Pediatrics

Bronchopulmonary sequestration

OVERVIEW: What every practitioner needs to know

Are you sure your patient has bronchopulmonary sequestration? What are the typical findings for this disease?

The term bronchopulmonary sequestration (BPS) is applied to a nonfunctioning part of the lung that is set apart (i.e., sequestered) from the normal bronchial and vascular anatomy of the lung. Typically, there is an absence of a normal connection to the tracheobronchial tree, and the blood supply to the sequestration is from a systemic artery or arteries.

Bronchopulmonary sequestrations are classified as intralobar and extralobar. An intralobar sequestration (ILS) is encased within the pleura of the otherwise normal lung. An extralobar sequestration (ELS) is outside of the visceral pleura but is covered by its own pleural investment. Apart from this anatomic differentiation, ILS and ELS differ in other important ways (Table I).

Table I.

Comparison of Extralobar and Intralobar Sequestrations
Type Pleural Involvement Usual Location Age at Presentation Cause
ILS Within the visceral pleura 98% occur in the lower lobes, usually the posterior segment of the left lower lobe Late childhood, adolescence Recurrent infection
ELS Outside the visceral pleura Left lower hemithorax, between the diaphragm and lower lobe Infancy, resulting from associated lesions Often discovered incidentally in infants with associated lesions, e.g., diaphragmatic hernia

The diagnosis of BPS relies in large part on the clinician being aware of the varied presentations of this condition. Imaging studies may then be used to establish the diagnosis so that treatment options can be determined.

What are the typical symptoms for this disease?

Patients with ILS typically present in late childhood, adolescence, and adulthood with recurrent pneumonia. Common symptoms include cough, fever, chest pain, and sometimes hemoptysis. Digital clubbing, cyanosis, and congestive heart failure have been reported when there is a significant shunt from the systemic arterial to pulmonary venous systems within the ILS.

Patients with ELS are often diagnosed in infancy (or prenatally with fetal ultrasonography), because of the presence of other congenital anomalies, most commonly diaphragmatic hernia. If not diagnosed during infancy, ELS can go undetected or can be found incidentally in asymptomatic adults. Rarely, infection, hemothorax, and right heart failure occur. Chest pain and bloody pleural effusion have been reported in patients with twisting of an ELS resulting in torsion and infarction.

What other disease/condition shares some of these symptoms?

There are many congenital and acquired pulmonary masses that mimic BPS. Identification of a feeding artery to the mass is the best indication that it may be a BPS.

Congenital cystic adenomatoid malformation (CCAM) of the lung: If air is present within a BPS, the mass may have a radiographic appearance similar to that a CCAM. Also, hybrid congenital lung masses with features of both have been described.

Bronchogenic cyst: The typical location in the middle mediastinum, possible connection to the tracheobronchial tree, and lack of a feeding systemic vessel distinguish bronchogenic cyst from BPS.

Isolated congenital diaphragmatic hernia: ELS will often be associated with a diaphragmatic hernia.

Chronic infection secondary to retained foreign body: Retained foreign body with chronic infection may also lead to the development of some cases of ILS (see below).

Pulmonary arteriovenous malformation (PAVM): Because PAVM may be seen as a lung mass with associated systemic vessels on imaging, differentiation from BPS radiographically may be difficult. However, the presenting symptoms of a child with PAVM will help to differentiate PAVM from BPS.

Lung abscess: Be aware that an infected BPS may also present with abscess formation.

Pneumonia with or without atelectasis: Recurrent pneumonia in the same area of a lower lobe of the lung should trigger a work-up for a congenital malformation of the lung such as BPS if other causes (such as retained foreign body or other cause of bronchial obstruction, or isolated bronchiectasis) are ruled out.

Neuroblastoma or other neoplasm (e.g., pleuropulmonary blastoma): The differentiation of BPS from a neoplastic thoracic/lung tumor is essential in asymptomatic patients in whom surgical exicision is deferred.

Pulmonary hamartoma, teratoma

Enteric/esophageal duplication cyst

What caused this disease to develop at this time?

The cause of BPS is controversial, although the most common opinion is that both ILS and ELS arise from an abnormal accessory lung bud off of the primitive foregut. Some cases of ILS may develop as a result of chronic infection of a specific part of the lung from bronchial obstruction (such as foreign body aspiration). Enlargement and parasitization of assocated systemic arteries present in the pulmonary ligament or, alternatively, neovascularization of the affected portion of lung then occurs.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

The diagnosis of BPS is made primarily by imaging studies (see below).

