ANATOMY AND PHYSIOLOGY
The esophagus is a muscular tube that functions pri-marily as a conduit for transporting ingested solids and liquids from the mouth into the intra-abdominal gastrointestinal tract. It extends from the pharynx to the stomach, traversing the posterior mediastinum, and is bounded posteriorly by the vertebral column and thoracic duct, anteriorly by the trachea, laterally by the pleura, and on the left by the aorta (Figs. 19-1 and 19-2). It begins at the cricoid cartilage in the neck and courses downward to the left, then to the right, and back to the left to pierce the diaphragm and join the cardia of the stomach. The intra-abdominal portion of the esophagus measures <3 cm. The upper one third of the esophageal musculature is skeletal, whereas the lower two thirds is smooth muscle. Unlike the intra-abdominally located stomach, small intestine, and colon, there is no true serosal layer covering the esophagus.
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Figure 19-1 • Clinical divisions of the esophagus. From Lawrence PF. Essentials of General Surgery. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2006. |
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Figure 19-2 • Esophagus and associated structures. A. Schematic drawing of a lateral view of the head, neck, and trunk showing the esophagus and the structures associated with it. The esophagus descends posterior to the trachea and leaves the thorax through the esophageal hiatus in the diaphragm. B. Transverse section of the esophagus showing the muscular layers and microscopic structure of its wall. C. Coronal section of the esophagus, diaphragm, and stomach (superior part). Observe the phrenicoesophageal ligament that connects the esophagus flexibly to the diaphragm; it limits upward movement of the esophagus while permitting some movement during swallowing and respiration. From Moore KL, Dalley AF II. Clinically Oriented Anatomy. 4th ed. Baltimore, MD: Lippincott Williams & Wilkins, 1999. |
The vagus nerves form a plexus around the esophagus, which condenses distally to form two trunks on the lateral esophagus. These trunks, in turn, rotate so that the left trunk moves anteriorly, whereas the right trunk moves posteriorly.
The esophageal mucosa is lined by squamous epithelium that becomes columnar near the gastro-esophageal junction. The next layer encountered moving radially outward is the submucosa, which contains the submucous (Meissner) plexus. Next are two muscular layers, the inner circular muscle layer and the outer longitudinal muscle layer. Sandwiched in between these two muscular layers is the myenteric (Auerbach) plexus.
The arterial supply of the esophagus involves vessels from the neck, chest, and abdomen. The superior and inferior thyroid arteries supply the upper esophagus, whereas the intercostals, left gastric, and phrenic arteries supply the lower esophagus. Venous drainage of the upper esophagus is into the inferior thyroid and vertebral veins, whereas the mid and lower esophagus drains into the azygous, hemiazygous, and left gastric veins. Submucosal veins can become engorged in patients with portal hypertension, causing varices and potentially life-threatening bleeding. Lymphatics drain into cervical, mediastinal, celiac, and gastric nodes. Innervation is from the vagus, cervical sympathetic ganglion, splanchnic ganglion, and celiac ganglion. These nerves are responsible for esophageal motility.
Peristasis conveys food into the stomach. Gastric reflux is prevented by increased tone in the lower portion of the esophagus; there is no true sphincter. Air ingestion is prevented by resting tone in the upper esophagus.
ESOPHAGEAL NEOPLASMS
PATHOLOGY
Esophageal neoplasms are almost always malignant. Benign tumors account for fewer than 1% of cases and are usually leiomyomas or congenital cysts. Symptomatic benign esophageal neoplasms are treated with local resection or enucleation. Most malignant esophageal neoplasms seen worldwide are of squamous cell histologic type, whereas adenocarcinoma histology predominates in the United States and other industrialized nations. Most cases of adenocarcinoma arise in the distal third or gastroesophageal junction (80%). Metastases are usually to liver, lungs, and bones, with at least 35% of patients with distant metastases at the
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time of diagnosis. Early-stage cancers are usually diagnosed only incidentally or else discovered on screening studies. Prognosis is poor, with an overall 5-year survival rate of only 5%.
