Cystic and Bullous Lung Disease Robert R. Klingman, MD, Vito A. Angelillo, MD, and Tom R. DeMeester, MD Departments of Surgery and Pulmonary Medicine, Creighton University School of Medicine, Omaha, Nebraska
One of the most difficult problems facing clinicians is the evaluation and management of patients with dyspnea whose chest roentgenogram shows single or multiple large cystic spaces. This is made more difficult when underlying lung disease is present. The dilemma focuses on whether the obliteration or removal of the cystic areas
ost physicians refer to cystic air spaces seen on chest M roentgenograms as "bullae" and conclude that the patient has "bullous emphysema." This implies that all such lesions are part of a generalized destructive process, such as panlobular emphysema. Not commonly appreci- ated is that approximately 20% of patients with such roentgenographic findings do not have an underlying parenchymal abnormality and can benefit from surgical removal of the cyst [l, 21. Important in the management of such patients is whether the cystic space is an isolated entity or part of a more generalized destructive process. The approach to therapy will differ on how this question is answered.
Definition and Classification
Historically, the terms bulla, cyst, and bleb have been used interchangeably, and this has led to confusion. More precisely, cyst is used to describe a congenital bronchial or bronchogenic cyst or an acquired cyst. The first two refer to a developmental abnormality resulting from abnormal budding and branching of the tracheobronchial tree. Such a cyst is located in the lung or mediastinum and is lined by ciliated cuboidal respiratory epithelium. An acquired cyst is a thin-walled space that remains as a residuum of an injury to the lung. It results from a check-valve obstruc- tion of a small bronchiole that distends the distal lung to form a coalescent space or from inflammatory necrosis of the bronchial wall resulting in compression of adjacent pulmonary parenchyma to form a pneumatocele (Fig 1). Histologically, this parenchymal air space lacks an epithe- lial lining.
The term bleb usually connotes a subpleural collection of air within the layers of visceral pleura caused by a ruptured alveolus. The air dissects through the interstitial tissue into the thin, fibrous layer of visceral pleura where it accumulates to form a bleb. Rupture of a bleb is often associated with the development of a spontaneous pneu- mothorax.
The term bulla is used to describe an air-filled space
Address reprint requests to Dr DeMeester, Department of Surgery, University of Southern California School of Medicine, 2250 Alcazar St, Room 109F, Los Ange l s , CA 90033.
will benefit or cause further deterioration of the patient's condition. The pathophysiology of the problem is not completely understood, but accumulated clinical experi- ence has shown that surgical therapy can be beneficial but requires proper patient selection.
(Ann Tkorac Surg 1991;52:576-80)
within the lung parenchyma resulting from deterioration of the alveolar tissue. These lesions have a fibrous wall and are trabeculated by the remnants of alveolar septa. They can develop in a lung that is otherwise normal or in a lung in which the architecture has been destroyed by chronic obstructive disease. These are the lesions to which the term bullous emphysema is more appropriately applied.
Consequently, acquired cyst or bulla describes an air- space lesion that possesses a smooth wall of minimal thickness ranging in volume size from a cubic centimeter to one that fills the entire hemithorax. If the wall is thicker than 3 mm, it i s often called a cavity. Although this term implies a different etiology, it may not be so, as both cysts and bullae can become infected and develop thick walls (Fig 2).
Patients with bullae or acquired cysts can be divided into two groups: those with structurally abnormal lung parenchyma in addition to the bulla or bullae and those with normal pulmonary parenchyma. The second group accounts for 20% of patients, but this figure can be misleading because of problems of semantics, which result in the inappropriate inclusion of patients with congenital cysts, blebs, and hyperlucent lungs. The last is due to agenesis or atretic pulmonary vessels or bronchi or to complete or partial bronchial obstruction, which can lead to bullous changes through the process of collateral ventilation and air trapping.
