Bronchopulmonary sequestration: Prenatal diagnosis and management

INTRODUCTION — Congenital lung masses include bronchopulmonary sequestration (BPS, also called lung or pulmonary sequestration), congenital pulmonary airway malformation (CPAM), congenital lobar overinflation, bronchogenic cyst, and bronchial atresia. Hybrid lesions are common, which suggests that these masses represent a spectrum of abnormalities. BPS lies along a spectrum of abnormalities that can affect the normal development of the airways, lung parenchyma, and vasculature. Obstruction is thought to be the underlying etiology, and the level, degree, and timing of the obstruction determines the resulting pathology (figure 1) [1-3].

The majority of BPS cases are diagnosed in the second trimester, continue to enlarge during the second trimester, and then stabilize or partially regress during the third trimester. Thus, many cases can be managed expectantly; however, a subset of fetuses develop hydrops or massive pleural effusions with mediastinal shift, which usually requires intervention [4].

In the absence of other significant congenital anomalies, the postnatal short-term and long-term prognosis of BPS is usually very good, although surgical excision is sometimes performed to relieve respiratory symptoms or prevent future complication (eg, pulmonary infection; rarely heart failure, bleeding, or torsion). Surgery is generally performed in the first year of life and is curative.

This topic will focus on prenatal diagnosis and management of BPS and hybrid BPS/CPAM lesions. Prenatal diagnosis and management of CPAM alone is reviewed separately. (See "Congenital pulmonary airway malformation: Prenatal diagnosis and management".) Postnatal management and outcome of BPS and CPAM are also reviewed separately. (See "Bronchopulmonary sequestration" and "Congenital pulmonary airway malformation".)

ANATOMIC AND EPIDEMIOLOGIC FEATURES OF BPS — Bronchopulmonary sequestration (BPS) accounts for a small proportion, 0.15 to 6.4 percent, of congenital lung malformations [5]. The lesion consists of a nonfunctioning mass of lung tissue that lacks normal communication with the tracheobronchial tree and receives its blood supply from the systemic (rather than the pulmonary) circulation [6]. The feeding vessel most commonly originates from the thoracic aorta, although origins from the abdominal aorta or divisions of the abdominal aorta (eg, splenic, celiac, or gastric artery) have been described [7]. Eighty percent of cases occur on the left [8].

BPS is classified anatomically as intralobar (ILS) or extralobar (ELS). ILS and ELS are histologically similar but occur in different locations and often have different venous drainage.

●ILS – In ILS (also known as intrapulmonary sequestration), the mass is located within the normal lung and is covered by the visceral pleura of the lung. ILS accounts for approximately 75 percent of BPS and is almost always located in the lower lobes, most commonly in the left medial or posterior segment [9,10]. Because ILS is connected to normal lung, abnormal connections between it and either the bronchi or the gastrointestinal tract can develop, which increases the risk of postnatal respiratory infections [11].

Most ILS drains via the pulmonary vein to the left atrium, although connections to the vena cava, azygous vein, or right atrium also occur.

ILS is distributed equally between the sexes.

●ELS – In ELS (also known as extrapulmonary sequestration), the mass is located outside of the normal lung and has its own visceral pleura. Postnatally, approximately 25 percent of BPS is extralobar [12]. An extralobar lesion can occur between the neck and diaphragm, within the diaphragm, or infradiaphragmatically, where it can mimic a suprarenal neuroblastoma [9,12,13]. The most common location is between the left lower lobe and hemidiaphragm (80 percent) [10,14]. Ten to 15 percent are subdiaphragmatic (usually in the suprarenal space) and 90 percent are left-sided [15]. One case report described ELS with combined gastric and intradiaphragmatic locations [16]. Because ELS is not connected to normal lung, both abnormal intrapulmonary connections and postnatal infectious complications are uncommon.

