**1. Esophageal atresia**

#### **1.1. Embryology**

Esophageal atresia (EA) and trachea esophageal fistula (TEF) are important human birth defects of unknown etiology and represent a challenge to the pediatric surgeons. The great

majority of cases of EA and TEF occur as sporadic events. However, there is emerging evidence of an important role for genetic factors.

Embryologically, the respiratory system is derived from the foregut endoderm with the appearance of the laryngo tracheal groove in the ventral floor of the foregut, just caudal to the level of the pharynx [1].

In broad terms, there have been two contrasting theories to explain how the respiratory foregut separates from the gastrointestinal foregut.

In first theory, the respiratory system develops as a result of rapid outgrowth from the original foregut tube [2], but in an alternative theory, there is active growth of a mesenchymal septum which develops in the coronal plane and, as a result, separates the foregut lumen into ventral (respiratory) and dorsal (gastrointestinal) structures [3]; however, direct evidence of septum formation has been lacking, casting doubt on this theory.

The separate process occurs in human embryo between 28 and 37 days of postfertilization. A number of theories have been put forward for disturbed TE malformation, which themselves reflect the theories of normal development.

In first theory, the normal development of trachea is the result of rapid longitudinal growth of the tracheal primordium away from the foregut, and TE malformation is caused by a failure of tracheal growth, the result of which is a compensatory overgrowth of the undivided foregut with the bronchopulmonary buds originating directly from the foregut [4].

In second theory, failure of separate process of ventral trachea and dorsal esophagus is the main case of TE malformations [5].

Interestingly, EA is not a part of this initial malformation. Atretic proximal esophagus is a result of late rearrangement of the cranial foregut, resulting in a blind-ending structure.

Finally, genetic models show that the expression of some factors is fundamental for separation of anterior foregut and loss of this dorsoventral boundary expression domains disrupts the physical separation of the foregut [3].

#### **1.2. History and classification**

The first survivors of EA and TEF were not recorded until 1939 with Leven and Ladd achieving success with staged esophageal repair. Cameron Haight is fully credited with the first successful primary repair and survival of a 12-day-old female neonate [6].

In 1929, Vogt proposed the first anatomical classification of EA and TEF, based on radiological and postmortem findings. **Figure 1** and **Table 1** show a working classification based on the frequency of each anomaly (gross classification).

#### **1.3. Associated anomalies**

EA can be divided clinically into isolated EA and syndromic EA, occurring at the same rate. The most frequent associated malformations encountered in syndromic EA are [7]:

Cardiac (20–30%) Vertebra (10–15%) Limb (5–19%) Anorectal (15–25%) Renal (5–14%)

majority of cases of EA and TEF occur as sporadic events. However, there is emerging evi-

Embryologically, the respiratory system is derived from the foregut endoderm with the appearance of the laryngo tracheal groove in the ventral floor of the foregut, just caudal to the

In broad terms, there have been two contrasting theories to explain how the respiratory fore-

In first theory, the respiratory system develops as a result of rapid outgrowth from the original foregut tube [2], but in an alternative theory, there is active growth of a mesenchymal septum which develops in the coronal plane and, as a result, separates the foregut lumen into ventral (respiratory) and dorsal (gastrointestinal) structures [3]; however, direct evidence of

The separate process occurs in human embryo between 28 and 37 days of postfertilization. A number of theories have been put forward for disturbed TE malformation, which them-

In first theory, the normal development of trachea is the result of rapid longitudinal growth of the tracheal primordium away from the foregut, and TE malformation is caused by a failure of tracheal growth, the result of which is a compensatory overgrowth of the undivided foregut

In second theory, failure of separate process of ventral trachea and dorsal esophagus is the

Interestingly, EA is not a part of this initial malformation. Atretic proximal esophagus is a result of late rearrangement of the cranial foregut, resulting in a blind-ending structure.

Finally, genetic models show that the expression of some factors is fundamental for separation of anterior foregut and loss of this dorsoventral boundary expression domains disrupts the

The first survivors of EA and TEF were not recorded until 1939 with Leven and Ladd achieving success with staged esophageal repair. Cameron Haight is fully credited with the first successful

In 1929, Vogt proposed the first anatomical classification of EA and TEF, based on radiological and postmortem findings. **Figure 1** and **Table 1** show a working classification based on the

EA can be divided clinically into isolated EA and syndromic EA, occurring at the same rate.

The most frequent associated malformations encountered in syndromic EA are [7]:

dence of an important role for genetic factors.

gut separates from the gastrointestinal foregut.

selves reflect the theories of normal development.

main case of TE malformations [5].

physical separation of the foregut [3].

**1.2. History and classification**

**1.3. Associated anomalies**

septum formation has been lacking, casting doubt on this theory.

with the bronchopulmonary buds originating directly from the foregut [4].

primary repair and survival of a 12-day-old female neonate [6].

frequency of each anomaly (gross classification).

level of the pharynx [1].

120 Esophageal Abnormalities

Nonrandom association has been documented as well. Two of these are the VACTERL (**V**ertebral, **A**norectal, **C**ardiac, **T**racheo-**E**sophageal, **R**enal and **L**imb abnormalities) and CHARGE association (**C**oloboma, **H**eart defects, **A**tresia of choan, developmental **R**etardation, **G**enital hypoplasia and **E**ar deformities).

#### **1.4. Clinical presentation**

A newborn with EA is often noted to have difficulty clearing saliva. Episodes of coughing, choking and even transient cyanosis may be observed.

**Figure 1.** Schematic presentations of EA and TEF.


**Table 1.** Gross classification of EA and TEF.

#### **1.5. Diagnosis**

#### *1.5.1. Antenatal*


#### *1.5.2. Postnatal*

The diagnosis of EA and TEF is confirmed by the failure of passage of a firm nasogastric tube. Coiling of the tube can be demonstrated in plain chest and abdominal X-ray (**Figure 2**). Presence of gas-filled intestine loops below the diaphragm is a landmark of associated TEF. In isolated EA, a featureless gasless abdominal X-ray is observed.

#### **1.6. Preoperative preparation**

After a complete physical examination, routine blood work including cross match should be performed.

Other evaluations are included as:


#### **1.7. Operative technique**

Extrapleural approach through the right fourth intercostal space allows the identification of azygos vein, TEF and upper pouch. Division of TEF and primary anastomosis of the esophagus are essential elements of operative technique. TEF is identified along the vagus nerve. TEF is encircled by tape and divided nearly trachea and closed. One-layer stitch anastomosis is the most standard procedure for end-to-end anastomosis [8].

#### **1.8. Postoperative care**

The infant should be nursed in the intensive care unit following repair of EA and TEF. Intravenous fluids and broad spectrum antibiotics are continued. Weaning from ventilation need not to be unduly prolonged in the stable infants with satisfactory anastomosis. In most cases, transanastomotic tube feeding can be commenced after 48 h and slowly increased as tolerated by the infant.

**Figure 2.** Example of a CXR demonstrating EA.
