Congenital Bronchopulmonary Malformations Flashcards
Which of the following correctly describes a pulmonary sequestration?
A. Vascular connections are to the pulmonary artery and vein
B. Is a result of air trapping due to minimal expulsion of air with exhalation
C. Can be located both extralobar and intralobar
D. Communicates with the bronchial tree
E. Has minimal risk of infectious complications
ANSWER: C
COMMENTS: Bronchopulmonary sequestration (BPS) is characterized by nonfunctional pulmonary tissue that has an anomalous systemic vascular supply and does not communicate with the bronchopulmonary tree.
BPSs can be either intralobar, within the actual lung parenchyma, or extralobar, which are completely separate from the lung.
In fact, BPS may be found anywhere within the chest or even below the diaphragm. It is often identified on prenatal ultrasound as a well-defined mass.
If it is not detected prenatally, the typical presentation is with recurrent pneumonia within the BPS.
There is an increased risk for malignant transformation.
Surgical resection is generally recommended.
Other lung malformations include congenital pulmonary airway malformation (CPAM) and congenital lobar emphysema (CLE).
Congenital cystic lung lesions are usually CPAM. This entity was formally termed congenital cystic adenomatoid malformation (CCAM) but was renamed because cystic components are not always present.
There are five subtypes of CPAM: 0, affecting the proximal lung; 1 to 3, varying sizes of cysts from large to smallest; and 4, peripheral lung cysts.
A CPAM is connected to the bronchopulmonary tree, and its blood supply is from the pulmonary arteries and veins.
These lesions most commonly arise from the lower lobes of the lungs and can be identified on prenatal ultrasound.
As with BPS, CPAMs may become infected and present as recurrent pneumonia and have a risk for malignant transformation.
Surgical resection is generally recommended.
CLE is the third lung abnormality in this group.
Normal lung parenchyma becomes hyperinflated because of impaired expulsion of air on exhalation.
This is due to either an obstruction of the feeding bronchus from dysplastic bronchial cartilages or extrinsic compression.
Management is lobar resection.
Discuss congenital lung malformations.
This chapter discusses the major pearls and tricks in the diagnosis and management of congenital lung lesions, which include congenital pulmonary airway malformations, bronchogenic cysts, bronchopulmonary sequestrations, and congenital lobar emphysema.
Collectively, congenital lung malformations can be uniquely challenging for pediatric surgeons in part because they are rarely encountered in most clinical practices and often require multi-disciplinary expertise, including maternal-fetal medicine specialists, neonatologists, and pediatric radiologists.
Moreover, lung lesions can have highly variable clinical presentations and unclear natural histories.
The current standard of care for the most common clinical scenarios is discussed, and specific areas of controversy are highlighted.
What are the four major types of lung malformations?
The four major types of lung malformations are:
[1] congenital pulmonary airway malformation (CPAM), formerly congenital cystic adenomatoid malformation;
[2] bronchopulmonary sequestration (BPS);
[3] congenital lobar emphysema (CLE); and
[4] bronchogenic cyst.
What are the main differences between congenital pulmonary airway malformations (CPAM) and bronchopulmonary sequestrations (BPS)?
CPAMs communicate with airways of the native lung and have a vascular supply derived from the pulmonary circulation.
In contrast, BPS lesions are non-aerated lung tissue that has a large systemic arterial blood supply, often coming directly
off of the aorta.
What are the two major types of bronchopulmonary sequestrations and how do you tell the difference between them on postnatal cross-sectional imaging?
BPS lesions are classified as intralobar (75%) or extralobar (25%).
Intralobar BPS is entirely invested with the visceral pleura with venous drainage usually to the pulmonary venous system.
In contrast, extralobar BPS represents accessory pulmonary lung tissue that is invested in its own pleural lining that is completely separate from normal lung parenchyma.
Extalobar BPS usually has both a systemic arterial and venous blood supply.
What is the most common anatomic locations for each of the lung malformations?
Most CPAM and BPS lesions are located in one of the lower lobes of the lung.
CLE most commonly involves the left upper lobe.
The second most common site is the right middle lobe.
Bronchogenic cysts tend to be centrally located within the mediastinum in the paratracheal or subcarinal regions.
What are hybrid lung lesions?
Hybrid lung lesions have characteristics of at least two different types of lung malformations.
The most common hybrid lesion is a CPAM with a systemic arterial blood supply.
This is seen in approximately 9–25% of all resected lung malformations.
How common are congenital lung malformations?
Recent reports suggest that the incidence has been increasing and may be approximately 1 in 2,500 live births.
The increasing incidence is likely secondary to wide- spread prenatal screening by ultrasound as well as improvements in sonographic image quality.
How are CPAMs usually diagnosed?
Lung malformations can have a highly variable clinical presentation.
However, the majority of CPAM and BPS lesions (>75%) are now diagnosed during fetal life as an echogenic lung mass.
