6.1 Congenital Anomalies

Embryologically the gastrointestinal and respiratory tracts start out as a single tube; however, by the second month of gestation they have completely divided. Problems with this process lead to various congenital anomalies, the most common being tracheoesophageal fistula with esophageal atresia. In 85-90% of cases, the proximal esophagus ends in a blind pouch while the distal esophagus consists of a blind pouch in continuity with the stomach. Neonates with this abnormality develop immediate aspiration with feeding. There is no air in the bowel on x-ray films of the abdomen, contrary to what is observed in those with fistulas involving the distal esophagus. In 1-2% of cases there is an "H-type" fistula with atresia. The patient presents with repeated pulmonary infections and abdominal distention. The latter is caused by air getting into the gastrointestinal tract via the fistula when the infant cries. Because the H-type fistula may be very small, the condition may go unnoticed until adulthood, when it is detected during the investigation of recurrent pulmonary infections. Some of these fistulas may close spontaneously but produce paraesophageal inflammation and ultimately localized esophageal stricture formation.

Treatment of esophageal fistulas (with or without atresia) is surgical. The prognosis is now quite good and mortality is usually related to coexistent congenital malformations. It is important to remember that many of these patients will have gastroesophageal reflux as well as abnormal esophageal peristalsis following surgery, which may cause significant long-term problems.

Congenital esophageal stenosis is a rare anomaly that is also probably related to abnormal differentiation of the gastrointestinal and respiratory tracts, as resected specimens have been found to have pulmonary epithelium and/or bronchial remnants. Sequestered pulmonary remnants with connections to the esophagus but not associated with stenosis have also been described.

The majority of hiatus hernias are acquired. Rarely, a hiatus hernia can be caused by a congenitally short esophagus. Hiatus hernias can be divided into two types: (1) sliding and (2) paraesophageal (Figures 3 and Figure 4, respectively). A sliding hiatus hernia refers to the condition where a circumferential cuff of cardia and proximal stomach migrates up through the diaphragmatic hiatus and into the thorax. This may reduce and reform spontaneously. These hernias are very common and increase in incidence with advancing age. Generally they are of no clinical significance, despite the fact that many patients and physicians persist in attributing a wide variety of symptoms to them. Large hiatus hernias may be associated with iron deficiency anemia that is presumably caused by recurrent superficial ulcerations at the site where the diaphragm exerts pressure on the herniated stomach. If no other source of GI blood loss is discovered after thorough investigation, and patients continue to be iron-deficient despite supplementation and antiulcer treatment, surgical correction of the hernia should be performed.

The etiology of the sliding hiatus hernia is obscure. Certainly there is laxity and dilation of the diaphragmatic hiatus and associated laxity of the phrenoesophageal ligament; however, these may well be secondary and not primary pathophysiologic factors. In some cases, persistent gastroesophageal reflux may result in inflammation and consequent esophageal shortening, which in turn leads to the development of a hiatus hernia.

Paraesophageal hiatus hernias are uncommon. These consist of the fundus of the stomach migrating through the hiatus alongside the esophagus without any displacement of the gastroesophageal junction. Although these hernias are often asymptomatic, most physicians believe that they should be treated surgically when the diagnosis is made because the herniated portion may become strangulated and infarcted.