Most ELS drains into the systemic circulation through the azygous or hemiazygous vein or vena cava, but sometimes directly into the right atrium [5,11]. Because of the systemic arterial supply and venous drainage, large ELS may develop severe left to right shunts, leading to high-output heart failure [11]. 

ELS is more likely to affect males and to be associated with anomalies, including congenital diaphragmatic hernia or eventration, heart defects, and foregut anomalies.

Hybrid combinations of BPS and congenital pulmonary airway malformation (CPAM) are relatively common, have connections with both the pulmonary and systemic arterial supply, and can have the appearance of a CPAM with multiple cysts.

PRENATAL DIAGNOSIS — Ultrasound is the primary modality for imaging the fetal chest and detecting fetal chest masses [17], but can have low specificity [18]. Magnetic resonance imaging (MRI) can be a useful adjunct for confirming the presence of a mass, further characterizing normal and abnormal anatomy, and assessing residual lung volume. MRI of lung parenchyma is less limited by maternal obesity, oligohydramnios, overlying ribs, and fetal lie than ultrasound. (See 'Role of magnetic resonance imaging' below.)

The normal fetal lung is shown in the following ultrasound image (image 1) and MRI (image 2); imaging the normal fetal lung is reviewed separately. (See "Congenital pulmonary airway malformation: Prenatal diagnosis and management", section on 'Appearance of normal lung'.)

Ultrasound findings

Diagnostic findings — Prenatal diagnosis of bronchopulmonary sequestration (BPS) should be suspected upon visualization of a solid appearing, triangular, echogenic chest mass, which is often located in the lower hemithorax adjacent to the diaphragm. Hybrid lesions (BPS and congenital pulmonary airway malformation [CPAM]) have solid and cystic components. The mass is usually unilateral, but bilateral cases have been described [19]. The diagnosis is confirmed by identification of a systemic artery to the mass: usually the thoracic aorta; sometimes the abdominal aorta or one of its divisions (image 3 and image 4 and image 5).

Color and power Doppler assessments are critical for imaging the systemic vascular supply (image 4) [20]. The systemic feeding vessel can be noted above, within, or below the diaphragm. Identifying a systemic fetal vessel is important in differential diagnosis because BPS usually receives its blood supply from a feeding vessel arising directly from the aorta, whereas CPAM receives its blood supply from the normal pulmonary vasculature, and hybrid BPS/CPAM receives its blood supply from both a feeding vessel arising from the aorta and from the normal pulmonary vasculature. However, even with thorough assessment, the vascular supply may not be visualized prenatally due to various factors including fetal lie, maternal obesity, and oligohydramnios [9,21].

It is also important for surgical planning to specifically assess the supra-, intra-, or infra-diaphragmatic location of the mass, and to specify the origin of the feeding vessel. For example, if the vessel originates from an infra-diaphragmatic artery, and the mass is intralobar, the surgeon will need access to both the thoracic and abdominal cavities.

Postdiagnostic imaging evaluation

●Fetal anatomic survey – Thorough assessment of the entire fetus is important to look for additional anomalies [9,22]. ILS is not associated with an increased risk of additional anomalies [9,22]. ELS is associated with anomalies in up to two-thirds of cases [23]. These anomalies include chest wall and vertebral anomalies, hindgut duplications, diaphragmatic hernia, congenital heart disease, and renal and intracranial abnormalities [9,22].

●CVR – Quantitative ultrasound evaluation helps predict the prenatal course of BPS and includes measuring the congenital pulmonary airway malformation volume ratio (CVR). This is obtained by calculating the volume of the lung mass using the formula for the volume of a prolate ellipsoid and normalizing it by gestational age. To normalize by gestational age, the lung mass volume should be divided by the head circumference [24]:

The use of CVR allows direct comparison of fetuses of different gestational ages. In BPS, a CVR >1.6 is associated with a higher risk for development of hydrops but does not uniformly result in hydrops; 58 percent of fetuses with a high CVR developed hydrops in one study [25]. Thus, CVR can be used to identify fetuses in need of closer follow-up. (See 'Follow-up imaging' below.)

