Radiology of the chest after thoracic surgery

Radiology of the Chest After Thoracic Surgery By Paul W. Spirn, George W . Gross, Richard J. Wechsler, and Robert M. Steiner

N THE UNITED STATES over the past 30 years, the number of cardiac operations, bolstered by the growing volume of coronary bypass grafts, has come to far exceed the number of operations performed on the lungs, chest cage, and esophagus, which has remained nearly constant. ~There is then still a need for the radiologist to know about the state of the art of general thoracic surgery, the techniques, the postoperative alterations, the complications, and the radiologic appearance.

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PNEUMONECTOMY

Indications and Types The great majority of pneumonectomies performed in the United States are for treatment of non-small cell bronchogenic carcinom~i. In less affluent parts of the world, pulmonary infections, including tuberculosis, bronchiectasis, and widespread necrotizing pneumonia, provide the bulk of cases for pneumonectomy.2'~ The number of other indications for pneumonectomy is small.4'5 In the standard intrapleural, extrapericardial pneumonectomy, resection is in the plane of the pleural space. However, when there is extension of neoplasm to the pericardium or heart, it is necessary to perform an intrapericardial pneumonectomy.6a A tracheal sleeve pneumonectomy may be performed for bronchogenic carcinoma involving a main bronchus close to or involving the carina. The contralateral main bronchus is sutured to the distal trachea) When there is also disease involving the pleural space or parietal pleura, an extrapleural or Front the Department of Radiology, Hahnemann University Hospital Philadelphia; and the Department of Radiology, Thomas Jefferson University tlospitaL Philadelphia. Paul W. Spirn: Assistant Professor of Radiology, Hahnemann University Hospital; George W. Gross: Assistant Professor of Radiology, Thomas Jefferson University Hospital; Richard J. Wechsler: Associate Professor of Radiology, Thomas Jefferson University Hospital; Robert M. Steiner: Professor of Radiology, Associate Professor of Medicine, Thomas Jefferson University Hospital Address reprint requests to Robert )~L Steiner, )liD, Department of Radiology, Thomas Jefferson University Ilospital, 111 S l l th St, Philadelphia, PA 19107. 9 1988 by Grune & Stratton. Inc. 0037-198X/88]2301-000855.00]0 Seminars in Roentgenology, Vol XXlll, No 1 (January), 1988: pp 9-31

pleuropneumonectomy may be performed; the plane Of dissection is between the parietal pleura and the endothoracie fascia. Radical pneumonectomy may be performed with en bloc mediastinal dissection for local tumor invasion or nodal involvement. 6,9 Technical Considerations

The bronchialstttmp. The integrity of bronchial closure depends on an adequate blood supply. Therefore, the bronchial arteries are ligated no more than 5 mm from the resection; the bronchus is divided as close to the carina as possible; intraoperative crush injury to the bronchus is avoided; and, within the constraints of hemostasis, dissection around the lower trachea is keptto a minimum. Methods and materials vary widely; the automatic stapler represents a significant technical advance.6a'9 Many surgeons routinely cover the bronchial suture line with living tissue in order to augment the blood supply and re-enforce the closure, using flaps of pericardium or pleura, pedicled intercostal muscle, or, on the right, the azygos vein. The need for this augmentation is greater on tlie right, and is particularly important when there has been paratracheal lymph node dissection? The pericardiuni. When the pericardium and mediastinal pleura are opened, steps must be taken to prevent subsequent ca'rdiac herniation through the defect. A small defect on either side is generally closed completely. If there has been substantial resection of the left pericardium, the defect may be extended to a full left-sided pericardiotomy, or patched with Teflon strips or other graft materialY If a portion of the right pericardium has been excised, the defect must be patched or the free edges must be tacked securely to the heart. 4"6 The diaphragm. The parietal pleura is inseparable from the central tendon of the diaphragm. In extrapleural pneumonectomy, as for malignant mesothelioma, significant diaphragm injury is likely. Patches to the diaphragm must be fashioned from Prolene mesh or other material .5 The pneumoneetomy space. Fluid accumulates in the operated hemithorax by virtue of bleeding, weeping from lymphatics, and passive 9

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SPIRN ET AL

transudation as air is resorbed. With an uncomplicated intrapleural pneumonectomy, some surgeons are content to evacuate enough air from the pneumonectomy side at the end of surgery to return the mediastinum to midline or slightly toward the operated side. 6 After a pleuropneumonectomy, fluid accumulates more rapidly, and may compromise the volume of the remaining lung, so a small catheter is left in the pneumonectomy space for the first 24 to 48 hours. Mediastinal position is monitored radiographically and air and fluid are withdrawn from the pneumonectomy space as needed (Fig 1). 5

B

Normal RadiographicAppearance FollowingPneumonectomy There is a wide variation in the rate at which pleural fluid accumulates in the pneumonectomy space, in the duration of persistent collections of air, and in the degree to which pneumonectomy fluid is converted to solid fibrothorax. Usually the bulk of fluid accumulates steadily in the first week after pneumonectomy, even more rapidly after pleuropneumonectomy, but it may take months until all the air is resorbed and the hemithorax becomes completely opacified. In

t

Fig 1. Early postoperative pleuropneumonectomy. (A) AP chest film immediately after extrapleural right pneumonectomy for malignant mesothelioma. The pneumonect o m y space has no fluid as yet. A f t e r surgical closure, a small catheter was inserted in the right hemithorax (arrows), air was introduced until the mediastinum approximated the midline, and the catheter was left clamped. (B} Twenty-four hours after surgery. A large volume of fluid has accumulated under sufficient pressure to displace the mediastinum contralaterally. Although this finding is common after uncomplicated pleuropneumonectomy, after standard pneumonectomy it may signal a stump leak, hemorrhage, or empyema.

