Esophageal Atresia And Tracheoesophageal Fistula Imaging and Diagnosis

Introduction

Esophageal atresia is a birth defect in which the esophagus fails to form properly while the fetus is developing in the womb. The esophagus or food pipe is a tube connecting the throat to the stomach, and the trachea is a tube that connects the larynx to the lungs. In esophageal atresia (closure or absence of the orifice), one part of the esophagus connects to the throat, and the other part connects to the stomach. However, these two segments are not connecting to each other. Tracheoesophageal fistula is a condition in which there are one or more abnormal connections between the esophagus and the trachea that are not usually connected. Esophageal atresia remains the most common gastrointestinal malformation in neonates which may or may not be associated with tracheoesophageal fistula (TEF).

What Are the Causes of Esophageal Atresia and Tracheoesophageal Fistula?

1. Esophageal Atresia: The exact cause of esophageal atresia is not known. However, researchers found it to be due to genetic abnormalities. Some of the risk factors include:

• Age of the father - Increased age of the father might have increased the risk of developing esophageal atresia.

• Assisted Reproductive Technology - Women conceived with assisted reproductive technology have an increased risk of developing esophageal atresia.

2. Tracheoesophageal Fistula: The most common causes of tracheoesophageal fistula include the following:

• Use of Imidazole derivative decongestants in the first trimester.

• Iatrogenic injury.

• Blunt neck or chest trauma.

• Prolonged ventilation through a tracheostomy or endotracheal tube.

• Increased tube cuff pressure in patients with lung disease.

What Are the Symptoms of Esophageal Atresia and Tracheoesophageal Fistula?

In EA, the symptoms appear as soon as the baby is born. But TEF alone may take a few weeks to detect the disease as their symptoms usually appear as mild respiratory problems.

• Difficulty in breathing.

• Choking, gagging, or coughing when feeding.

• Bluish discoloration of the skin while feeding.

• Drooling or spitting up.

• Foamy, white bubbles from the mouth.

• Vomiting.

• Round belly due to gas entrapment.

• Difficult to pass a tube through the mouth into the stomach.

What Is the Pathophysiology of Esophageal Atresia and Tracheoesophageal Fistula?

Both the trachea and esophagus develop from the primitive foregut as a single tube. At four to eight weeks of pregnancy, the tracheoesophageal fold fuses to form a wall between the trachea and esophagus that separates them into two distinct tubes. The posterior deviation of the septum or wall causes incomplete separation of the trachea and esophagus, resulting in TEF. EA results from the incomplete formation of the food tube.

What Are the Diseases That Are Commonly Associated With EA and TEF?

1. Trisomy 13, 18, or 21 (Down’s syndrome) - Genetic disorders in which there is a presence of an additional chromosomal copy instead of two chromosomes.

2. Gastrointestinal Disorders-

• Duodenal atresia (a condition in which the duodenum has not developed completely).

• Imperforate anus (blocked or missing anal orifice).

• Congenital diaphragmatic hernia (a birth defect in which a hole is present in the diaphragm).

3. Cardiac Disorders -

• Ventricular Septal Defect: A congenital heart condition in which there is a defect in the wall separating the ventricles.

• Tetralogy of Fallot: A birth defect that affects the blood flow to the heart.

• Patent Ductus Arteriosus: A congenital heart condition that is characterized by failure in the closure of the fetal ductus arteriosus.

4. Renal and Urinary Tract Disorders -

• Absence of kidney.

• Hypospadias: A condition in which a urethral opening is found under the penis.

• Horseshoe Kidney (Renal Fusion): A condition in which two kidneys are fused together to form a horseshoe shape.

• Polycystic Kidney Disorder: An inherent disorder in which multiple cysts are found inside the kidney.

5. VACTERL Syndrome - A condition in which a group of defects such as vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal abnormalities, and limb abnormalities are found.

6. Muscular or skeletal disorders.

What Are the Imaging Techniques Used in the Diagnosis of Esophageal Atresia and Tracheoesophageal Fistula?

1. Plain Radiography:

• The lateral and posteroanterior chest radiography shows a coiled nasogastric tube in the esophageal pouch of children with EA that confirms the diagnosis. The tube coils due to the external compression of the esophagus.