●Venous drainage – The venous draining pattern should be assessed, given systemic rather than pulmonary venous drainage is a poor prognostic factor and has been linked with outcome [26]. (See 'Poor prognostic factors' below.)

●Mediastinal shift, pleural effusions, hydrops – It is important to assess for mediastinal shift and pleural effusions/other signs of hydrops (image 6), which generally require intervention. (See 'Hydrops' below and 'Pleural effusion with mediastinal shift' below.)

Role of magnetic resonance imaging — MRI can be performed to confirm ultrasound diagnosis or in cases where the ultrasound is inconclusive or images are suboptimal (due to maternal body habitus, fetal lie, oligohydramnios). In either case, MRI can be of help to assess for associated extrathoracic anomalies that could change the prognosis.

In BPS, MRI typically reveals a hyperintense T2w mass often located in the lower lobe (image 7) [9,20,27]. The feeding vessel may be a low signal line coursing from the aorta into the mass. MRI is also helpful for delineating the mass and its location (chest, diaphragm, or infradiaphragmatic), evaluating the contralateral lung, and assessing for other congenital abnormalities (image 8) [9,21]. In a series of 103 fetal lung masses resected for suspected congenital lung malformations [28], ultrasound detected 85 (82.5 percent) lung lesions and correctly diagnosed whether or not a lesion was a CPAM in 75 percent of cases (sensitivity 93 percent, specificity 32 percent). MRI had a similar concordance rate for diagnosing CPAM (73 percent), but was superior in correctly determining whether a systemic feeding vessel was present (overall accuracy 80 percent, sensitivity 71 percent, specificity 88 percent) compared with ultrasound (overall accuracy 72 percent, sensitivity 49 percent, specificity 93 percent).

At times, a feeding vessel may not be identified prenatally by either ultrasound or MRI. In the series described above, postnatal computed tomography (CT) diagnosed whether a systemic feeding vessel was present in 90 percent of cases (sensitivity 92 percent, specificity 88 percent), which was superior to both prenatal ultrasound and MRI [28]. Thus, obtaining additional cross-sectional imaging postnatally with a contrast CT scan is typically recommended. However, performing a second fetal MRI late in gestation may add information to that obtained by an early MRI because MRI after 32 weeks of gestation can better identify the feeding vessel and has better correlation with postnatal imaging [29].

DIFFERENTIAL DIAGNOSIS — The prenatal differential diagnosis of bronchopulmonary sequestration (BPS) depends on whether it is intrathoracic or extrathoracic.

●Differential diagnosis of intrathoracic lesions includes:

•Congenital pulmonary airway malformation (CPAM) – Both microcystic CPAM and BPS appear solid and homogeneous on ultrasound and magnetic resonance imaging (MRI). Identification of a systemic arterial feeder helps differentiate BPS from microcystic CPAM, which connects to the normal pulmonary vasculature, although a hybrid lesion still could be present. (See "Congenital pulmonary airway malformation: Prenatal diagnosis and management" and "Congenital pulmonary airway malformation".)

•Congenital lobar overinflation (CLO)/congenital lobar emphysema (CLE) – The sonographic features of CLO include a bright echogenic lung with pulmonary arterial blood flow through the mass; cystic lesions may be present [30]. Prenatally, this diagnosis can be difficult to differentiate from microcystic CPAM and BPS. The presence of normal pulmonary vascularity through the mass excludes BPS and microcystic CPAM. The diagnosis is confirmed postnatally by computed tomography (CT), which shows emphysematous alveoli in CLO and distorted lung tissue in microcystic CPAM [31]. (See "Congenital lobar emphysema".)

