Introduction

A pulmonary sequestration is a rare congenital pulmonary malformation, characterized by a mass of non-functioning lung tissue, which is separated from the normal bronchopulmonary tree. Anatomically, it can be classified into two types, intralobar (ILS) and extralobar (ELS). Systemic blood supply is normally coming from the thoracic aorta, but arteries may occasionally arise from other sites including the abdominal aorta, intercostal arteries, internal mammarian artery, as well as the subclavian artery or even, if rarely, from the circumflex coronary artery. Venous drainage is usually going to the systemic pulmonary vessels, but might also drain to the superior and inferior cava, brachiochephalic or azygous vena. In the ILS, the malformation is incorporated into the normal pulmonary parenchyma of a lobe. The ELS consists of a pulmonary parenchyma separated from the rest of the lung by its own pleural envelope, thus forming an accessory lung [₁,₂,₃]. This study presents an unusual case of extralobar pulmonary sequestration with a bronchogenic cyst.

Case Report

A healthy, asymptomatic 20 year-old male was admitted to our hospital for evaluation of a left sided mass. He had no previous history of respiratory symptoms. His physical examination was unremarkable. The standard chest roentgenograms showed a rounded density on the left lower lobe, and rounded cystic density on the left upper lobe. A contrast-enhanced chest tomography was performed (Figure 1).

Figure 1

Figure 1: Chest tomography; a heterogeneous high-attenuating non-enhancing mass on the left lower lobe with dimension 5x4x5 centimeters.

Tomography demonstrated a heterogeneous high-attenuating non-enhancing mass on the left lower lobe with a size of 5x4x5 centimeters. There was another lesion on the left upper lobe. This lesion was cyst with a size of 3x2x3 centimeters. A bronchoscopic examination was normal. We performed a selective thoracic aortagraphy because of the suspicion that this could be a pulmonary sequestration. It showed an arterial supply from the thoracic aorta originating at the 9th or 10th posterior intercostals artery, as well as venous drainage to the inferior pulmonary venous system (Figure 2). Thoracic magnetic resonance imaging demonstrated two different high-attenuation masses on the left lower and upper lobes. With these findings we decided that the lesion on the lower lobe was an extralobar pulmonary sequestration and the lesion on the upper lobe was a cyst. We performed left posterolateral thoracotomy. The ELS was removed by a sequestrectomy and the systic lesion by a cystotomy and cystic wall resection. No pulmonary resection was carried out.

Figure 2

Figure 2: Selective thoracic aortagraphy; arterial supply was from the thoracic aorta originating at 9th or 10th posterior intercostals artery, venous drainage was to inferior pulmonary venous system

At pathological evaluation, the first specimen consisted of a 230-gram spongy structure filled with thick yellow-brown fluid. Its color was light brown and it was covered with a visceral pleura. Microscopic evaluation revealed dilated bronchioles lined by ciliated pseudostratified columnar epithelium. Amorphous material consisting of basophilic polygonal and rod-shaped calcifications filled the air spaces. Chronically inflamed cells were identified in the interstitium and the alveoli. The second lesion consisted of cyst wall specimens and fluid. Microscopic examination revealed ciliated columnar epithelium on a fibromuscular base. The cyst wall was thin and contained cartilage and bronchial glands. There were no postoperative complications. The patient was discharged on the fourth postoperative day and returned to his usual daily activities.

Discussion

Pulmonary sequestration is an unusual congenital malformation of nonfunctioning lung tissue that lacks a normal tracheobronchial connection as well as normal arterial supply, and has an anomalous venous drainage. Pulmonary sequestration arises from an abnormal pulmonary development along with pathological vascularisation [₁,₃]. It has two different anatomical forms: as an ILS when dysplastic tissue is encased within the lung's normal visceral pleura, and as an ELS when the tissue mass has its own pleura [₃].

Aortic arteriography is considered the diagnostic gold standard for a pulmonary sequestration. Systemic arterial supply consists of 50 % from the thoracic aorta and 30 % from the abdominal aorta. However, Sauvanet and colleagues reported that an arteriography was used as a diagnostic tool in only 28 of 40 cases [₄]. Magnetic resonance angiography is also useful in delineating the vascular anatomy of the sequestration. Besides arteriography, pulmonary angiography and magnetic resonance imaging, computed tomographic scanning, bronchography, and ultrasonographies have also been used in selected cases for preoperative diagnosis. In our case, we used the standard chest roentgenograms, a contrast-enhanced chest tomography, as well as bronchoscopy, thoracic magnetic resonance imaging and thoracic aortagraphy.

Extralobar pulmonary sequestration occurs in the left hemithorax in 80 % of cases. It occurs most commonly between the lower lobe and the diaphragm, but intradiaphragmatic, pericardial and retroperitoneal locations have been also reported [₅]. Although there may be an attachment of the mediastinum or diaphragm, upper mediastinal locations are unusual. In our case, the mass occurred on the lower left lobe adjacent to the pericardium and diaphragm.

Extralobar pulmonary sequestration may occur with other congenital foregut anomalies, such as within the spectrum of bronchopulmonary foregut malformations, which also include bronchogenic cysts and communicating bronchopulmonary foregut malformations. Yüksel and colleagues reported an unusual case, similar to ours, which had an extralobar pulmonary sequestration and a bronchogenic cyst [₇].

The definitive treatment of a pulmonary sequestration is a resection, especially in symptomatic cases, although limited success has been reported with the use of a simple ligation technique for the feeding artery. Preoperative embolization therapy may reduce operative blood loss [₂,₅]. We performed a sequestrectomy via left sided posterolateral thoracotomy.

There are several interesting cases concerning pulmonary sequestration. Jeanfaivre and colleagues reported about a case with bilateral bronchopulmonary sequestrations, one intralobar and the other extralobar [₈].

In conclusion: it must be kept in mind that a pulmonary sequestration, which is a congenital foregut anomaly, can be seen in conjunction with other congenital pulmonary anomalies such as a bronchogenic cyst.

Correspondence to

Sedat Gürkök MD GMMA Department of Thoracic Surgery 06018 Etlik Ankara-Turkey 090-312-3045172 sgurkok@gata.edu.tr