Relatively speaking, congenital duodenal atresia is one of the more common intestinal anomalies treated by pediatric surgeons, occurring 1 in 2500-5000 live births. In 25-40% of cases, the anomaly is encountered in an infant with trisomy 21 (Down syndrome).  The definitive intervention to correct the anomaly is surgical and consists of duodenoduodenostomy in the newborn period.
History of the Procedure
Calder published the first report of duodenal obstruction in 1733 when he described 2 children with "preternatural confirmation of the guts." Both infants died, as did subsequently reported infants with this defect. Scattered reports of duodenal obstruction appeared in the European literature over ensuing years. In 1916, the first survivor was reported, yet survival in the early 20th century remained rare. Morbidity and mortality significantly improved only over the last 50 years.  Because of progress in pediatric anesthesia, neonatology, and surgical techniques, survival is about 90% in infants who present with this anomaly. The standard operative procedure today consists of duodenoduodenostomy via a right upper quadrant incision, although recent advancements have enabled some surgeons to repair the defect by minimally invasive means. [3, 4]
Differential diagnosis of neonatal upper GI obstruction includes the following:
Malrotation with midgut volvulus
Duodenal atresia and stenosis
Preduodenal portal vein
Any intestinal atresia
Foreign body obstruction
Duodenal obstruction may be complete or incomplete. See the images below.
Duodenal atresia is an example of complete intrinsic obstruction. Duodenal stenosis is an example of an incomplete intrinsic abnormality; however, duodenal extrinsic stenosis can occur in association with malrotation or a preduodenal portal vein. Strictly speaking, annular pancreas does not cause an extrinsic duodenal obstruction because the duodenum within the collar of an annular pancreas is intrinsically narrowed.
Duodenal atresia can take many forms, but proximal and distal intestinal segments always end blindly.  The intestine on either side of the defect may be in apposition (type 1), separated by a fibrous cord (type 2), or gap (type 3). Regardless of atresia severity, the proximal intestinal segment is typically dilated and the distal segment empty; these are hallmarks of duodenal atresia. Although obstruction may occur anywhere within the duodenum, it is most common in the vicinity of the ampulla of Vater.
Stenosis may manifest as a stricture or a perforated intraluminal diaphragm. The perforation within the diaphragm is usually singular and centrally located within the lumen of the duodenum, although variations have been reported. A windsock abnormality is a thin diaphragm that has ballooned distally as a result of peristalsis. Together, both duodenal atresia and stenosis comprise a frequent cause of intestinal obstruction in the newborn. 
Reported incidence rates range from 1:2,500 to 1:40,000 live births; published rates in the United States and internationally do not appear to differ. Duodenal atresia is not usually regarded as a familial condition, despite isolated reports of this condition in multiple siblings.
Although the underlying cause of duodenal atresia remains unknown, its pathophysiology has been well described. Frequent association of duodenal atresia or stenosis with other neonatal malformations suggests both anomalies are due to a development error in the early period of gestation. Duodenal atresia differs from other atresias of the small and large bowel, which are isolated anomalies caused by mesenteric vascular accidents during later stages of development. No predisposing maternal risk factors are known. Although up to one third of patients with duodenal atresia have Down syndrome (trisomy 21), it is not an independent risk factor for developing duodenal atresia. [3, 6]
Duodenal maldevelopment occurs secondary to either inadequate endodermal proliferation (gut elongation outpaces proliferation) or failure of the epithelial solid cord to recanalize (failure of vacuolization).
Multiple investigators have demonstrated that the epithelium of the duodenum proliferates during 30-60 days' gestation, completely plugging the duodenal lumen. A subsequent process termed vacuolation occurs whereby the solid duodenum is recanalized. Vacuolation is believed to occur by way of apoptosis, or programmed cell death, which occurs during normal development within the lumen of the duodenum. Occasionally, duodenal atresia is associated with annular pancreas—pancreatic tissue that surrounds the entire circumference of the duodenum. This is likely due to failure of duodenal development rather than robust and/or abnormal growth of the pancreatic buds.
At the cellular level, the GI tract develops from the embryonic gut, which is composed of an epithelium derived from endoderm, surrounded by cells of mesodermal origin. Cell signaling between these two embryonic layers appears to play a critical role in coordinating patterning and organogenesis of the duodenum. Sonic hedgehog genes encode members of the Hedgehog family of cell signals. Both are expressed in gut endoderm, whereas target genes are expressed in discrete layers in the mesoderm. Mice with genetically altered sonic hedgehog signaling display duodenal stenosis, which suggests that genetic defects in the sonic hedgehog family of genes may influence the development of duodenal abnormalities.
Duodenal atresia is a disease of newborn infants. Cases of duodenal stenosis or perforated duodenal web (diaphragm) rarely remain undiagnosed until childhood or adulthood; these cases represent the exception rather than the rule. Duodenal atresia appears to be equally distributed between infants of both sexes, with no reported predilection for one race.
The use of modern ultrasonography has allowed many infants with duodenal obstruction to be identified prenatally. In a large cohort study of 18 different congenital malformation registries from 11 European countries, 52% of infants with duodenal obstruction were identified in utero.  Duodenal obstruction is characterized by a double-bubble sign on prenatal ultrasonography. The first bubble corresponds to the stomach and the second to the postpyloric and prestenotic dilated duodenal loop. Prenatal diagnosis allows the mother the opportunity to receive prenatal counseling and to consider delivery at or near a tertiary care facility that is able to care for infants with GI anomalies. [7, 8]
Presenting symptoms and signs are the result of high intestinal obstruction. Duodenal atresia is typically characterized by onset of vomiting within hours of birth. While vomitus is most often bilious, it may be nonbilious because 15% of defects occur proximal to the ampulla of Vater. Occasionally, infants with duodenal stenosis escape detection of an abnormality and proceed into childhood or, rarely, into adulthood before a partial obstruction is noted. Nevertheless, one should assume any child with bilious vomiting has a proximal GI obstruction until proven otherwise, and further workup should be begun expeditiously.
Once delivered, an infant with duodenal atresia typically has a scaphoid abdomen. One may occasionally note epigastric fullness from dilation of the stomach and proximal duodenum. Passing meconium within the first 24 hours of life is not usually altered. Dehydration, weight loss, and electrolyte imbalance soon follow unless fluid and electrolyte losses are adequately replaced. If intravenous (IV) hydration is not begun, a hypokalemic/hypochloremic metabolic alkalosis with paradoxical aciduria develops, as with other high GI obstruction. An orogastric (OG) tube in an infant with suspected duodenal obstruction typically yields a significant amount of bile-stained fluid.
Although duodenal atresia is a surgically treated disease, operating on an infant with duodenal obstruction in the middle of the night is unnecessary. Only 2 limitations apply to timing the repair: stabilization of the fluid and electrolyte balance and exclusion of overwhelming congenital defects that would preclude use of a general anesthetic (ie, complex congenital heart disease). Correction can begin any time after these issues are addressed and optimized.
Relevant anatomy of duodenal atresia is addressed in Problem.
Contraindications to immediate repair include electrolyte or fluid balance disturbances; severe cardiac defects, which should be repaired prior to addressing the duodenal abnormality; and severe respiratory insufficiency that would preclude a safe operation. Infants can be maintained on orogastric OG suction and intravenous nutrition with aggressive repletion of fluid and electrolyte losses while these life-threatening issues are addressed.
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