17. | Principles of Surgery, Companion Handbook

Chapter 16 Chest Wall, Pleura, Lung, and Mediastinum

Principles of Surgery Companion Handbook

CHAPTER

16
CHEST WALL, PLEURA, LUNG, AND MEDIASTINUM

Anatomy
Thoracic Incisions
Preoperative Evaluation
Postthoracotomy Considerations
Thoracic Injuries
	Conditions Requiring Urgent Correction
	Conditions Requiring Urgent Thoracotomy
	Dangerous But Less Compelling Injuries
Chest Wall
	Congenital Deformities
	Chest Wall Tumors
	Chest Wall Reconstruction
Diseases of the Pleura and Pleural Space
	Pleural Effusion
	Tumors
	Spontaneous Pneumothorax
Lung
	Anatomy
	Diagnostic Modalities
	Congenital Lung Lesions
	Pulmonary Infections
Tumors
	Primary Carcinoma
	Solitary Pulmonary Nodules
	Other Lung Tumors
Trachea
	Congenital Lesions
	Trauma
	Neoplasms
Mediastinum
	Tumors and Cysts
	Mediastinitis
	Superior Vena Caval Obstruction

ANATOMY

Framework The thoracic cage, which tapers sharply in the upper chest and is conical, consists of the sternum, 12 thoracic vertebrae, 10 pairs of ribs that end anteriorly in segments of cartilage, and 2 pairs of floating ribs. The cartilages of the first 6 ribs have separate articulations with the sternum; the cartilages of the seventh through the tenth ribs fuse to form the costal margin before attaching to the lower margin of the sternum. The extension of the pleural space above the clavicles and over upper abdominal viscera is critical in evaluating penetrating wounds.

Musculature The pectoralis major and minor muscles constitute the principal musculature of the anterior thorax. The latissimus dorsi, trapezius, rhomboid, and other shoulder girdle muscles form the muscular coat for the posterior thorax. The lower margin of the pectoralis major forms the anterior axillary fold, and the convergence of the latissimus dorsi and teres major muscles forms the posterior axillary fold.

Pleura The pleura is an active serous membrane with a vascular and lymphatic network. There is constant movement of fluid, phagocytosis of debris, and sealing of air and capillary leaks. The visceral pleura covers the lung and is insensitive. It is continuous over the hilum and mediastinum with the parietal pleura, which covers the inside of the chest wall and diaphragm. As opposed to the visceral pleura, the parietal pleura is well endowed with nerve endings; when altered by disease or injury, pain results. The parietal pleura has nerve endings for pain; only when disease extends to this pleura of the chest wall is pain produced. The pleura extends slightly beyond the lung border in each direction and is completely filled with normal lung expansion; only a potential space exists.

Intercostal Space The parietal pleura constitutes the innermost layer, followed by three layers of muscles, which elevate the ribs during quiet respiration. The vein, artery, and nerve of each interspace are located behind the lower margin of the rib. Thus a thoracentesis needle or a clamp used to enter the pleura should be inserted across the top of the lower rib of the selected interspace.

Diaphragm The peripheral muscular portions of the diaphragm arise from the lower six ribs and costal cartilages, from the lumbar vertebrae, and from the lumbocostal arches; the muscular portion converges to form a central tendon. The phrenic nerve supplies the motor innervation, and the lower intercostals supply the sensory innervation. The diaphragm, which rises as high as the nipple, contributes 75 percent of pulmonary ventilation during quiet respiration.

THORACIC INCISIONS

Lateral Thoracotomy Anterolateral This incision extends from the sternal border at the fourth interspace to the midaxillary line. It requires division of the pectoralis major and minor muscles and the serratus anterior. The incision allows rapid entry into the chest with the patient in the semidecubitus position. Therefore, it is the preferred incision for trauma and hemodynamically unstable patients. Exposure is adequate for mediastinal operations, for some cardiac procedures, and for resection of the middle and upper lung lobes.

Posterolateral This incision is used for the majority of pulmonary resections, for esophageal operations, and for the approach to the posterior mediastinum and vertebral column. The skin incision starts at the anterior axillary line just below the infrapectoral fold, extends posteriorly below the tip of the scapula, and ascends between the scapula and the vertebral column. Parts of the serratus anterior, latissimus dorsi, and trapezius are divided, and the thoracic cavity is entered usually in the fifth interspace.

Midlateral No major muscle groups are divided, allowing for quick closure and less patient discomfort. Good exposure is attained with single-lung ventilation.

In general, with lateral thoracotomies, postoperative respiratory therapy is essential because patients experience significant pain and avoid using their chest muscles. Patients must be properly positioned with an axillary roll to prevent brachial plexus injury.

Median Sternotomy Median sternotomy is the optimal incision for anterior mediastinal and cardiac surgery. The pleural spaces can be entered or avoided as desired. The skin incision extends from the sternal notch to the xyphoid, and the sternum is split to enter the chest. Since fewer muscles are divided, patients have less postoperative pain and impaired pulmonary function than with a lateral thoracotomy.

Bilateral anterior thoracotomy and thoracoabdominal incisions are used infrequently but have application in lung transplantation and retroperitoneal pathology.

Thoracoscopy Video-assisted thoracic surgery (VATS) has become an accepted approach to diagnosis and treatment of pleural effusions, recurrent pneumothoraces, lung biopsies, resection of mediastinal cysts, and esophagomyotomy. Major cancer resections are best performed with traditional open approaches.

PREOPERATIVE EVALUATION

All operations on the chest result in some short-term respiratory disability, and many cause permanent alterations in function of intrathoracic organs. Hence the following factors are examined to assess the ability of the patient to undergo surgery.

Pulmonary Function Pulmonary function must be adequate to tolerate the operation and the postoperative period. No single test is available that provides an adequate overall evaluation of lung function. Measurements of value include lung volumes, mechanics of breathing, regional lung function, diffusion capacity, and arterial blood gas determinations.

Spirometry Vital capacity (VC, normal 70 mL/kg), the amount of air that can be forcefully expelled from a maximally inflated lung position, is normal or near-normal in patients with moderately severe obstructive airway disease and is reduced in individuals with restrictive pulmonary or neuromuscular disease. The forced expiratory volume in 1 s (FEV₁) is reduced in obstructive airway disease, but the degree of reduction varies in the same individual. The FEV₁ may be the most useful test to monitor patients with marginal pulmonary function who are being prepared for operation by aggressive respiratory therapy. The FEV₁ is reported as an actual volume and as a percentage of the VC (FEV₁/VC). The values obtained with spirometry in patients are compared with those obtained from other normal individuals of the same sex, age, and height and are reported as a percentage of normal.

