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Bronchopulmonary sequestration (BPS) is a mass of abnormal lung tissue that can develop in fetal lungs. In some cases, the mass may not cause problems and can be removed after birth or may shrink on its own. Other times, however, the mass may have adverse effects on the chest and abdomen, causing extra fluid to build up inside the baby.
Under these circumstances, bronchopulmonary sequestration could be life-threatening, which is why early detection and observation at the Colorado Fetal Care Center is so important. Thanks to our state-of-the-art facility and team of fetal care specialists, we work with families to provide the best outcomes for babies diagnosed with BPS.
Bronchopulmonary sequestration (BPS) is a mass of nonfunctioning lung tissue that does not communicate with the bronchioles, the passages that move air and in out of the lungs.
There are two types of BPS: intralobar (inside a lung lobe) or extralobar (outside of the lung with its own pleural cover). Intralobar BPS is more common, accounting for 75 percent of cases, and it is located in the lower lobe of the lung in 98 percent of cases. Extralobar BPS is usually located in the lower part of the chest, closer to the back, with about 90 percent of masses occurring on the left side.
Bronchopulmonary sequestration can also be intrathoracic (inside the chest) or extrathoracic (outside the chest). These masses receive blood supply from a systematic "feeding" vessel, such as the pulmonary artery, which help them grow. As they increase in size, these masses may cause amniotic fluid to accumulate in the chest or abdomen of the baby, making intervention necessary.
While the cause of BPS is not entirely known, there is a slightly higher chance for male babies to be diagnosed with this condition. It is not believed to be genetic, as there is no familial predisposition. Extralobar BPS is much more common in the fetus and newborn than intralobar BPS.
Bronchopulmonary sequestration may compress lung tissue or push the heart into an abnormal position. Extralobar BPS can also twist, causing surrounding blood vessels to twist as well (called "torsion"). This could cause hydrops, or fluid accumulation, to develop. The BPS may cause extra fluid to build up around the fetus, as well, which is called polyhydramnios.
In some cases, other abnormalities seen in and around the chest and upper abdomen may be associated with BPS. It is less common to see associated abnormalities in the intralobar type of BPS (only 10% of cases), but abnormalities are seen in 60% of cases of extralobar BPS. Because of its size, a BPS mass might result in incomplete development or underdevelopment of a baby's lungs, which could significantly impact the ability to breath after delivery.
At least 75% of prenatally diagnosed cases of BPS become smaller spontaneously, while those associated with hydrops (fluid accumulation), pleural effusions (fluid in lung tissue) or mediastinal shift (organ movement) will require intervention during pregnancy or after delivery.
Bronchopulmonary sequestration will appear as a bright, white mass in the vicinity of a baby's lungs during routine ultrasound. There will be a clearly defined blood vessel feeding the lesion, which usually confirms the diagnosis of BPS. Usually, however, an ultrasound cannot determine if the BPS is intralobar or extralobar. Sometimes, the ultrasound will show fluid in the lungs, extra amniotic fluid or fluid in two more areas of the body, such as the skin, lungs, heart and/or abdomen (referred to as hydrops).
When a chest mass is identified, a very detailed ultrasound is needed to evaluate other potential diagnoses. An amniocentesis (a needle inserted into the amniotic sac under ultrasound guidance to remove some amniotic fluid) may be recommended to test for a genetic/chromosomal abnormality. In severe cases, a family may decide to end the pregnancy if the diagnosis is made prior to 24 weeks of pregnancy.
If the family decides to continue with the pregnancy, arrangements will be made with the Colorado Fetal Care Center team to deliver the baby at our facility. This way, both mother and baby will have access to experts in the field of fetal medicine during and after delivery. Our fetal care team will also manage any complications that may arise.
On top of delivery at our state-of-the-art facility, we also offer different options to treat a fetal BPS, depending on the severity. These treatment options include:
Fetuses who develop hydrops prior to 30 weeks of pregnancy may be at significant risk of stillbirth. In those fetuses, fetal intervention (surgical procedures performed while the fetus is still in the uterus) may be necessary. Sometimes, a tube (called a shunt) may be placed to correct hydrops and excessive amniotic fluid (polyhydramnios).