CHEST RADIOLOGY AFTER THORACIC SURGERY

some patients a small amount of air persists indefinitely.6 In the 3 or 4 weeks after surgery, there is progressive elevation of the pneumonectomy air-fluid level, while the mediastinum remains midline or shifts gradually toward the operated side. There is a normal contralateral shift of the mediastinum with expiration (up to 3.5 cm); this should not be confused with real displacement. I~ Genuine shift of the mediastinum away from the operated side, particularly when accompanied by increasing subcutaneous emphysema, indicates a pathologic elevation of the pressure in the operated hemithorax. If the air-fluid level has not continued to rise, this may represent a stump leak with a check value effect. If the air-fluid level has continued to rise, the shift may be due to hemorrhage, chylothorax, or empyema, with or without a bronchopleural fistula. A drop in the air-fluid level any time after pneumonectomy indicates that fluid is draining through a chest tube or by thoracentesis, or through a dehiscence of the incision, an opening in the bronchial stump, or a rent in the diaphragm. In the long run, as assessed by autopsy studies and CT scans, about two thirds of pneumonectomy patients maintain a unilocular fluid-filled space with thick fibrous margins; the remainder transform into a solid fibrothorax. "'~2 Marked volume loss on the operated side is the rule, more so when fibrothorax has developed. It is theorized that the degree of mediastinal shift depends on the hyperexpansion of the remaining lung. There is always pulmonary hernia across the midline anteriorly; after left pneumonectomy there is also a 50% incidence of posterior, prevertebral herniation, which does not occur after right pneumonectomy. In addition to elevation of the hemidiaphragm and contraction of the hemithorax on the operated side, CT also shows an interface between the pneumonectomy space and the mediastinum, which is generally convex toward the side of surgery (Fig 2). 12"13

Complications Mortality and morbidity. The mortality of pneumonectomy is approximately 6%, three times greater for right pneumonectomy than left, and also three times the mortality of Iobectomy.2'14The major causes of death are pneumonia, respiratory failure, pulmonary embolism, myo-

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Fig 2. CT 3 months after left pneumonectomy. Contrast-enhanced scan at the level of the carina. The mediastinum is shifted markedly into the contracted left hemithorax, the RUL herniating far across the midline (white arrow). The fluid collection in the pneumonectomy space (11 has a thick enhancing margin. Surgical clips denote the bronchial closure.

cardial infarction, bronchopleural fistula (from bronchial stump leak), and empyema. These major complications account for a combined incidence of morbidity and mortality of 30%, v 20% for IobectomyJ4 All the radiographic features need not be reviewed. However, it is important to note that any radiographic evidence of pulmonary edema or pneumonia in the remaining lung should occasion vigorous clinical investigation. Pulmonary edema, probably related to hypervolemia, typically appears 24 to 48 hours after right pneumonectomy, and is said to be uniformly fatal unless treated promptly with diureticsJ s Pneumonia complicating pulmonary resection is fatal 25% of the time. ~4 Empyema; bronchopleural fistula. These conditions are often associated, one leading to the other. In a review of many series of pneumonectomy, the incidence of empyema without bronchopleural fistula was 5% and of empyema with bronchopleural fistula w a s 2 % . x6 The overall incidence of bronchopleural fistula is 5% or 6%.2't7 The incidence of bronchopleural fistula without empyema is approximately 4%. Empyema without bronchopleural fistula

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occurring in the first week postoperatively is attributable to intraoperative soilage or preoperative pleural infection) 8 Postoperative assisted ventilation increases the likelihood of empyema fivefold)6 Empyema patients are febrile with leukocytosis. Since air normally persists in the pneumonectomy space through this time, the presence of air and fluid collections on the chest film is not a useful sign. Empyema in the closed

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pneumonectomy space exceeding the volume of resorbed air may shift the mediastinum contralaterally) 9 However, the previously intact bronchial stump may open after several days, decompressing the infected hemithorax. This will prevent mediastinal shift. Later onset of postpneumonectomy empyema, occurring from several months to many years after surgery, is often accompanied by little more

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Fig 3. Empyema w i t h o u t bronchopleural fistula. (A) PA chest film 8 weeks after right pneumonectomy. Disseminated H influenza pneumonia is seen in the left lung. The mediastinum is shifted into the fully opacified right hemithorax. Thoracentesis excluded infection in the pneumonectomy space. The pneumonia resolved w i t h antibiotics. (B) P A . chest film 11 weeks after surgery. The patient had been febrile for I w e e k , w i t h o u t cough or sputum production. The volume of the contents of the right hemithorax has increased, indicated by movement of the trachea and heart to the left. Thoracentesis showed H influenza empyema. Pleural drainage and antibiotics w e r e curative.

CHEST RADIOLOGY AFTER THORACIC SURGERY

than constitutional symptoms. Approximately half of these patients also have broncho- or esophagopleural fistula. Often there is recurrent carcinoma. A chest film shows air with or without fluid levels in a previously opacified hemithorax. 2~ Patients are treated with open drainage, often for an extended period of time. The other half of this group of patients have no fistula, and the cause of empyema is presumed to be hematogenous seeding of the inert fluid-filled pneumonectomy space from an infectious source elsewhere. There may be little radiographic evidence of empyema, since the operated hemithorax remains completely opacified. Mediastinal and tracheal shift toward the contralateral lung have been reported, along with the CT finding of a change in the contour of the interface between the pneumonectomy space and the mediastinum from convex to concave facing the operated side (Fig 3). t3"~~ Treatment is the same as for a nonsurgical empyema. Bronchopleural fistula after pneumonectomy occurs at the bronchial stump and has a 17% mortality. 2 When it occurs in the first week, most investigators ascribe it to poor closure, and recommend reoperation. 6'%18Appearance in the second or third postoperative week means a failure of the stump to heal by second intention. Predisposing factors relate to (1) bronchial ischemia from an overlong stump, too proximal a ligation of bronchial arteries, or extensive lymph node dissection disturbing the tracheobronchial blood supply; or (2) to defective bronchial tissue or poor healing secondary to preoperative radiaiion, resection through tumor or infection, malnutrition, or corticosteroid therapy. Patients may have chest pain, cough, and sputum that is initially serosanguinous but becomes purulent after empyema develops. Increased cough and dyspnea occurring when the patient lies on the contralateral'side may signal aspiration through the stump, a contraindicatio~a to radiographic study ih this positiofi.2~ The radiographic signal of bronchopleural fistula is a decrease in the volume of fluid, demonstrated by either a drop of more than 5 mm in the air-fluid level or the appearance of air in a previously fully opacified p n e u m o n e c t o m y space. 1~ The mediastinum may be midline or shifted to either side. Consolidation may develop in the remaining lung due to spillover aspiration.