Blood-Gas Determination The PaCO₂ measurement provides an immediate indication of the patient's alveolar ventilation; any value above 46 mmHg signifies hypoventilation. Elevation of the PaCO₂ suggests abnormalities in distribution of ventilation and perfusion; patients with chronic lung disease may be treated aggressively to improve pulmonary function and then be considered for operation. Normal PaO₂ is 85 mmHg at sea level. If it is below 70 mmHg, an attempt should be made to determine the cause and to improve the patient's respiratory exchange.

Specialized Tests Radionuclide perfusion scanning for regional lung function allows determination of the separate contributions of the right and left lungs to overall pulmonary function (“split-function” study) and is helpful for patients with compromised pulmonary reserve determined by spirometry. Postoperative VC and FEV₁ can be predicted for the patient who requires pulmonary resection (predicted postoperative FEV₁ = preoperative FEV₁ × percent perfusion in noninvolved lung segments). Perioperative mortality is increased significantly if the predicted postoperative FEV₁ is less than 800 mL.

Exercise Testing This is indicated for patients with reasonable exercise capability despite severe obstructive airway disease. These tests measure maximal oxygen consumption (MVO₂). Patients with an MVO₂ of less than 10 mL/kg/min have a prohibitive risk of postoperative complications.

Many patients are smokers, and every effort should be made to stop for 2 or more weeks before operation. Aggressive attention should be paid to reducing the amount and tenacity of secretions, as well as to identifying and treating any pulmonary infection.

Cardiac Status Electrocardiography is essential. If history, examination, or electrocardiogram (ECG) reveal any abnormalities, cardiology consultation is advisable. Exercise or pharmacologic stress tests and radionuclide angiograms provide excellent noninvasive evaluation of ischemia and ventricular function. Echocardiography and coronary angiography may be necessary (Fig. 16-1).

FIGURE 16-1 A suggested algorithm for investigating the cardiac status of all patients over age 45 or those with significant risk factors undergoing major thoracic surgery. (Adapted from Miller JI: Preoperative evaluation. Chest Surg Clin North Am 4:701, 1992, with permission.)

Nutrition Malnutrition increases the morbidity and mortality of any surgical procedure. Particularly important in thoracic surgery patients are the adverse effects of protein depletion on respiratory function. The muscle groups in the thorax, shoulder, and diaphragm that are involved in respiration and coughing share in the unselected loss of strength seen in all muscles. Coupled with the increased tendency for pulmonary edema and the relative immunosuppression of malnutrition, the risk of a thoracic operation rises. Nutritional status should be assessed by history, physical examination, and laboratory tests (i.e., hemoglobin, coagulation, liver enzymes, and total lymphocyte count).

POSTTHORACOTOMY CONSIDERATIONS

Pulmonary Function Changes Vital capacity is reduced 25–50 percent in addition to the amount of functioning lung that was removed. This is often accompanied by an increase in the closing volume, thus potentiating the development of atelectasis. The severe pain and the sedative effects of the postoperative analgesia produce reductions in tidal volume and elimination of normal sighs. Coughing is inhibited, as is ciliary function and alveolar macrophage activity; hence the protection against inhaled particulate matter and microbes is diminished.

Pain Incisional pain is severe, and unless it is well managed, it will cause diminished respiratory mechanics. It is a challenge to give patients enough pain medication so that they are able to cough without giving them so much that they lose their drive to do so. Analgesia is best administered intravenously or via an epidural catheter in a continuous fashion or with patient-controlled analgesia (PCA) and can be augmented in the early postoperative period with intraoperative intercostal blocks.

Complications Atelectasis involves closure of lung units, and it exists as microatelectasis (not visible on chest radiography) and macroatelectasis (the collapse of a segment, lobe, or entire lung). It is caused by retained bronchopulmonary secretions, decreased sighing, and decreased expiratory reserve volume and may lead to fever and ventilation-perfusion mismatch. Postoperative bronchopulmonary infectious complications consist of tracheobronchitis and pneumonitis. They are a consequence of diminished pulmonary function and can hinder postoperative recovery. The most common cardiovascular complication is supraventricular arrhythmia.

THORACIC INJURIES

The predominant types of injury include high-velocity penetrating wounds (usually military), knife or low-velocity gunshot wounds (civilian), and blunt injury from motor vehicle and industrial accidents.

Conditions Requiring Urgent Correction

Airway Obstruction The oropharynx should be cleared of debris and the neck positioned by an anterior chin-thrust motion while applying continuous cephalad traction to the head. Nasotracheal or orotracheal intubation or cricothyroidotomy should be performed as indicated.

Tension Pneumothorax When injury to the lung parenchyma allows air to enter (but not exit) the pleural space, the pressure increases, causing a shift of the mediastinum and compression of the contralateral lung as well as a decrease in venous return. Release of tension by a thoracostomy tube or large-bore needle is lifesaving.

Open Pneumothorax When a segment of chest wall is destroyed, air is sucked through the wound into the chest rather than through the trachea into the alveoli. A watertight seal (dressing) should be placed and a tube inserted into the pleural space, followed by early repair and closure.

Massive Flail Chest When severe blunt injury results in a two-point fracture of four or more ribs, the chest wall becomes flail. The patient is unable to develop sufficient negative pressure to maintain ventilation; intubation and positive-pressure ventilation are mandatory.

Massive Hemothorax If a patient has percussion dullness of a hemithorax after trauma, a chest tube should be inserted. If massive hemothorax is found (> 1500 mL initially or > 200 mL/h for 4 h), the patient should be explored.

Conditions Requiring Urgent Thoracotomy

Massive air leak. This signifies disruption of the trachea or a major bronchus. Greater than 80 percent of injuries are within 2.5 cm of the carina.
Pericardial tamponade in the presence of trauma.
Esophageal perforation.

Dangerous But Less Compelling Injuries

Diaphragm Rupture Rupture is caused most commonly by penetrating trauma or crush injuries. The left hemidiaphragm is more prone to rupture (ratio of 9:1 compared with the right side). Repair is required to prevent herniation of abdominal contents, which can strangulate and perforate or prevent adequate ventilation by occupying the thoracic cavity. When the diagnosis is made early, repair should be performed via laparotomy.

Pneumothorax Pheumothorax is usually the result of injury to the lung or the tracheobronchial tree and can be associated with a hemothorax. In patients with more than 50 percent collapse, in those with hemopneumothorax, and in patients with penetrating chest trauma, an intercostal catheter should be inserted and attached to 10–25 cmH₂O of suction. If the pneumothorax is stable, it can be observed and will resorb at a rate of 1.25 percent per day.

Interstitial Emphysema This condition is caused by disruption of the respiratory tract or esophagus without air entering the pleural space; the air spreads into the mediastinum, the deep tissue planes, and the subcutaneous space. The patient's appearance is markedly distorted, but there is no reason to “treat” the condition, except to take steps to stop the air leak.