Would imaging studies be helpful? If so, which ones?

Chest Radiography: Often, a BPS is first noted as a density in a lower lobe on a plain chest radiograph. Typical findings of an ILS include a solid or cystic density, with air-fluid levels noted in some cases. ELS will most often be of uniform/solid density and triangular or oval. . Confirmation that the density on a chest radiograph is likely a BPS is dependent on the identification of a systemic feeding artery by other imaging studies or direct surgical visualization.

Ultrasonography: BPS may be seen as a uniformly echogenic mass on a prenatal ultrasonogram; after birth, BPS may have a homogeneous or cystic appearance on ultrasonography. Also, ultrasonography may be helpful in identifying an abnormal systemic feeding vessel to the mass, supporting a diagnosis of BPS.

Computed tomography (CT): CT provides excellent images ,and CT with intravenous contrast may identify the feeding vessel associated with a BPS. ELS will be seen as a homogeneous mass lesion (Figure 1), whereas ILS may be homogeneous or hetergeneous. Cavitation and air-fluid levels may also be seen with ILS.The primary disadvantage is the dose of ionizing radiation exposure associated with CT. Imaging with CT should be done using ALARA (as low as reasonably achievable) guidelines for radiation dose exposures. A useful website for providers and families regarding radiation safety in pediatric imaging is http://www.pedrad.org/associations/5364/ig/index.cfm?page=610.

Figure 1.

View of the base of an ELS demonstrating the feeding vessel.

Magnetic resonance imaging (MRI): The lack of ionizing radiation exposure with MRI is the primary advantage of MRI over CT. MRI may be useful in identifying a feeding systemic vessel and the venous drainage of the BPS. However, MRI images of the BPS will be less detailed than those obtained with CT, and the prolonged scanning times with MRI may require the use of sedation in younger children.

Radionuclide scans: These scans are generally not useful in evaluating BPS. In certain cases, radionuclide angiography may add information regarding evidence of a feeding artery to the area of a BPS. With ventilation scans, the lack of a direct connection with the tracheobronchial tree results in no uptake with the initial inhalational phase. Collateral airway channels may then result in delayed uptake.

Angiography: The advances in CT, MRI, and ultrasonographic technologies have supplanted the need for digital subtraction angiography (DSA) in most patient with BPS. DSA may be useful when BPS is still strongly suspected but an abnormal feeding vessel could not be identified with CT, ultrasonography , or MRI. Other instances in which DSA may be useful are if the exact locations of the arteries and veins associated with the lesion are needed for safe excision, or if embolization of the feeding vessels is being considered.

Upper gastrointestinal study with contrast: In the rare instance of air within a BPS, this study may be useful in evaluating for a connection with the stomach or esophagus.

Bronchography: This modality is rarely used at present given the advances in other imaging techniques.

If you are able to confirm that the patient has a bronchopulmonary sequestration, what treatment should be initiated?

Surgical excision is recommended for patients with BPS who are symptomatic. Neonates may be symptomatic from mass effect of the BPS on normal lung tissue or from congestive heart failure. Some have advocated embolization or ligation of the feeding artery in infants with congestive heart failure, although this may predispose the infant to recurrent infection of the remaining infarcted BPS.

Older patients may become symptomatic from a previously undetected ILS because of recurrent infection. Often, lobectomy is required with ILS excision, whereas ELS usually can be removed without disruption of the normal lung. Thoracoscopic resection has been used for both ILS and ELS.

There is controversy regarding the optimal course of action in patients with asymptomatic BPS. Many advocate surgical excision for all patients discovered to have a BPS because of the possibility of future complications such as pneumonia or abscess formation. Others advocate elective excision for asymptomatic patients with ILS, because of the likelihood of recurrent infection, and cautious observation in patients with asymptomatic ELS in which there is no known connection to the normal airways of the lung. Therefore in asymptomatic children with BPS, a thorough discussion with parents regarding the pros and cons of excision versus cautious observation is necessary to come to a decision that is most appropriate for the individual patient.

What are the adverse effects associated with each treatment option?

Although the vast majority of patients who undergo surgical excision of BPS do very well without complications, inadvertent division of the systemic artery during resection may lead to potentially lethal hemorrhaging. Therefore vessels (arteries and veins) associated with the mass should be as well characterized as possible with imaging studies before surgery (Figure 2). There have been reports of embolization being performed before resection to reduce this risk of significant bleeding.

Figure 2.