•Congenital diaphragmatic hernia (CDH) – Herniated bowel loops in the hemithorax can mimic a multicystic, heterogeneous lung mass. Mediastinal and cardiac deviation may be the only hint that a CDH is present in the relatively rare instances where the stomach remains infradiaphragmatic. When the stomach is herniated into the hemithorax, nonvisualization of the stomach bubble within the abdomen is helpful for making the diagnosis [9,22]. Peristalsis of bowel loops in the thorax can sometimes be seen by ultrasound [9]. Deviation of the umbilical portion of the portal vein suggests liver herniation into the thorax. Direct visualization of hepatic vessels extending into the chest confirms liver in the thoracic cavity. MRI is particularly useful in assessing the amount of liver herniation and delineation of small and large meconium-filled bowel in the chest. Meconium is dark on T2 and bright on T1, while liver is bright on T1w and intermediate on T2w, thus easily differentiated from adjacent lung. (See "Congenital diaphragmatic hernia: Prenatal issues".)

•Lung tumors – Though rare, malignancies such as pleuropulmonary blastoma can present as an asymptomatic congenital lung lesion. In a retrospective postnatal study involving 99 asymptomatic congenital lung lesions with 91 diagnosed prenatally, only 2 percent consisted of tumors [32].

●Differential diagnosis of extrathoracic lesions includes:

•Neuroblastoma – Neuroblastoma, as well as other intraabdominal masses, such as mesoblastic nephroma, can mimic an infradiaphragmatic BPS. Thorough examination to assess origin can help differentiate between these lesions: mesoblastic nephroma arises from the kidney, is most common on the right side, and can be cystic [9], whereas BPS is more common on the left and appears solid.

Neuroblastoma is often diagnosed in the third trimester and tends to grow over time, while BPS is more often identified in the second trimester and tends to regress over time [9]. (See "Fetal abdomen: Differential diagnosis of abnormal echogenicity and calcification", section on 'Neuroblastoma'.)

•Adrenal hemorrhage – In contrast to BPS, the key to diagnosis of adrenal hemorrhage is the change in appearance over time. The initial appearance is that of an echogenic and solid-appearing lesion without internal blood flow. Subsequently, a hypoechoic central region develops, and then a more cystic appearance and a decrease in size are observed. Dystrophic calcifications may develop. On MRI, hemosiderin may be seen in a hemorrhage.

In addition, BPS has a systemic feeding vessel and is diagnosed in the second trimester whereas adrenal hemorrhage typically occurs in the third trimester and has no feeding vessel. (See "Fetal abdomen: Differential diagnosis of abnormal echogenicity and calcification", section on 'Adrenal hemorrhage'.)

PRENATAL COURSE — Bronchopulmonary sequestration (BPS) is usually a small lesion relative to the chest and decreases in size in late gestation in approximately 75 percent of cases [9,20,33]. The apparent resolution has been attributed to decompression into the normal lung, overgrowth with respect to the amount of blood supplied by the systemic circulation, or torsion around the vascular pedicle resulting in vascular and lymphatic obstruction [9]. Although torsion has been associated with size regression, a case of mass torsion with impaired venous return from the mass leading to tension hydrothorax, heart/mediastinal compression, and hydrops has also been described [34].

As BPS regresses, the lesion becomes more difficult to visualize on ultrasound. On MRI, it initially has similar signal intensity to the adjacent lung and then becomes darker than adjacent lung when it is almost completely collapsed/resolved. Masses that appeared to resolve in utero are typically found on postnatal computed tomography (CT) [35,36].

In a series of 103 fetuses with intralobar sequestration (ILS) (n = 44) and extralobar sequestration (ELS) (n = 59) managed at a single institution, 94 percent of ILS and 71 percent of ELS decreased in size or became isoechoic compared with the normal adjacent lung parenchyma from initial to final evaluation [37]. Lesions achieved their peak size at 26 to 28 weeks of gestation.

Poor prognostic factors

●ELS has a poorer prognosis than ILS. In one series, hydrothorax only developed in fetuses with ELS, and four of these eight cases also developed hydrops [37]. All 103 fetuses survived; 41/44 ILS (93 percent) and 35/59 ELS (59 percent) were resected postnatally.