Rib Fractures and Lesser Flail Injuries The main concerns are pain control and for the patient to maintain adequate ventilation. Intubation and positive-pressure ventilation are required if there is any respiratory distress. Associated factors to beware of include delayed pneumothorax, hemothorax, pulmonary contusion, and subclavian injury from an anterior first rib fracture.

Sternal Fractures Sternal fractures are usually transverse, occurring at or near the manubrium, and are painful. It is essential to rule out injury to underlying structures, especially the heart (echocardiograms, continuous ECG monitoring for at least 24 h, determination of creatine phosphokinase levels).

Hemothorax Massive or continued intrathoracic bleeding requires a thoracotomy. If the costophrenic angle is merely blunted (implying < 300 mL), a hemothorax may be followed. Larger amounts of blood need to be evacuated with a thoracostomy catheter. If the hemothorax persists because of a poorly functioning tube, thoracotomy and removal of the clot are indicated to prevent fibrothorax and empyema.

Pulmonary Injury The lungs have a remarkable ability to tolerate penetrating and blunt trauma. Any penetrating object causes a degree of pneumothorax and bleeding. With insertion of an intercostal catheter, the lung reexpands, tamponades the injury, and then eventually heals. Thoracotomy is rarely needed to control bleeding. Contusion is caused by blunt injury and is characterized by capillary disruption and a “fluffy” infiltrate on chest radiograph 24–48 h after the injury. If a significant area is involved, mechanical assistance may be required, but usually not for more than 48–72 h.

CHEST WALL

Congenital Deformities

PECTUS EXCAVATUM

Pectus excavatum is the most common congenital deformity of the chest wall and is attributed to overgrowth of the lower costal cartilages and ribs. The body of the sternum is displaced posteriorly to produce a funnel-shaped depression. Asymmetry is common, and the defect varies widely in expression. The anomaly is three times more common in males, and there is a familial tendency. Between 30 and 70 percent of patients report symptoms, including exercise intolerance, atypical chest pain, dyspnea, bronchospasm, and arrhythmias. However, there is little solid evidence to support functional cardiopulmonary impairment. Operative correction is recommended between 18 months and 5 years to prevent postural and psychological consequences of the defect, but correction in adolescence is also justifiable in order to allow evolution of the defect. The operative technique involves excising the deformed costal cartilage, separating the intercostal muscle bundles from the sternum, and then correcting the sternal concavity. This is done by combining a forward fracture of the sternum with an insertion of bone posteriorly, inserting a metal strut to elevate the sternum, or inverting the entire sternum.

PECTUS CARINATUM

The protrusion deformities of the sternum are much less common than pectus excavatum. Most patients are asymptomatic, and operative treatment consists of resection of the deformed cartilage and contouring of the sternum with transverse osteotomies.

STERNAL FISSURES

Fissures are caused by failure of the sternal primordia to fuse. The superior sternal cleft is broad and extends to the fourth costal cartilage. Osteotomies of each half and reapproximation usually can be performed. Distal sternal cleft is invariably part of Cantrell's pentology, which consists of other defects in the heart, diaphragm, and ventral abdominal wall. Complete sternal cleft is the rarest form of fissure and should be repaired during infancy.

Chest Wall Tumors

Metastatic lesions and direct invasion from breast or lung primaries are the most common chest wall tumors. About half of primary tumors are malignant, and hence the initial biopsy should provide adequate tissue for proper diagnosis.

BENIGN TUMORS

Fibrous Dysplasia (Osteofibroma, Bone Cyst) This entity presents as a slowly enlarging, nonpainful mass.

Eosinophilic Granuloma This is a solitary destructive process associated with pain and tenderness that may heal spontaneously.

Osteochondroma This is a slowly growing tumor from the cortex of a rib.

Chondroma This occurs at the costochondral junction in children and young people. It can be confused pathologically with a chondrosarcoma, and therefore, initial wide local excision is recommended.

Desmoid Tumors These have a tendency to recur and should be resected with a wide margin.

MALIGNANT TUMORS

Although the sarcomas arising in the adult chest wall usually are classified by the cell type of origin, prognosis is related to histologic grade rather than cell classification. The currently recommended grading system groups these tumors as adult soft tissue sarcomas. These tumors include fibrosarcoma, chondrosarcoma, osteogenic sarcoma, Ewing's sarcoma, and myeloma. These tumors are potentially curable, usually by wide surgical resection. Factors that influence prognosis include age, tumor size, histologic grade, and stage.

Chest Wall Reconstruction

Radical excision of malignant chest wall tumors can be accomplished with respiratory support and adequate reconstruction to provide chest wall stability. Many techniques for reconstruction are used, including synthetic meshes, acrylic plates, and myocutaneous flaps.

DISEASES OF THE PLEURA AND PLEURAL SPACE

Pleural Effusion

A pleural effusion is an accumulation of fluid in the pleural space. A concave meniscus in the costophrenic angle suggests the presence of at least 250 mL of fluid. Lateral decubitus views can detect smaller amounts of fluid and can confirm that the fluid is free. A transudate is a protein-poor ultrafiltrate of plasma that is caused by alterations in systemic hydrostatic colloid osmotic pressure. Examples include chronic heart failure, cirrhosis, nephrotic syndrome, hypoproteinemia, and peritoneal dialysis. Changes in capillary permeability caused by inflammation or infiltration of the pleura produce a protein-rich effusion classified as an exudate. Examples include malignancy, infection, infarction, trauma, and sympathetic effusion. Characteristics of the fluid that distinguish exudate from transudate are pH < 7.2, high protein content, foul smell, red cell count > 100,000/mm³, elevated amylase level, and Gram's stain positive for bacteria. Pleural effusions can produce dyspnea. Thoracentesis is the mainstay of diagnosis. Therapeutic drainage of transudative effusions is rarely indicated because they will reaccumulate unless the underlying condition is improved. Exudative effusions usually warrant a more aggressive approach (surgical drainage).

MALIGNANT PLEURAL EFFUSION

Malignant effusions are caused by interference of venous and lymphatic drainage by direct tumor invasion and frequently are massive and symptomatic. The fluid is exudative and often bloody. The presence of a malignant effusion is a poor prognostic sign, and treatment is palliative, consisting of tube thoracostomy or videothoracoscopy to evacuate all fluid, followed by chemical pleurodesis. Talc has become the most popular sclerosant, with reported success rates of 80–90 percent.

EMPYEMA

Empyema is a suppurative infection of the pleural space, most often associated with pneumonia (Staphylococcus, Streptococcus, and gram-negative organisms), trauma, pulmonary infarction, or extension from an intraabdominal source. Initially, the fluid is free, but the suppuration leads to a fibrinous “peel” that traps the lung and prevents reexpansion. Thoracentesis with Gram's stain confirms the diagnosis, and a computed tomographic (CT) scan is useful in delineating abscess, loculations, and lung parenchyma.

