83 INTESTINAL OBSTRUCTION OF NEONATES AND INFANTS
Richard J. Hendrickson M.D., Denis D. Bensard M.D.

1. What signs or symptoms suggest intestinal obstruction in the neonate?

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Signs and symptoms vary according to the level of obstruction. Proximal intestinal obstruction leads to the early onset of bilious emesis, generally with minimal abdominal distention. In contrast, neonates with distal intestinal obstruction present after the first day of life with bilious vomiting and pronounced abdominal distention. Bilious emesis should always be interrogated further in infants and children.

2. What is the differential diagnosis of intestinal obstruction in neonates?

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Look for an anal opening, which eliminates the diagnosis of imperforate anus. Next obtain an abdominal radiograph. The extent of gaseous distention of the bowel implicates a proximal or distal bowel obstruction. No attempts should be made to distinguish small from large bowel obstruction.

3. When are contrast studies of the gastrointestinal (GI) tract indicated? Show answer
If peritonitis or pneumoperitoneum is present, proceed to exploratory laparotomy without delay. Malrotation with volvulus must be distinguished from the other cause of congenital duodenal obstruction (duodenal atresia). In this setting, upper GI is the study of choice. In volvulus, the upper GI demonstrates distention of the proximal duodenum, corkscrewing of the distal duodenum, and limited or no progression of contrast into the distal bowel. Conversely, duodenal atresia appears as a blind ending pouch in the first or second portion of the duodenum. Contrast enema is generally the preferred study in all other forms of neonatal intestinal obstruction.

4. Describe intestinal atresia.

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Atresia can occur anywhere in the GI tract: duodenal (50%), jejunoileal (45%), or colonic (5%). Duodenal atresia arises from a failure of recanalization during the 8th-10th week of gestation; jejunoileal and colonic atresia are caused by an in utero mesenteric vascular accident.

5. Distinguish duodenal atresia from other forms of intestinal atresia.

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Duodenal atresia is characterized by the onset of bilious vomiting (85% of atresia distal to the ampulla of Vater) within the first day of life; significant abdominal distention is absent. Approximately 25% of affected infants have trisomy 21. The abdominal radiograph demonstates a “double bubble” caused by the distended stomach and first or second portions of duodenum. Surgical correction is performed by duodenoduodenostomy.
Jejunoileal atresia produces bilious vomiting at 2-3 days of life with moderate to severe abdominal distention. The abdominal radiograph shows dilated loops of bowel with air-fluid levels. Barium enema reveals a microcolon and no reflux of contrast into the dilated bowel. Associated anomalies are uncommon. Surgical correction involves end-to-end anastomosis with or without limited intestinal resection.
Colonic atresia, similar to jejunalileal atresia, is associated with the late onset of bilious vomiting, no passage of meconium, and moderate to severe abdominal distention. The abdominal radiograph reveals dilated loops of bowel with air-fluid levels suggesting distal intestinal obstruction. Barium enema demonstrates a microcolon with a cutoff observed in a proximal colonic segment. Twenty percent of affected infants suffer an associated anomaly of the heart, musculoskeletal system, abdominal wall, or GI tract. Surgical management includes limited colonic resection with primary anastomosis.

6. Describe malrotation with midgut volvulus.

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During the 6th-12th week of gestation, the intestine undergoes evisceration, growth, return to the abdominal cavity, and counterclockwise rotation with fixation. Malrotation is an error in both rotation and fixation. Abnormal fixation and a narrow-based mesentery predispose to twisting of the midgut on its blood supply (superior mesenteric artery), vascular occlusion (strangulation), and obstruction (malrotation with midgut volvulus). Typically, a previously well neonate or child without a history of surgery presents with bilious vomiting, abdominal distention, and variable degrees of shock. If the infant is acutely ill, no further studies are needed and surgical exploration is indicated. If the diagnosis is in question and the infant is stable, an upper GI study, not a barium enema, is performed. Surgical treatment entails four parts: (1) division of abnormal peritoneal bands, (2) correction of malrotation, (3) restoration of a broad-based mesentery, and (4) appendectomy because of the location of the cecum in the right upper quadrant.