• The aortic arch location can also be useful in the diagnosis of esophageal atresia.

• Findings of right-sided aortic arch include the following:

• A right ascending aorta appears as an opaque shadow on the right side of the mediastinum.

• Right-sided deviation or indentation of the trachea.

• The aberrant left subclavian artery's enlarged inlet appears as a round shadow at the normal aortic knot.

• Aspiration pneumonia (a lung infection that causes swelling of the air sacs of the lungs) is often in the right upper lobe, and patchy atelectasis is often seen in chest radiography.

• Plain radiography is also helpful in evaluating the condition of TEF and EA after surgical repair.

• Surgical placement of gastrotomy tube is helpful in evaluating gastrointestinal anomalies and the gap length using barium study. The barium swallow study is a special test using barium to detect diseases affecting the upper gastrointestinal tract (GI).

• Videofluoroscopy can detect abnormal esophageal motility in children with EA.

• Narrowing at the anastomotic site and a peristaltic discontinuity occurs at about 6 to 15 centimeter segments extending above and below the anastomosis area.

• Isolated atresia appears as an air-filled, dilated, blind-ending pouch that causes anterior displacement of the trachea.

• A gasless abdomen may be found. Air is usually found in the stomach for about 15 minutes after birth.

• EA with distal fistula appears as gaseous distension of the small bowel (small intestine) and stomach. However gasless abdomen is found if the fistula is obliterated.

• Increased air in the esophagus; however, the presence of some air in the esophagus is normal in children.

• EA with proximal fistula also appears as a gasless abdomen and has an appearance similar to that of the isolated EA.

• In isolated TEF, recurrent pneumonia and increased air may be found in the esophagus. Therefore, a barium swallow study is the choice of examination in this case. In a barium swallow study, the tracheal filling is seen at the site of the fistula.

2. Computed Tomography (CT) Scan:

• Computed tomography (CT) scan is not often used in the evaluation of TEF and EA. However, a CT scan is helpful in the three-dimensional examination of the esophagus and its adjacent structures.

• Interpretation of axial images is difficult, and identification of fistula may be partially or completely missed.

• A direct sagittal CT scan is effective in diagnosing EA and TEF in newborns. This method visualizes the entire length of the esophagus, gap length, fistulas, and atresia.

• CT scan helps identify the location of the aortic arch; however, other imaging techniques are commonly used.

• A helical ultrafast CT scan is used to evaluate the result of surgical repair in EA and TEF. In addition, the broad posterior tracheal wall, abnormal size, and shape of the tracheal increased air and fluid inside the esophagus are recorded.

3. Magnetic Resonance Imaging (MRI):

• Though MRI has no role in imaging EA and TEF, it is helpful in imaging the entire length of the esophagus in both coronal and sagittal views, and also its resolution is superior when compared to CT.

• Prenatal MRI is useful for the detection of congenital malformations. Prenatal MRI visualizes the anatomic relationship of the entire lesion.

4. Ultrasonography:

• Ultrasonography has a limited role in the evaluation of EA and TEF postnatally; however prenatal ultrasonography is an effective tool in the screening of TEF and EA.

• Endoscopic ultrasonography provides five layered images of the esophageal wall.

• The location of the aortic arch can be detected with ultrasonography and is helpful in the repair of EA and TEF.

• Prenatal ultrasonography shows a small or absence of stomach bubble in addition to maternal polyhydramnios is indicative of EA and TEF.

• The pouch sign is the most reliable ultrasonography sound, indicating EA with or without TEF. The pouch sign refers to the dilated blind end of the esophageal pouch, which is directly visualized after twenty-six weeks of pregnancy.

Conclusion

Pain radiography cannot detect the location of EA and TEF and requires additional imaging tools such as ultrasonography, computed tomography, and magnetic resonance imaging. Identification of the fistula is also difficult in plain radiography and may require additional imaging techniques such as bronchoscopy, endoscopy, or tracheoscopy. Fetal MRI has 100 percent sensitivity in diagnosing EA prenatally. The diagnostic accuracy of ultrasound increases with the presence of an anechoic area in the middle of the fetal neck, which differentiates EA from other swallowing impairments.