●Large lesions have a poorer prognosis than small lesions. When BPS presents as a large intrathoracic mass (which can be defined by CVR >1.6), mediastinal shift can occur, placing the fetus at risk of compression of the heart, thoracic venous structures, and esophagus, resulting in large pleural effusions that may progress to hydrops and may be associated with polyhydramnios [9,33,38]. Hydrops can also result from shunting when there is a systemic arterial feeder and the mass drains via the pulmonary circulation. However, large lesions with mediastinal shift, cardiac dextroposition, or cardiac compression do not always cause hydrops [21].

●Systemic drainage is more common in ELS than ILS and systemic rather than pulmonary venous drainage is another poor prognostic factor. In a study of 71 fetuses with BPS, fetuses with systemic venous drainage had a higher incidence of associated anomalies, hydrops, and polyhydramnios compared with those with a pulmonary venous drainage [26].

ROUTINE OBSTETRIC MANAGEMENT — In addition to routine prenatal care, we suggest the following.

Genetic counseling — The incidence of chromosomal abnormalities is not increased above baseline in fetuses with bronchopulmonary sequestration (BPS) alone; this should be considered when weighing the risks and benefits of invasive procedures for prenatal diagnostic genetic studies. If performed, microarray is preferable to a karyotype and should be offered in cases with associated anomalies, as the frequency of genetic abnormalities is increased in fetuses with additional anomalies [39-45] and/or nonimmune hydrops [46]. (See "Prenatal genetic evaluation of the fetus with anomalies or soft markers".)

Parental counseling — Parental counseling includes:

●The differential diagnosis of prenatally suspected BPS. (See 'Differential diagnosis' above.)

●The possible prenatal course of the BPS. If diagnosed in the second trimester, the mass can continue to grow and hydrops may develop. There are no reliable criteria for determining which lesions will grow and thus potentially lead to development of hydrops versus those that will stabilize or regress in size and thus have minimal fetal impact. In general, a fetus with a large BPS (defined by congenital pulmonary airway malformation volume ratio [CVR] >1.6) who develops hydrops in the second trimester is likely to have a poor prognosis (eg, fetal demise, very or extremely preterm birth, pulmonary hypoplasia). By comparison, if a small BPS is diagnosed at the end of the second trimester or in the third trimester, subsequent development of hydrops is unlikely and the prognosis is good. (See 'Prenatal course' above.)

●The potential need for and the options for prenatal intervention (eg, thoracoamniotic shunt, laser ablation, sclerotic treatment and steroids, and early delivery). (See 'Pleural effusion with mediastinal shift' below and 'Hydrops' below.)

●Choosing an appropriate site for planned delivery, with consideration of the need for resources for newborn resuscitation and surgery. (See 'Delivery' below.)

●Postnatal issues (clinical manifestations, postnatal evaluation, postnatal management, potential complications, prognosis of associated anomalies, and range of outcomes). (See "Bronchopulmonary sequestration".)

Follow-up imaging — All patients should have serial prenatal follow-up ultrasound examinations to assess change in size of the lung mass and development of hydrops [9]. The frequency depends on the size of the lesion and gestational age at diagnosis; larger lesions should be followed more closely. Although follow-up ultrasound might not identify the lung lesion since BPS can acquire the same echogenicity of adjacent normal lung, assessment for hydrops and mediastinal shift is still possible.

We suggest serial prenatal follow-up ultrasound examinations every one to four weeks, similar to the protocols recommended for congenital pulmonary airway malformation (CPAM) [24]. The frequency within this range depends on the gestational age and CVR.

●Closer follow-up should be performed in those patients with CVR ≥1.6 and <26 weeks as they are at high risk of developing hydrops. In these cases, consultation with a maternal fetal medicine (MFM) specialist for medical intervention is appropriate. When incipient hydrops is suspected, assessment every two to three days is reasonable. Depending on gestational age and severity of hydrops, consultation for fetal surgical intervention should be considered.

