What is bronchopulmonary sequestration?

Bronchopulmonary sequestration, also known as BPS or pulmonary sequestration, is a rare birth condition in which an abnormal mass of nonfunctioning lung tissue forms while the baby is growing in the womb. It can form outside (extralobar) or inside (intralobar) the lungs, but is not connected directly to the airways.

The abnormal lung tissue does not function like normal lung tissue. These masses have by abnormal blood supply, in which a systemic arterial blood vessel coming from the aorta feeds the lung mass.

Treatment for bronchopulmonary sequestration depends on the type and size of lung lesion, as well as whether the condition is causing any serious health complications for mother or baby.

While many cases of small extralobar BPSs will not require surgery, large extralobar BPSs and all intralobar BPSs can lead to breathing problems, infection, and life-threatening complications like heart failure. Surgery is needed to remove the abnormal tissue.

Most children with bronchopulmonary sequestration can be safely treated with surgery after birth. In rare cases — when the lesion has grown abnormally large, is restricting lung growth or impairing blood flow, putting your baby at risk for heart failure — fetal intervention may be necessary.

Types of BPS

There are two types of bronchopulmonary sequestration:

• Intralobar, in which the mass forms inside the lungs. These lesions account for about 75% of cases of BPS, affect males and females equally, and are generally isolated birth defects. All intralobar lesions require surgical removal (resection) after birth.
• Extralobar, in which the abnormal mass forms outside — but nearby — the lungs. In some instances, this type of BPS may be located in the abdomen. These lesions account for only about 25% of BPS cases, and are more likely to affect males than females. Small extralobar BPS can frequently be managed without surgery after birth, while large lesions will require surgery.

Causes of BPS

The cause of bronchopulmonary sequestration remains unknown. It has not been linked to a genetic or chromosomal anomaly, and does not appear to run in families.

Most clinicians believe the condition begins during prenatal development when an extra lung bud forms and migrates with the oesophagus. Depending on when the extra lung bud forms, it may become part of one of the lungs (intralobar), or grow separately (extralobar).

Signs and symptoms of BPS

Symptoms of bronchopulmonary sequestration can vary, and depend on the size of the lesion.

After birth, children with BPS may experience:

• Usually they have no symptoms, but sometimes:
• Trouble breathing
• Wheezing or shortness of breath
• Frequent lung infections like pneumonia
• Upper respiratory infections that take longer than usual to resolve
• Feeding difficulties and trouble gaining weight as infants

All suspected lung lesions, whether found before or after birth, require careful imaging. Determining the type, size and location of the lesion will guide treatment recommendations.

Evaluation and diagnosis of BPS

Bronchopulmonary sequestration is one of several types of lung lesions and may be confused with congenital pulmonary airway malformation (CPAM). While similar in some ways, BPS and CPAM are unique conditions that require individualised treatment. A child can also develop a hybrid lesion, which has characteristics of both a BPS and CPAM. This unusual condition makes diagnosis challenging.

Thanks to improvements in prenatal imaging, most cases of BPS are discovered during routine ultrasounds between 18 to 20 weeks’ gestation. A solid mass will typically appear on the ultrasound as a bright spot in the fetus’s chest cavity. Expert fetal imaging specialists experienced in evaluating fetal lung lesions can detect the source of the blood flow to the lung lesion as well how blood is drained from the lesion. This is an important step to confirm an accurate diagnosis and distinguish between an intralobar and extralobar BPS, hybrid lesion, CPAM, or other type of fetal lung lesions.

Management of pregnancy with BPS

Depending on the gestational age of your baby and the size of the mass, you will continue to have regular ultrasounds to closely monitor the growth of the lung lesion.

Rarely, these masses can grow quite large, taking up valuable space in the chest. This can restrict normal lung growth and can lead to underdeveloped lungs which will not function adequately at birth. Large masses can also shift the heart and impair blood flow. This can lead to fetal heart failure (fetal hydrops) and cause the buildup of fluid in the fetus and placenta.

Some of these masses are associated with a large pleural effusion, or fluid collection in the chest cavity. This fluid collection can also compromise the ability of the fetal heart to function normally.

Over several visits, clinicians will determine how quickly your child’s BPS is growing.

Fetal intervention for BPS

Treatment for bronchopulmonary sequestration depends on the type and size of lung lesion, as well as whether the condition is causing any serious health complications.

Some babies with bronchopulmonary sequestration cannot wait for treatment after birth because the lesion is too large, growing too rapidly, or causing life-threatening complications in utero such as fetal heart failure.

Fetal interventions may include:

Draining fluid from the chest

A small number of bronchopulmonary sequestrations can develop a large pleural effusion, or accumulation of fluid in the chest, outside of the lung, which can compress the lungs and heart. This fluid can be drained prenatally and a shunt can be left in place to provide continued drainage of the fluid.

The shunting procedure itself is performed under ultrasound guidance. A large trocar (hollow needle) is guided through the mother’s abdomen and uterus, and into the fetal chest. The shunt is passed through the trocar to divert the accumulated fluid from the fetal chest to the amniotic sac. The shunt will remain until delivery. The goal of these procedures is to decrease the accumulation of fluid to ward off heart failure (fetal hydrops).

Delivery of babies with BPS

Mothers carrying babies with small lung lesions — without other associated anomalies — may be able to deliver at their local hospital, without the need for high-risk neonatal care. Babies with larger lesions, or those with complications or associated disorders, should be delivered at St Michael’s hospital in Bristol, that offers expert surgical care for both mother and baby in one location.

Surgery for bronchopulmonary sequestration after birth

BPS lesions can be successfully treated with surgery after birth. 

• All intralobar BPS lesions should be surgically removed because of an increased risk of infection as well as the potential for high blood flow through the tissue that can lead to heart failure later in life.
• Large extralobar BPS, especially those with high blood flow, may compromise your baby’s ability to breathe or put too much stress on your baby’s heart, and should be surgically removed.
• Small extralobar BPS may not require surgery to remove the lesion.

Removing the BPS mass when your child is young has multiple benefits, including promoting compensatory lung growth (ability of lungs to grow and fill the space in the chest) and avoiding potential complications such as lung infections.

First, you will come in for an appointment for your child to be evaluated by the surgical team.

A CT scan with contrast will be performed in the months following the baby’s birth to confirm the diagnosis and determine the exact location of your child’s lung lesion.

Follow-up care

Follow-up care for children with bronchopulmonary sequestration will depend on the treatment the child received.

Most children treated for small lesions after birth will only need monitoring for the first year after surgery to ensure normal lung growth and lung function. The majority will require no additional long-term follow-up care.

Long-term outlook

The vast majority of children with congenital lung lesions, including BPS, do extremely well and have normal lung function after their lesions are removed. This is due to rapid compensatory lung growth that occurs during childhood. Having surgery early maximises this compensatory growth.

Children with moderate to large lesions can also do extremely well, but their outlook depends on expert treatment to avoid potential complications. These babies require highly specialised expert care from time of diagnosis to delivery and surgery to ensure the best possible long-term outcomes.