CASE REPORTS. Idiopathic Unilateral Hyperlucent Lung

Transcription

1 CASE REPORTS Idiopathic Unilateral Hyperlucent Lung The Swyer-James Syndrome J. Judson McNamara, M.D., Harold C. Urschel, M.D., J. H. Arndt, M.D., Herman Ulevitch, M.D., and W. B. Kingsley, M.D. I diopathic unilateral hyperlucent lung was first described clinically in 1953 by Swyer and James [15]. Since that time, several other reports have appeared under a number of descriptive headings that characterize this disease clinically [4, 9, 12, 141. Thus, it remains a relatively unusual but distinct clinical syndrome, the pathogenesis of which remains undetermined. The present report represents a brief clinical summary of the current understanding of the diagnostic characteristics, therapeutic approach, and theories of pathogenesis of the disease. A typical case is presented as a basis for discussion. B. L., a 29-year-old Negro female, presented with a five-year history of intermittent asthmatic attacks associated with recurrent pulmonary infection. She had otherwise enjoyed good health. Physical examination was unremarkable, except for coarse inspiratory wheezes over the entire left lung field. Chest x-ray revealed exceptional radiolucency of the left lower lung field, with diminished vascular marking in the area of the lower lobe distribution (Fig. 1A). Lung volumes appeared normal. Fluoroscopy showed persistent expansion of the left lower lobe during expiration, with some concomitant mediastinal shift to the opposite side (Fig. 1B). Bronchoscopy was normal except for moderate changes of acute and chronic bronchitis, and all lower lobe bronchi on the left side were visualized and were widely patent. Bronchography demonstrated a normal bronchial tree bilaterally, except for distinct clubbing of the terminal bronchi to the From the Departments of Thoracic and Cardiovascular Surgery, Radiology, Medicine, and Pathology, Baylor University Medical Center, Dallas, Tex. Address reprint requests to Drs. Paulson and Urschel, 3810 Swiss Ave.. Dallas, Tex Accepted for publication Nov. 26, VOL. 7, NO. 4, APRIL,

2 McNAMARA ET AL. A B FIG. 1. (A) Chest x-ray showing radiolucency of the left lung field with diminished vascular markings. (B) Expiration film showing persistent left lower lobe expansion with minimal mediastinal shift. left lower lobe, with virtual absence of alveolar pattern in that area (Fig. 2). Pulmonary angiography revealed an abnormally small vessel to the left lower lobe, with diminished vascularity of that lobe (Fig. 3). A cine-esophagogram demonstrated massive gastroesophageal reflux on the basis of criteria previously described [161. Following evaluation and under antibiotic coverage, the patient underwent left thoracotomy. The left lower lobe appeared diffusely emphysematous and remained inflated in spite of gentle pressure on the lung surface. A left lower lobectomy was performed. The specimen remained completely expanded even FIG. 2. Bronchography demonstrated a normal major bronchial tree on the left, with marked clubbing of terminal bronchi and diminished alveolar pattern. 352 THE ANNALS OF THORACIC SURGERY

3 CASE REPORT: Idiopathic Unilateral Hyperlucent Lung FIG.?. Pulmonary angiography demonstrated apparent reduction in size and flow through the left lower lobe artery and its branches. after removal from the chest. The pulmonary artery, though small, appeared qualitatively normal, and this was subsequently confirmed by injecting the resected specimen with Slessinger mass. A modified Belsey type of reconstruction of the gastroesophageal angle was then performed and the chest closed. The patient recovered uneventfully and remains alive and well without subsequent infection or asthmatic attack one year after her surgery. The gross appearance of the specimen was remarkable because of its spongy consistency and its marked propensity to remain fully expanded. Microscopically, the major abnormality was located in the terminal bronchi, which were dilated and bronchiectatic, with some chronic peribronchial inflammation. Diffuse emphysema was also prominent. No peribronchiolar muscular proliferation was noted. DISCUSSION The clinical picture and characteristic radiological findings in patients with idiopathic unilateral hyperlucent lung are best understood in terms of the pathophysiology of the disease. Currently, the majority opinion holds that the disease is due to an inflammatory process, probably of infectious origin, in which only the smaller bronchi and bronchioles primarily are affected [3, 4, 12, 14, 151. The recurrent inflammatory insults result in widespread obliterative bronchitis and bronchiolitis, leading to scarring and fibrosis and predisposing to subsequent recurrent infections and progression of the disease. In this regard, the only consistent clinical finding is a history of recurrent episodes of bronchitis and pneumonia. The recurrent infection and resulting fibrosis result in check-valve obstruction of the smaller bronchi, bronchi-

