Intralobar and extralobar bronchopulmonary sequestration complicated by Nocardia asteroides infection. (Case Report).

Abstract: Pulmonary sequestration is a rare congenital or acquired pulmonary anomaly. Pulmonary sequestration may be classified as intralobar, located within normal lung, or extralobar, in which it is separated by pleura. The coexistence of both forms is extremely rare. Infection, mainly bacterial, is a major complication of sequestration. We report the case of a young man in whom a sequestration with both intralobar and extralobar components was complicated by Nocardia asteroides infection.

Key Words: extralobar, intralobar, Nocardia asteroides, pulmonary sequestration

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Bronchopulmonary sequestration accounts for 0.15 to 6.4% of congenital lung malformations. (1) Sequestrations are classified as intralobar or extralobar depending on the visceral pleural investment of the abnormal tissue. The sequestered mass serves as a nidus for repeated infections. We present a patient in whom both intralobar and extralobar sequestrations were complicated by Nocardia asteroides infection.

Case Report

A 22-year-old Hispanic man presented with a 2-week history of high-grade fever, cough productive of brown sputum, left-sided pleuritic chest pain, shortness of breath, and abdominal pain. He had recently emigrated from the Dominican Republic. He denied prior illness, exposure to tuberculosis, or smoking. He worked in a bakery, and had no history of gardening or construction work.

Initial physical examination revealed a toxic-appearing, thin man in respiratory distress. His temperature was 104[degrees]F, blood pressure was 121/77 mm Hg, and heart rate was 129/mm. Dullness to percussion, bronchial breath sounds, and egophony were elicited in the left lower lung zone. Mild epigastric tenderness was elicited. Laboratory data revealed the following values: white blood cell count, 18,000/[mm.sup.3] (89% neutrophils); aspartate aminotransferase, 134 U/L; alanine aminotransferase, 104 U/L; amylase, 240 U/L; and lipase, 245 U/L. Chest radiograph showed dense opacification of the left hernithorax with shift of the mediastinum toward the right side (Fig. 1).

The patient was admitted to the medical intensive care unit, and broad-spectrum antibiotics were administered. Computed tomography (CT) revealed dense heterogeneous left lower lobe consolidation; the arterial blood supply was identified from two branches arising from the posterior left lateral descending thoracic aorta (Fig. 2A) and venous drainage into the enlarged left inferior pulmonary vein was identified (Fig. 2B). Sputum culture grew Nocardia asteroides and treatment with trimethoprim-sulfamethoxazole was initiated. Test for human immunodeficiency virus (HIV) was negative. Sputum cultures were negative for acid-fast bacilli. Upper gastrointestinal series with small bowel follow-through and CT of abdomen did not reveal communication between the gastrointestinal tract and the sequestered lung tissue.

The patient underwent left thoracotomy with resection of the sequestered tissue with wedge resection of the posteroinferior part of the left lower lobe. A portion of the tissue was embedded within the left lower lobe and the remainder was enveloped within pleura, thus establishing both intralobar and extralobar components. Pathologic examination revealed chronic pneumonia, with the postobstructive features of focal ossification, dilated alveolar spaces, and marked remodeling of lung parenchyma. The postoperative period was uneventful and he completed 9 months of antibiotic therapy.

Discussion

A pulmonary sequestration refers to nonfunctioning lung tissue with no direct communication with the tracheobronchial tree and with an anomalous blood supply from the systemic vessels. Pryce, (1) in 1946, first described this entity, and subdivided it morphologically into intralobar sequestration (ILS) and extralobar sequestration (ELS). Intralobar sequestrations comprise 75% of sequestrations, and are encountered in young adults, usually by the age of 20 years. The ILS shares the visceral pleura with the normal lung tissue, and receives its blood supply from the aorta in 94% of cases and its drainage into the pulmonary venous system in 95% of cases. Extralobar sequestration is almost exclusively discovered in infancy, due to early onset of symptoms. The sequestered lung has its own visceral pleura, and may even occur outside the thorax. The ELS blood supply is usually systemic, from branches of the aorta (80% of cases); however, the venous drainage is mainly via the azygos-hemiazygos system (80% of cases). ( 2)

The association of ELS with other congenital anomalies (65% of the cases), such as bronchopulmonary foregut malformation, supports an embryonic origin of this entity. (3) In contrast, ILS may be acquired: an endobronchial obstruction triggers recurrent pneumonias, with interruption of the pulmonary vascular supply to the infected area and subsequent hypertrophy of small systemic arteries that supply this area. (4) Both forms are usually located in the posterobasal segment of the left lower lobe and in the posterior costodiaphragmatic sulcus between the left lower lobe and the hemidiaphragm, but may occur anywhere in the thorax, or even below the diaphragm. (2)

The occurrence of ILS and ELS in the same patient is an exceedingly rare phenomenon. Among the 8 cases reported in the literature, 7 patients had both forms on the same side of the thorax. Some authors argue that both types thus share an embryonic origin. (5)

Pathologic characteristics include extensive fibrosis and chronic inflammation and cystic changes replacing the lung parenchyma. (2) Contrast CT of the chest reveals the complex character of the lesion with its anomalous blood supply. Preoperative aortogram may confirm the diagnosis and identify the vascular supply, in order to avoid catastrophic intraoperative bleeding. (6)

The standard treatment is resection of the segment or lobe that contains the sequestered tissue. Other options are ligation or embolization of the vascular pedicle. Some authors advocate conservative antibiotic treatment with surgical intervention only in cases of repeated infections; however, this strategy is rarely used because of the potential of bleeding complications from repeated infections.