PATHOGENESIS
Mucosal insult seems to be a common pathway toward the genesis of esophageal cancer. Chronic ingestion of extremely hot liquids, esophageal burns from acid or base ingestions, radiation-induced esophagitis, and reflux esophagitis are all implicated in causing esophageal cancer. Alcohol, smoking, nitrosamines, and malnutrition/vitamin deficiency also play a role in cancer development. Barrett esophagus, which occurs when the normal squamous epithelium becomes columnar in response to injury from acid reflux, is considered a premalignant lesion. Approximately 10% of patients with Barrett esophagus will develop adenocarcinoma.
In patients with achalasia, approximately 6% will develop squamous cell carcinoma of the esophagus.
EPIDEMIOLOGY
The incidence of esophageal cancer varies according to the presence of the etiologic factors described previously. For example, in places with high soil nitrosamine content, the prevalence of esophageal cancer is almost 1% of adults. In the United States, the incidence of esophageal cancer is four in 100,000 White men and 12 in 100,000 Black men. It is most commonly a disease of men between 50 and 70 years of age.
HISTORY
At the time of diagnosis, most patients have advanced disease and are not surgical candidates for curative resection. The lack of a serosal lining and the rich submucosal lymphatic network of the esophagus allows early extension of tumor into adjacent mediastinal structures as well as early local lymph node spread. Approximately 75% of patients have mediastinal or extrathoracic lymph node metastases at the time of diagnosis.
The classic presentation of distal esophageal adenocarcinoma is an older man with a history of gastro-esophageal reflux disease complaining of progressive dysphagia to solids initially, and then to liquids. Typically, patients feel well and have no other symptoms. Some report noting mild weight loss, more often related to diminished caloric intake resulting from obstructive symptoms than to cachexia from metastatic disease. Chest pain and odynophagia (pain with swallowing) may also occur. Invasion of a recurrent laryngeal nerve may cause hoarseness from vocal cord paralysis.
Patients with esophageal squamous cell carcinoma often have a history of heavy alcohol and tobacco use and present with more pronounced symptoms owing to more advanced disease.
PHYSICAL EXAMINATION
Signs are nonspecific, and patients appear well unless significant metastatic disease is present. Supraclavicular lymphadenopathy at presentation is rare.
DIAGNOSTIC EVALUATION
Barium esophagogram detects malignant lesions in 96% of patients. Findings range from small mucosal defects to "apple core" lesions to complete obstruction (Fig. 19-3). This is usually the initial study for the evaluation of new onset dysphagia. Definitive diagnosis of cancer requires confirmation by flexible endoscopy with tissue biopsy. If Barrett esophagitis alone is noted, the extent of disease can be determined and biopsies performed to look for dysplasia or carcinoma in situ.
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Figure 19-3 • A. Contrast radiograph showing the typical "apple core" lesion of carcinoma of the middle one third of esophagus. B. Ragged edge seen in carcinoma of the distal esophagus. From Lawrence PF. Essentials of General Surgery. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2006. |
To determine the stage of the primary tumor (T) and regional lymph node status (N), endoscopic ultrasound
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(EUS) is used. Ultrasound is best for evaluating local staging: the intramural extent of the tumor as well as assessing for lymph node enlargement or abnormality. Ultrasound depicts the normal five layers of the esophagus and can accurately determine the T status in 85% to 90% of patients. Fine-needle aspiration biopsy of abnormal-appearing lymph nodes under ultrasound guidance may be performed.
Evaluation of regional and distant disease is best done by computed tomography (CT) scan and positron emission tomography scan. CT scanning should be performed first after initial diagnosis, because lung and liver metastases are often detected. If CT is negative for metastases, then EUS is performed. Combined preoperative CT and EUS have an accuracy rate of 86% for TNM staging.
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STAGING
The TNM system is used for staging esophageal cancer. Clinical stage (cTNM) is determined by evaluation of all information derived from physical examination, imaging studies, endoscopy, biopsy, and occasionally laparoscopy or thoracoscopy. Once the clinical stage is determined, rational treatment plans can be proposed to the patient (Table 19-1 and Fig. 19-4).