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Because a drop in the fluid level may also occur with a leak through the incision or a rent in the diaphragm, most surgeons desire clear evidence of fistula before undertaking invasive therapy unless the clinical evidence is compelling. 18 Bronchoscopy is preferred, but since the likely

I B Fig 4. Bronchopleural fistula. (A} PA chest film 2 weeks after plauropneumonectomy. Residual air w i t h Ioculations in the pneumonectomy space is normal. The mediastinum is midline. (B) Four weeks after surgery. The volume of fluid in the compartments has decreased, indicating a leak, either through the bronchial stump, through a t o r n diaphragm, or as suggested by progressive angulation of a surgical rib fracture (arrow), through the incision. The patient had no symptoms, the soft tissues of the chest w a l l were normal, and thoracentesls from the pneumonectomy space excluded empyema. Bronchoscopy showed a small stump leak.

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site of the fistula .is known, it is adequate to install methylene blue in the pneumonectomy space and find it in the sputum. Bronchography is less helpful than it is in the investigation of bronchopleural fistula after lobectomy, where it identifies the size and location of the fistula and helps predict the likelihood of spontantous clos u r e . 23

Occasionally, bronchopleural fistula may

present with little clinical evidence 6 weeks or more after pneumonectomy (Fig 4). Presumably these patients have a small stump leak and no empyema as yet. Of 14 patients in one series, 11 healed spontaneously without pleural drainage or other surgery, and the operated hemithorax again filled with fluid. 24 Gas in the gut from a surgical traumatic diaphragmatic hernia may be confused with postpneumonectomy air (Fig 5).

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Fig 5. Diaphragmatic hernia a f t e r pneumonectomy. (A, B) PA and lateral films several years after pneumonectomy. There are several clues to the diagnosis of gastric hernia. The fluid-level is wavy, suggesting semisolid food. The upper margin of the gas collection is dome-like and smooth. (C} Upper Gl series. All of the stomach and a segment of colon have traversed the diaphragm.

CHEST RADIOLOGY AFTER THORACIC SURGERY

Cardiac herniation and precipitous mediastinalshift. Intrapericardial pneumonectomy exposes the patient to the risk of cardiac herniation unless the surgical defect in the pericardium is closed, patched, or otherwise stabilized. Nearly 50 instances of cardiac herniation have been reported, nearly all following pneumonectomyY "~7Cardiac herniation usually occurs within the first few hours after surgery, sometimes within moments after the patient has been turned supine or to the operated side. Severe clinical findings include tachycardia, hypotension, and elevated central venous pressure. Unless the hernia is reduced by a fortunate postural maneuver or by immediate surgery, the patient usually dies. Recognition of the radiographic findings is critical if cardiac herniation is to be distinguished from clinically similar events, such as massive pulmonary embolus, acute myocardial infarction, pericardial tamponade, and tension pneumothorax. In a right-sided hernia, the heart rotates counterclockwise twisting around the venae cavae. The mediastinum shifts to the right, the cardiac portion even more so, and the apex of the heart points to the right. The empty pericardial sac may sometimes be seen in the left hemithorax (Fig 6). With left-sided herniation, some or most of the left heart protrudes through

Fig 6. Cardiac herniation. AP chest film eight hours after intrapericardial right pneumonectomy. The heart has herniated through the open pericardiotomy into the right pneumonectomy space, rotating so that the left atrial appendage (white arrow) and ventricular apex form the right cardiac border. The pericardium (black arrows) is anchored to the left hemidiaphragm. The trachea and esophagus are in nearly normal position. The heart was returned t o the pericardial sac and a Prolene mesh patch was applied to the large right pericardial defect.

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the pericardium, producing a bulge in the cardiac margin or a bulbous left cardiac contour, with a sharp incisura made by the constricting edge of the open pericardium. Leftward mediastinal shift is usually presentY '26 It may be helpful to note positional changes in a left thoracostomy tube, or if a left pleural effusion obscures the heart, to induce a pneumothoraxY After pneumonectomy, care should be taken to minimize the extent of mediastinal shift toward the operated side. Excessive or precipitous mediastinal shift that may embarrass either venous return or cardiac output is generally recognized before the patient leaves the operating room. However, if a chest tube left in the pleural space is inappropriately drained by prolonged negative pressure, severe mediastinal shift may occur. Although the clinical findings of this condition overlap with those of cardiac herniation, the therapy and reversibility differ completely, and radiographic differentiation must be made. Unlike cardiac herniation, the mediastinum shifts as a whole--the cardiac silhouette is displaced more than the trachea. ~s Further, there is neither rotation of the cardiac apex nor contour change of the left cardiac margin (Fig 7). Esophagopleural fistula. The majority oi" reported cases of esophagopleural fistula after

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SPIRN ET AL

Fig 7. Excessive mediastinal shift due to thoracost o m y drainage immediately after pneumonectomy. The entire mediastinum is shifted into the evacuated right pleural cavity. The thoracostomy tube had been connected to suction. Some patients w i t h this degree of mediastinal shift are not symptomatic.

