What is bronchopulmonary sequestration (BPS)?

Bronchopulmonary sequestration (BPS) consists of nonfunctional lung tissue that has its own blood supply. In BPS, the abnormal lung tissue does not communicate with the tracheobronchial tree. The sequestered lung may lie within the fetal chest, or in some instances, in the abdominal cavity. A characteristic feature of BPS is the identification of a systemic blood supply, usually from the aorta. Not all cases of BPS result in compromise of the pregnancy. However, in some cases, the growth of the tissue within the fetal chest hinders the normal development of the normal lung. In such cases, arrest of normal lung development, also called pulmonary hypoplasia, may result, with an increased risk for neonatal death. Pulmonary hypertension may also result from the lung compression. In some cases, the growth of the BPS tissue may result in obstruction of the lymphatic return to the chest, causing non-immune hydrops.

How is BPS diagnosed?

BPS is diagnosed antenatally with ultrasound by showing a hyperechogenic (white) lung tissue, associated with a blood vessel usually from the aorta. The normal lung tissue may be compressed, and the heart position may also be shifted. Features of nonimmune hydrops, including ascites, skin edema, pleural effusion, and others, may also be present.

Are there different degrees of BPS?

BPS patients can be classified as having a good or a poor prognosis. Patients with a poor prognosis are those in which expectant management is more likely to result in loss of the pregnancy. Poor prognosis findings include:

• Compressed, small lung. This can be assessed by measuring the healthy lung using the Quantitative Lung Index (QLI) described by Quintero and collabotors.
• Non-immune hydrops. Third-space accumulation of fluid in the fetus, including ascites (fluid in the abdomen), skin and/or scalp edema, pleural effusion (fluid in the chest).
• Polyhydramnios, defined as a maximum vertical pocket (MVP) > 8 cm.
• Abnormal Dopplers. Dopplers may show evidence of impending heart failure in this twin. Typically, the ductus venosus or the umbilical vein are most reflective of these changes. The function of the heart may also be affected, and can be measured using the myocardial performance index (MPI), also known as the Tei index.
• Short cervical length or signs/symptoms of preterm labor. A short cervical length is defined as a cervical length of <2.5 cm via transvaginal ultrasound. Patients may have a short cervix in the absence of polyhydramnios or other poor prognostic factors. However, a short cervical length is associated with an increased risk for pregnancy loss or extreme premature delivery.

How can BPS be treated?

Depending on the gestational age at which BPS is diagnosed, delivery may be an option. If the diagnosis is made far from viability, different treatment options have been proposed, including:

• Expectant management. This may be associated with an increased risk of neonatal demise from pulmonary hypoplasia and pulmonary hypertension.
• Devascularization of the BPS. If the systemic blood supply can be readily identified on ultrasound, occlusion of such blood supply can be accomplished in a number of ways. This includes intravascular injection of sclerosing chemicals, or extravascular laser photocoagulation (insterstitial laser).
• Fetal bronchoscopy. We have noticed that BPS may obstruct the normal lung by causing accumulation of debris within the fetal airway. In one case, we were able to clear the fetal airway with fetal bronchoscopy, which allowed the normal lung to expand. The baby underwent removal of the BPS 9 months after birth. In that case, the blood supply to the BPS was not from the aorta, but from a pulmonary vessel, which did not allow its antenatal identification or treatment. Fetal bronchoscopy can possibly play a role in the evaluation and treatment of patients with BPS.