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DEVELOPMENTAL ANOMALIES OF THE ESOPHAGUS
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The esophagus develops from the proximal aspect of the embryonic foregut. The tracheoesophageal septum partitions the developing trachea from the esophagus. The epithelium and glands of the esophagus derive from endoderm. Initially, proliferating epithelium obliterates the esophageal lumen; recanalization occurs by the end of the embryonic period. Innervation of the esophagus is by branches of the vagus nerves.
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Esophageal Atresia and Tracheoesophageal Fistula
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Esophageal atresia and tracheoesophageal fistula comprise a spectrum of congenital abnormalities in which there is failure of normal formation of the tubular esophagus and/or there is an abnormal communication between the esophagus and trachea. This group of anomalies represents the most common congenital malformation of the esophagus. This anomaly occurs in approximately 1:3000 livebirths. Associated anomalies are present in more than 50% of children with esophageal atresia or tracheoesophageal fistula. About one-quarter of these children have an additional GI tract anomaly, such as imperforate anus, pyloric stenosis, duodenal atresia, or annular pancreas. Cardiac, genitourinary, and vertebral anomalies can also occur. Esophageal atresia and tracheoesophageal fistula are important components of the VACTERL complex: vertebral, anal, cardiovascular, tracheoesophageal, renal, radial, and limb malformations.
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Although there is an incomplete understanding of the pathophysiology of esophageal atresia and tracheoesophageal fistula, it apparently involves defective formation and separation of the primitive foregut into the trachea and esophagus (Table 34-1). The esophagus and trachea comprise a single tube during early fetal development. There is subsequent division into 2 structures by infolding of the lateral walls of the foregut. A tracheoesophageal fistula is due to incomplete folding of these walls such that the mesodermal surfaces fail to come into contact. Esophageal atresia results if the lateral folds turn dorsally and thereby cut through the esophageal lumen. An alternative mechanism is intrauterine anoxia or stress that causes vascular compromise and focal necrosis of the esophagus.
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The traditional classification system for esophageal atresia and tracheoesophageal fistula recognizes 5 types. Type A is pure esophageal atresia without a fistula. Type B is esophageal atresia with a fistula between the proximal pouch and the trachea. Type C is esophageal atresia with a fistula from the distal esophageal segment to the trachea or a main bronchus (Figure 34-1). This is by far the most common type, accounting for approximately 75%. Type D is esophageal atresia with both proximal and distal fistulas (Figure 34-2). Type E is a tracheoesophageal fistula (H-type) without associated atresia.
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