The first step of treatment is chest tube insertion and closed suction. If the lung reexpands and the cavity is obliterated, the tube simply can be removed. If the drainage persists and the lung is adherent to the chest wall, the closed drainage can be converted easily to open drainage. If the lung is trapped and does not reexpand with high suction, thoracotomy and decortication are indicated.

CHYLOTHORAX

Chylothorax is a milky, odorless effusion consisting of leaking lymphatic fluid from the thoracic duct. The most common cause is surgical trauma followed by noniatrogenic trauma and malignancy. Chylothorax is frequently massive (average loss > 750 mL/day) and can produce dehydration, malnutrition, and loss of circulating lymphocytes. Conservative treatment is usually successful and consists of keeping the lung expanded and decreasing chyle production by eliminating oral intake and starting parenteral nutrition. A 7–10-day trial of conservative management is justified. If this fails (persistent drainage after 7–10 days or > 500 mL/day in an adult), surgical treatment is indicated. If it is hard to find the actual site of injury, the thoracic duct is ligated in the right chest close to the diaphragm.

Tumors

Mesothelioma This neoplasm originates from the mesothelial lining of serosal cavities. Eighty percent of cases present in the pleura, with 20 percent in the peritoneum. It is associated with asbestos exposure, with smoking as an important cofactor. Mesothelioma exists in both benign (15 percent of the total) and malignant (85 percent of the total) forms. The benign form is usually asymptomatic and unifocal, and resection is the treatment of choice.

Malignant mesothelioma is locally aggressive, 2:1 male predominant, and multicentric, with multiple pleural-based nodules forming sheets separated by loculated, cystic spaces. Most patients die of the primary tumor, although hematogenous and lymphatic spread occurs in one-half of cases. Radical extrapleural pneumonectomy or complete pleurectomy combined with radiation can extend survival in selected patients with Stage I–II tumors, but long-term survivors are rare.

Metastatic Pleural Tumors Over 90 percent of pleural tumors are metastatic, with lung and breast primaries being the most common.

Spontaneous Pneumothorax

Spontaneous pneumothorax most commonly results from rupture of a pulmonary bleb or bullae and occurs in young males without significant pulmonary disease. The incidence of recurrence increases after each episode. An asymptomatic pneumothorax with less than 30 percent collapse that does not increase in size over 8 h can be observed; otherwise, a thoracostomy tube is inserted to allow lung reexpansion. Operation may be required for a persistent air leak (> 1 week), for a massive air leak preventing lung expansion, or after the second episode. At thoracoscopy or thoracotomy, the site of leak is closed, and a pleural abrasion or parietal pleurectomy is performed.

LUNG

Anatomy

Segmental Anatomy The right lung has three lobes (upper, middle, lower), whereas the left lung has two lobes (upper and lower). Each lobe contains a segmental blood supply and bronchial network, with the right lung containing 10 segments and the left lung containing 9 segments. Separation of the bronchial and vascular stalks allows subsegmental and segmental resections when lung tissue needs to be preserved (Fig. 16-2).

FIGURE 16-2 A and B. The segmental anatomy of the lungs. An appreciation of these anatomic divisions often makes it possible to preserve pulmonary tissue by performing segmental resections for localized disease.

Lymphatic Drainage Two groups of lymph nodes drain the lungs: the pulmonary, or N1, nodes and the mediastinal, or N2, nodes. In turn, the pulmonary nodes consist of intrapulmonary, lobar, interlobar (referred to as the lymphatic sump of Borrie because all lobes of the corresponding lung drain into this group of nodes), and hilar nodes. The mediastinal nodes consist of anterior mediastinal, posterior mediastinal, tracheobronchial, and paratracheal nodes. Lymphatic drainage of the right lung is usually ipsilateral, whereas drainage from the left lung is as frequently contralateral as ipsilateral.

Diagnostic Modalities

AIRWAY INVESTIGATION

Sputum Sputum is needed for culture and cytology and must be obtained past the level of the larynx. This is done by percutaneous transtracheal or orotracheal aspiration or by saline-induced coughing.

Bronchoscopy Bronchoscopy allows direct visual examination of the tracheobronchial tree, direct biopsies of bronchial neoplasms, and the ability to assess mobility of surrounding structures, extent of endobronchial involvement, and on occasion, the source of bleeding. Therapeutic uses include removal of foreign bodies or inspissated secretions, ablation of endobronchial tumors, and management of hemoptysis.

Imaging The standard posteroanterior chest radiograph remains the most frequently used study and is an adequate screening tool. For better definition, the CT scan and magnetic resonance imaging (MRI) are used. Nuclear medicine imaging plays an important role in ventilation-perfusion studies (for diagnosing pulmonary embolus and split function testing). Bronchography is used rarely. Pulmonary angiography is useful for embolization of intrapulmonary bleeding sources.

BIOPSIES

Needle Biopsies Percutaneous transthoracic needle biopsy (PTNB) is commonly performed to evaluate intrathoracic lesions. It is performed under local anesthesia and is associated with trivial pneumothoraces in up to 30 percent of patients. It can help identify malignancies, infections, sarcoidosis, and other pulmonary diseases. Contraindications include coagulopathy, pulmonary hypertension, bullous lung disease, and positive-pressure ventilation.

Mediastinoscopy Mediastinoscopy is used to evaluate and biopsy paratracheal masses or identify spread of pulmonary neoplasms. The paratracheal, tracheobronchial, and subcarinal nodes are accessible, whereas posterior nodes, nodes between the trachea and esophagus, and anterior mediastinal masses are not.

Parasternal Mediastinotomy The second and third costal cartilages are spread apart or removed, and the mediastinum visualized. This is particularly useful for evaluation of nodes left of the aortic arch and in the pulmonary hilum.

Thoracoscopy With improved equipment and single-lung ventilation, thoracoscopy has become an extremely versatile technique for evaluating the pleural space, inspecting the mediastinum, obtaining lung biopsies, and removing peripheral pulmonary nodules.

Open Lung Biopsy The chief indication for open lung biopsy is failure of other less invasive techniques to make a diagnosis. A formal operation under general anesthesia is required, and there is some morbidity associated with the procedure.

Congenital Lung Lesions

Agenesis Bilateral pulmonary agenesis is not compatible with life. Isolated unilateral agenesis (usually on the left) allows for normal life.

Hypoplasia Hypoplasia is seen most often in association with anomalies that compete with the lungs for space, such as diaphragmatic hernia.

Cystic Adenomatoid Malformation Neonates present with acute respiratory distress in the first few hours of life. Chest radiograph shows a multicystic “swiss cheese” region with overexpansion and mediastinal shift toward the normal lung. Lobectomy is the treatment of choice, and prognosis is excellent.

