Jejunoileal Atresia

Jejunoileal atresia is complete obstruction of the small bowel from congenital absence of a segment of lumen, and is the commonest cause of neonatal small bowel obstruction. It is thought to follow an in utero mesenteric vascular accident.

It occurs in about 1 in 3000 to 5000 live births. Jejunal and ileal atresia occur with similar frequency. Associated problems are cystic fibrosis (especially with ileal atresia and meconium peritonitis), malrotation, volvulus and gastroschisis. Trisomy 21 is not strongly associated, unlike duodenal atresia.

Types are classified by the appearance: type I (mucosal web with intact bowel and mesentery); type II (blind ends joined by a fibrous cord); type IIIa (blind ends with a V-shaped mesenteric gap); type IIIb (apple peel or Christmas tree deformity, with absent distal superior mesenteric artery, short bowel and a high risk of loss); and type IV (multiple atresias).

Pathophysiology.

Interruption of the mesenteric blood supply in utero leads to ischaemic necrosis and resorption of a bowel segment. Bowel proximal to the atresia dilates, and distal bowel is collapsed (microcolon), as no luminal contents pass.

• Antenatal: polyhydramnios and dilated bowel loops on ultrasound.
• Bilious vomiting in the first 24 to 48 hours, increasing abdominal distension (less in proximal atresia), and failure to pass meconium in the first 24 hours (though some pass meconium).
• Jaundice, dehydration and visible loops. Peritonitis if perforation has occurred.

Red flags.

• Bilious vomiting in any newborn (surgical emergency until proven otherwise).
• Abdominal wall erythema, tenderness, rigidity or shock (perforation, volvulus).
• Meconium peritonitis calcification on X-ray, suggesting cystic fibrosis.

• Abdominal X-ray (supine and cross-table lateral): dilated bowel loops with air fluid levels, with fewer loops in proximal atresia ("triple bubble" for jejunal atresia) and absence of distal gas. Free air indicates perforation, and calcification suggests meconium peritonitis.
• Contrast enema: microcolon, with the contrast not passing beyond the terminal ileum, and to exclude other causes of obstruction such as meconium ileus and Hirschsprung disease. An upper gastrointestinal study may be used if malrotation is suspected.
• Blood tests: electrolytes, glucose, full blood count, group and save, coagulation and culture. Cystic fibrosis testing (immunoreactive trypsinogen and genetics).
• Echocardiography and renal ultrasound for associated anomalies.

Differential diagnosis. Malrotation with volvulus, meconium ileus, Hirschsprung disease, colonic atresia, duodenal atresia, necrotising enterocolitis, ileal duplication and sepsis with ileus.

Preoperative.

• Nil by mouth, wide bore nasogastric tube on free drainage with 6-hourly aspiration, and IV fluids (10% glucose with electrolytes at 60 to 80 mL/kg/day on day 1, plus replacement of nasogastric losses with 0.9% sodium chloride with potassium).
• Antibiotics in the first week of life: ampicillin 50 mg/kg IV every 12 hours and gentamicin 5 mg/kg IV every 48 hours (later doses directed by levels), with metronidazole 15 mg/kg IV loading then 7.5 mg/kg every 12 hours if perforation or peritonitis is suspected. Intervals shorten with age and with gestation of 32 weeks or more. Vitamin K 1 mg IM if not given.
• Keep the infant warm, correct fluid deficits, and transfer to a paediatric surgical centre.

Surgery.

• Laparotomy (or laparoscopy) after resuscitation. Resect the dilated, poorly functioning proximal bowel, and do an end-to-end primary anastomosis. Tapering enteroplasty if the proximal bowel is greatly dilated.
• Stoma or staged repair for peritonitis, volvulus, or unfavourable conditions. Preserve maximum bowel length, and measure remaining length.

Postoperative care.

• Parenteral nutrition until bowel function returns, which may take weeks, then gradual enteral feeding with human milk or hydrolysed formula.
• Monitor for anastomotic leak, stricture, adhesive obstruction, and sepsis.
• Short bowel syndrome (especially with type IIIb or IV): intestinal rehabilitation with parenteral nutrition, trophic feeds, and consider bowel lengthening or transplantation.

Monitoring. Growth, stool output, electrolytes, liver function, vitamin B12, fat soluble vitamins and iron in long term follow up.

Referral and escalation. Early referral to paediatric surgery for any bilious vomiting. Refer to an intestinal rehabilitation team for short bowel.

Special groups. Preterm infants and those with cystic fibrosis, multiple atresias or gastroschisis have the highest rates of complications. Overall survival is over 90%.