●Conversely, the interval between studies can be lengthened in patients with CVR <0.91 [47] and in whom BPS growth has plateaued or is regressing, especially after 30 weeks of gestation [48]. A decrease in mass area/head circumference or mass volume/estimated fetal weight ratio is associated with regression [49].

MANAGEMENT OF COMPLICATED CASES

Hybrid BPS/CPAM — Macrocysts within bronchopulmonary sequestration (BPS) are consistent with a hybrid lesion (BPS with macrocystic congenital pulmonary airway malformation [CPAM]). The management of hybrid lesions, which may include maternal betamethasone therapy and cyst drainage, is based on the CPAM component and described separately. (See "Congenital pulmonary airway malformation: Prenatal diagnosis and management".)

Hydrops — Hydrops is uncommon [38], but it is a sign of impending fetal demise and thus an indication for intervention [27]. However, management of these complex cases must be individualized based on gestational age, severity of hydrops, available resources, and shared decision-making.

●≥32 to 34 weeks of gestation – For pregnancies greater than 32 to 34 weeks of gestation, delivery with immediate postnatal resection is a reasonable option, especially with increasing severity of hydrops [33], given that newborn mortality (and morbidity) substantially decreases after 32 and particularly after 34 weeks of gestation [50]. (See "Preterm birth: Definitions of prematurity, epidemiology, and risk factors for infant mortality", section on 'Birth weight and gestational age'.)

●20 and 32 weeks – For pregnancies between 20 and 32 weeks, fetal therapy in an attempt to improve fetal hemodynamics, reverse hydrops (and prevent pulmonary hypoplasia), and allow further in utero maturation is generally preferable to very preterm birth, which has high mortality and morbidity. Several interventions have been described and appear to improve survival [36]. Invasive interventions should only be undertaken at centers experienced in fetal surgery. Prenatal intervention requires extensive parental counseling on the potential risks versus benefits of surgery. The procedures are investigational and have not been compared in randomized trials.

•The most common intervention is thoracentesis or thoracoamniotic shunt placement. In fetuses under 30 weeks of gestation, a thoracoamniotic shunt may be preferred to avoid the need for repeated thoracenteses.  

-In a series including four fetuses with extralobar sequestration (ELS), tension hydrothorax, and secondary hydrops, hydrops resolved after serial thoracenteses in one fetus and after thoracoamniotic shunt placement in two fetuses; all three neonates underwent resection of the lesion after delivery in the mid to late third trimester [33]. The fourth hydropic fetus was not treated in utero and died of pulmonary hypoplasia after a prolonged neonatal course. The shunting procedure and complications are similar to those in CPAM. Potential complications include displacement or malfunction of the catheter, thrombus occlusion of the catheter, fatal fetal hemorrhage, procedure-related placental abruption, preterm prelabor rupture of membranes, and preterm labor [51-53]. (See "Congenital pulmonary airway malformation: Prenatal diagnosis and management", section on 'Second-line therapy: Invasive procedures'.)

-In a series of four cases of ELS with hydrops, maternal betamethasone was administered and three also underwent thoracentesis and/or thoracoamniotic shunt placement, with subsequent resolution of hydrops [37].

•Percutaneous laser ablation of the feeding vessel has been reported to decrease tumor size, allow growth of normal lung parenchyma, and reverse pleural effusion or hydrops in over 75 percent of cases reported in several small studies [8,54-59]; it also decreases the need for postnatal sequestrectomy, as infants are often asymptomatic [60]. Sometimes two procedures are necessary [8] and a postnatal intervention could be required to remove the residual sequestration [61]. In a retrospective study that compared shunt placement with intrafetal vascular laser ablation for treatment of BPS with pleural effusion, complete regression of the lesion occurred more often with laser ablation (four of five completely regressed) than with shunt placement (zero of seven completely regressed), and gestational age at birth was lower with shunt placement (37.2 versus 39.1 weeks) [58].

