The Esophagus

Surgical Anatomy and Physiology

The esophagus is a hollow muscular tube connecting the pharynx to the stomach. It courses in the posterior mediastinum posterior to the trachea, passes through the esophageal hiatus of the diaphragm, and joins the stomach at the cardia. Embryologically, the esophagus and trachea both develop together from the foregut. During the fourth week of gestation, the foregut endoderm differentiates into a ventral respiratory part and a dorsal esophageal part. The separation of the respiratory part from the esophageal part is achieved by the formation of lateral longitudinal tracheoesophageal folds. By 7 weeks of gestation, the separation of the esophagus and trachea is complete. Familiarity with the embryologic development of the esophagus and trachea is important to understand the congenital abnormalities that may arise from impairment in the process of septation of the trachea and esophagus.

The length of the esophagus is 8–10 cm at birth and doubles in the first few years of life. The esophageal wall is composed of four layers: mucosa, submucosa, muscularis propria, and adventitia. The esophagus lacks a distinct serosa. The mucosa is lined by nonkeratinizing, stratified squamous epithelium. The muscularis mucosa is the deepest layer of the mucosa and contains longitudinal smooth muscle fibers. The submucosa contains the venous and lymphatic plexuses. The muscularis propria contains the inner circular and outer longitudinal muscle layers. The upper third of the esophagus is composed primarily of striated muscle fibers under voluntary control. The middle third comprises mixed striated and smooth muscle fibers, and the lower third of the esophagus contains only smooth muscle fibers under autonomic control. The mucosa is the strongest layer of the esophageal wall, in contrast to the small intestine, in which the submucosa is the strongest. When the esophagus is divided, the mucosa will retract. Meticulous approximation of the esophageal mucosa is essential for a technically sound anastomosis. Two sphincters control passage of contents into the gastrointestinal (GI) tract: an anatomic upper esophageal sphincter (UES), consisting of the cricopharyngeus and inferior pharyngeal constrictors, and a physiologic lower esophageal sphincter (LES).

The blood supply to the proximal esophagus is derived from the fourth branchial arch. The fourth branchial arch gives rise to the subclavian artery and its branches, including the inferior thyroid artery, which supplies the cervical esophagus. The thoracic esophagus is supplied directly from branches of the aorta. The abdominal esophagus has a generous vascular supply from the phrenic branches and gastric vessels. The excellent submucosal plexus of the proximal esophagus allows for extensive mobilization without compromise to the vasculature, whereas caution should be taken distally because of the segmental esophageal blood supply.

Lesions of the upper esophagus are best approached through the right chest to avoid problems with the aortic arch. The azygos vein should be ligated and divided where it crosses the esophagus. As long as the superior vena cava is patent, the azygos vein can be divided without consequence. Lesions of the lower esophagus can be explored through either the right or left chest. To expose the distal esophagus via the left chest, the inferior pulmonary ligament must be divided, taking care not to injure the inferior pulmonary vein that runs in the upper part of the pulmonary ligament.

Clinical Evaluation of the Esophagus

The structure and function of the esophagus can be assessed with radiographic contrast studies, manometry, and flexible or rigid endoscopy. A barium esophagogram provides anatomic information regarding mechanical obstruction or stricture, leak, and extrinsic compression from mediastinal lesions. It also provides some functional information regarding peristalsis, LES relaxation, and the presence/absence of GER. Manometry, which uses a flexible catheter to measure pressures at multiple points along the esophagus, is the gold standard for evaluating motility disorders. Diagnostic esophagoscopy is frequently used to evaluate dysphagia and gastroesophageal reflux. Therapeutic esophagoscopy is used to dilate esophageal strictures, evaluate for trauma, aid in sclerotherapy for bleeding esophageal varices, and place gastrostomies. Both rigid and flexible esophagoscopes are available for use in children of all ages.

Flexible endoscopy is the technique of choice for routine diagnostic esophagoscopy. The rigid esophagoscope is more versatile and provides a larger diameter that allows for better visualization and a larger channel for biopsies. It also does not require air insufflation, which is important in the setting of trauma so that air is not forced through a perforation into the mediastinum. The main value of rigid esophagoscopy in current pediatric practice is for therapeutic procedures such as dilation of an esophageal stricture or removal of a foreign body.

Rigid esophagoscopy requires general anesthesia with endotracheal intubation and muscle relaxation. The child is positioned supine with a roll under the shoulders to extend the neck. With care taken to protect the teeth, the esophagoscope, with its bevel up, is introduced into the oral cavity along the hard and soft palates to identify the cricopharyngeus muscle and enter the esophagus. Once the most distal aspect of evaluation is reached, it is easy to examine the esophagus fully when withdrawing the scope to identify any lesions or foreign bodies missed on insertion.

Endoscopy with a flexible scope can be performed under sedation or general anesthesia. The endoscope is passed though the pharynx and cricopharynx into the upper esophagus. This is most safely done under direct vision. The scope should be advanced down the esophagus carefully, making sure to always maintain visualization of the esophageal lumen. The endoscope should never be advanced blindly. If the lumen is not apparent, the scope should be withdrawn slightly with gentle insufflation until the lumen is identified. Once the stomach is entered, it can be insufflated to allow inspection of the mucosa. In small infants, overdistention of the stomach may lead to respiratory distress.

Complications related to passage of a rigid or flexible endoscope are typically at the level of the cricopharyngeus muscle. Fortunately, perforation during diagnostic esophagoscopy is exceedingly rare. Perforation of the cricopharyngeus occurs in about 0.10% with flexible endoscopy and 0.07% in rigid esophagoscopy.

Congenital Anomalies of the Esophagus

Congenital anomalies of the esophagus include EA, TEF, congenital esophageal stenosis, and duplication cysts. EA and TEF are discussed in Chapter 27 .