Pulmonary Sequestration

Pulmonary Sequestration Aberrant lung tissue that No normal connection with the bronchial tree or with the pulmonary arteries. Supplied by a systemic artery (usually from the aorta.) Extralobar: contained within its own viseral pleural envelope. 14~25 % of sequenstration. Intralobar: contained within the substance of the lung. 75~86%.

Pulmonary Sequestration Intralobar sequestrations Two major patterns of the radiographic appearance A solid-water density mass or area of consolidation. An air-containing single or multicystic lesion. The air gains entry into the sequestered lung from the collateral ventilation. Infection → an air-fluid level. Contrast-enhanced CT and coronal MR show the abnormal systemic artery in the majority of cases. Failure to identify a systemic artery on these examinations does not exclude the diagnosis. Angiography: to demonstrate the anomalous systemic vessel.

Intralobar sequestration Intralobar sequestration. > PA radiograph: a solid mass-like lesion in the LLL abutting the diaphragm. > Lateral tomogram confirms a well-defined mass posteriorly in the LLL.

Intralobar sequestration (air-filled) Intralobar sequestration (air-filled). PA radiograph: > The pulmonary vessels at the right base display an abnormal course; this suggests they may be draped around a space-occupying but air-filled lesion. >The right hemidiaphragm is slightly depressed, and the heart is shifted slightly to the left.

> Aortogram: a large single vessel arising from the distal aorta supplying a portion of the right lower lobe. > Contrast-enhanced CT scan confirms the vascular supply.

Pulmonary Sequestration Extralobar sequestration: Diagnosis can be made without angiography by using CT and MRI, which may demonstrate the anomalous feeding and draining vessels. CXR: a single well-defined homogeneous area of increased opacity in the lower thorax close to the posterior medial hemidiaphragm. no air bronchograms. It may also occur in the mediastinum and in the pericardium or upper thorax, and rarely as a subdiaphragmatic mass. Esophagrm: to demonstate the fistulous communication between the sequestration and the GI tract. Aortography: to show the anomalous systemic artery or arteries feeding the lesion. Demonstration of the venous drainage may require selective angiography of the anomalous feeding vessels. Ultrasound: in the diagnosis of pulmonary sequestration in neonates and infants. a uniformly echogenic mass with a hyperechoic rim. Color Doppler flow imaging: aberrant arterial and venous structures supplying and draining these lesions.

Pulmonary Sequestration Intralobar Extralobar Clinical Features Adults M=F Pneumonia or incidental finding Infants M>F Asymptomatic or symptoms due to associated abnormalities Location 60% left Posterior lower lobe 90% left Above or below diaphragm, or in the mediastinum Arterial supply Large vessel from aorta Single or multiple systemic arteries Venous drainage Pulmonary vein Systemic (azygos, hemiazygos, vena cava) Connection with foregut Rare Occasionally Pleura No separate pleural covering Separate pleural covering

Extralobar sequestration in the RLL Extralobar sequestration in the RLL. > CT scans show an abnormal systemic arterial supply (arrow) that originates within the abdomen above the celiac artery between the diaphragmatic crura.

> CT scans demonstrate extensive calcification (arrowheads) at the superior aspect of the sequestrated segment. Note also the systemic artery that enters the sequestrated segment (arrow).

> Bedside left coronal sonogram shows a very large, fluid-filled hemithorax with concave medial and lateral borders. A seemingly small left lung with reverberating echoes from air is floating superiorly. The unaerated sequestration (arrows) is present inferiorly. > Spectral Doppler tracing of the feeding artery shows systolic peaks with high-frequency shift and diastolic flow reversal. Two systoles were missed due to patient motion.

>　Left coronal color Doppler sonogram reveals the feeding artery through unaerated sequestration (S) arising from the left lateral aspect of the aorta, just below the diaphragm. Solid arrows = thoracic aorta open arrow = abdominal aorta (Figure is turned 90°ckwise.)

References Thoracic Radiology THE REQUISITES 3rd Ed., Chapter 2 T. C. McLoud et.al. Congenital Anomalies of the Tracheobronchial Tree, Lung, and Mediastinum RadioGraphics. 2003;24:e17 High-Resolution CT and CT Angiography of Peripheral Pulmonary Vascular Disorders RadioGraphics. 2002; 22:739–764

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