Controversies in the Pathophysiology of Bullous Lung Disease
The rationale for operation for bullous disease is to allow a normal, compressed lung to reexpand. This is based on the conventional view of the pathophysiology of bullous disease, which defines a bulla as a localized area of parenchymal destruction supplied by airways that contain a valvular obstruction allowing gas to enter but not leave the cystic space. Continued alveolar destruction and the inflating effect of gas entering the space expand it, causing compression and collapse of the surrounding lung. This has been conceptually referred to as an "intrapulmonary pneumothorax."
This concept has rarely been challenged despite evi- dence that a bulla is unlikely to grow in such a manner. It
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to the mouth. It is conceivable that positive pressures transmitted to the walls of bullae during coughing could enlarge the space by further rupture of the lung paren- chyma, but this pressure would not be maintained during normal respiration [3].
Direct observation of the volume change and ventila- tion of bullae by computed tomography also contradicts the conventional pathophysiological view of bullous dis- ease [4]. A bulla observed on computed tomography during inspiration and expiration does not change to any appreciable degree in size, and the change that does occur is always in phase with the rest of the lung during respiration, ie, growth during inspiration and reduction during expiration. This observation is further substanti- ated by recent studies [3] that show bullae contain gas that is identical to that in the alveoli during normal respiration. Overall gas flow into and out of bullae appears to be small but unimpeded [3, 51.
The evidence that a bulla compresses surrounding lung
Fig 1. TonzOgram Of the chest 5hows a PostinflammatoyY (5taPhYlococ- cal) pneumatocele of the right lung.
has been observed during operation and on examination of resected specimens that in the floor of a bulla, there are bronchial openings that are widely patent with no evi- dence of a valvular mechanism [3]. It has been postulated that these openings could be floppy and close prema- turely at low airway pressures and act as a trap valve. Such a valvular mechanism implies that either extreme negative pleural pressures result in preferential inflation of the bulla or the bulla is filled in expiration or during coughing. The latter is unlikely, as expiratory positive pleural pressure will be applied equally to the bulla and the lung, and the gas should follow the pressure gradient
- - is based on the observation that adjacent lung appears collapsed on computed tomograms or at operation. Al- though it is agreed that collapsed lung may adjoin a bulla, the lung need not be compressed for this to occur. In fact, it is more likely for computed tomography not to show evidence of adjacent collapsed lung, and the density of the peribullous lung is not increased by maneuvers that compress the lung. Morgan and colleagues [3] measured pressures within a bulla and related them to simultaneous measurements of airway and pleural pressures during the induction of anesthesia. Pressures in the bulla were never positive in inspiration and were never more positive than pleural pressure at end-expiration, and the pressure swings were always in phase. This suggests that at least during spontaneous respiration, bullae are spaces that are subject to the same forces as the surrounding lung and respond in a similar manner.
If a bulla is not expanded by positive pressure, then how does it inflate preferentially and assume a spherical shape? Ting and co-workers [6] explained the preferential filling of a bulla by examining the pressure-volume char- acteristics of isolated bullae. They found that bullae be- have like paper bags, which are extremely compliant until they are full, when they become tense. The lung sur- rounding the bulla is less compliant, and the pressure required to inflate it exceeds the pressure necessary to inflate the bulla. This means that when bulla and lung are exposed to the same negative intrapleural pressure, the bulla will fill preferentially and always completely before the remainder of the lung is filled. Consequently, once a parenchymal weakness in the lung exceeds a certain size, it will result in a space within the lung that fills preferen- tially. The force of elastic recoil will produce retraction of the surrounding lung away from the hole or space and enlarge it. Even though the bulla remains in free commu- nication with the airway, it will not participate in ventila- tion to any important extent because of its large volume, or in gas exchange because of its relatively small and avascular internal surface area [3].
The degree to which bullae contribute to dyspnea depends more on the amount of lung they replace and the
Fig 2 . Chest roentgenogram demonstrates an infected cystic cavity of the right upper lobe with thickening of the walls and an air-fluid level.
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extent of underlying destructive lung disease present than on the amount of lung they compress [7-91. Conse- quently, the decision regarding surgical intervention is difficult, as it benefits only the latter. With this under- standing of the pathophysiology of bullous disease, it is easier to understand that the expected clinical improve- ment after surgical obliteration is highly variable.
