THE KURSK STATE MEDICAL UNIVERSITY
Department of surgical diseases № 1
Disorders of Esophageal Motility
Information for self-training of English-speaking students
The chair of surgical diseases N 1 (Chair-head - prof. S.V.Ivanov)
By ass. professor M.V. Yakovleva
KURSK-2010
HISTORY
Traumatic lesions of the cervical esophagus were identified in ancient times, and survival was observed when a cervical esophageal fistula formed that allowed the wound to heal gradually by secondary intention. Benign as well as neoplastic strictures of the esophagus were treated by dilatation at this time. Anatomic dissections performed during the Renaissance provided a systematic way to study the consequences of esophageal injury and stricture, so by the middle of the 18th century, techniques had been developed to remove foreign bodies and to dilate strictures of the cervical esophagus. By the middle of the 19th century, strictures were being approached by internal as well as external myotomies with some success but with a prohibitive leak and death rate. Major advances in esophageal surgery awaited the imaging potential of radiography and endoscopy, which occurred in the early part of the 20th century. Successful transthoracic operations on the thoracic esophagus were enhanced by the development of endotracheal anesthesia, antibiotics, and blood transfusions during World War II. More recently, video-assisted thoracoscopic techniques gained popularity.
ANATOMY
Esophagus
The esophagus is a hollow tube of muscle approximately 25 to 30 cm long, beginning at C6 (cricoid cartilage level) and ending at T11, that penetrates the diaphragm and joins the cardia of the stomach . The esophagus lies anterior to the vertebral column and longus colli muscles and posterior to the trachea. It is divided into four segments: pharyngoesophageal, cervical, thoracic, and abdominal. The length between the laryngopharynx and cervical esophagus is the pharyngoesophageal segment. The pharyngeal musculature includes the superior, middle, and inferior constrictors, as well as the stylopharyngeus muscles. The inferior pharyngeal constrictor (thyropharyngeus muscle) passes obliquely and superiorly from its origin on the thyroid cartilage to its posterior insertion in the median raphe. The esophageal introitus (cricopharyngeus muscle or upper esophageal sphincter) is the most inferior portion of the inferior pharyngeal constrictor and is identifiable by the transverse direction of its fibers. The transition between the oblique fibers of the thyropharyngeus muscle and the transverse fibers of the cricopharyngeus muscle creates a point of potential weakness in the pharyngoesophageal segment (site of origin of a pharyngoesophageal diverticulum and a common site of perforation during esophagoscopy). The cricopharyngeal sphincter is unique to the gastrointestinal tract because it does not consist of a circular ring of muscle, but rather it is a bow of muscle connecting the two lateral borders of the cricoid cartilage. The cricopharyngeus muscle fibers blend into the longitudinal and circular muscle of the cervical esophagus, a 5- to 6-cm segment that extends to the beginning of the first thoracic vertebra.
Although the cervical esophagus is a midline structure positioned posterior to the trachea, it tends to course to the left of the trachea and is therefore more easily approached surgically through a left-sided neck incision. The cervical esophagus lies just anterior to the prevertebral fascia and can normally be separated from its loose fibrous posterior attachments by blunt finger dissection of the prevertebral space. On each side of the cervical esophagus lie the carotid sheath and the thyroid gland, with the recurrent laryngeal nerves passing bilaterally in the groove between the esophagus and the trachea.
The thoracic esophagus passes into the posterior mediastinum, passes behind the aortic arch and great vessels, and curves to the left of the trachea behind the left main stem bronchus. It then deviates to the right for several centimeters in the subcarinal area and returns to the left of midline and anterior to the thoracic aorta as it proceeds behind the pericardium to the level of the seventh thoracic vertebra. At this point, the esophagus deviates farther to the left and anteriorly, and it enters the esophageal diaphragmatic hiatus at the level of the eleventh thoracic vertebra. The lateral boundaries of the thoracic esophagus are the right and left parietal pleurae.