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TABLE 19-1 AJCC TNM Classification of the Esophagus |
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Figure 19-4 • Visual representation of TNM staging of esophageal cancer. Reprinted with permission of The Cleveland Clinic Foundation. |
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TREATMENT
Because there is no serosal layer covering the esophagus, disease is often locally advanced or metastatic on presentation, leading to poor overall survival statistics. Surgical cure rates are 20% to 30% at best. The goals of surgical treatment are removal of the tumor and regional lymph nodes followed by re-establishment of gastrointestinal tract continuity. For early-stage disease, esophagectomy provides the possibility of cure. Preoperatively, induction chemoradiotherapy may be administered, especially to downstage patients with resectable bulky tumors. Some evidence has shown that induction chemotherapy and radiotherapy preoperatively, followed by surgery, can improve long-term survival, but this remains an area of controversy. The extent of lymphadenectomy is also an area of ongoing controversy.
Various operations with varying degrees of invasiveness have been developed for treating esophageal cancer. In deciding which procedure to perform, the surgeon must take into consideration the location of the tumor, the proposed esophageal substitute, and the physical condition and body habitus of the patient. Generally, the most common surgical approaches are transthoracic (thoracotomy) and transhiatal without thoracotomy. Incisions may be required in the neck, chest, and abdomen.
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The most common transthoracic esophagectomy is one called the Ivor Lewis esophagectomy, named after the distinguished Welsh surgeon who developed the approach. In brief, it involves upper midline laparot-omy with mobilization of the stomach and is followed by right thoracotomy with esophageal resection and anastomosis. It is useful for patients with tumors of the middle and lower esophagus. For tumors of the upper esophagus, many surgeons use a modified approach, called the McKeown modification, which involves additional intrathoracic esophageal mobilization and anastomosis in the right neck through a separate cervical incision (three-hole technique). The tubularized stomach is used as the esophageal substitute in most cases. Other possible substitutes are the colon and small bowel (Fig. 19-5).
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Figure 19-5 • Three-hole Mckeown modification (using additional cervical incision) of the standard Ivor Lewis abdominal and right thoracic approach. |
Esophagectomy without thoracotomy is termed the transhiatal approach. This technique uses laparot-omy for gastric and esophageal mobilization, followed by left cervical incision for the anastomosis. The major benefit of this approach is avoiding the complications that arise from thoracotomy.
Although open surgical approaches remain the standard for esophagectomy, recent advances in minimally invasive surgery have allowed esophagectomy to be performed using laparoscopic and thoracoscopic techniques. A cervical incision is also used (Fig. 19-6). This is a complex and challenging procedure that has a steep learning curve. Early results of laparoscopic esophagectomy seem to compare favorably with open surgery, but long-term data are presently not available.
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Figure 19-6 • Completed cervical anastomosis after laparoscopic transhiatal esophagectomy without thoracotomy. From Shields TW, LoCicero J III, Ponn RB, et al. General Thoracic Surgery. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2004. |
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ACHALASIA
PATHOPHYSIOLOGY
The term "achalasia" is derived from the Greek, meaning "failure to relax." It is defined as absence of peristalsis in the smooth muscle of the distal esophagus and failure of the lower esophageal sphincter (LES) to relax with swallowing. The exact cause of primary achalasia is not well understood, but studies have shown abnormalities in the myenteric plexus (Auerbach). Histologic evidence shows inflammation, fibrosis, and loss of ganglion cells. Possible causes are infectious (neurotropic virus) or degenerative.
In South and Central America, the most common cause of secondary achalasia is Chagas disease (American trypanosomiasis).
EPIDEMIOLOGY
Achalasia is the most common disorder of esophageal motility but is actually rare, with an incidence of 0.5 per 100,000. Men and women are equally affected. Patients usually present between 20 and 50 years of age.
HISTORY
Patients complain of dysphagia to solids and liquids. Because ingested material is unable to pass into the stomach, a column of food or liquid rises in the esophagus. When there is a change in position, liquid spills into the mouth or into the lungs, and patients complain of regurgitation or have a history of recurrent aspiration pneumonia. Because the regurgitant does not include gastric contents, it is usually not sour tasting.
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DIAGNOSTIC EVALUATION
Chest x-ray may show an air-fluid level in the esophagus. A prominent gastric bubble may be noted because of the highly competent LES. Changes from aspiration pneumonia may be present. CT scan shows a dilated, thin-walled esophagus containing food material.
Contrast esophagogram shows a dilated, smooth-walled esophagus tapering to a "bird's beak" at the LES. Dynamic video imaging or fluoroscopy reveals reduced or absent peristalsis of the distal esophagus.
