Congenital lung malformations are rare disorders that emerge during a fetus’ development in the womb and are present at birth. Although usually one area of the lung is affected, the malformations can cause difficulty with breathing, recurrent lung infection and, in very rare instances, lung cancer. 

Congenital lung malformations occur in 4 of 10,000 live births. Though they are rare, congenital lung malformations are the most common birth defect affecting the lungs.

Types of Congenital Lung Malformations

There are two primary types of malformations:

Congenital Pulmonary Airway Malformation (CPAM)

Sometimes called congenital cystic adenomatoid malformation (CCAM), a CPAM is a benign mass that forms in the lower respiratory tract when lung tissue in the fetus grows larger than normal. This lesion may cause large fluid-filled cysts (macrocysts), small cysts (microcysts) or a mix of both. The fetus can have one or more CPAMs, and most occur in only one section (known as the lobe) of the lung.

The lesions usually stop growing at approximately 26 weeks gestation, at which time many begin to slowly shrink until term.

Large CPAMs can lead to a dangerous condition in the womb known as hydrops, the accumulation of fluid in two or more compartments of the body of the fetus. Hydrops develops when too much blood flows into the area of the lesion. This causes the fetus’ heart to work harder to support the extra blood flow in the body, which can lead to congenital heart failure. Hydrops can be life-threatening to the fetus, especially those under 30 weeks gestation.

Bronchopulmonary Sequestration (BPS)

Bronchopulmonary sequestrations are solid masses of lung tissue that do not connect to the rest of the lung airways. BPS lesions have an abnormal blood supply through a vessel connected to the aorta. These lesions can be inside the lungs (known as intralobar) or outside the lungs (known as extralobar).

Other Types of Congenital Lung Malformations

• Hybrid lesion: a combination of CPAM and BPS
• Bronchogenic cysts: A growth of tissue that usually develops on the esophagus or trachea. They can cause blocked airways when large or infected.
• Bronchial atresia: A rare condition that causes partial blockage of the bronchus, the part of the airway that lets air into the lungs.
• Congenital lobar emphysema: A rare, yet serious, condition in which a blockage of the airway traps the airflow during breathing and leads to overinflation of the newborn’s lungs.

Causes of Congenital Lung Malformations

The causes of congenital lung malformations are not yet known.

Congenital Lung Malformation Diagnosis

Before Birth

Congenital lung malformations are typically found on a prenatal ultrasound. 

Additional imaging may sometimes be helpful. These include:

• Fetal MRI (magnetic resonance imaging). Imaging used to see the lesion in more detail and measure the air moving in and out of the lungs.
• Fetal echocardiogram. An ultrasound of the fetus’ heart that can view the function of the heart.

A measurement called CVR (CPAM-volume-ratio) is usually performed during each ultrasound evaluation. CVR helps to determine the risk of hydrops, and it may help predict the risk of breathing problems at birth.

More than 90% of babies diagnosed with congenital lung malformations during pregnancy do not have any fetal problems. More than 80% of babies diagnosed with a congenital lung malformation during pregnancy do not have any breathing problems at birth.

After Birth

All babies with a suspected congenital lung malformation are recommended to undergo a CT scan to best characterize the anatomy of the lesion. In those who have no symptoms, the study may be delayed until a child is at least 2 months old. X-rays alone are not helpful in determining the best treatment plan.

Congenital Lung Malformation Symptoms

A child with a congenital lung malformation may show symptoms after birth, such as:

• Rapid breathing
• Shortness of breath or wheezing
• Recurring pneumonia (lung infections)
• Collapsed lung (pneumothorax)

Congenital Lung Malformation Treatment

Treatment Before Birth

When a congenital lung malformation is found, the care team will monitor the lesion’s size through regular prenatal ultrasounds. If hydrops occurs, several fetal treatments may be suggested:

Steroid Therapy

For microcystic lesions, two doses of a steroid called betamethasone may be given to the mother to prevent hydrops in the fetus when large lesions are present, or reverse hydrops that is already present.

Thoracoamniotic shunts

A thin tube is placed into a large macrocyst to drain the extra fluid from around the fetus’ lung and into the womb. This decreases the mass, which removes pressure on the fetus’ lungs, heart and blood vessels in an effort to remove hydrops.

Fetal Surgery

Lobectomy – Surgical removal of the entire mass while still in the womb may be recommended if the baby has severe hydrops and evidence of heart failure. Fortunately, the need to do fetal surgery to remove congenital lung malformations is very rare.

EXIT (ex utero intrapartum treatment) delivery: Another option is a special type of cesarean section in which the lung mass is removed by pediatric surgeons while the fetus is still attached to the placenta. The umbilical cord is then cut, and the baby is supported by a breathing machine. This allows the surgeon to remove the tumor before delivery so that the remaining lungs can expand and function better.

Treatment After Birth

Postnatal Surgery

Most babies born with a congenital lung malformation will usually require surgery soon after birth to remove the lesions. Many lesions that remain in the lungs will eventually become infected and cause pneumonia. There is also a small risk that some will become cancerous.

Babies with breathing problems at birth due to congenital lung malformations need to have surgery soon after birth to remove the mass. Babies who do not have breathing problems are observed for 48 hours and discharged home with outpatient surgical follow-up care arranged.

The typical age recommendation of surgery for babies with a congenital lung malformation and no breathing problems is between 3 and 6 months of age. Delaying the procedure until an infant is a little older is ideal because they can better handle anesthesia and have grown enough to undergo minimally invasive (keyhole) surgery to remove the lesion. Keyhole surgery results in less pain and smaller scars. Most babies do not need to recover in an intensive care unit, and they can be discharged within two to three days of the surgery.

There are situations in which it may be better to observe small congenital lung malformations rather than to remove them. This recommendation is determined by the surgeon. In those cases, follow up CT scans or other imaging is recommended.

Outlook

The prognosis is excellent in the vast majority of children with congenital lung malformations. After treatment, most children go on to lead normal, healthy lives.