Friday, January 19, 2007

Bowel Obstruction in the Newborn

Synonyms and related keywords: gastrointestinal surgical emergencies of the newborn, newborn bowel obstruction, neonatal bowel obstruction, bilious vomiting, proximal bowel obstruction, distal bowel obstruction, newborn constipation, neonatal constipation, constipation in the newborn, neonatal intestinal obstruction, meconium ileus, meconium plug syndrome, abdominal distention, ileus, chronic neonatal ileus, functional bowel obstruction, polycystic kidney disease, malrotation, volvulus, midgut volvulus, duodenal atresia, duodenal web, duodenal obstruction, jejunoileal atresia, esophageal atresia, tracheoesophageal fistula, hypertrophic pyloric stenosis, Hirschsprung disease, Hirschsprung's disease, congenital megacolon, colonic atresia, imperforate anus

Bowel obstruction in the newborn is one of the most common and potentially dire newborn surgical emergencies. Successful management of a newborn with a bowel obstruction depends upon both timely diagnosis and prompt therapy. Many causes of bowel obstruction in the newborn can be readily diagnosed with physical examination and simple radiographic examinations. Crucial to the management of most newborn bowel emergencies is effective nasogastric or orogastric decompression.
Early consideration of the need for surgical intervention may mean the difference between intestinal salvage and catastrophe. Have a high index of suspicion; often, a surgeon's approach to a newborn with a potential bowel obstruction is to rule out the worst possibility first. Important signs to identify are stools containing occult blood, hypotension, metabolic acidosis, progressive respiratory failure, and thrombocytopenia.
A delay in diagnosis of a newborn bowel obstruction may exacerbate the compromise of dilated bowel upstream of the obstruction; result in clinical deterioration with dehydration, fever, and unconjugated hyperbilirubinemia; and predispose the child to complications such as aspiration pneumonia.
For example, a child with bilious emesis must be considered to have malrotation with volvulus until proven otherwise. A few hours may make the difference between full recovery and massive bowel necrosis. If a newborn in distress demonstrates evidence of a high-grade proximal small-bowel obstruction with some air past the duodenum, suspect volvulus and urgently consider an exploratory laparotomy.
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.
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