Pulmonary Sequestration A portion of lung may be isolated during development and receive its blood supply from the aorta instead of the pulmonary artery. Intralobar sequestrations rest within a lobe and do not have a visceral pleural envelope but rather communicate with the tracheobronchial tree. They occur in the posteriobasal segments and present as recurrent pneumonias; the treatment is lobectomy. Extralobar sequestration is less common, does not have tracheobronchial communication, is enclosed by its own pleural sheath, and appears as an unexplained triangular mass in the posterior lung field. Treatment is resection.

Congenital Cysts These cysts can be single or multiple and are confined to a segment or lobe. They invariably present with infection, since the viscous fluid they contain becomes contaminated after communication with the airway. Resection, after preoperative bronchoscopy and arteriography, is indicated. These bronchogenic cysts also can present as mediastinal masses, and resection of these is controversial.

Arteriovenous Malformation Pulmonary arteriovenous malformation (AVM) is a fistula between pulmonary arteries and veins. Multiple small lesions associated with the Osler-Weber-Rendu syndrome account for half of all patients. The other half have lesions that are fewer in number and larger in size. When shunt fraction exceeds 25 percent of total blood flow, patients can present with cyanosis and polycythemia. Pulmonary angiography confirms the diagnosis. Invasive angiographic embolization is effective and has replaced pulmonary resection as primary therapy in most cases.

LOBAR EMPHYSEMA

Lobar emphysema presents with massive distention of a lobe or segment that shifts the mediastinum and compresses the contralateral lung. Involvement of the upper or middle lobe is the most frequent finding; lower lobe involvement is rare. Resection is straightforward and curative.

EMPHYSEMA

Emphysema is characterized by enlarged airspaces produced by coalescence of damaged alveoli, resulting in air trapping and hyperexpansion of the lung. Localized emphysema (blebs, bullae) may rupture and produce pneumothorax or enlarge massively and compress remaining normal lung. Patients with large, well-defined bullae with normal underlying lung are most likely to have symptomatic improvement after resection. Selected patients with diffuse emphysema involving predominantly the upper lobes may be candidates for lung volume-reduction surgery (LVRS). Improvement in dyspnea and pulmonary function last up to 2 years, but long-term results are unknown. Lung transplantation is reserved for patients with end-stage disease who are unsuitable for LVRS.

Pulmonary Infections

LUNG ABSCESS

Lung abscess is a focus of infection with parenchymal necrosis and cavitation. It is most commonly a complication of necrotizing pneumonia secondary to aspiration and is, therefore, located in segments that are dependent in the supine position (i.e., posterior segments of the upper lobes and superior segments of the lower lobes). Other causes are bronchial obstruction, seeding from systemic sepsis, pulmonary trauma, and direct extension from extraparenchymal infection. Patients present with fever, appear chronically ill, and describe recent onset of copious foul-smelling sputum production. Hemoptysis can occur and be massive; dyspnea is not common.

Treatment is primarily high-dose antibiotics and drainage. Spontaneous drainage by expectoration is adequate, but bronchoscopic aspiration may be needed. Conservative treatment is successful in 75 percent of patients. When internal drainage is inadequate, external drainage is established by tube pneumonostomy or pneumonotomy, which opens the cavity to the outside. Both procedures depend on pleural symphysis; spillage of the abscess material into the free pleural space can be catastrophic. Lobectomy is the definitive treatment. The indications are chronic symptoms, serious hemorrhage, and suspicion of carcinoma.

OPPORTUNISTIC INFECTIONS

Cancer chemotherapy, organ transplantation, major trauma, and the acquired immune-deficiency syndrome (AIDS) have created an increasing population of immunologically compromised patients. Pulmonary infections are the most common infections seen in this population. In the AIDS population, Pneumocystis carinii is the most common pathogen and is treated effectively with trimethoprim-sulfasoxisole. Transbronchial biopsy combined with bronchalveolar lavage can establish a specific infectious diagnosis and has reduced the need for direct lung biopsy. Surgical lung biopsy is reserved for confusing mixed infections not responding to empirical treatment. Surgical treatment of pulmonary complications in the AIDS population may be complex with poor prognosis. The spectrum of infections in non-AIDS patients is wider and should be approached aggressively using indications for surgery applied to normal hosts with similar infections.

BRONCHIECTASIS

Bronchiectasis is characterized by bronchial dilatation and variable involvement of surrounding parenchyma. The bronchial mucosa usually remains intact, but the bronchi are filled with pus, mucus, and an occasional broncholith. Segmental bronchi of the lower lobes, the right middle lobes, and the lingula are involved most frequently. The disease is most commonly idiopathic; it can be associated with cystic fibrosis or obstruction by tumor, foreign body, or bronchostenosis.

The clinical picture is dominated by cough and mucopurulent sputum production (scant to 1000 mL/day), low-grade fever, weight loss, and hemoptysis. Complete bronchography is the definitive test. Postural drainage, chest physical therapy, and antibiotics will obviate operative treatment in most patients. If symptoms persist and the disease is localized, segmentectomy or lobectomy is indicated.

TUBERCULOSIS

Pulmonary infection with Mycobacterium tuberculosis behaves like a lung abscess: The smoldering central focus of infection communicates with the tracheobronchial tree, providing drainage for bacilli-loaded sputum and allowing ingress of air to cause cavitation. The intense inflammatory process promotes arterial hypertrophy, and erosion into these vessels can cause life-threatening hemoptysis. Chest radiograph showing upper lobe cavitary changes or a positive purified protein derivative test is suggestive of the diagnosis. Definitive diagnosis rests on growth of the organism in culture.

Treatment is primarily medical with a combination of drugs, including isoniazid and rifampin; oral pyrazinamide has largely replaced parenteral streptomycin. Pulmonary destruction with bronchopleural fistula and empyema, persistently active disease, hemorrhage, or inability to rule out cancer are indications for surgical resection. If limited pulmonary reserve precludes resection, thoracoplasty (resection of the ribs) can be used to collapse the pleural space and obviate infection.

CHRONIC GRANULOMATOUS INFECTIONS

Actinomycosis Actinomyces israelii is an anaerobic bacillus (not fungus) that inhabits the oral cavity and tonsilar crypts. Thoracic infection is thought to occur from aspiration and is characterized by suppuration, abscess, and sinus tract formation and relentless invasion. Diagnosis is suggested by sulfur granules (yellow-brown clusters of microorganisms) from sputum, sinus tracts, or biopsies and is proven by identifying the bacillus using special stains. The organism is sensitive to penicillin, and surgical resection is very rarely required.

Nocardia Nocardia asteroides is a rare pathogen except in immunocompromised hosts and begins as a pneumonic process grossly similar to tuberculosis and carcinoma. It is a bacillus (not fungus), is relatively easy to culture, and is usually treated successfully with sulfonamides.