The diaphragmatic esophageal hiatus is a sling of muscle fibers that arise from the right crus in approximately 45% of patients; however, both the left and the right crura may contribute to the hiatus. The abdominal esophagus (1 to 2 cm long) extends from the esophageal hiatus to the cardia of the stomach to form the esophagogastric junction. The location of the esophagogastric junction has been defined in different ways: (1) the junction of esophageal squamous and gastric columnar epithelium; (2) the point at which the tubular esophagus joins the gastric pouch; and (3) the junction of the esophageal circular muscle layer with the oblique sling fibers of the stomach (loop of Willis or collar of Helvetius). Clinically, the squamocolumnar epithelial junction (ora serrata or Z line), as identified endoscopically, is the most practical definition of the gastroesophageal junction, provided the patient does not have a columnar-lined lower esophagus. The phrenoesophageal membrane is a fibroelastic sheet of tissue that extends circumferentially from the muscular margins of the diaphragmatic hiatus to the esophagus. The majority of the phrenoesophageal membrane arises from the endoabdominal fascia and inserts into the esophagus for 2 to 3 cm above the hiatus and 3 to 5 cm above the mucosal junction. Fibrous strands from the upper surface of the diaphragm (fascia of Laimer) contribute to the phrenoesophageal membrane. The functional significance of the phrenoesophageal membrane is unknown; however, this tissue lacks sufficient strength to reliably anchor the esophagogastric junction in the abdomen during an antireflux operation.
The esophagus has three distinct areas of anatomic narrowing. The cervical constriction occurs at the level of the cricopharyngeus sphincter, the narrowest point of the gastrointestinal tract (14 mm in diameter). The bronchoaortic constriction (15 to 17 mm) is located at the level of the fourth thoracic vertebra behind the tracheal bifurcation where the left main stem bronchus and the aortic arch cross the esophagus. The diaphragmatic constriction (16 to 19 mm) occurs where the esophagus traverses the diaphragm. Between these areas of constriction, the esophagus has a wider caliber, termed the superior and inferior dilatations. The normal adult thoracic esophagus has a maximum diameter of approximately 2.5 cm on barium swallow examination.
The esophagus is a mucosal-lined muscular tube that lacks a serosa and is surrounded by a layer of loose fibroalveolar adventitia. Beneath the adventitia is a layer of longitudinal muscle overlying an inner layer of circular muscle. Between the two muscular layers is a thin intramuscular septum of connective tissue that contains fine blood vessels and ganglion cells (Auerbach plexus). Both the longitudinal and the circular muscle layers of the upper third of the esophagus are striated, whereas the layers of the lower two thirds are smooth. The fatty and relatively thick submucosa permits considerable mobility of the esophageal mucosa. The submucosa contains the mucus glands, blood vessels, the Meissner neural plexus, and an extensive lymphatic network. The esophageal mucosa consists of squamous epithelium except for the distal 1 to 2 cm, which is junctional columnar epithelium. Occasionally, ectopic gastric mucosa may be found throughout the length of the esophagus.
The esophagus is nourished by numerous segmental arteries. The cervical esophagus receives blood from the superior thyroid artery as well as the inferior thyroid artery of the thyrocervical trunk, with both sides communicating through collateral vessels. The major blood supply of the thoracic esophagus is from four to six aortic esophageal arteries, supplemented by collateral vessels from the inferior thyroid, intercostal and bronchial, inferior phrenic, and left gastric arteries. The aortic esophageal arteries terminate in fine capillary networks before they actually penetrate the esophageal muscle layer. After penetrating and supplying the muscle layers of the esophagus, the esophageal capillary network runs longitudinally in the submucosa. The extensive venous drainage of the esophagus includes the hypopharyngeal, azygous, hemiazygous, intercostal, and gastric veins.
The esophagus has both sympathetic and parasympathetic innervation. In the neck, the superior laryngeal nerves arise from the vagus nerve and divide into the external and internal laryngeal branches. The external laryngeal nerve innervates the cricothyroid muscle and also, in part, the inferior pharyngeal constrictor. The internal laryngeal nerve is the sensory nerve of the pharyngeal surface of the larynx and the base of the tongue. The recurrent laryngeal branches of the vagus nerve provide parasympathetic innervation to the cervical esophagus as well as innervation to the upper esophageal sphincter. Injury to the recurrent laryngeal nerve may result in hoarseness as well as upper esophageal sphincter dysfunction, with secondary aspiration on swallowing. In the thorax, the vagus nerve sends fibers to the striated muscle as well as parasympathetic preganglionic fibers to the smooth muscle. Sympathetic innervation consists of fibers to the cervical esophagus from the superior and inferior cervical sympathetic ganglia, to the thoracic esophagus from the upper thoracic and splanchnic nerves, and to the intra-abdominal esophagus from the celiac ganglion. The Meissner and Auerbach plexuses provide an intrinsic autonomic nervous system within the esophageal wall. The Meissner plexus of nerves is located in the submucosa, whereas the Auerbach plexus is in the connective tissue between the circular and longitudinal muscle layers. The two major branches of the vagus nerves lie along either side of the thoracic esophagus and form two large nerve plexuses supplying the esophagus and the lungs. The esophageal vagus plexuses coalesce and become single trunks, 2 to 6 cm above the esophageal hiatus. The left branch of the vagus nerve lies anterior to the esophagus, and the right branch is posterior, at the diaphragmatic hiatus.
