent fluid loss, nasogastric decompression, intravenous fluids and glucose, and antibiotics. If the contents of the omphalocele will fit into the abdomen, a primary surgical closure is done. If not, a staged closure is performed, with gradual reduction of the omphalocele contents into the abdominal cavity and a secondary closure. Postoperatively, third-space fluid losses may be extensive; fluid and electrolyte therapy, therefore, must be monitored carefully.

2. GASTROSCHISIS
In gastroschisis, the intestine extrudes through an abdominal wall defect lateral to the umbilical cord. There is no membrane or sac and no liver or spleen outside the abdomen. Gastroschisis is associated with no anomalies except intestinal atresia. The herniation is thought to occur as a rupture through an ischemic portion of the abdominal wall.
Therapy is as described for omphalocele; however, primary closures can be successfully performed more frequently.


DIAPHRAGMATIC HERNIA
This congenital malformation consists of herniation of abdominal organs into the hemithorax (usually left) through a posterolateral defect in the diaphragm. It presents in the delivery room as severe respiratory distress in an infant with poor breath sounds and scaphoid abdomen. The rapidity and severity of presentation—as well as ultimate survival—depend on the degree of pulmonary hypoplasia, which is a result of compression by the intrathoracic abdominal contents in utero. Affected infants are prone to development of pneumothorax.
Treatment includes intubation and ventilation as well as decompression of the gastrointestinal tract with a nasogastric tube. An intravenous infusion of glucose and fluid should be started. Chest x-ray confirms the diagnosis. Surgery to reduce the abdominal contents from the thorax and to close the diaphragmatic defect is performed after the infant is stabilized. The postoperative course is often complicated by severe pulmonary hypertension, requiring therapy with high-frequency ventilation, inhaled NO, or ECMO. The mortality rate for this condition is 50%, with survival dependent on the degree of pulmonary hypoplasia.


GASTROINTESTINAL BLEEDING

Upper Gastrointestinal Bleeding
Upper gastrointestinal bleeding is not uncommon in the newborn nursery. Old blood (coffee-ground material) may be either swallowed maternal blood or infant blood from a bleeding gastric irritation such as gastritis or stress ulcer. Bright red blood from the stomach is most likely acute bleeding, again due to gastritis. Treatment generally consists of gastric lavage (a sample can be sent for Apt testing to determine if it is mother’s or baby’s blood) and antacid medication. If the volume of bleeding is large, intensive monitoring, fluid and blood replacement, and endoscopy are indicated .

Lower Gastrointestinal Bleeding
Rectal bleeding is less common than upper gastrointestinal bleeding in the newborn and is associated with infections (eg, Salmonella acquired from the mother perinatally), milk intolerance (blood streaks with diarrhea), or, in stressed infants, necrotizing enterocolitis. An abdominal x-ray should be obtained to rule out pneumatosis intestinalis (air in the wall of the bowel) or other abnormalities in gas pattern (eg, obstruction). If the x-ray is negative and the examination is benign, a protein hydrolysate or predigested formula (eg, Nutramigen or Pregestamil) should be tried or the mother instructed to avoid all dairy products in her diet if nursing. If the amount of rectal bleeding is large or persistent, endoscopy will be needed.


GASTROESOPHAGEAL REFLUX

All people reflux occasionally, and physiologic regurgitant reflux is extremely common in infants. Reflux is pathologic and should be treated when it results in failure to thrive owing to excessive regurgitation, poor intake due to dysphagia and irritability, apnea or cyanotic episodes (acute life-threatening events), or chronic respiratory symptoms of wheezing and recurrent pneumonias. Diagnosis is clinical, with confirmation by barium swallow or pH probe study.
Initial steps in treatment include prone positioning, with thickened feeds (rice cereal, 1 tbsp/oz of formula) for those with frequent regurgitation and poor weight gain. Gastric acid suppressants such as ranitidine (2 mg/kg twice a day) or cimetidine, along with a prokinetic agent such as metaclopramide (0.1 mg/kg three to four times daily), can also be used (see cautions page 529). Because most infants improve by 12–15 months, surgery is reserved for the most severe cases, especially those with chronic neurologic or respiratory conditions that exacerbate reflux and those who have life-threatening events caused by reflux.