Intralobar Sequestration

Intralobar Sequestration

Jud W. Gurney, MD, FACR

Coronal CECT reconstruction shows sequestration image surrounded by hyperlucent lung image and fed by arteries image crossing the hemidiaphragm.

Axial CECT shows a small artery image that had arisen from the aorta adjacent to the hemidiaphragm.



  • Malinosculation: Congenital abnormal connection of 1 or more of 4 components of lung (airways, arterial supply, venous drainage, and parenchyma)

  • Pulmonary sequestration represents nonfunctioning lung tissue separated from normal lung

    • Receives its blood supply from systemic artery

    • Normal communication with bronchi lost

  • 2 major forms

    • Intralobar sequestration (90%)

      • Shares visceral pleura of normal lung

    • Extralobar sequestration (10%)

      • Has separate pleura from normal lung

    • Communicating bronchopulmonary foregut malformation is uncommon form of sequestration, usually seen with extralobar type


General Features

  • Best diagnostic clue: Persistent left-sided inferior paraspinal opacity with history of recurrent pneumonia

  • Patient position/location

    • 95% lower lobes

      • Left lower lobe (65%), right lower lobe (55%)

      • Posterior basal segment > medial basal segment

  • Size: Variable, but cystic lesions often quite large

CT Findings

  • Sequestrum characteristics

    • Cystic-bronchiectatic form

      • Cysts may be single or multiple

      • Cysts contain fluid or air (air-fluid levels)

      • Cystic form often quite large

    • Pseudotumor form

      • Spiculated mass mimics bronchogenic carcinoma

      • Homogeneous or inhomogeneous

      • May enhance with intravenous contrast

    • Emphysematous form

      • Emphysematous lung only

  • Lung bordering sequestration often hyperinflated or emphysematous

  • Systemic artery

    • Identification from aorta is diagnostic

    • Artery can measure up to 1 cm in diameter, often shows intimal calcification

    • Nonvisualization of systemic artery does not exclude diagnosis

    • Occasionally, multiple small arteries supply sequestration (15-20%)

    • Systemic arterial supply without sequestration (known as Pryce type 1 sequestration)

      • Anomalous artery only

      • Prominent inferior pulmonary vein

      • Absence of interlobar artery distal to origin superior segmental artery

      • Normal bronchial system (absent sequestrum)

  • Pulmonary artery supply normal or absent

  • Venous drainage via inferior pulmonary vein

  • Calcification and effusions uncommon

Radiographic Findings

  • Inferior paraspinal mass or opacity located in posterior basal segment adjacent to diaphragm

    • Margins may be either sharp, lobulated, or ill-defined

  • Concurrent volume loss common

  • 1/3 of cystic sequestrations contain air or air-fluid levels

    • Localized emphysema without consolidation or fluid is well described but uncommon

  • Chronic or recurrent bacterial pneumonia

    • May decrease in size with antibiotic therapy, but will not resolve

  • Pleural effusion (4%) and calcifications rare

MR Findings

  • Excellent depiction of complex cystic, solid, and fibrotic components

    • Cysts have variable signal depending on fluid

      • Often higher signal on T2WI sequences

  • Hemorrhage within lesion represented by high signal on both T1WI and T2WI sequences

Angiographic Findings

  • Traditional method of diagnosis but now replaced by CT angiography

  • Used to embolize feeding arteries

  • Origin of feeding artery

    • Thoracic aorta (75%)

    • Abdominal aorta (20%)

    • Intercostal artery (5%)

    • Multiple (16%)

      • Vessels < 3 mm likely 1 of multiple supplying arteries

  • 95% have pulmonary venous drainage

    • 5% systemic venous drainage, usually via azygos, hemiazygos, superior vena cava, or intercostal routes


Extralobar Sequestration

  • Congential lesion, often presents in 1st 6 months

    • Completely distinct entity from intralobar form

  • Associated with other congential anomalies

  • Systemic arterial supply from aorta

    • Drainage into systemic veins (80%), not pulmonary

    • Invested in own pleural lining, separated from normal lung

      • Essentially accessory lung

  • Located on left in 90%, although may lie within or below diaphragm

Transpleural Systemic-Pulmonary Artery Anastomoses (Pseudosequestration)

  • Systemic arterial supply across pleural adhesions

  • Seen with pulmonary artery stenosis, less perfused upper lobes fed by intercostal arteries

  • Pleural arterial blush not seen with sequestration

  • Vessels often tangled on surface of mass

Placental Transmogrification of the Lung

  • Etiology unknown

  • Large multiloculated cystic mass

  • Histology: Placental villus-like structures

  • No aberrant arterial supply

  • Associated with giant bullous emphysema

  • Hamartomatous tissue often contains fat

Chronic Pneumonia/Lipoid Pneumonia

  • Chronic consolidation in lower lobe, such as lipoid pneumonia

    • No aberrant arterial supply

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Intralobar Sequestration

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