Pulmonary Sequestration: Symptoms, Diagnosis and Treatment

What is pulmonary sequestration?

Pulmonary sequestration is a rare congenital malformation, present from birth, in which a piece of lung tissue develops separately from the normal airways. Because it is not connected to the bronchial tree in the usual way, it does not take part in breathing. It also has an unusual blood supply: instead of the pulmonary artery, it is fed by a branch arising directly from the aorta or one of its branches.

There are two main types:

• Intralobar sequestration: the more common type, lying within a normal lobe and sharing its pleural covering. It usually drains back into the pulmonary veins and most often affects the lower lobes, especially on the left. It typically presents in older children or adults with repeated infections.
• Extralobar sequestration: a separate mass with its own pleural covering, sometimes below the diaphragm. It drains into the systemic veins, is often detected on antenatal ultrasound or in infancy, and is more often associated with other congenital anomalies such as congenital diaphragmatic hernia.

Symptoms

Symptoms depend on the type and age at diagnosis. Some sequestrations cause no symptoms and are found by chance. When symptoms occur, they include:

• Recurrent pneumonia in the same part of the lung: the most typical presentation of intralobar sequestration in adolescents and adults.
• Persistent cough with sputum: sometimes with fever and weight loss when the sequestration becomes chronically infected or forms an abscess.
• Coughing up blood: this can occasionally be heavy because of the high-pressure systemic artery.
• Chest pain or breathlessness, particularly with infection.
• Breathing or feeding difficulty in newborns with large extralobar lesions, or rarely heart strain from high blood flow through the abnormal vessels.

Causes

Sequestration arises during early development of the lung in the womb, when an extra bud of lung tissue forms from the primitive foregut and keeps its early blood supply from the aorta. It is not caused by anything the mother did during pregnancy and is not usually inherited. Some experts believe that a proportion of intralobar sequestrations in adults are acquired after chronic infection, but the congenital explanation applies to most cases.

In India, a sequestration presenting as a recurrent lower-lobe shadow with cough and weight loss is sometimes treated as tuberculosis before the true diagnosis is made. A pneumonia that keeps returning to exactly the same place should always prompt a search for an underlying structural cause.

How pulmonary sequestration is diagnosed

The key to diagnosis is showing the abnormal artery from the aorta.

Needle biopsy is generally avoided, because the abnormal vessels can bleed. Other conditions that can look similar include congenital pulmonary airway malformation, lung abscess, bronchiectasis, a pulmonary arteriovenous malformation and lung cancer.

Treatment

Surgery

Surgical removal is the standard treatment for symptomatic sequestration and is generally advised for intralobar sequestration even when symptoms are mild, because infection tends to recur and can become severe. For intralobar lesions this usually means removing the affected lobe or segment, while extralobar lesions can often be removed on their own. Most operations are now performed by video-assisted thoracoscopic surgery, which means smaller incisions and quicker recovery. The abnormal artery must be identified and secured carefully, and planning is done with a thoracic surgeon using the CT angiogram.

Endovascular treatment

Blocking the feeding artery with coils or plugs through a catheter (embolisation) can control bleeding and is sometimes used alone, particularly in small children or in patients who are not fit for surgery, or before surgery to reduce bleeding.

Treatment of infection

Active infection is treated with antibiotics before planned surgery wherever possible.

Children and antenatally detected lesions

Children are managed jointly with paediatric pulmonology and paediatric surgery. Some small extralobar sequestrations without symptoms are observed, and some shrink over time. The decision between surgery and monitoring is individual.

Outlook and follow-up

The outlook after complete removal is excellent. Recurrent infections stop, and the remaining lung compensates fully for the removed segment or lobe, so most people return to normal activity, including sport. A follow-up visit with a chest X-ray is arranged after surgery. Patients who are being observed rather than operated on need regular review and should report any chest infection promptly.

When to seek urgent care

Seek emergency care for coughing up more than a small amount of blood, high fever with breathlessness, chest pain, or breathlessness at rest. In infants, rapid breathing, poor feeding, bluish colour or difficulty breathing need immediate assessment.

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