Pulmonary Sequestration

Pulmonary sequestration is a mass of abnormal lung tissue that has no connection to the normal bronchial tree and has systemic arterial supply (usually from the aorta). Two types exist: intralobar sequestration (ILS, 75% — within normal lung parenchyma, not surrounded by its own visceral pleura, drained by pulmonary veins) and extralobar sequestration (ELS, 25% — has its own pleural covering, presents as a separate mass in left lower thorax or subdiaphragmatic location, drained by systemic veins). The diagnostic key is demonstration of aberrant feeding artery from the aorta or other systemic arteries on CT angiography. ILS typically presents with recurrent pneumonia in childhood/adulthood, while ELS is often detected prenatally or neonatally. Treatment is surgical resection.

Synonyms: Pulmonary sequestration · Bronchopulmonary sequestration · BPS · Intralobar sequestration · Extralobar sequestration · Pulmoner sekestrasyon · Pulmonale Sequestration

Age Range

0-18

Peak Age

0.5

Gender

Male predominant

Prevalence

Rare

◆Key Diagnostic Clues

1Aberrant feeding artery from aorta on CT angiography — pathognomonic finding
2Solid or cystic mass in left lower lobe posterobasal segment — most common location (60%+ ILS)
3Recurrent pneumonia at same location — typical clinical presentation of ILS
4Absence of normal bronchial connection — no airway connection to affected area on bronchoscopy
5ELS: Separate pleural-covered mass in left lower thorax or subdiaphragmatic — CDH association common

♦Pathophysiology

Pulmonary sequestration forms from an abnormal lung bud separating from the foregut during embryological development and developing independently. This anomalous tissue retains systemic arterial supply (from aorta) because its connection with the fetal splanchnic vascular plexus persists — in normal pulmonary development these connections regress. The intralobar type, not surrounded by visceral pleura, lacks a distinct barrier from surrounding normal lung parenchyma and may develop partial airway connection over time through the porous boundary — making it prone to recurrent infections. The extralobar type has its own pleural sheath and remains as a completely isolated mass. The aberrant artery on CT angiography directly reflects persistence of the embryological systemic vascular connection. ILS venous drainage is to normal pulmonary veins (left atrium) — creating a left-to-left shunt. ELS venous drainage is to systemic veins (usually azygos or hemiazygos, IVC).

★

Key SignCTarterial

Aberrant feeding artery from aorta

The signature finding of pulmonary sequestration is demonstration of an aberrant feeding artery from the aorta (thoracic or abdominal) on CT angiography. This finding is pathognomonic and definitively differentiates sequestration from other congenital lung lesions (especially CPAM). The artery's origin, diameter, course, and branching pattern provide critical information for surgical planning — resection without arterial control can cause massive hemorrhage.

Imaging Features

CTarterialpathognomonic

Aberrant Systemic Arterial Supply From Aorta (Pathognomonic)

The most diagnostic finding on CT angiography is demonstration of an aberrant feeding artery from the aorta (thoracic or abdominal) or other systemic arteries (intercostal, phrenic, celiac). This artery is usually single and large caliber (5-10 mm diameter). In ILS, the feeding artery usually comes from the thoracic aorta (T6-T12), in ELS from thoracic or abdominal aorta. MIP and VR reconstructions show arterial origin, course, and branching in detail. This finding definitively differentiates sequestration from CPAM.

Report Sentence

On CT angiography, an aberrant feeding artery measuring ___ mm arising from the thoracic/abdominal aorta at the ___ level is seen supplying the mass in the left/right lower lobe posterobasal segment; pathognomonic for pulmonary sequestration.

CTnon-contrasthighly-suggestive

Solid Or Cystic Mass In Left Lower Lobe Posterobasal Segment

Sequestration appears on CT as a solid, cystic, or mixed mass in the left lower lobe posterobasal segment. ILS usually appears as a solid or cystic infected mass — bronchiectasis-like cystic changes may develop due to recurrent infections. ELS usually appears as a homogeneous solid mass. Mass margins are generally smooth. Left side is 3-4 times more common than right. Subdiaphragmatic ELS (suprarenal area) is rare but must be recognized — may be confused with neuroblastoma.

Report Sentence

A solid/cystic mass measuring ___ × ___ cm is seen in the left/right lower lobe posterobasal segment.

CTarterialhighly-suggestive

Venous Drainage Assessment (Pulmonary Vs Systemic)

Venous drainage of sequestration is assessed on the venous phase of CT angiography — critical for ILS vs ELS differentiation. ILS drains to the left atrium via normal pulmonary veins (left-to-left shunt). ELS drains via systemic veins — usually azygos, hemiazygos, or IVC. Venous drainage pattern affects surgical technique selection.

Report Sentence

Venous drainage of the sequestration is via pulmonary veins/systemic veins (azygos/IVC), consistent with ILS/ELS.