The esophagus has an extensive lymphatic drainage that consists of two lymphatic plexuses, one arising in the mucosa and the other in the muscular layer. Mucosal lymphatic capillaries may pierce the muscular layer and drain to regional lymph nodes. These lymphatic capillaries may run longitudinally in the esophageal wall before they exit through muscle into adjacent lymph nodes. The flow of lymphatics of the upper two thirds of the esophagus tends to be upward, whereas the distal third tends to be downward; however, all lymphatics intercommunicate. Therefore, esophageal carcinomas may metastasize to internal jugular nodes in the neck, paratracheal nodes in the superior mediastinum, subcarinal nodes in the middle chest, paraesophageal nodes in the lower mediastinum, and inferior pulmonary ligament, perigastric, and left gastric artery lymph nodes.
Thoracic Duct
The proximity of the thoracic duct to the esophagus makes it vulnerable to injury during esophageal surgery. The thoracic duct forms at the confluence of the cisterna chyli at a level between the twelfth thoracic and second lumbar vertebrae and to the right side of the abdominal aorta. The duct enters the posterior mediastinum through the aortic hiatus at the level of T10 to T12 and continues cephalad on the anterior surface of the vertebral column between the aorta and the azygous vein and behind the esophagus. At T4 to T5, the duct crosses to the left of the spine, passes under the aortic arch, and continues along the left side of the esophagus, to ascend into the neck posterior to the left subclavian artery. In the neck, the duct lies anterior to the vertebral artery and vein, thyrocervical trunk, and phrenic nerve, and it enters the venous system at the junction of the left subclavian and left internal jugular veins. Operations on the thoracic esophagus, particularly after previous surgery or radiation therapy with consequent periesophageal fibrosis, may result in chylothorax from thoracic duct injury.
PHYSIOLOGY
The basic function of the esophagus is to transport swallowed material from the pharynx into the stomach. Secondarily, retrograde flow of gastric contents into the esophagus is prevented by the lower esophageal sphincter (LES). The entry of air into the esophagus with each inspiration is prevented by the upper esophageal sphincter (UES), which normally remains closed as a result of tonic contraction of the cricopharyngeus muscle. Еsophageal motility studies have become a basic diagnostic tool in evaluating disorders of esophageal motor function such as dysphagia, chest pain of undetermined origin, and gastroesophageal reflux.
Three types of contractions are seen in the esophageal body. Primary peristalsis is progressive and is triggered by voluntary swallowing. Secondary peristalsis is also progressive, but it is generated by distention or irritation, not by voluntary swallowing. Tertiary contractions are nonprogressive (simultaneous) contractions that may occur either after voluntary swallowing or spontaneously between swallows. As the swallowed bolus enters the esophagus from the pharynx, a primary peristaltic wave is activated that transverses the esophageal body at a speed of 2 to 5 cm per second and propels the swallowed material from the pharynx into the stomach in 4 to 8 seconds in an orderly, progressive manner. Normally, a progressive peristaltic contraction (primary wave) follows 97% of all wet swallows. If the entire swallowed bolus of food does not empty from the esophagus into the stomach, secondary peristaltic waves are initiated. These contractions, like the primary waves, are progressive and sequential, but they begin in the smooth muscle segment of the esophagus (near the level of the aortic arch) and continue until retained intraesophageal contents are emptied into the stomach. Thus, unlike the primary wave, the secondary contraction is not initiated by a voluntary swallow, but rather it is initiated by local distention of the esophagus. Tertiary contractions are simultaneous, nonprogressive, nonperistaltic, monophasic, or multiphasic waves that can occur throughout the esophagus and represent uncoordinated contractions of the smooth muscle that are responsible for the classic "corkscrew" appearance of esophageal spasm on barium swallow examination. Increased resting pressures within the body of the esophagus and abnormal motor function are seen in patients with either mechanical or functional obstruction.
The term lower esophageal sphincter implies the presence of an anatomic sphincter such as the pylorus. Although no such anatomic LES has been demonstrated, manometry has defined an elevated distal esophageal resting pressure that is 3 to 5 cm in length, which serves as the barrier against abnormal regurgitation of gastric contents into the esophagus and represents a functional sphincter . Thus, the LES is more accurately referred to as the LES mechanism or the distal esophageal high-pressure zone (HPZ). The factors responsible for maintaining competence of the LES are poorly understood, but the presence of an intra-abdominal segment of distal esophagus, under the influence of positive intra-abdominal pressure, seems important to the success of most antireflux operations.