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