FUNGAL INFECTIONS

Histoplasmosis Histoplasma capsulatum is the most common systemic fungal infection in the United States. The severity of infection is determined by the size of the inoculum and the immune competence of the host. The disease can take many forms and is distinguishable from tuberculosis only by culture. Amphotericin B is effective in the majority of patients and is the treatment of choice for serious illness. Asymptomatic patients with positive skin tests need not receive chemotherapy. The presence of large, thick-walled cavities that fail to improve after a course of amphotericin B is the most common indication for surgery. Lymphogenous dissemination leads to compression of mediastinal structures or sclerosing mediastinitis.

Aspergillosis Aspergillus infection presents in three forms: allergic bronchospasm, invasive (invariably fatal), and saprophytic. Saprophytic disease is caused by colonization of a preexisting pulmonary cavity (“fungus ball,” or aspergilloma). Diagnosis can be made by skin tests and sputum cultures. Amphotericin B is the treatment for disseminated disease, but it does not enter into a cavity. Excellent results have been obtained with intracavitary instillation of amphotericin B. Operation is most often justified as prevention of hemoptysis, which occurs in more than half of patients, but morbidity is considerable.

TUMORS

Primary Carcinoma

Lung cancer is the main cancer killer for both sexes. The primary cause is tobacco addiction; long-term exposure or cocarcinogens are required, and the risk is reduced by cessation of smoking.

Pathologic Classification Most primary bronchogenic carcinomas arise from basal or mucous cells in the surface epithelium of the bronchial tree. Other sites of origin are the neurosecretory cells (Clara cells) and Kultchitsky cells (carcinoid tumors). The simplest division, based on approach and management, is between non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC).

NSCLC Squamous Cell Carcinomas Though more common in the upper lobes, bronchogenic carcinomas develop in all parts of the lung. They are relatively slow growing, are late to metastasize, and may present as central bulky masses with bronchial obstruction or as peripheral lesions with cavitation. Peripheral tumors may present with extensive chest wall invasion before metastases occur. The Pancoast syndrome represents a specific example wherein a tumor in the superior sulcus may invade the brachial plexus, the upper two ribs, and the vascular structures at the thoracic apex. Squamous cell carcinoma was the leading pulmonary neoplasm in the United States, but adenocarcinoma is now the predominant cell type.

Adenocarcinomas These tumors arise in the subsegmental bronchi away from the hilum. Growth is more rapid than in squamous tumors, and early metastasis by the vascular route is common, particularly to the brain and adrenals.

Bronchoalveolar Carcinomas An uncommon form of adenocarcinoma develops in the very distal airways and lines the alveoli. It often presents as a peripheral nodule or multifocal carcinoma and is appropriately managed by resection. Less frequently, it presents as lobar consolidation and is rarely cured with surgery.

Small Cell Lung Cancer The small cell anaplastic carcinoma (oat cell carcinoma) is a highly malignant, rapidly growing neoplasm, often located centrally because of its origin from a proximal bronchus. It spreads by lymphatic and hematogenous dissemination and local invasion. The only variant considered for surgical resection is the rare solitary peripheral tumor without associated adenopathy.

Staging The most recent AJCC/UICC TNM classification is used.

	Primary tumor = T:
	T1:	£3.0 cm, without invasion.
	T2:	> 3.0 cm, invades the visceral pleura, or has associated obstructive pneumonitis. The proximal extent of the tumor must be within a lobar bronchus or at least 2.0 cm distal to the carina.
	T3:	Any size with direct extension to the chest wall, diaphragm, pericardium, or mediastinal pleura or within 2.0 cm of the carina without involving the carina.
	T4:	Invasion of the heart, great vessels, trachea, esophagus, or carina or presence of a pleural effusion.
	Nodal involvement = N:
	N1:	Metastasis to peribronchial or ipsilateral hilar nodes.
	N2:	Metastasis to ipsilateral mediastinal or subcarinal nodes.
	N3:	Metastasis to scalene, supraclavicular, or contralateral mediastinal or hilar nodes.
	Distant metastasis = M:
	M1: Distant metastasis present.

TNM Stage Groupings


	Stage IA:	T1N0M0
	Stage IB:	T2N0M0
	Stage IIA:	T1N1M0
	Stage IIB:	T2N1M0; T3N0M0
	Stage IIIA:	T1–3 N2M0; T3N1M0
	Stage IIIB:	T4 Any N M0; Any T N3 M0
	Stage IV:	Any T Any N M1

Surgical therapy is directed at those tumors for which a complete excision can be accomplished. These generally include clinical Stages I–IIIA.

Clinical Manifestations Bronchogenic carcinoma is seen with increasing frequency in patients over age 50, with a peak incidence between the ages of 60 and 70 years. The incidence of carcinoma in now 1.5:1 in favor of men. Asymptomatic patients are most likely to have early-stage disease and be potentially cured. Clinical manifestations include those due to local airway growth (e.g., cough, hemoptysis, pneumonia) and symptoms due to growth into surrounding structures (e.g., hoarseness due to recurrent nerve invasion, localized or radicular chest pain, superior vena cava obstruction, dyspnea from pleural effusion). Loss of appetite and weight loss are ominous signs; such patients usually have an unresectable tumor or systemic metastases.

A small percentage of patients, not necessarily with systemic spread, present with extrapulmonary nonmetastatic manifestations, which may be relieved by resection of the primary tumor. These include pulmonary hypertrophic osteoarthropathy with clubbing of the digits, secretions of hormone-like substances (e.g., adrenocorticotropic hormone, antidiuretic hormone, serotonin, parathyroid hormone), or myasthenia-like syndrome.

Diagnosis and Workup At presentation, approximately two-thirds of patients have disease beyond that treatable by surgical excision. Diagnostic evaluation should determine whether the disease is localized (Stage I–II), locally advanced (Stage IIIA–B), or metastatic (Stage IV). The key modalities are history and physical examination, imaging studies (e.g., chest x-ray and CT scan of chest and upper abdomen), and tissue diagnosis (e.g., sputum cytology, needle biopsy, bronchoscopy, mediastinoscopy, or thoracic exploration). Additional studies for metastatic disease include bone scan and brain CT scan or MRI. Any mediastinal nodes larger than 1 cm warrant investigation before pulmonary resection.

Treatment Patients with clinical Stages I and II non-small cell lung cancer should be considered for surgical treatment. Resection of the tumor generally requires lobectomy or pneumonectomy. The aim of surgical resection is to completely remove the primary tumor and all involved lymph nodes.

Stage I Disease In Stage IA disease, less than 20 percent of patients recur after surgical resection. Most frequently, a lobectomy is required. Lesser resections are reserved for patients with very poor pulmonary function who cannot tolerate a lobectomy and carry a higher rate of local recurrence.

Stage II Disease Involvement of hilar lymph nodes more frequently mandates pneumonectomy for complete resection. Most recurrences occur at distant sites, but to date, randomized trials have failed to demonstrate a survival benefit from adjuvant chemotherapy or radiation. Tumors that directly invade adjacent structures (T3) can be removed with en bloc resections of the lung and involved structure, including chest wall, superior sulcus, and central airways.