Alternatively, a laser fiber can be inserted under ultrasound guidance to close off the blood supply to a mass. Open fetal surgery may be necessary in extreme cases.
Fetuses beyond 30 weeks of pregnancy may be considered for early delivery followed by removal of the lesion after birth.
Newborn babies who have been diagnosed with BPS may need vigorous stimulation and resuscitation in the minutes after birth. The greatest concern at delivery is the amount of lung development and the newborn's ability to breathe once the umbilical cord is cut. In severe cases, the baby may need to be placed on a breathing machine (ventilator) or a very specialized heart-lung machine, known as ECMO, to uniquely provide oxygen to the blood.
If there is fluid in the chest or abdomen, a tube known as a shunt may need to be placed to drain it. In many cases, babies will need surgery to remove the chest mass, but as many as 75 percent of cases spontaneously shrink after birth. Monitoring the mass after birth is critical to decide if removal is needed. If the mass grows, the fetal surgery specialists at the Colorado Fetal Care Center will remove it in our specifically-designed fetal surgery suite. After the baby recovers, remaining lung tissue should enlarge to fill the space left from the mass.
Bronchopulmonary sequestration (BPS) is a mass of nonfunctioning pulmonary tissue that lacks an obvious communication with the tracheobronchial tree and receives all or most of its blood supply from anomalous systemic vessels (Carter, 1959). There appears to be a spectrum of sequestration with, at one extreme, an abnormal vessel supplying a nonsequestered lung and, at the other extreme, abnormal pulmonary tissue but without anomalous vascular supply. While much emphasis has been placed in the past in differentiating between BPS and CPAM, it is now clear that aspects of both can coexist in the same lesion, where it is referred to as a hybrid lesion. There are two forms of BPS: intralobar and extralobar. Intralobar is the more common malformation seen in infants and children, accounting for 75% of cases of BPS, and it shares the same pleural investment with the normal lung (Savic et al., 1979; Collin et al., 1987). Extralobar BPS accounts for 25% of cases in infants and children, has a separate pleura from the lung and may be either intrathoracic or subdiaphragmatic in location (Savic et al., 1979; Collin et al., 1987).
The most widely accepted theory about the embryogenesis of BPS is that a supernumerary lung bud arises caudal to the normal lung bud and migrates caudally with the esophagus. If this lung bud arises prior to the development of the pleura, the bud is invested with adjacent lung and becomes an intralobar BPS. If supernumerary development occurs subsequent to pleura formation, the bud will grow separately and become invested with its own pleura, forming an extralobar BPS (Carter, 1959). There is no familial predisposition. There is a slight male predominance. Extralobar BPS is much more common in the fetus and neonate than intralobar BPS (Sauerbrei, 1992). Intralobar BPS is located within the lower lobe in 98% of cases. Extralobar BPS is usually located in the posterior lower chest and 90% of extralobar BPS is located on the left side. Up to 15% of extralobar BPS can be found either within or below the diaphragm (Berrocal et al., 2004).
BPS is a solid, highly echogenic mass with a clearly defined systemic feeding vessel. The demonstration of the systemic blood supply to the mass by color Doppler sonography usually confirms the diagnosis. Occasionally, these vessels cannot be demonstrated sonographically, making it difficult to distinguish BPS from type III congenital pulmonary airway malformation (CPAM) of the lung. Intralobar and extralobar BPS usually cannot be distinguished by prenatal ultrasound. Additional sonographic findings seen in association with BPS include pleural effusion, mediastinal shift, hydrops and polyhydramnios (Morin et al., 1989, 1994a, 1994b; Gross et al., 1992).