pneumonectomy occurred after surgery for thoracic suppuration, especially tuberculosis.29 A fistula that appears early usually is attributable to direct injury of the esophagus during lymph node or pleural dissection. Esophagopleural fistula developing after postoperative recuperation probably reflects recurrent infection. The incidence of esophagopleural fistula following pneumonectomy for lung carcinoma is 0.5%. Most follow the treatment of bronchopleural fistula.29 The presumption is that the esophageal fistula is the sequel of an empyema or mediastinal abscess. Esophagopleural fistula is ten times more common after right pneumonectomy. This is understandable since the esophagus is contiguous with the right pleura but separated from the left by the aorta. Fever, chest pain, and dysphagia occur. Empyema is usually present and the presence of food particles in the thoracostomy drainage makes the diagnosis. Barium or gastrografin swallow is invariably positive. 29,3~ Treatment requires drainage of the empyema and excision of the fistula if the patient can tolerate surgery or palliative gastrostomy, if not. Right pneumonectomy syndrome. A rare complication of right pneumonectomy performed in childhood or adolescence is delayed obstruction of the left main bronchus, resulting in recurrent left pneumonia and dyspnea.3xThe condition probably arises because the considerable corn-

pliance of the juvenile left lung permits its marked hyperinflation and extreme rightward shift of the mediastinum. CT has demonstrated that this shift and the accompanying counterclockwise rotation of the mediastinum attenuate the left main bronchus across the spine and between the aorta and pulmonary artery. In the largest published series of these cases, Shepard et a132found that the more marked the mediastinal shift, the shorter the interval between pneumonectomy and onset of symptoms, ranging from one to 37 years. In some of their cases, fluOroscopy demonstrated more severe functional narrowing from tracheobronchomalacia. Therapy is by a variety of corrective procedures directed :at reducing rightward mediastinal shift, relieving vascular compression of the left bronchus, :and stenting the bronchus (Fig 8). Tension chylothorax. This condition, well known after esophageal surgery, has now been seen as a complication of right pneumonectomy for bronchogenic carcinoma?3 In both reporIed cases, the operated hemithorax was nearly filled with fluid by the end of the first week. Two 'weeks later, both patients had symptoms of acute pleural tamponade. Chest films showed an opaq.ue right hemithorax and a leftward mediasfina] shift. Thoracentesis yielded chyle. Treatment consists of pleural drainage to relieve respiratory and hemodynamie embarrassment, a trial of

CHEST RADIOLOGY AFTER THORACIC SURGERY

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Fig 8. Right pnaumonectomy syndrome in a 19year-old severely dyspneic patient. (A} PA chest film 1 year after pneumonectomy for severe congenital bullous disease. There is marked mediastinal shift and rotation w i t h the cardiac apex completely subsumed into the pneumonectomy space. The low left hemidiaphragm suggests air-trapping, consistent w i t h the bronchoscopic findings of a slitlike narrowing of the left main bronchus. (B) PA chest film after surgical mediastinal repositioning. The mediastinum is near midline and the cardiac apex n o w points to the left. The left hemidiaphragm is less depressed. A silicone breast prosthesis was placed in the right hemithorax to stabilize mediastlnal position. CT, which initially showed occlusion of the left main bronchus, n o w revealed only moderate narrowing as it passed between the descending aorta and left pulmonary artery.

hyperalimentation with a lipid-regulated diet, and ligation of the thoracic duct, if necessary. LOBECTOMY

Indications

Generally, a more difficult surgical procedure than pneumonectomy, lobectomy is usually per-

formed for resection of bronchogenic carcinoma. Less common indications include giant emphysematous bullae, a large or centrally located benign tumor, such as bronchial adenoma, chronic suppurative pulmonary disease, fungus infection, and congenital anomalies such as a pulmonary cyst, bronchopulmonary sequestration, and ar-

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teriovenous malformation)438 Bronchiectasis and pulmonary tuberculosis are much less frequently treated with Iobectomy than in the past. 36 Operative mortality due to lobectomy is approximately 2%. 39 Because of the more elastic hilar structures and the infrequency of pulmonary scarring and matted lymph nodes, lobectomy is technically much easier in children than in adults.4~

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SPIRN ET AL

Technical considerations. Lobectomy is usually performed with the patient in the lateral position, through the fourth intercostal space for upper lobe resection, and the fifth or sixth intercostal space for right middle lobe, lingula, or lower lobe resection.36'41 The surgical route may be indicated on the postoperative chest radiograph by rib fractures, narrowing of the intercostal space, or overlying soft tissue swelling and

Fig 9. Right upper and middle Iobectomy for bronchoalvaolar carcinoma. The RLL has expanded to occupy the entire right hemithorax, which is diminished in volume. There is mild postoperative mediastinal shift to the right, accompanied by antarolataral bowing of the trachea. Mild elevation of the right hemidlaphragm is accompanied by a "'juxtaphrenic peak sign."

CHEST RADIOLOGY AFTER THORACIC SURGERY

subcutaneous emphysema.42 If the supine position is used, additional exposure is often obtained by resection of adjacent ribs and cartilage. Postoperatively, a pleural chest tube is placed temporarily for control and removal of pleural fluid collections and air leaks. Continuous suction is customary following upper lobe resection, whereas intermittent suction usually suffices otherwise, in the absence of postoperative air leak.36