Patient Presentation and Selection of the Operative Candidate The current rationale for surgical intervention for bullous disease is to allow normal but compressed lung to reex- pand. The manner of presentation of patients wiih bullae varies enormously, ranging from incidental findings of small bullae in patients with normal lung function to the ”vanishing lung syndrome” where all tissue appears to have been replaced by multiple bullae, associated with severe dyspnea, respiratory failure, and cor pulmonale.
Patients with normal lung function rarely require oper- ation, and if in that situation the bullae enlarge and result in dyspnea, good postoperative improvement is the rule. Most patients referred for surgical consideration have bullae associated with chronic obstructive pulmonary disease and show little difference clinically or functionally from patients with chronic obstructive pulmonary disease without bullae. It is difficult to know to what degree a lung with an emphysematous process will improve. If the process of emphysema is paraseptal or periacinal (nonob- structive) instead of panlobular (obstructive), then sub- stantial improvement can be expected. However, no method can diagnose the type of emphysema during life, so selection of patients suitable for operation must be based on clinical, physiological, and radiographic consid- erations.
Clinical Evaluation The history and physical examination should be aimed at distinguishing between patients who have primarily em- physema (pink puffers) from those with chronic bronchi- tis (blue bloaters). Clinical experience [lo] has shown that it is in this latter group with productive cough, frequent respiratory infections, carbon dioxide retention, broncho- spasm, and heart failure that surgical outcome has been less successful. Continued smoking also adds to the morbidity [7].
Physiological Evaluation Severe reduction in forced expiratory volume in 1 second and severe dyspnea in the presence of a single bulla or small bullae occupying less than one third of the lung suggest that symptoms are related to diffuse disease and that operative intervention will not ameliorate them [4, 9-11]. With large bullae, two physiological signs relate the cause of the dyspnea to the bullae: a reduction in forced vital capacity almost equal to the reduction in forced expiratory volume in 1 second, a finding suggesting a restrictive pattern, and a discrepancy between functional residual capacity measured by body plethysmography and gas dilution technique [lo]. This discrepancy will
Fig 3. Chest roentgenogram demonstrates a large solitary bulla of the left chest.
often be between 2 to 4 L and represents the amount of trapped gas.
Although attempts have been made to correlate opera- bility and survival with pulmonary function variables, they have been unsuccessful. Long-term survival with improved functional status has been shown in patients with forced expiratory volume in 1 second of less than 1 L [4, 9, 111. Lack of specificity has also been shown with single-breath diffusing capacity and bronchospirometry [lo].
Radiographic Evaluation Most observers [4, 9-11] have agreed that the volume occupied by the bulla is the most important variable in determining clinical and physiological outcome. Bullous lesions that occupy more than 50% of a hemithorax with normal underlying parenchyma have the best results (Fig 3), whereas lesions occupying less than one third of the lung may not show any substantial improvement. This is also valid for patients with underlying emphysema.
Determining the size and number of bullous lesions from a plain chest roentgenogram is not always reliable. Computed tomography is more sensitive and provides better localization of bullae and consequently is a greater aid to surgical planning [4, 101. It is also an excellent noninvasive method of evaluating lung architecture and assessing the extent of underlying lung disease [12]. Ventilationlperfusion scanning, previously used to local- ized bullae, has been replaced by the computed tomo- graphic scan.
Angiography can provide useful information about
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A
B Fig 4 . ( A ) Chest roentgenogram demonstrates large biapical bullae. ( B ) Pulmonary angiogram demonstrates intact but crowded vascula- ture.
unaffected areas of the lung but is not always necessary. If the vasculature surrounding the bulla is intact but crowded (Fig 4), there is a high probability of good expansion of functioning lung tissue after bullectomy, whereas lack of crowding with thinning and disruption of the vasculature suggests a poor result from resection.