Coronal (A) and axial (B) CT scan demonstrating a teardrop-shaped ELS of homogeneous attenuation in the lower posterior left hemithorax of a 4-year-old boy.

Other potential complications of surgery include the development of bronchocutaneous or bronchopleural fistulas, postoperative emphysema, pneumothorax, and hemothorax. Patients with ELS who have other associated congenital abnormalities such as diaphragmatic hernia or cardiac or gastrointestinal anomalies may be at heightened risk for complications with surgery.

If a BPS is not excised in an asymptomatic patient, the primary risk is infection of the sequestration, sometimes serious and/or recurrent. Other reported complications include bleeding/hemoptysis, pneumothorax, congestive heart disease, and cystic changes.

In general, BPS is not felt to undergo malignant transformation if left undisturbed in an asymptomatic patient. However, some congenital cystic lesions have features of both BPS and CCAM ("hybrid lesions"), and pleuropulmonary blastoma has been reported in patients with CCAM.

What are the possible outcomes of bronchopulmonary sequestration?

In a symptomatic patient discovered to have BPS, surgical excision typically results in an excellent outcome and cure rate. See above for risks/benefits of observation without excision in asymptomatic patients.

What causes this disease and how frequent is it?

The cause of ELS and ILS is controversial. ELS may be the result of an abnormal accessory lung bud off the foregut. ILS may also be the result of an accessory lung bud (later in embryogensis than ELS), but some ILS may be the result of chronic localized inflammation or infection of the lung such as with retained foreign body aspiration.

No genetic predisposition to the development of BPS has been proved, although there have been rare case reports of this condition occurring within families.

The true incidence of BPS in the general population is not known. One report stated that BPS represents between 0.15% and 6.4% of all congenital pulmonary malformations. ILS accounts for 75%-90% of all cases of BPS. There is no gender preference with ILS; most authors state that ELS is three or four times more common in males than in females.

Other clinical manifestations that might help with diagnosis and management

Advances in prenatal ultrasonography and MRI have made prenatal diagnosis of BPS more common. As in postnatal cases, the establishment of a fetal intrathoracic mass as a BPS is primarily dependent on identification of a systemic feeding artery by these imaging techniques. Similar to CCAM, BPS discovered in a fetus may spontaneously resolve on subsequent imaging studies (usually ultrasonography) in early infancy. Fetal surgery may need to be considered if complications such as hydrops or polyhydramnios pose a significant risk to the viability of the fetus.

ELS has been reported below the diaphragm.

There are instances when a BPS is suspected, but definitive diagnosis by imaging is lacking because a systemic feeding vessel cannot be clearly identified. In these cases, surgery may be the only manner in which to establish the diagnosis of an unidentified lung mass. As an example, torsion and subsequent infarction of an ELS is a rare complication that may be difficult to diagnose. Patients present with chest and/or abdominal pain and a pleural effusion that is often bloody. Cessation of blood flow resulting from the torsion results in an inability to identify a feeding systemic vessel by imaging. Surgery (open or thoracoscopic) is usually indicated for definitive diagnosis of the mass and cure by excision.

What is the evidence?

What are some useful references?

Abbey, P, Das, CJ, Pangety, GS. "Imaging in bronchopulmonary sequestration". J Med Imaging Radiat Oncol. vol. 53. 2009. pp. 22-31.

(A good review of BPS, with emphasis on imaging guidelines. The authors also review the pathogenesis, clinical presentation, and pathologic features of ELS and ILS.)

Halkic, N, Cuénoud, PF, Corthésy, ME. "Pulmonary sequestration: a review of 26 cases". Eur J Cardiothorac Surg. vol. 14. 1998. pp. 127-33.

(A review of this center's experience with this rare condition. Twenty-six cases in children and adults are reviewed and discussed.)

Laberge, JM, Puligandla, P, Flageole, H. "Asymptomatic congenital lung malformations". Semin Pediatr Surg. vol. 14. 2005. pp. 16-33.

(The authors weigh in on the controversy of observation versus surgical excision in asymptomatic patients.)

Uchida, DA, Moore, KR, Wood, KE. "Infarction of an extralobar pulmonary sequestration in a young child: diagnosis and excision by video-assisted thoracoscopy". J Laparoendosc Adv Surg Tech A. vol. 20. 2010. pp. 399-401.

(Description of a rare complication of ELS and brief review of previously reported cases.)

Ongoing controversies regarding etiology, diagnosis, treatment

The primary controversy involves whether surgical excision should be performed in an asymptomatic infant or child with a BPS. See above for discussion.

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