A 23-year-old man presented with recurrent hemoptysis since 12 years. The hemoptysis was streaky and on and off. There is no history of tuberculosis or bleeding from other sites. Physical examination was unremarkable.

RADIOLOGICAL FINDINGS:

Frontal and lateral radiographs of the chest show a hyperlucent left hemithorax - especially in the left mid and lower zones and a doubtful soft tissue shadow overlying the heart shadow.

Fig. 1	Fig. 2

Plain and contrast enhanced CT scans of the thorax reveals an ill defined opacity in relation to the left lower lobe. .The lesion shows early enhancement in the arterial phase. "Coning" of the aorta is seen at the level of lesion and suggests that the lesion may be supplied by the descending thoracic aorta.

Fig. 3	Fig. 4
Fig. 5	Fig. 6

A descending thoracic aortogram reveals hypervascularity in left lower posterior basal segment with a prominent feeding vessel arising from the left lateral aspect of lower descending thoracic aorta subsequently draining into the left pulmonary vein.

These findings are suggestive of intralobar bronchopulmonary sequestration.

Fig. 7	Fig. 8

The pulmonary angiogram showed no arterial branch to or venous drainage from the left lower lobe.

Fig. 9	Fig. 10

DISCUSSION:

Pulmonary sequestration is an embryonic mass of lung tissue that has no bronchial communication and that receives its blood supply from systemic arteries.

Bronchopulmonary sequestrations are classified as
1) Extralobar sequestration (ELS)
2) Intralobar sequestration (ILS).

ELS is the nonfunctioning primitive pulmonary parenchymal tissue which has no connection with the tracheobronchial tree. It consists of dilated bronchioles, alveolar ducts, and alveoli, which form the bulk of the lesion. The interstitium is composed of connective tissue, the thickness of which is depending upon the age of patient. This type of sequestration is called extralobar because the mass lies outside of the normal investment of visceral pleura; it also may lie outside of the thorax in subdiaphragmatic region.

ELS is widely accepted to be congenital in origin The accepted theory is that ELS arises as an accessory lung bud that develops from the ventral aspect of the primitive foregut. The accessory lung bud migrates caudally with the foregut and receives its blood supply from the splanchnic plexus - just as the foregut does. If the bud arises after the pleure have developed, it is not incorporated within the lung visceral pleura, and an ELS is formed.

ELS is associated with other congenital abnormalities. The most common association is with diaphragmatic hernias (20%); others include - congenital cystic adenomatoid malformation (CCAM), bronchogenic cysts, and foregut malformations.

ILS is also a nonfunctioning area of pulmonary parenchyma and usually is not in communication with the tracheobronchial tree; however, it may contain air via the pores of Kohn or a connection to normal small bronchi. ILS is incorporated within the normal visceral pleura of the lung, An ILS, when discovered, usually contains dense fibrous parenchyma, which has replaced the normal pulmonary tissue as the result of chronic inflammation and fibrosis. Multiple cysts are noted which contain viscid fluid. The pleura is thickened by adhesions to mediastinal and diaphragmatic parietal pleura. Remnants of bronchi and bronchioles are replaced by fibrous connective tissue containing inflammatory infiltrates, as are alveolar ducts and alveoli. The current widely accepted theory hold that ILS is acquired - after one or more episodes of necrotizing pneumonia resulting in obliterative bronchitis and obstruction of a lower lobe bronchus. This phase is followed by interruption of the pulmonary arterial supply to the infected lung parenchyma and hypertrophy of the systemic arterial supply from the thoracic aorta,. The diaphragmatic pleural supply involves the celiac axis aorta and abdominal aorta, and these vessels also may be recruited. Venous drainage remains via the pulmonary veins.

Clinical Presentation:

Extralobar sequestration: A majority patients present in the first six months of life. Antenatal USG showing maternal polyhydramnios, fetal ascites and hydrothorax may indicate the diagnosis. On the first day of life, patients can present with dyspnea, cyanosis, and feeding difficulties. In addition, patients with ELS may present with recurrent chest infections, Symptoms can occur as a result of other associated anomalies.

Intralobar sequestration Patients generally present with respiratory tract infection. Symptoms may occur from associated anomalies. The most common anomalies associated with ILS are esophagobronchial fistule and diverticula, implying the presence of a bronchopulmonary foregut malformation. Physical examination may reveal signs of pulmonary consolidation. Auscultation may identify a bruit or continuous murmur over the sequestered lung segment from a large systemic blood supply.

Radiographic findings vary depending upon:

1) Size of the lesion
2) Whether the lesion is infected.
3) The presence or absence of communication with an airway
4) Te presence of associated anomalies.

An uninfected sequestration is seen as a well-defined mass or as a cyst in the medial aspect of lung bases. An infected sequestration appears ill defined, and may contain fluid levels. Large sequestrations may present with an opaque hemithorax, with or without ipsilateral effusion. Intralobar sequestration appears as a mass, cystic lesion, or infiltrative shadow with ill-defined borders .

Extralobar sequestrations are small lesions and are not visible on chest radiographs. However, they may present as an infiltrate or mass in the region between the lower lobes.

The vascular supply and venous drainage of both ILS and ELS lesions can be defined with CT scans. CT scan also provide information regarding the morphologic structure and attenuation values of any focus. In ELS, 80% of sequestrations lie between the lower lobe and the diaphragm. Lesions are usually located in the region of the posterior basal segments of the lower lobes. .In ILS, sequestrations occur within pulmonary visceral pleurae and do not communicate with the bronchial tree. Lesions of ILS may be solid, fluid, hemorrhagic, or mucous containing cystic elements may be present, and t collapse of adjacent lung may be noted.. Most lesions appear hypervascular. Super-added infection may lead to consolidation in adjacent segments. Mucoid impaction of a bronchus surrounded by hyperinflated lung is believed to be characteristic of ILS.

Angiography:- Pulmonary sequestrations are mainly supplied from thoracic or abdominal aorta. In the remaining cases the blood flow may be from the subclavian, intercostal, pulmonary, pericardiophrenic, innominate or internal mammary arteries, The arterial supply typically enters the lung via the pulmonary ligament if the artery originates above the diaphragm. Arteries originating below the diaphragm reach the sequestration by piercing the diaphragm or via the aortic or esophageal hiatus. The arterial supply usually is composed of a dilated single vessel. This vessel is typically 0.5-2.0 cm in diameter and multiple arteries are present in some cases in which the arteries are 3 mm or smaller in diameter. Venous drainage occurs most often via the pulmonary vein in ILS - thus establishing a left-to-right shunt and the drainage occurs via bronchial or other systemic veins in ELS. Occasionally, drainage is solely to the azygos or hemiazygos systemic veins.

Treatment is dependent on the severities of symptoms and is invariably a surgical removal of the offending lesion. Hemoptysis in emergent situations can be treated by transurethral embolisation of the feeding systemic vessel.