Normal Radiographic Appearance Following Lobectomy Early postoperative chest radiographs in the child or adult usually show mediastinal shift toward the side of lobectomy, reduced volume of the hemithorax, elevation of the ipsilateral hemidiaphragm, and compensatory hyperexpansion of the remaining lobes to help fill the residual space of the resected lobe (Fig 9). Reorientation of pulmonary arteries and major bronchi is often visible radiographically. For example, following upper lobectomy, the lower lobe bronchus and artery rotate outward and uoward with expansion, resulting in wider spacing between arteries and bronchi. The ipsilateral hilus is usually distorted, displaced upward, and smaller than the opposite hilus. A small pneumothorax or hydropneumothorax may be present, as well as limited pneumomediastinum and subcutaneous emphysema.4345 The mediastinum later returns to its normal position, with further hyperinflation of the remaining lobes. After chest tube removal, a small transient pleural effusion often occurs. 4244.46 This may resolve completely or leave localized pleural thickening.4246 There is usually a predictable pattern of realignment of the remaining lobes. Following upper or lower lobe resection, because the lobes and segments anterior to the midcoronal plane are more mobile than those more dorsal, the lingula or middle lobe shifts into the zone of resection. 43"46With lingula or middle lobe resection, minor upper and lower lobe shifts usually o c c u r . 43,46

The chest radiograph following Iobectomy may show the same signs as in lobar collapse. The "upper triangle sign" may be seen with either right lower lobe collapse or following lobectomy. It consists of a triangular shadow in the right upper medial thorax with the apex

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pointing toward the hilum and the base disappearing at the right clavicle. The triangle consists of right and left anterior pleuromediastinal lines laterally and the anterior junction line extending inferiorly. Residual thymie, lymphoid, and areolar tissue are present within the triangle.47 The "fiat waist sign" and the "top-of-the-knob sign" may be seen with severe left lower lobe collapse or following left lower lobectomy. The former is a straightening of the left heart border at the pulmonary outflow tract level on the frontal projection caused by rotation of the heart. The latter is obliteration of the top of the aortic knob, attributed to displacement of the upper mediastinum to the left.47The "juxtaphrenic peak sign" (Fig 9A) is a small, sharply defined shadow projecting superiorly from either hemidiaphragm at or near its highest point, that varies in shape from a broad tent to a sharp peak. It occurs with upper lobe collapse or upper lobectomy.4s'49 In contrast to lobar collapse, lobectomy involves removal of the entire lobe and all its connections to the hilum and mediastinum, including the lobar bronchus, artery, and vein, so that differences in appearance of the postlobectomy space from severe lobar collapse may be evident.4s In addition, there is usually greater loss of volume after lobectomy than with collapse, which is seldom complete.

Complications Bronchopleural fistula and postlobectomy empyema are particularly related to lobectomy (Fig 10).34,44 Although less common than after pneumonectomy, reopening of a bronchial stump early in the postoperative period may result in tension pneumothorax, with ipsilateral lung compression and contralateral midline shift.36Noninfected bronchopleural fistula with pleural air and fluid collections will usually gradually resolve over several weeks to months. A bronchial stump leak that occurs late is usually caused by or followed by empyema; a new intrapleural airfluid level is typically present on the chest radiograph.36,44, 5o

Postoperative empyema usually results from operative contamination, less commonly from spread of infection via a bronchopleural fistula or hematogenously to preexisting pleural fluid collection. Tube thoracostomy is usually adequate

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Fig 10. Postlobectomy bronchopleural fistula and empyema. (A) Erect AP view of the chest four days after right upper Iobectomy for bronchogenic carcinoma demonstrates moderate opacification of the right hemithorax from apex to diaphragm, and several air collections, the largest of which contains an air-fluld level. There is no mediastinal shift. (B} CT scan just above the carinal level, following contrast enhancement. A large collection of fluid, containing several pockets of air and one fluid level is present in the posterior right hemithorax, indicating empyema secondary to a bronchopleural fistula. Some rim enhancement is seen anteriorly. The trachea is deformed, but not displaced. An anterior substernal soft tissue density accounts for the paramedlan density seen on the PA chest film, and probably represents a hematoma or Ioculated empyema.

treatment when the pleural contents are liquid and free of loculation. When the empyema is loculated or contains thick purulent material, open drainage that may include resection of a short segment of one or two ribs may be required. A long-standing empyema will require thoracotomy and decortication with the addition of thoracoplasty if the empyema cavity is large) 6"sl Other postlobectomy pulmonary complications include atelectasis: ~ pneumonia, 34 and hemothorax: ~ A rare complication of pulmonary resection, lobar torsion, may result in pulmonary infarction. Right middle lobe torsion following right upper lobectomy may present as a wedgeshaped opacity in the right upper hemithorax with the oblique fissure extending tangentially to

a point below the right hilus. Lower lobe torsion following upper lobectomy has been reported as well. 52 Pulmonary lobar gangrene following lobectomy may present radiographically as lobar consolidation initially, with subsequent development of bronchopleural fistula and empyema: 3 Unilateral pulmonary edema due to postlobectomy pulmonary vein thrombosis presents radiographically as unilateral airspace disease. Selective pulmonary angiography may be necessary for correct diagnosis. 54 Postlobectomy right-to-left shunting through a patent foramen ovale does not show plain film signs. Echocardiography or cardiac catheterization is required for diagnosis: s

CHEST RADIOLOGY AFTER THORACIC SURGERY

SEGMENTECTOMY

Indications Because bronchopulmonary segments are sufficiently distinctive anatomic units, they can be removed individually. Certain lesions are often segmentally confined, so that segmental pulmonary resection is not only feasible, but also permits conservation of the healthy pulmonary tissue that would be lost in lobectomy. Compensatory overdistention is also reduced by segmental resection: 6 Indications for segmentectomy include benign pulmonary neoplasm, bronchiectasis, lung abscess, pulmonary cyst, metastatic neoplasm, and well-localized areas of tuberculosis: 6 When appropriate criteria are met, segmental resection for lung cancer may also be performedY Wedge resection, a procedure used routinely for sublobar resection before the development of segmental resection, involves removal of a wedge-shaped area of parenchyma without regard for intersegmental planes. It is frequently used for removal of small peripheral lesions: 6 Technical Considerations The lateral position for the patient is preferred. The incisional approach is generally the same as for lobectomy, but depends on the location of the segmental tissue to be resected: 6 Segmental surgery is technically more difficult than lobectomy, due partly to variations in segmental anatomy) 7 Operative mortality is approximately 0.5%. 39

