Case of the Month: October, 2012, Page 3

Answer: C. Intralobar pulmonary sequestration

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Imaging Findings:

  • Axial contrast-enhanced CT images in lung and soft tissue windows demonstrate a left lower lobe infiltrative mass-like region with a linear area of contrast enhancement.
  • Coronal MR angiogram and 3D reformat images demonstrate the left lower lobe mass with a feeding vessel arising from the abdominal aorta above the origin of the left renal artery. The venous drainage appears to be into the left lower pulmonary vein.

Discussion:

  • Pulmonary sequestration is a rare congenital malformation which consists of a nonfunctioning mass of lung tissue that does not communicate with the tracheobronchial tree and receives blood supply from the systemic circulation.
  • The most common location is the left lower lobe, followed by the right lower lobe. Approximately 75% of pulmonary sequestrations receive blood supply from the thoracic or abdominal aorta. The remaining 25% receive blood flow from the subclavian, intercostal, pulmonary, pericardiophrenic, innominate, internal mammary, celiac, splenic, or renal arteries.
  • The intralobar type of sequestration is located within a normal lobe without its own visceral pleura, and accounts for 75% of all sequestrations. Intralobar sequestrations have venous drainage to the pulmonary venous system to the left atrium, establishing a left to right shunt. This type of sequestration is rarely associated with other developmental abnormalities.
  • The extralobar type of sequestration is located outside the normal lung with its own visceral pleura, and accounts for 25% of all sequestrations. It usually drains via the systemic venous system to the right atrium, vena cava, or azygous systems. Extralobar sequestration is more frequently associated with other congenital anomalies such as congenital pulmonary airway malformation (CPAM), congenital diaphragmatic hernia, vertebral anomalies, congenital heart disease, pulmonary hypoplasia, and colonic duplication.
  • Pulmonary sequestration should always be considered in a pediatric patient with recurrent pneumonias in the same location, particularly in the left lower lobe.   Imaging modalities typically demonstrate a soft tissue lung mass with characteristic feeding systemic artery arising from the aorta.
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