Infection is the major complication of pulmonary sequestration and the sequestered tissue is frequently infected with bacterial pathogens. (2) Mycobacterium tuberculosis and fungi, such as Aspergillus and Blastomyces, are uncommon pathogens.

Nocardia are important pathogens in immunocompromised patients, particularly transplant recipients, patients with malignancies, individuals receiving corticosteroids or cytotoxic agents, and patients infected with HIV. (7, 8) Nocardia infection, acquired through the respiratory tract, may disseminate to involve, most commonly, the brain and the skin. (8) Renal, myocardial and musculoskeletal involvement may also occur.

Pulmonary nocardiosis has been reported in patients with underlying lung disease. Infection may present as an acute or chronic respiratory illness, with clinical and radiographic findings consistent with pneumonia or abscess. Nocardia asteroides is a ubiquitous environmental saprophyte found in soil, organic materials, and water. It is classified as a bacteria, with a distinctive branching, filamentous, gram-positive rod morphology; staining positive by acid-fast stain due to the mycolic-acid content of its cell wall. Examination of an adequate specimen is an important step in recovering the organism; and the microbiology laboratory must be alerted to test for this organism, which has a prolonged incubation period of 2 to 3 weeks duration. Therapy with sulfonamides for 6 to 12 months has been considered the treatment of choice. Amikacin, imipenem, third-generation cephalosporins, minocycline, and dapsone are alternative treatment agents. (7)

There is only one previous report of Nocardia species infection with intralobar bronchopulmonary sequestration. That patient was a 26-year-old man who experienced recurrent infections, despite antimicrobial therapy. An aortic arteriogram identified the underlying lung anomaly, and resection of the sequestered tissue provided a complete resolution. (9)

Conclusion

Our patient demonstrated the unique occurrence of simultaneous intralobar and extralobar sequestration with acute N. asteroides infection. When clinicians encounter a healthy young person with a severe lung infection, an underlying lung malformation, such as pulmonary sequestration, should be suspected. Prompt imaging with attention to vascular anatomy will lead to early diagnosis and treatment.

Accepted January 15, 2002.

References

(1.) Pryce DM. Lower accessory pulmonary artery with intralobar sequestration of lung: A report of seven cases. J Pathol 1946;58:457-467.

(2.) Stocker JT. Sequestrations of the lung. Semin Diagn Pathol 1986;3:106-121.

(3.) Gerle RD, Jaretzki A III, Ashley CA, Berne AS. Congenital bronchopulmonary-foregut malformation: Pulmonary sequestration communicating with the gastrointestinal tract. N Engl J Med 1968;278:1413-1419.

(4.) Stocker JT, Malczak HT. A study of pulmonary ligament arteries: Relationship to intralobar pulmonary sequestration. Chest 1984;86:611-615.

(5.) Kim HJ, Kim JH, Chung SK, Rhi S, Chung SH. Coexistent intralobar and extralobar pulmonary sequestration: Imaging findings. AJR Am J Roentgenol 1993;160:1199-1200.

(6.) Frazier AA, Rosado de Christenson ML, Stocker JT, Templeton PA. Intralobar sequestration: Radiologic-pathologic correlation. Radiographics 1997;17:725-745.

(7.) Lerner PI. Nocardiosis. Clin Infect Dis 1996;22:891-905.

(8.) Kontoyiannis DP, Ruoff K, Hooper DC. Nocardia bacteremia: Report of 4 cases and review of the literature. Medicine (Baltimore) 1998;77:255-267.

(9.) Kilpatrick GR Jr, Koontz CH, Nelson RA. Nocardia infection in a bronchopulmonary sequestration. Chest 1976;69:786-788.

RELATED ARTICLE: Key Points

* Severe pneumonia in a young, previously healthy individual should raise the suspicion of an anomaly, such as a pulmonary sequestration.

* Radiographic imaging of the vascular supply will establish the diagnosis of a sequestration.

* Infection by Nocardia species, although usually diagnosed in immunocompromised patients, is an important consideration in an immunocompetent patient with an underlying pulmonary disorder.

From the Division of Pulmonary and Critical Care Medicine, Division of Cardiothoracic Surgery, Columbia University College of Physicians & Surgeons/St. Luke's-Roosevelt Hospital Center, New York, NY.

Reprint requests to Janet M. Shapiro, MD, Division of Pulmonary and Critical Care Medicine, St. Luke's-Roosevelt Hospital, 1111 Amsterdam Avenue, MU 316, New York, NY 10025.

Copyright [c] 2003 by The Southern Medical Association 0038-4348/03/9601-0078