Pulmonary Sequestration

Epidemiology

  • First described in 1946 by Pryce and defined at that time as an abnormal artery from the artery supplying a bronchopulmonary mass or cyst which is dissociated from the normally connected bronchial tree
  • Familial cases of bronchopulmonary sequestration have been reported, but are rare
  • Associated With: Cystic Adenomatoid Malformation (which accounts for 25% of all congenital lung malformations)

Etiology

  • Developmental

Physiology

  • During development, bronchial branches are supplied by primitive aorta
  • Local growth arrest of the pulmonary artery during bronchial division results in disrupted tracheobronchial integrity and persistence of the aortic blood supply
  • The developing lung bud lies close to the developing foregut, from which it is derived (explaining the high incidence of associated foregut anomalies)
  • Blood Supply: usually from the descending thoracic aorta (or can also be from the upper abdominal aorta or the celiac, splenic, or intercostal arteries)

Pathology

  • Intralobar Sequestration: shares a common visceral pleura with the adjacent lung tissue
  • Extralobar Sequestration: has a separate pleura from the adjacent lung tissue

Diagnosis

  • FOB: not useful, as sequestrations are isolated from the tracheobronchial tree
  • HRCT: useful to define anatomy
  • CT with Contrast: appears as mass or polycystic lesion (usually in posterobasal segments of lower lobes)
    • Frequently contain dilated bronchial elements (bronchiectasis) and other abnormal bronchoalveolar structures
    • CT with contrast is useful to define the feeding vessels

MRA: probably will become the best modality to define vasculature


Clinical

Intralobar Sequestration

  • Definition: shares a common visceral pleura with the adjacent lung tissue
  • Relative Incidence: 75%
  • Age at Clinical Presentation: 38% present at <10 y/o
  • Arterial Supply: aorta in >90% of cases (thoracic aorta in 75% of cases)
    • Occasionally shared with the PA (or from the PA alone)
    • Right-to-left shunting has been reported
    • One reported case with supply from circumflex coronary artery led to myocardial ischemia from coronary steal
  • Venous Supply: pulmonary veins (into the LA)
  • Vascular Resistance: low (with high input pressures and high blood flow) -> this may lead to right-to-left shunting
    • Feeding artery is thin-walled, like a pulmonary artery (not thick-walled like a typical aortic branch)
  • Presence of Other Foregut Anomalies: 14% of cases
  • Tracheobronchial Connections: usually absent (although connections may occur via collateral channels in some cases)
  • Location: left posterior basal segment (in 60% of cases)
    • Present in lower lobes in 98% of cases
  • Infections: common (present with cough, purulent sputum, hemoptysis)
    • Lung parenchyma is usually well-differentiated (becomes bronchiectatic and cystic from recurrent infection)
  • Treatment: surgery (after careful work-up of anatomy)
    • Embolization of feeder vessels can be used in selected cases

Extralobar Sequestration

  • Definition: has a separate pleura from the adjacent lung tissue
  • Relative Incidence: 25%
  • Age at Clinical Presentation: 60% present at <10 y/o
  • Arterial Supply: aorta in 78% of cases (thoracic aorta in 46% of cases)
  • Venous Supply: azygous vein or vena cava
  • Vascular Resistance: high (with low input pressures and low blood flow)
    • Feeding artery is thick-walled, like a typical aortic branch
  • Presence of Other Foregut Anomalies: 50% of cases (such as congenital diaphragmatic herniation, etc)
  • Tracheonbronchial Connections: always absent
  • Location: left side above diaphragm (in 90% of cases)
  • Infections: absent (extralobar sequestrations are usually asymptomatic)
  • Treatment: only required for associated abnormalities