Normal Radiographic Appearance After Segmental or Wedge Resections The chest radiograph after segmental or subsegmental resection is similar to that following lobectomy, although an important difference is the frequent presence of surgical staple material (Fig 11) and the minimal mediastinal shift and compensatory hyperinflation, less extensive than with lobectomy.42:3'46 Complications The principle complications of segment resection are bronchopleural fistula and empyema. Postoperative pneumothorax may occur in as many as 25% of cases; persistent air leak may require suturing of the fistula and decortication

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of the lung. Postoperative empyema usually resolves with suction through a pleural chest tube. Postoperative infiltrates occur frequently in the involved lobe, and may reflect hemorrhage, contusion, or atelectasis. These infiltrates typically resolve within a few weeks, but may leave focal parenchymal scarring. Fluid may collect at t h e site of a resected nodule, resulting in a pseudotumor that is usually transient, but may persist as a permanent nodule. 43'46"56'57 THORACOPLASTY

Originally developed for the treatment of extensive unilateral fibrocaseous pulmonary tuberculosis accompanied by atelectasis and mediastinal displacement, thoracoplasty is occasionally indicated as a procedure for reducing thoracic cavity Volume.39'586t The basic surgical approach to the three major types of thoracoplasty (conventional [Alexander type], tailoring, and Sehede) is described elsewhere: 1'6~ More recently, a surgical technique for treatment of chronic tuberculosis empyema that involves collapsing the parietal chest wall without rib resection has been described. Thoracoplasty is now generally used only in certain high-risk situations, where primary resection of locally extensive, drug-resistant tuberculosis is judged excessively hazardous. In such circumstances, a preliminary thoracoplasty may permit sufficient control of disease and improvement in the patient's clinical status to allow later primary resection) 9 An additional indication for thoracoplasty is in the treatment of postoperative complications of lung resection, such as persistent bronchopleural fistula and empyema. Thoracoplasty usually requires resection of six or seven ribs. The ribs are removed subperiosteally to allow their regeneration in the collapsed position, preventing prolonged paradoxical motion and partial reexpansion. The postthoracoplasty chest radiograph demonstrates variable degrees of rib resection and regeneration, beginning at the lung apex with the first rib. Diminished lung and hemithorax volume and pleural thickening are apparent (Fig 12). 6v63 Complications of thoracoplasty include paradoxical lung and chest wall movement, scoliosis with convexity toward the operated side, and ipsilateral frozen shoulder: 2

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Fig 11. Segmantectomy. (A, B) PA and lateral chest films after resection of the superior segment of the RLL for a metastatic adenocarcinoma of the colon. In addition to the vascular clips in the right hilum, there is a line of surgical staples at the site of segment e c t o m y (small arrows). Partial volume loss involving the RLL is indicted by mild postoperative elevation of the right hemidiaphragm and reorientation of the right major fissure (thick a r r o w ) . There is no mediastinal shift and the peripheral pulmonary vascular pattern appears normal.

ESOPHAGEAL SURGERY: ENDOSCOPY

The frequency of chest abnormalities related to surgery or endoscopy of the esophagus has increased markedly in recent years because of the modern aggressive approach to treatment of diseases of this vulnerable organ. The plain chest film, CT, and contrast esophagography are valuable procedures for following the patient's course

after identifying complications related to these procedures. Postsurgical complication rates may be as high as 40% and endoscopic complication rates up to 1.0% have been reported (Table 1).64, 65

Anatomy The relationship of the esophagus to neighboring structures leads directly to many of its unique

CHEST RADIOLOGY AFTER THORACIC SURGERY

23

Fig 12. Thoracic configuration after right thoracoplasty for tuberculosis. (A) PA chest film shows collapse w i t h rib deformity. There is a s s o ciated thoracic dextrosc'oliosis. Residual fibrosis is present in the remainder of the right lung and the left apex. (B| CT scan at the level of the aortic arch. Reduction of the right lung volume accompanies extensive upper right rib deformity and chest wall collapse. Mild vertebral rotation is a component of the scoliosis.

complications. 64'66Points of weakness are present above and below the cricopharyngeus, where perforation may occur with instrumentation. As the esophagus passes into the thorax, it lies behind the left subclavian artery and is related closely to the left pleural space. Below the aortic arch, the esophagus is located to the right of the descending aorta, contiguous with the right pleural space, forming part of the border of the azygoesophageal recess. Within the thoracic esophagus, physiologic narrowing oe-

curs at the level of the aortic arch and the left main stem bronchus. At the gastroesophageal junction, the esophagus returns to a midline position and is closely related to both pleural surfaces, especially the left. Physiologic narrowing is present at the esophageal hiatus.

Esophageal Perforation Interruption of the esophagus wall may produce abnormalities of the lung, mediastinum, or pleura related to the location of the leak. If the

SPIRN ET AL

24 Table 1. Causes of Esophageal Perforation Dilatation of stricture Dilatation of achalasia Diagnostic esophagoscopy Removal of foreign bodies Mediastinal tube drains Mediastinoscopy Fundoplication Double contrast esophagoscopy Vagotomy Tumor resection Inadvertent intubation of hypopharynx Esophageal obturator airway Modified with permission. 7:

thoracic esophagus is ruptured, a right pleural effusion is most common. If a cervical or subdiaphragmatic perforation occurs, a left pleural effusion is more likely. Because it is essential to recognize esophageal injury early in order to institute timely treatment, the physician must think of the diagnosis. Acute onset of chest pain, dyspnea, dysphagia, shock, or vomiting, especially following instru-

mentation, should suggest perforation. Although symptoms are usually acute, in some cases of perforation, particularly when mediastinitis is absent, symptoms may be delayed or mild, and the diagnosis is not readily apparent. ~6"67 Radiographic findings. Although 10% of chest films are normal following esophageal injury, most will demonstrate characteristic abnormalities that will confirm and localize the site of the perforation. Lateral plain films of the soft tissues of the neck, PA and lateral chest radiographs, and an upright abdominal film should be obtained. Subcutaneous emphysema, pneumomediastinum, pneumothorax, hydropneumothorax, mediastinal widening, or pneumonia strongly suggest perforation. Films,taken within an hour after perforation may yield a false-negative result, because soft tissue air or pneumomediastinum may take a while to appear. Whether or not the plain film yields evidence of perforation, contrast esophagography should be performed with dispatch if the diagnosis is suspected. It will confirm a leak and show its size,