Extralobar BPS may undergo torsion of its vascular pedicle, causing venous and lymphatic obstruction, leading to pleural effusion and hydrops due to systemic venous obstruction (Vode and Kramer, 1989; Morin et al., 1994a). Fetal hydrops may result from compression on the inferior vena cava with venous obstruction and compromised cardiac output. Polyhydramnios may be seen in association with BPS due to esophageal obstruction or decreased swallowing. BPS associated with hydrops uniformly results in fetal or neonatal death if untreated. There is a high incidence of associated anomalies, especially in extralobar BPS (60% of cases) (Collin et al., 1987). The most commonly associated anomalies include congenital diaphragmatic hernia (CDH), pectus excavatum, tracheoesophageal fistula, esophageal duplication and congenital heart disease (Buntain et al., 1977). The intralobar type has a lower incidence of associated anomalies (10% of cases).
The differential diagnosis of intrathoracic BPS includes type III CPAM, mediastinal or thoracic teratoma and CDH (Moulik et al., 1987; Morin et al., 1994a). Type III CPAMs have a dense hyperechoic appearance that may be indistinguishable from BPS. Mediastinal teratomas usually have a higher density, causing acoustic shadowing behind the mass (Golladay and Mollitt, 1984). The distinction between CPAM and BPS when a systemic feeding vessel is not demonstrated usually comes down to the echotexture of the mass. The presence of cysts suggests CPAM, whereas solid triangular lesions are more consistent with BPS, especially in the lower thoracic region. The main considerations in the differential diagnosis of intra-abdominal extralobar BPS are mesoblastic nephroma and neuroblastoma. Intra-abdominal extralobar BPS can occur as a discrete suprarenal echogenic mass with a systemic blood supply. This mass can be mistaken for neuroblastoma or mesoblastic nephroma (Ohnichi et al., 1989; Oh et al., 1993). However, mesoblastic nephroma can usually be seen arising from the kidney (Ohnichi et al., 1989). Neuroblastomas arising from the adrenal glands are most commonly cystic lesions, which distinguish them from BPS (Oh et al., 1993).
Ultrafast fetal MRI may be very useful in sorting out the differential diagnosis, demonstrating the feeding vessels and excluding other potential associated anomalies. A sequestration cyst typically appears as a well-defined mass in the chest with a T2 signal intensity that is higher than that of the normal lung (Hubbard et al., 1999). The efficacy of MRI for detecting systemic feeding vessels is no better than that of Doppler ultrasonography.
The natural history of BPS depends on whether it is an intralobar or an extralobar BPS, whether it has a thoracic or abdominal location and the presence or absence of hydrops and other associated anomalies (Adzick et al., 1993). It was once thought that in fetuses with BPS, hydrops invariably developed and the fetus died in utero or during the neonatal period (Warner et al., 1958; Williams and Enumah, 1968). However, MacGillivray et al. (1993) subsequently reported six cases of BPS associated with contralateral mediastinal shift that dramatically decreased in size over the course of the pregnancy and spontaneously resolved, leading to a good neonatal outcome. Adzick et al. (1994, 1998) subsequently reported that 75% of cases of BPS diagnosed prenatally resolve spontaneously. The mechanism by which these lesions shrink is unknown. Intra-abdominal extralobar BPS has an outcome that is somewhat better than that for intrathoracic lesions and is rarely associated with hydrops. However, polyhydramnios may still develop secondary to esophageal or gastric compression. The BPS associated with hydrothorax is usually of the extralobar type. Tension hydrothorax in the fetus with BPS is fatal unless there is intervention.
The fetus with an echodense chest mass should be evaluated to exclude CDH, mediastinal teratoma and CPAM. The adrenal glands and kidneys should be delineated to distinguish an abdominal extralobar BPS from mesoblastic nephroma and neuroblastoma. It is noteworthy that most cases of BPS diagnosed prenatally are isolated sequestrations without associated anomalies (Felker and Tonkin, 1990). A fetal karyotype should be obtained to exclude associated chromosomal anomalies if they might influence the decision to continue the pregnancy or for cases in which fetal treatment is contemplated. Because of the reported association of BPS with congenital heart disease, fetal echocardiography should be performed. The family may choose not to continue the pregnancy if the diagnosis of BPS is made prior to 24 weeks and there are other life-threatening anomalies. If they elect to go forward with the pregnancy, arrangements should be made for delivery at a center with appropriate neonatal and pediatric surgical expertise.