Stage IIIA Disease Management of tumors with ipsilateral mediastinal node involvement remains controversial. Multiple clinical trials of induction chemotherapy or chemoradiotherapy indicate that complete surgical resection is possible with up to 30 percent of patients cured. Similar results have been achieved with chemoradiation alone. Two large randomized trials are comparing these methods, and both approaches presently appear valid.

Stage IIIB Disease Surgical cure is very unlikely. Patients are offered chemotherapy and radiation to control disease with a small chance of cure.

Metastatic Disease (Stage IV) Occasionally, patients with a curable primary tumor and solitary brain metastasis realize a 10–15 percent cure with resection of both lesions.

SCLC Median survival without treatment is 2–4 months. Chemotherapy can prolong survival up to 2 years with a small percentage of cure. Stages I and II patients treated by resection and adjuvant therapy have a reported 5-year survival of 30 percent, but most patients present initially with diffuse disease.

Solitary Pulmonary Nodules

The solitary pulmonary nodule has been defined as an abnormal density up to 4 cm in diameter, rounded or ovoid, surrounded by lung tissue, and free of cavitation or lung infiltrates. Because of the relatively favorable outlook of the nodule if it is a cancer, and because of the possible benign lesions presenting this way, there is considerable interest in the differential diagnosis of these “coin lesions.” The differential diagnosis includes hamartoma, granuloma, arteriovenous malformation, pulmonary infarction, and benign and malignant tumors. Approximately 80 percent of all coin lesions are malignant in patients over 50 years of age. Histologic diagnosis should be delayed only if the nodule has been present without growth for a long period of time with a benign pattern of calcification. With tuberculosis less frequent and rising lung cancer rates, current odds favor early resection. With the advent of VATS, resection of peripheral nodules is well tolerated. In patients over 50 years, smokers, those with inadequate proof of the nodule being present longer than 2 years, and failure to make a diagnosis by other means, resection is indicated (Fig. 16-3).

FIGURE 16-3 Algorithm for decision making in patients presenting with solitary pulmonary nodules.

Other Lung Tumors

Carcinoid Tumors This group includes all neuroendocrine neoplasms arising from Kulchitsky cells. All are malignant and represent a spectrum from typical carcinoids to small cell lung cancer. Typical carcinoid tumors are slowly growing tumors and metastasize late. Since 80 percent arise in the proximal bronchi, bronchial obstruction with infection and atelectasis is the most common clinical presentation. The carcinoid syndrome is rare. Lobectomy is the most common method of resection, but parenchyma-sparing procedures (sleeve resections) are appropriate whenever feasible anatomically. The long-term survival rate is over 90 percent.

Tumors of Bronchial Gland Origin Cylindroma and mucoepidermoid tumors are the most common neoplasms arising from the bronchial glands. Their location is predominantly central, and they may show a spectrum of behavior from benign to malignant, with distant metastases. Treatment is en bloc surgical resection, with cure rates higher than those for primary carcinoma.

Sarcomas A number of mesodermal sarcomas may occur in the lung (e.g., carcinosarcoma, leiomyosarcoma, lymphosarcoma, fibrosarcoma, and others) with the same symptoms as primary carcinoma. There is no increased incidence with cigarette smoking. Treatment is surgical resection, with prognosis depending on the stage of the neoplasm.

Benign Tumors Benign tumors comprise only 1 percent of pulmonary neoplasms. Hamartoma, which is composed of disorganized adipose, muscular, and fibrous tissue, is the most common. Hamartomas are usually asymptomatic and can be simply enucleated. Other tumors from epithelial, mesenchymal, or lymphoid origin can occur; their significance is related to the differential diagnosis from malignancy.

Metastatic Tumors Metastases to the lung are common during the clinical course of many extrathoracic primary neoplasms, and resection of these nodules can result in a significantly improved survival rate. Five factors important in selecting patients are (1) control of the primary tumor, (2) no extrathoracic metastases, (3) all lung metastases can be technically removed, (4) the patient can tolerate the operation, and (5) no better treatment exists. It is important to preserve as much lung tissue as possible; hence wedge resections or segmental resections are strongly preferred.

TRACHEA

Anatomy The trachea is a centrally located unpaired organ that has an average length in adults of 11 cm segmented by 18 to 22 cartilaginous rings. The rings are rigid for the anterior two-thirds, with a membranous portion posteriorly. This allows for flexibility without collapse. The blood supply is derived laterally from the inferior thyroid and bronchial arteries.

Congenital Lesions

The most common lesion is the tracheoesophageal fistula. Congenital stenosis, which is rare, presents in several variants: weblike diaphragms, tracheomalacia at sites of compression by a vascular ring, or absence of the membranous trachea with fusion of the rings posteriorly. Congenital stenosis should be suspected in infants with noisy breathing, wheezing, and retractions after birth. Operative treatment is indicated if repeated dilatation or tracheostomy fails to allow growth. When possible, the stenotic segment is resected and the trachea reconstructed with an end-to-end anastomosis. Diffuse involvement may require bone or cartilage splints.

Trauma

The most common injury requiring treatment is that occurring as a complication of tracheal intubation. Soft, low-pressure tubes have reduced but not eliminated the problem. Ischemic necrosis at the tube cuff site can produce stricture, tracheomalacia, or erosion and fistula formation. Blunt and penetrating trauma produce a spectrum of injury ranging from laceration to complete transection.

Resection and end-to-end anastomosis constitute the preferred treatment. Fistulas are repaired by separating the two structures, closing the defects, and interposing muscle.

Neoplasms

Primary tracheal neoplasms are uncommon; more than 80 percent are malignant, and squamous cell and adenoid cystic carcinomas account for the majority of histologic types. Patients present with dyspnea, cough, wheezing, stridor, or hemoptysis. Bronchoscopy is an essential part of the evaluation. Airway stents and laser ablation are used for palliation, with excellent results in 60 percent of treated patients. Radiation therapy is used for long-term control. Operative resection is both a surgical and anesthesia challenge because obstructing lesions make ventilation difficult. Ventilation is delivered by placing an endotracheal tube through the distal trachea or bronchus or by “jet” ventilation. Up to one-half of the trachea can be resected and reconstructed with an end-to-end anastomosis. Upper tracheal lesions are approached through the neck, whereas distal lesions may require sternotomy or right thoracotomy. Prostheses and allografts for tracheal reconstruction generally have been unsuccessful.

MEDIASTINUM

The mediastinum is the central cavity of the thorax bounded laterally by the pleural cavities, inferiorly by the diaphragm, and superiorly by the thoracic inlet. It is divided into three compartments: (1) the anterior mediastinum, which lies above the heart and contains the thymus along with lymphoid and adipose tissue, (2) the posterior mediastinum, which lies behind the heart and contains the esophagus, thoracic duct, descending aorta, and the autonomic nerve trunks, and (3) the middle mediastinum, which contains the heart, pericardium, aorta, trachea, main stem bronchi, and related lymph nodes.