#

41k L

Fig 13. Breakdown of an esophagogastrojejunal anastomosis in a 50-year-old man. A right esophagopleural fistula is shown (arrow). There is a right chest tube in place. Note the diluted barium in the right pleural space.

CHEST RADIOLOGY AFTER THORACIC SURGERY

A

Fig 14. Esophagobronchial fistula in a 62-year-old man who had undergone esophagogastrectomy for carcinoma. (A} PA film of the chest 6 months postoperatively demonstrates a LLL pneumonia w i t h cavitation. (B) GI series with barium shows a fistula to the anteromedial basal segment bronchus.

location, and extent (Figs 13 and 14). The leak may seal if th e study is delayed. 64'6g The choice of contrast medium for esophagography for esophageal injury has been controversial. 66"69In general, water-soluble contrast agents

25

are the preferred choice, followed by barium if no perforation is demonstrated. Barium alone may suffice for mucosal tears and esophagotracheal fistula when excellent mucosai coating is required or the risk of aspiration of water-soluble contrast media is a problem. Most symptomatic perforations of the esophagus are iatrogenic, often related to esophageal dilatation and less frequently to fiberoptic endoscopy, esophageal intubation, surgery, vagotomy, pneumatic balloon rupture, and esophagography (Table 1).7~ A perforation may be self-limited: it may be walled-off, re-enter the esophageal lumen, or may close spontaneously. The perforation usually occurs at a point of physiologic narrowing, at the site of a tumor or esophagitis. Perforation may permit leakage of refluxed gastric juice and esophageal contents into the mediastinum, causing local or diffuse inflammation. As stated above, this is characterized radiographically by mediastinal contour widening; mediastinal, cervical, or subcutaneous emphysema; pneumothorax; pleural effusion; or pneumonia. A fistula between the esophagus and the pleura (Fig 13), mediastinum, and occasionally the trachea or a bronchus (Fig 14) may develop. Plain films or CT will show tissue emphysema and/or hydropneumothorax, usually lateralized to the pleural cavity nearest the site of the perforation, as demonstrated by contrast esophagography. Cervical esophageal perforation is likely to occur at the cricopharyngeus muscle. A catheter tip in the pyriform sinus or along the posterior pharyngeal wall above the cricopharyngeus may perforate the esophageal wall. Contributory factors include faulty positioning of the head in hyperextension, lack of control of tongue position, or gagging. Localized subcutaneous emphysema may be present in the connective tissue planes between the prevertebral muscles and may spread to the mediastinum or subcutaneous soft tissues, or may result in pneumothorax. Plain films of the soft tissues of the neck or CT will demonstrate air in 60% of patients with cervical perforation, s5 The radiographs should be performed in hyperextension so as not to obscure the esophagus and the periesophageal soft tissues with the overlying clavicle. Anterior displacement of the trachea and esophagus, prevertebral

26

air parallel to the esophagus, and a wide retropharyngeal soft tissue stripe are typically found with cervical perforation. Treatment of cervical perforation usually requires mediastinotomy with drainage of the prevertebral space. When shock, fever, and abscess are present, esophagectomy or esophageal exclusion is performed. Perforation of the thoracic esophagus is relatively common. In a series of 50 perforations reported by Goldstein and Thompson 86 27% occurred in the cervical esophagus, 54% in the thoracic esophagus, and 1% in the abdominal portion of the esophagus. Perforation usually

SPIRN ET AL

occurs at the level of a tortuous proximal descending aorta or the left main stem bronchus, points of physiologic narrowing. At this site, the mortality rate following perforation is approximately 30%. 87 Water-soluble contrast medium will reveal the site of extravasation in at least 75% of patients. An esophagopleural fistula may present with fever, shortness of breath, pleural friction rub, and back pain. Symptoms may occur immediately after perforation or may be delayed or even absent if the fistula spares the mediastinum. In such cases, the esophageal contents spill into the pleura and no mediastinitis occurs. 66 A large

Fig 15. Right esophagopleural and parenchymal communication in a 56-year-old man due t o perforation after overdistension during pneumatic dilatation for achalasia. (A, B} PA and lateral chest films demonstrate contrast medium in the right hemithorax (arrows) w i t h a right lower lobe pneumonia and pleural reaction. (C) CT shows a small collection of air and contrast medium in the right pleural space (arrow) secondary to the fistula.