The fetus with isolated BPS of either the intrathoracic or intra-abdominal type has a good chance of survival in the absence of hydrops, polyhydramnios or pleural effusion and when there is a planned delivery at an appropriately staffed facility with immediate resuscitation and surgery available. BPS may regress in size in 75% of cases, even when it is associated with mediastinal shift (MacGillivray et al., 1993; Adzick et al., 1995).
Fetuses at 30 weeks’ gestation or more should be considered for early delivery and resection ex utero. The fetus with hydrops and intrathoracic BPS diagnosed prior to 30 weeks’ gestation may be a candidate for fetal intervention. Hydrops may be seen in cases of BPS with tension hydrothorax, causing mediastinal shift, compromised venous return to the heart, and cardiac output. Thoracoamniotic shunting in these cases may correct the pleural effusion, mediastinal shift, polyhydramnios and hydrops.
An alternative is interstitial laser ablation of the systematic feeding vessel and aspiration of the pleural effusion. This procedure causes the BPS to infest which prevents recurrence of the pleural effusion. Shunting is not an option for the fetus with intrathoracic BPS associated with mediastinal shift and hydrops from a large thoracic mass without pleural effusion. Because BPS associated with hydrops is uniformly fatal, open fetal surgery should be considered in these cases. The prognosis for isolated intra-abdominal BPS is better than that for intrathoracic BPS because the intraabdominal location does not result in pulmonary hypoplasia.
Ideally, a fetus diagnosed with a large BPS should be delivered in a setting where vigorous resuscitation and appropriate therapy for a newborn with pulmonary hypoplasia can be initiated immediately. In contrast, small lesions do not require a change in delivery plans, and delivery in a community setting may be appropriate. There is a wide range of severity with BPS; the degree of pulmonary hypoplasia is the primary determinant of outcome. The newborn with intra-abdominal BPS usually has no respiratory compromise and can undergo elective resection. Therapeutic needs may vary from minimal (not requiring ventilator support) to severe [requiring ventilator and vasopressor support, high-frequency oscillatory ventilation and/or extracorporeal membrane oxygenation (ECMO)]. Large pleural effusions should be treated immediately by tube thoracostomy.
The surgical approach to BPS is straightforward with the exception of the management of anomalous blood supply. These vessels are often huge, thin-walled and elastic, rather than muscular arteries. In 20% of cases, these vessels are subdiaphragmatic in origin; in 15%, more than one vessel is present. These vessels can retract into the mediastinum or diaphragm and continue to bleed. In the rare case of the prenatally diagnosed BPS that appears to regress, postnatal imaging studies should be obtained. If the lesion is evident on plain chest radiography, surgical resection should be planned. If chest radiography does not demonstrate the malformation, a CT or MRI scan should be performed. Even though these lesions are asymptomatic, postnatal resection should be considered because of the risks of infection, hemorrhage and malignant transformation (Elias and Aufses, 1960; Juettner et al., 1987). When cardiac decompensation is the result of BPS, embolization of the feeding vessels may be considered.
The resection of the intra-abdominal extralobar BPS has no effect on the pulmonary parenchyma, and the operative risks and long-term complications are the same as those for laparotomy in the newborn. The long-term outcome of intrathoracic BPS is determined by the extent of pulmonary hypoplasia. In extralobar BPS, resection results in no loss of pulmonary parenchyma. In the long term, removal of the BPS will provide room for compensatory lung growth in the remaining pulmonary tissue. It has been suggested that infants treated for BPS are at increased risk for gastroesophageal reflux, pneumonia and pectus excavatum (Corbett et al., 2004).
There is no known genetic predisposition to the development of BPS. There has been a case reported of BPS recurring in male siblings (Abuhamed et al., 1996).
Maternal-Fetal Medicine, Ob/Gyn Obstetrics & Gynecology
Ob/Gyn Obstetrics & Gynecology
Anesthesiology, Anesthesiology - Pediatric
Maternal-Fetal Medicine, Ob/Gyn Obstetrics & Gynecology