Operative Procedure A number of operative procedures have been described for the surgical therapy of bullous lung disease or ac- quired cysts. They include local excision, plication, wedge resection, lobectomy, bilobectomy, segmental resection, Monaldi’s tube drainage, and marsupialization. Improved understanding of the pathophysiology of bullous lung
disease has resulted in the discarding of most of these procedures. A disease characterized by loss of lung pa- renchyma cannot be optimally treated by removal of further lung tissue. Lobectomy results in far greater reductions in forced expiratory volume in 1 second in both the early and late postoperative periods than do proce- dures that conserve lung tissue [13]. Consequently, lobec- tomy is not only undesirable but rarely necessary. Indeed, observations have shown intact residual lung tissue in lobectomy specimens obtained because the impression at operation was that no functional lung tissue remained in the lobe [8].
The operative procedure should aim at conservation of lung tissue. Narrow-necked bullae are excised after liga- tion of their pedicled stalk, whereas smaller bullae can be obliterated by coagulation. Broad-based bullae are over- sewn or plicated. Giant bullae with wide bases are re- moved by first opening the cavity and excising the trans- parent wall along the line where it merges with normal lung. Any trabeculae are divided, and a careful search is carried out for air leaks. The cavity is closed airtight by approximating the pleural edges of the lung with a running mattress suture. The correct placement of at least two chest tubes is very important to properly evacuate postoperative air leaks [8, 9, 14, 151.
If the patient has clinical respiratory failure and is receiving continuous oxygen therapy, intracavitary suc- tion drainage as described by Monaldi [16] is the preferred procedure. The Monaldi tube suction procedure was initially performed in two stages: the first was a rib resection and iodoform gauze packing to adhere the visceral pleura to the parietal pleura, and the second was the insertion of a tube into the bulla. Recently it has been modified to a single-stage procedure. A small piece of rib is resected, and a pursestring suture of absorbable mate- rial is placed so that it encompasses both pleura and cyst wall. A large Foley catheter is inserted within the purse- string, and 5- to 10-mm Hg suction is applied for 36 to 48 hours, followed by underwater seal for 21 days [17]. Small bronchiolar leaks close and the bulla contracts during this period as a result of the inevitable secondary infection with resultant scar contracture of the bulla [8].
Simultaneous operation on both lungs through a me- dian sternotomy has been recommended for patients i v i t h bilateral disease [18, 191. Advocates of this appro.ich emphasized that median sternotoniv produces the least degree of morbidity and allows simultanecius correction ot bilateral disease with a single operation.
Large bullae can be confused with ‘1 ~incuiiicitiior~i\, particularly in patients complaining of suddcn chcst p,im and dyspnea. The knee-jerk reaction of placcmcnt of ,i
chest tube in such a patient often causes troublesome air leaks that may require thoracotomy for management.
Conclusion The proper management of cystic and bullous lung dis- ease requires careful evaluation. Because there is no effective medical management, these patients should be considered for surgical therapy.
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Ann Thorac Surg 1991;52576-80
Single, isolated bullae in asymptomatic patients should be observed. In individuals who are symptomatic, deter- mination of whether the process is isolated and possibly expanding or is part of a diffuse process with major underlying lung disease should be determined. The size of the lesion is important. If it occupies greater than 50% of the hemithorax, further evaluation is necessary, for these patients may have the most dramatic benefits from operation. Pulmonary function tests are mandatory, but computed tomography is the most useful method of assessing the extent of underlying lung disease. If the underlying lung architecture is diffusely cystic, then any surgical option is of a palliative nature. Nevertheless, these patients should not be precluded from surgical consideration.
It is essential that fundamental surgical principles be observed. Potentially viable parenchyma must not be sacrificed. Limited resections that preserve all functioning lung tissue ensure maximal improvement. The high inci- dence of postoperative complications demands careful attention to tracheobronchial toilet, daily chest roentgen- ograms, and immediate treatment of mechanical compli- cations.
The indications for resection of large bullae in the face of hypercapnia and diffuse emphysema require careful individual study because in these patients, a small incre- ment in function may be of great clinical benefit.
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