•Radiofrequency ablation has also been safely used in a fetus with significant pleural effusion, mediastinal shift, and secondary lung collapse [62].

•Percutaneous ultrasound-guided fetal sclerotherapy has also been described [63].

•One in utero open resection has been successfully performed to salvage a hydropic fetus remote from term [54]. This infant had good pulmonary function and development at 20 months of age.

•Two case reports described favorable effects (resolution of hydrops, resolution of pleural effusion) after betamethasone therapy [64,65].

Pleural effusion with mediastinal shift — The fetus with BPS rarely develops a pleural effusion with mediastinal shift. If tension hydrothorax or cardiac decompensation with hydrops develops, thoracoamniotic shunting may be considered as a temporizing maneuver (similar to cases with CPAM). Resolution of hydrops after in utero therapy is predictive of postnatal survival [33,51,66,67]. (See "Congenital pulmonary airway malformation: Prenatal diagnosis and management", section on 'Second-line therapy: Invasive procedures'.)

DELIVERY — Delivery planning should be in conjunction with the pediatric staff (neonatology, pediatric surgery).

●Timing and route

•If the lung mass has resolved or is small with no mediastinal shift or hydrops, bronchopulmonary sequestration (BPS) itself is not an indication for early delivery or cesarean birth [51]. Neonatal respiratory problems would be unlikely. A CVR <1.1 has been used to select patients who can safely give birth at their hospital of choice, even if the facility does not have resources for intensive neonatal care [68].

•For fetuses with large masses that cause mediastinal shift and/or hydrops, delivery should be planned for a tertiary care center with an intensive care nursery capable of resuscitation of a neonate with respiratory difficulties, including and with pediatric surgeons experienced in care of these infants [66,69]. (See 'Hydrops' above.)

●Role of EXIT – Rare fetuses may benefit from availability of EXIT. In EXIT, the fetus is partially delivered and intubated without clamping the umbilical cord. Uteroplacental blood flow and gas exchange are maintained by using inhalational agents to provide uterine relaxation, and amnioinfusion is performed to maintain uterine volume. EXIT is not usually helpful for isolated BPS because of the absence of a connection between the abnormal lung and the normal bronchial tree. However, a fetus with hybrid BPS/congenital pulmonary airway malformation (CPAM) with a large CPAM component and systemic feeding vessel may benefit as lung parenchyma may fill with air and not decompress. (See "Congenital pulmonary airway malformation: Prenatal diagnosis and management", section on 'Ex utero intrapartum therapy (EXIT) procedure'.)

POSTNATAL MANAGEMENT — Postnatal presentation, evaluation, complications, and management are discussed separately. (See "Bronchopulmonary sequestration".)

SUMMARY AND RECOMMENDATIONS

●Anatomy – Bronchopulmonary sequestration (BPS) consists of a nonfunctioning mass of lung tissue that lacks normal communication with the tracheobronchial tree and receives its blood supply from the systemic circulation (rather than the pulmonary circulation, which would be seen with congenital pulmonary airway malformation [CPAM]). The feeding vessel most commonly originates from the thoracic aorta, but origin from the abdominal aorta or its divisions can also occur. BPS is classified anatomically as intralobar (ILS) or extralobar (ELS), which are histologically similar, but have different locations and often different venous drainage and prognosis. (See 'Anatomic and epidemiologic features of BPS' above.)

●Prenatal diagnosis – The sonographic diagnosis of BPS is based on its typical appearance of a solid, triangular, echogenic usually unilateral mass, which is often located in the lower hemithorax adjacent to the diaphragm or within leaves of the diaphragm, or subdiaphragmatic. A necessary feature for diagnosis is identification of a feeding systemic artery to the mass. Hybrid BPS and CPAM lesions can occur and are characterized by both solid and cystic components in a lung mass with a systemic feeding artery. (See 'Diagnostic findings' above.)