Esophagoscopy should also be performed to evaluate for strictures and rule out cancer. Malignant tumors of the gastroesophageal junction can mimic the findings of achalasia, known as pseudoachalasia.
Motility and pressure studies confirm the diagnosis. The two key findings on manometry that are required to make the diagnosis are incomplete relaxation of the LES and aperistalsis of the body of the esophagus.
TREATMENT
There is no cure for achalasia, given the still unelucidated underlying process that causes esophageal neural pathology. Treatment is focused on relief of symptoms (dysphagia) caused by achalasia.
Medical treatment consists mainly of pneumatic balloon dilatation (Fig. 19-7) of the lower esophageal sphincter to reduce outflow obstruction and facilitate gravity drainage. This technique is minimally invasive, has good initial results, and can be repeated. However, it carries the risk of esophageal perforation and over the long term has inferior results when compared with surgical therapy. Another medical treatment is LES relaxation by paralysis achieved by endoscopic injections of botulinum toxin (Botox). This may be an option for frail, high-risk patients, as all patients experience symptomatic relapse.
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Figure 19-7 • Pneumatic balloon dilatation of lower esophageal sphincter for achalasia. (A-C) The dilator is passed, guided by a previously inserted guidewire. (D) When the balloon is in proper position, it is distended by pressure sufficient to dilate the narrowed area of the esophagus. From Smeltzer SC, Bare BG. Brunner & Suddarth's Textbook of Medical-Surgical Nursing. 9th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2000. |
Surgical therapy by esophageal myotomy (Heller myotomy) is the definitive treatment for achalasia.
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The goal of myotomy is to reduce LES pressure to facilitate gravity drainage while also performing a partial fundoplication to ensure a degree of gastro-esophageal reflux control. The procedure is performed using the laparoscopic approach, with low morbidity. Longitudinal separation of the esophageal musculature is carried from the distal esophagus onto the proximal stomach, and partial fundoplication (Dor or Toupet wrap) completes the procedure. Myotomy can also be performed through the chest by thoracoscopy or thoracotomy, but with greater morbidity. Surgical therapy provides superior long-term results over medical interventions.
ESOPHAGEAL PERFORATION
ETIOLOGY
Esophageal perforation occurs most commonly after instrumentation (iatrogenic) but also from ingested foreign bodies or penetrating trauma. Spontaneous esophageal rupture occurring after violent emesis is known as Boerhaave syndrome. The latter is named after Hermann Boerhaave, who first reported distal esophageal rupture in 1724 during the autopsy of Baron von Wassenaer, the infamous overindulging Grand Admiral of the Dutch Fleet who showed very poor judgment by engaging in self-induced, chemically assisted vomiting after feasting and drinking.
HISTORY
Recent instrumentation of the upper airway or esophagus should raise the possibility of esophageal injury. Boerhaave syndrome should be suspected in cases involving recent emesis. Epigastric abdominal pain and shoulder pain are frequent complaints.
PHYSICAL EXAMINATION
The degree of presenting symptoms is usually proportional to the time from when perforation occurred. Subcutaneous emphysema in the cervical region is often found, as well as abdominal tenderness or distention. If a major delay in diagnosis has occurred (i.e., because of lack of history in an unconscious patient), then fever, tachycardia, and hypotension resulting from sepsis is common. The presence of a hydropneumo-thorax can result in diminished breath sounds over the involved hemithorax.
DIAGNOSTIC EVALUATION
Chest x-ray can demonstrate pleural effusion, hydro-pneumothorax, and mediastinal emphysema. An esophageal contrast study with either water-soluble contrast medium or water-suspended barium sulfate can confirm the location of perforation. If diagnosis is still uncertain, then intraluminal examination by flexible endoscopy can also be used. Thoracentesis can reveal empyema.
TREATMENT
Immediate exploratory thoracotomy and repair of the perforation is indicated in almost all cases. Iatrogenic injuries can usually be closed primarily if surgical intervention is immediate. Perforations with devitalized surrounding tissue or with significant soilage and infection should be repaired with the use of a pedicled flap (i.e., intercostal muscle flap). Pleural space drainage with chest tubes continues postoperatively. Although small cervical lacerations may occasionally be managed with antibiotics and close observation alone, mortality from perforation of the thoracic esophagus is >50% if not treated within 24 hours.
KEY POINTS