Tumors and Cysts

The most common mediastinal neoplasms are thymic tumors, lymphoma, neurogenic tumors, and germ cell tumors. Primary cystic lesions account for 25 percent of all mediastinal masses. In children, almost half the tumors are lymphoma, followed by neurogenic tumors.

Manifestations and Diagnosis The most common symptoms are nonspecific (e.g., chest pain, cough, dyspnea) and are ascribed to compression of the trachea and esophagus. Other symptoms include superior vena cava syndrome, hoarseness from recurrent nerve palsy, and Horner syndrome. Nerve root compression through the intervertebral foramen (“dumbbell extension”) can produce localized neurologic deficits. Ninety-five percent of mediastinal masses that are discovered as incidental radiographic findings are benign, whereas symptomatic lesions are about half benign and half malignant. CT scans and MRI provide great potential for imaging the mediastinum. Tissue for pathologic examination may be obtained by endoscopy, percutaneous needle biopsy, mediastinoscopy, or mediastinotomy. Small, anatomically discrete, encapsulated mediastinal masses are best managed with resection without preoperative biopsy. Large masses should be biopsied first because most will be treated nonoperatively (e.g., lymphoma) or with a combined-modality approach using preoperative chemotherapy (e.g., germ cell tumors or thymomas).

NEUROGENIC TUMORS

Neurilemmoma Neurilemmomas account for 40–60 percent of all neurogenic tumors. They arise from mature Schwann cells in intercostal nerves and are usually benign.

Neurofibromas Neurofibromas contain elements of both nerve sheath and nerve cells and account for 10 percent of all neurogenic tumors. Advanced age or presence of neurofibromatosis increases the risk of malignancy to 30 percent, which carries a poor prognosis.

Neuroblastomas These are poorly differentiated tumors arising from the sympathetic nervous system that can be hormonally active. More than 75 percent occur in children under 4 years of age. Bone, liver, and lymph node metastases are not infrequent and may make the lesion unresectable. Neuroblastomas are radiosensitive, and debulking followed by radiation can have favorable results.

PHEOCHROMOCYTOMAS

Intrathoracic primary pheochromocytomas are rare and are usually nonsecreting. Thirty percent are malignant.

THYMOMA

Thymoma is the most common anterior mediastinal mass in adults, is rare in children, and has a peak age incidence between 40 and 50 years. Symptomatic patients present either with mass effects on adjacent organs or with paraneoplastic syndromes such as myasthenia gravis or, rarely, hypogammaglobulinemia and red cell aplasia. Histology contributes nothing to the distinction between malignant and benign, which is based entirely on invasive gross characteristics. Benign thymomas can be resected for cure, but malignant thymomas have a poor prognosis. Postoperative radiation is of unknown benefit and does not compensate for an incomplete surgical resection.

LYMPHOMAS

Mediastinal lymphoma is most frequently located in the anterior compartment and is present in 50 percent of patients with Hodgkin's and non-Hodgkin's lymphoma. Chemotherapy and radiation are the standard treatment for lymphomas, and resection is almost never indicated. Surgery is performed as a diagnostic procedure.

TERATODERMOID TUMORS

Teratomas are found in the anterior mediastinum, are often partially cystic, and consist of ectodermal elements, including hair, teeth, and sebaceous glands. Surgical excision through a median sternotomy is the preferred treatment. Eighty percent are benign, and resection is curative. The prognosis for malignant tumors is poor because of local recurrence and distant metastases.

GERM CELL TUMORS

Five cell types of extragonadal germ cell tumors are present. Seminoma and embryonal cell carcinoma are the most common, followed by choriocarcinoma, malignant teratoma, and endodermal sinus carcinoma. The tumors are highly malignant, and 90 percent of patients present with symptoms of compression of adjacent structures. Because of improved chemotherapy during the past decade, most patients are now managed with chemotherapy initially. Residual mediastinal masses are resected to determine if active tumor remains, which determines subsequent therapy. Seminoma is very radiosensitive, and 5-year survival approaches 75 percent.

MESENCHYMAL TUMORS

Lipomas are the most common, followed by fibromas. The malignant forms are rare. Other tumors include hamartoma, leiomyoma, and others. Surgical resection is the treatment of choice.

MEDIASTINAL CYSTS

Congenital cysts constitute 20 percent of mediastinal masses and account for a majority of middle mediastinal lesions. A CT scan demonstrating a mass with near water density occurring in a characteristic location is diagnostic.

PERICARDIAL CYSTS

These are the most common cysts occurring in the mediastinum. They appear at the right cardiophrenic angle as a smooth-walled cystic mass and can communicate with the pericardium. If diagnosis is certain, they may be observed.

BRONCHOGENIC CYSTS

Bronchogenic cysts are most frequently located posterior to the carina or main stem bronchi. They can communicate with the tracheobronchial tree, producing an air-fluid level and allowing for confusion with lung or mediastinal abscess. All bronchogenic cysts should be resected to remove a site for potential chronic inflammation.

ENTERIC CYSTS

Enteric cysts are located in the posterior mediastinum adjacent to the esophagus. When lined with aberrant gastric mucosa, peptic ulceration can lead to perforation and abscess formation. Resection is always indicated.

Mediastinitis

ACUTE MEDIASTINITIS

Acute mediastinitis is a fulminant infectious process with high morbidity and mortality. It is initiated most frequently by esophageal perforation and less often by tracheal rupture and direct spread from oropharyngeal infections. Substernal and interscapular pain, dysphagia, respiratory distress, and crepitus are the chief findings, with florid sepsis and hemodynamic instability supervening rapidly in untreated patients.

Antibiotics and fluid resuscitation are begun immediately. The primary problem, such as esophageal rupture, is treated according to accepted principles. Drainage through the chest and neck is created as required.

CHRONIC MEDIASTINITIS

Chronic inflammation and fibrosis in the mediastinum are thought to result from granulomatous infections, although identification of an organism is rare. The process remains silent until it progresses to produce obstruction. Operative exploration is frequently required to establish a diagnosis and to relieve obstruction.

Superior Vena Caval Obstruction

Superior vena caval obstruction is caused by bronchogenic carcinoma in 85 percent of cases. Presenting signs include venous distention, facial edema, plethora, headache, and respiratory symptoms. The dismal prognosis in these patients often relates as much to the underlying malignancy as to the venous obstruction. Contrary to traditional teaching, a tissue diagnosis should be obtained prior to treatment. Palliative radiation with or without chemotherapy is the most common treatment. Rare benign cases may warrant venous bypass.

For a more detailed discussion, see Rusch VW, Ginsberg RJ: Chest Wall, Pleura, Lung, and Mediastinum, chap. 16 in Principles of Surgery, 7th ed.