The systemic feeding vessel is not always identified on prenatal imaging. Magnetic resonance imaging (MRI) can be a useful adjunct in demonstrating the systemic feeding vessel when ultrasound imaging is limited by maternal body habitus, oligohydramnios, or fetal lie, but MRI is not 100 percent sensitive in vessel identification. (See 'Role of magnetic resonance imaging' above.)

●Differential diagnosis – The differential diagnosis of thoracic BPS includes CPAM, congenital lobar emphysema, and congenital diaphragmatic hernia. When intraabdominal, BPS can mimic adrenal hemorrhage, neuroblastoma and mesoblastic nephroma. (See 'Differential diagnosis' above.)

●Prenatal course – BPS is usually a small lesion relative to the chest, enlarges during the second trimester to a peak size at 26 to 28 weeks of gestation, and then decreases in size in late gestation in approximately 75 percent of cases. Although some masses appear to resolve in utero, they are typically detected on postnatal computed tomography.

Prognosis is typically very good in the absence of mediastinal shift, large pleural effusions, hydrops, and associated anomalies. Poor prognostic factors include ELS (which has a higher risk of associated anomalies and torsion), large lesions (which can be defined by CVR >1.6 and can cause cardiac, vascular, and esophageal compression), systemic venous drainage, and hydrops. (See 'Prenatal course' above and 'Poor prognostic factors' above.)

●Postdiagnostic evaluation – Initial evaluation should include assessment for other congenital anomalies. The incidence of chromosomal abnormalities is not increased above baseline in fetuses with BPS alone, but microarray can be offered for further evaluation, and should be offered in cases with associated anomalies, as the frequency of genetic abnormalities is increased in fetuses with additional anomalies and/or nonimmune hydrops. (See 'Genetic counseling' above.)

We suggest serial prenatal follow-up ultrasound examinations every one to four weeks to assess change in size of the lung mass and development of hydrops. The frequency within this range depends on the gestational age and congenital pulmonary airway malformation volume ratio (CVR). Closer follow-up should be performed in those patients with CVR ≥1.6 and <26 weeks as they are at high risk of developing hydrops. When incipient hydrops is suspected, assessment every two to three days is reasonable. On the other hand, the interval between studies can be lengthened in patients with CVR <0.91 and in whom BPS growth has plateaued or is regressing, especially after 30 weeks. (See 'Follow-up imaging' above.)

●Management of hydrops – Management of these complex cases must be individualized based on gestational age, severity of hydrops, available resources, and shared decision-making. (See 'Hydrops' above.)

•For hydropic fetuses greater than 32 to 34 weeks of gestation, delivery with immediate postnatal resection is a reasonable option, given that newborn mortality (and morbidity) substantially decreases after 32 and particularly after 34 weeks of gestation.

•For hydropic fetuses between 20 and 32 weeks, several interventions with the goal of improving fetal hemodynamics, reversing hydrops (and preventing pulmonary hypoplasia), and enabling further in utero maturation have been described and appear to improve survival. Invasive interventions should only be undertaken at centers experienced in fetal surgery. The most common intervention is thoracentesis or thoracoamniotic shunt placement. Other in-utero interventions include laser or radiofrequency ablation, sclerotherapy, and open resection.

●Delivery – Delivery planning should be in conjunction with the pediatric staff (neonatology, pediatric surgery). If the lung mass has resolved or is small with no mediastinal shift or hydrops, BPS itself is not an indication for early delivery or cesarean birth. Neonatal respiratory problems would be unlikely. For fetuses with large masses that cause mediastinal shift and/or hydrops, delivery should be planned at a tertiary care center with an intensive care nursery capable of resuscitation of a neonate with respiratory difficulties, including and with pediatric surgeons experienced in care of these infants. (See 'Delivery' above.)