7. Is midgut volvulus a surgical emergency?

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Yes! The risk of strangulation caused by the rotational anomaly and abnormal peritoneal bands implies a surgical emergency. Delay places the infant at risk of losing the entire midgut and potentially dying.

8. What is meconium ileus (MI)?

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MI is the obstruction of the terminal ileum by highly viscid, tenacious meconium. MI is a complication of cystic fibrosis (CF). Fifteen percent of neonates with CF present with MI. The combination of hyperviscous mucus secreted by the abnormal intestinal glands and pancreatic insufficiency leads to abnormal meconium and obstructs the lumen of the terminal ileum. Symptoms of feeding intolerance, bilious emesis, and abdominal distention begin in the second to third days of life. Unlike most forms of neonatal intestinal obstruction, surgery is reserved for patients refractory to nonoperative treatment or complex MI (atresia, volvulus, perforation). Sixty percent of infants with simple MI can be treated successfully with Gastrografin enemas and rectal irrigation. If an operation is indicated, the objective is to remove the obstructing meconium by limited resection or enterostomy with evacuation of the meconium and irrigation of the distal bowel.

9. What is Hirschsprung’s disease?

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In this disease, the intestine is innervated by cells originating in the neural crest. During the 5th-12th week of gestation, neural crest cells migrate in a craniocaudal direction and disperse within the wall of the intestine (intermuscular, to Auerbach’s plexus; submucosal, to Meissner’s plexus). Hirschsprung’s disease arises from the failure of normal enteric innervation. The bowel remains in a contracted, spastic state and produces a functional rather than a true mechanical obstruction. Abdominal distention, feeding intolerance, and delayed or absent meconium within the first 48 hours of life are the presenting findings in infants. Older patients suffer chronic constipation, abdominal distention, and failure to thrive. Because the disease always affects the most distal bowel (80-85% rectosigmoid) with a variable involvement of proximal bowel, barium enema demonstrates the characteristic radiographic appearance of a spastic, contracted rectum with dilated proximal bowel. Suction rectal biopsy documenting the absence of ganglion cells and presence of nerve hypertrophy confirms the diagnosis. Surgical correction is performed by excision of the aganglionic (distal colorectal) segment and coloanal anastomosis.

10. What is intussusception? What are the therapeutic options?

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Intussusception is the invagination of proximal bowel (intussusceptum) into the distal bowel (intussuscipien). Swelling, vascular compromise, and obstruction follow. Nearly two thirds of cases occur in the first 2 years of life. The cause is thought to be a result of lymphoid hyperplasia in the terminal ileum after viral infection. The diagnosis should be suspected in previously well infants, 6-9 months of age, with vomiting, crampy abdominal pain, and bloody stools. Barium or air enema is both diagnostic and therapeutic. Injection of contrast demonstrates colonic obstruction with no reflux into the proximal bowel. Controlled hydrostatic reduction with barium or air is successful in 90% of cases. If hydrostatic reduction is unsuccessful or in children with peritonitis, operative reduction is indicated. The risk of recurrent intussusception is 5% for either radiographic or surgical reduction.

11. What examples of neonatal obstruction can escape early detection and present later in life?

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Although most conditions are identified within the first week to month of life, lesions other than atresia may be identified in children and even adults.
Duodenal stenosis. Unlike duodenal atresia, stenosis results in narrowing but not complete obstruction of the duodenum. Thus, infants fed formula or pureed foods may not become symptomatic until childhood. Children with intermittent abdominal pain and symptoms of gastric outlet obstruction require an upper GI study, particularly if they have trisomy 21.
Malrotation. One third of patients with malrotation are identified after the first month of life. Children present with bilious emesis and intermittent abdominal pain, and malrotation is generally identified by an upper GI series. Malrotation with midgut volvulus should be suspected in any ill child with signs of intestinal obstruction and no history of abdominal surgery.
Hirschsprung’s disease. One third of patients are diagnosed after the first year of life. A long history of constipation refractory to therapy mandates rectal biopsy, particularly in patients with trisomy 21.
Intussusception. One third of cases occur after age 2 years. A pathologic lead point (i.e., polyp, tumor, hematoma, Meckel’s diverticulum) is present in one third of older patients.

References
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