4 McNAMARA ET AL. ectasis, and circumferential scarring around the subsegmental bronchi. Culiner [3, 41 and others [14] have stressed the role of collateral ventilation and consequent peripheral air trapping in the development of the observed pathological anatomy. The diseased lobe or lung characteristically does not change volume with respiration, does not collapse even after removal, and compresses the pulmonary vascular bed (arterial, capillary, and venous), thereby reducing blood flow through the affected lung tissue. The diagnosis is established radiographically and can frequently be suspected from plain chest x-rays. Plain x-rays show a hyperlucent lobe or lung, a small main pulmonary artery, and virtual absence of peripheral vascular markings. Expiration films and fluoroscopy may show either no appreciable mediastinal shift or slight shifting of the mediastinal structures away from the involved side. Bronchography characteristically demonstrates bronchiectasis and clubbing of the most peripheral bronchi, with obstruction to filling of the terminal bronchioles and alveoli by contrast medium. Angiography typically demonstrates apparent pulmonary arterial hypoplasia, although, as in our case, pathological specimens usually reveal an essentially normal pulmonary arterial tree [7, 151. Radiological documentation of patients in whom the disease was acquired in adulthood further mitigates against congenital pulmonary hypoplasia as an etiological factor in the disease [51. Several entities enter into the differential diagnosis of this lesion. An embolus occluding a main pulmonary artery can produce the same plain x-ray appearance. Such a catastrophic event should be readily apparent clinically and can be differentiated by angiography and bronchography. Hypoplasia of the pulmonary artery is associated with diminished volume of the lung on the involved side and other cardiovascular anomalies in most cases. Although bronchial anomalies are also frequently present in patients with pulmonary artery hypoplasia, bronchiectasis, particularly the peculiar beaded form seen in patients with idiopathic hyperlucent lung, is not a feature of that disease. Pulmonary emphysema localized to a lobe or lung is associated with small peripheral pulmonary arteries, but the main pulmonary artery and its segmental branches are enlarged. Acute obstruction of a bronchus, such as is seen with aspiration of a large foreign body, is excluded by bronchography and is not associated with reduction in the caliber of the pulmonary artery. The association of massive gastroesophageal reflux in the reported patient raises the interesting possibility that the initial and possibly recurrent cause of her obliterative bronchitis and bronchiolitis was aspiration of gastric juices. The association of gastroesophageal reflux and a variety of other pulmonary problems has been previously reported 354 THE ANNALS OF THORACIC SURGERY

5 CASE REPORT: Idiopathic Unilateral Hyperlucent Lung by a number of authors [2, 6, 10, 13, 161. This relationship is conjectural and must be judged on clinical grounds until specific means of identifying subclinical aspiration from gastroesophageal reflux are developed. The treatment of the problem depends on the ability to control recurrent infections and the degree of damage incurred by the involved lung tissue at the time the patient is seen. If significant distal bronchiectasis and emphysema exist, recurrent infection will frequently occur on that basis alone, and contamination and involvement of adjacent normal lung becomes a serious threat. In such situations, removal of the diseased lung tissue is indicated as well as efforts directed at preventing further infection or controlling factors, such as respiratory allergens or gastroesophageal reflux, which may produce recurrent chemical bronchial inflammation and consequent infection. However, if recurrent infection is not a problem or can be controlled by other methods, the disease represents a radiological finding that requires only periodic evaluation. Although the involved lung contributes little to ventilation [l, 5, 7, 8, 11, 121, the concomitant observed decrease in pulmonary arterial blood flow results in only a very small ventilation perfusion defect, and thus no significant shunting occurs [l, 4, 71. Furthermore, the propensity of the involved lobe to occupy only its share of the thoracic cavity results in no significant compromise to ventilation in the remaining uninvolved lung tissue. That the disease can remain quite stable in the absence of recurrent infection has been previously demonstrated, and in this situation, surgical removal of the abnormal lung tissue is not justified. SUMMARY A case of unilateral hyperlucent lung is presented, and the disease is discussed. Patients with this disease characteristically present with recurrent pulmonary infection and unilateral radiolucency of one lung, or a single lobe, on chest x-ray. Pathogenesis of the disease appears to involve an obliterative bronchitis or bronchiolitis of only the peripheral bronchi. The etiology of the inflammation is not well defined, but is usually attributed to pulmonary infection, although in some cases it may be associated with aspiration due to gastroesophageal reflux. Treatment depends on the ability to control the problem medically and the extent to which the disease has progressed at the time the patient is seen. REFERENCES 1. Belcher, J. R., and Pattinson, J. N. Hypoplasia of the lobar pulmonary arteries. J. Thorac. Surg. 34:357, VOL. 7, NO. 4, APRIL,

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