CHEST RADIOLOGY AFTER THORACIC SURGERY

pleural effusion, pneumothorax, or hydropneumothorax with pulmonary infiltrate, and basilar atelectasis usually occurs. If the mediastinum is involved, subcutaneous emphysema, widened medistinum, and pneumomediastinum will be present. The diagnosis of esophagopleural fistula is made by contrast esophagography; if in doubt, CT will show the contrast medium in the pleural space (Fig 15).66'67 Esophagopericardial and esophagobronchial fistulas have also been reported following esophagogastrectomy. 7s'ss Esophagopericardial fistula, an unusual and highly lethal complication, results in purulent pericarditis, cardiac tamponade, and sepsis. Esophageal intubation. Mucosal tear and postcricoid ulcers have been described in 26% of patients in whom a nasogastrie tube has been in place for at least five days. Perforation of the stomach from a nasogastric tube, especially within a hiatal hernia may occur. Polyethylene tubes become rigid due to gastric secretions and should be removed within a few days to reduce the possibility of esophageal or gastric perforation. 72Celestin tubes and other large caliber rigid tubes are commonly inserted into the esophagus to maintain patency in patients with stenosing esophageal carcinoma. Esophageal perforation develops in 10% of these patients after insertionY ,7~ Pneumatic dilatation catheters used for achalasia or inflammatory stricture may cause disruption of the lower esophageal circular muscle fibers and lead to perforation, hematoma, or wall dissection. Frank perforation occurs in 4% of such patients, s7 Sengstaken-Blakemore tubes may cause mucosal disruption, perforation, and esophagopleural or esophagomediastinal fistulas due to improper positioning or overdistention in 5% of cases.66. 8s.89

The widespread use of fiberoptic endoscopy has improved the diagnosis of esophageal disease, but the cost has been a variety of complications, including hemorrhage at the biopsy site, aspiration pneumonia, respiratory and cardiac arrest, and perforation. A survey by the American Society of Gastrointestinal Endoscopy showed a complication rate of 1.32/!,000 examinations. Endoscopy is the most i:ommon cause of iatrogenic perforation. The incidence is nearly

27

0.1% with fiberoptic endoscopy,s7 and 0.2% with rigid endoscopy.9~If pneumatic dilatation is performed, the incidence of complications increases to 4.25 to 18.5/1,000 cases. 6s'7~The incidence of perforation increases following biopsy of cervical esophageal carcinoma, areas of ischemia or ulceration, and other pliable lesions. Most of these perforations are small, but symptomatic. Treatment with antibiotics may suffice. In a series of 29 patients with esophageal carcinoma, perforation diagnosed by contrast studies occurred in 45% of patients, but only one had signs and symptoms of mediastinitis or pneumonia. 72The mortality rate of perforation following stricture, dilatation, and endoscopy is 9% to 31%.65'91 Early diagnosis is essential so that prompt treatment can be instituted, usually consisting of surgical drainage, antibiotics, and surgical closure. Pharyngeal motor dysfunction after endoscopy is not rare and may lead to aspiration pneumonia. It is recognized by delayed clearance of contrast material from the hypopharynx. Hematemesis with aspiration may occur following biopsy of a patient with an unsuspected bleeding diathesis or esophageal varices. Impaction of the flexible fiberoptic endoscope may occur above a stricture or at the site of a hiatal hernia and a mucosal tear may occur during manipulation to remove the endoscope. Esophageal surgery. Transhiatal esophagogastrectomy may be performed for benign disease, such as stricture and previous rupture, or for carcinoma. The esophagus is replaced by the stomach, or the colon may be used if there is a history of previous gastric surgery or injury. Complications shown on the plain chest radiograph include pneumothorax (58%), chylothorax (6%), and anastomotic leak with pleural effusion or mediastinitis (6%). A lymphocele following esophagogastrectomy has been reported. 92'9~ Transpleural esophagogastrectomy is commonly performed for the treatment of carcinoma of the distal esophagus or stomach. The major complications of this procedure include anastomotic dehiscence, leading to pleural or mediastinal extravasation, and fistula formation. In such patients, there is an early postoperative mortality of 25% to 50%. 79,85 Rapid diagnosis is important for treatment. Although the plain film may be suggestive, esophagography is definitive in locat-

28

SPIRN ET AL

Fig 16. A l e f t esophagopleural fistula occurred in this 75-year-old man following esophagogastrectomy for gastric carcinoma. It was discovered t w o weeks after surgery during routine postoperative barium swallow. (Reprinted w i t h permission. M )

ing the leak and establishing its extent (Fig 16). CT may also show extravasation, but may not be able to precisely reveal the site (Fig 17). 67'85 In a series of 29 postoperative patients studied with contrast esophagography, four showed a leak at the stapling line, two developed bronchoesophageal fistula, two showed reflux esophagitis, and one had aspiration pneumonia. Plain chest films showed a sudden increase.in the pleural effusion in all four patients with anastomotic leak. CT will occasionally show extravasation not seen with plain films, but its greatest advantage is in identifying recurrent tumor or abscess near or distant to the surgical site. 74,85 Replacement or exclusion of the esophagus

with colonic interposition is a well-established procedure, but is performed less commonly than gastric pull-through procedures. As with esophagogastrectomy, anastomotic leak is common and life threatening. Other complications include aspiration pneumonia due to incoordinated swallowing, herniation of small bowel through the diaphragmatic hiatus, and reflux into the retained but bypassed esophagus. Typical location of the anastomic leak is proximal, producing pharyngocolic or cervicocolic fistula. It occurs in 25% of patients. The higher the anastomotic site, the greater the likelihood of anastomotic disruption. The diagnosis is established by careful contrast esophagography using 76% sodium meglumine diatrizoate with the patient lying

P

Fig 17. Esophagogastrectomy in a 68-year-old man. CT shows a small collection of oral barium (arrowhead) administered just before the scan. Note the right-sided pleural reaction (arrows). A diagnosis of esophagopleural fistula was made. (Reprinted w i t h permisslon, eT)

CHEST RADIOLOGYAFTER THORACIC SURGERY

29

supine or semierect in the left posterior oblique position. If no leak is seen, dilute barium is used for diagnosis. 77 The pulmonary complications following revascularized jejunal graft, 7~esophageal laser therapy,76 or resection for varices (such as the Sugiura

procedure 7s) include gastrointestinal leakage with sepsis, pleural effusion, and pneumonia. Direct injury to the distal esophagus following vagotomy during dissection of the vagus nerve results in perforation in 0.5% of patients. Rupture may be acute or delayed.

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