USdopplerhighly-suggestive

Prenatal/Postnatal US: Echogenic Mass With Feeding Artery On Doppler

On prenatal US, sequestration appears as a homogeneous echogenic mass — usually in left lower thorax or subdiaphragmatic. Color Doppler can demonstrate the feeding artery from aorta — critical for prenatal diagnosis. ELS is usually detected prenatally. ILS is harder to identify prenatally. Postnatal US can assess solid mass and feeding artery on Doppler but CT angiography is needed for definitive evaluation.

Report Sentence

On US, an echogenic mass is seen in the left/right lower thorax/subdiaphragmatic location with a feeding artery from the aorta demonstrated on Doppler; consistent with pulmonary sequestration.

MRIT2highly-suggestive

MRI/MRA: Mass With Systemic Arterial Supply Confirmation

MRI can be used for fetal sequestration evaluation prenatally and as an alternative to CT postnatally. On T2, sequestration usually appears hyperintense (fluid-containing cystic areas and edematous tissue). MR angiography (MRA) can demonstrate the aberrant feeding artery without contrast or with gadolinium MRA — evaluates vascular anatomy without radiation exposure. Fetal MRI can also assess lung volume and hernia content. MRI may be preferred over CT in pediatric patients with radiation concerns.

Report Sentence

On MRI, a T2 hyperintense mass is seen in the left/right lower lobe with an aberrant feeding artery from the aorta demonstrated on MRA.

Subtypes

Intralobar sequestration (ILS)

Criteria

75% of cases. Within normal lung parenchyma, no own pleural sheath. Drainage via pulmonary veins. Left lower lobe posterobasal segment (60%+).

Distinct Features

Presents with recurrent pneumonia. Associated anomalies rare. Usually diagnosed in childhood/adulthood. Lobectomy is treatment.

Extralobar sequestration (ELS)

Criteria

25% of cases. Has own pleural sheath. Drainage via systemic veins (azygos, IVC). Left lower thorax or subdiaphragmatic. 60% associated with CDH.

Distinct Features

Usually prenatal/neonatal diagnosis. Associated anomalies frequent (60%+ CDH, cardiac, pulmonary). Simple resection (separate mass). Infection rare (isolated mass).

Differential Diagnosis

Congenital Pulmonary Airway Malformation (CPAM)CT angiography

Distinguishing Feature

CPAM is supplied by pulmonary artery (no systemic artery), sequestration by aorta. CT angiography provides definitive differentiation. Hybrid lesions possible.

Congenital Diaphragmatic HerniaCXR + CT

Distinguishing Feature

CDH has diaphragmatic defect with abdominal organs in thorax. In sequestration, diaphragm is intact and lesion is pulmonary origin. However ELS frequently coexists with CDH.

NeuroblastomaCT angiography + lab

Distinguishing Feature

Subdiaphragmatic ELS may be confused with neuroblastoma. Neuroblastoma elevates catecholamine metabolites, calcification common, fed by SMA/celiac. ELS shows direct aortic supply, catecholamines normal.

Clinical Relevance

Urgency

routine

Management

surgical

Biopsy

Not Needed

Follow-up

specialist-referral

Pulmonary sequestration is treated with surgical resection. ILS requires lobectomy (sequestered tissue inseparable from normal parenchyma). ELS is simply excised (separate pleural sheath). Preoperative CT angiography for precise aberrant artery localization is mandatory — this artery arises directly from aorta and carries massive hemorrhage risk if uncontrolled. Surgery recommended even in asymptomatic cases. Endovascular embolization is an alternative in some centers. Prognosis after surgery is excellent.

Differential Tips

→CPAM: pulmonary arterial supply (sequestration has systemic artery), cystic dominant structure
→Bronchogenic cyst: single, unilocular, water density, may have bronchial connection
→CDH: diaphragmatic defect, bowel loops in thorax
→Lower lobe pneumonia: infectious signs, no systemic feeding vessel, resolves on follow-up

●Clinical Significance

Second most common congenital lung anomaly after CPAM. The most critical diagnostic step is demonstrating the systemic arterial feeding vessel — sequestration cannot be diagnosed without this finding. CTA is the gold standard for preoperative vascular mapping. Intralobar type presents with recurrent pneumonias, extralobar type is usually detected prenatally or in the neonatal period. Surgical resection is definitive treatment. Hybrid lesions (CPAM + sequestration) can occur — may have both pulmonary and systemic arterial supply.

References

Wei Y, Li F. Pulmonary sequestration: a retrospective analysis of 2625 cases in China. Eur J Cardiothorac Surg. 2011;40(1):e39-42.
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ACR Appropriateness Criteria: Neonatal Respiratory Distress. 2020.
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Related Diseases

Congenital Pulmonary Airway Malformation (CPAM)Congenital Diaphragmatic Hernia Neuroblastoma

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