How can congenital lung malformations affect the developing fetus?
Large lung malformations can compress the esophagus, resulting in impaired fetal swallowing and polyhydramnios.
Analogous to the situation in congenital diaphragmatic hernia, mass effect may also lead to pulmonary hypoplasia and pulmonary hypertension.
Rarely, the mass can impair venous return to the heart and lead to hydrops, in which fluid accumulates in body cavities in conjunction with generalized skin edema.
In severe cases of hydrops, placentomegaly and right heart failure are signs of impending fetal demise.
Are fetal lung lesions associated with other birth defects?
In greater than 90% of cases, a fetal lung malformation is an isolated finding, and screening for karyotype anomalies is not indicated.
You are asked to counsel a pregnant woman carrying a 21-week fetus with a lung malformation identified on ultrasound. What imaging information are most important in terms to determining the potential morbidity of the lesion at birth?
The most important characteristic is its relative size, most often measured in terms of the CVR (CPAM volume ratio). It is the volume of the CPAM mass normalized for gestational age.
CVR = (L x W x H x 0.52) / head circumference
Serial monitoring of the CVR is required because many of these lesions increase in size until 26 weeks.
Fetuses with lesions with a CVR less than 0.9 are usually born asymptomatic and can be delivered at the birthing center of the family’s choosing.
However, lesions with a CVR greater than 0.9 are at increased risk for respiratory symptoms at birth, and these fetuses should probably be delivered at a tertiary care referral center with pediatric surgery coverage.
A CVR > 1.6 or a CPAM with a dominant large cyst increases risk of developing hydrops. Lesions with a CVR of > 1.6 may be followed 2 to 3 times per week.
Other characteristics on ultrasound that may influence the delivery plan include the presence of mediastinal shift and macrocystic disease.
What is the Stocker classification?
The Stocker classification scheme* was the original description of CPAMs based on pathologic specimens.
Type I lesions have macrocysts, and type III lesions are solid or microcystic.
Type II lesions have a mixed of both microcysts and macrocysts.
—
The classification of CPAM type based on cyst diameter on histology, as originally defined by Stocker, has been largely replaced by the simple separation of lesions into microcystic (cysts <5 mm) and macrocystic (cysts ≥5 mm), based on prenatal and postnatal imaging.
This classification has clinical utility and helps define the therapeutic options for symptomatic lesions.
For example, microcystic CPAM typically appears solid on ultrasound, is more likely to become symptomatic during fetal life, and is more likely to respond to maternal steroid treatment.
Sherif
A pregnant woman is carrying a 23-week fetus with a microcystic lung malformation. The ultrasound shows a CVR of 2.5, and there is ascites. What are some potential management options for this fetus?
Lesions with a CVR greater than 1.6 are at increased risk for hydrops.
The first line of therapy is the administration of maternal betamethasone.
Other options include fetal resection, which is uncommonly performed and associated with high mortality.
If the lesion has a large, dominant macrocyst, fetal thoracocentesis or thoracoamniotic shunting can be helpful to reduce the mass effect of the lesion.
In near-term fetuses, another option is to resect the lesion while still on placental support, otherwise known as ex utero intrapartum treatment (EXIT)-to-resection.
Can fetal CPAMs regress in size prior to delivery? What about postnatal regression of a CPAM identified on CT?
Many CPAMs regress in size during the third trimester of pregnancy.
Other microcystic CPAMs can become isoechoic with the adjacent lung tissue by ultrasounds after 32 weeks of gestation.
Therefore, these lesions can be difficult to visualize in utero but are usually subsequently identified on postnatal cross-sectional imaging.
For this reason, all fetal lung malformations, regardless of whether they have “disappeared” on subsequent fetal sonograms, should undergo postnatal chest CT, usually at 2–3 months of age [3].
Postnatal regression of a CPAM is a controversial topic, but most investigators believe that complete regression after a child is born is extremely rare.
You are called to the neonatal intensive care unit to see a 6-hour old neonate in respiratory distress. Chest x-ray shows mediastinal shift to the right hemi-thorax and a hyperlucent left chest. How would you manage this patient?
This child has a left upper lobe CLE and should go to the operating room in an expeditious manner in preparation for a thoracotomy and left upper lobectomy.
If the baby is in extremis, a bedside thoracotomy with exteriorization of the affected lung can be a life-saving maneuver.
Intubation should generally be avoided because positive pressure can exacerbate air trapping.
Describe the basic steps involved in a neonatal lung resection for a CPAM.
A thoracotomy with formal lobectomy represents the standard of care in neonates.
Lung isolation is not required.
Since most of these lesions involve one of the lower lobes, the inferior pulmonary ligament is divided.
If this is a hybrid lesion, any systemic feeding vessels are identified and controlled with clips, energy devices, or ligatures.
The pulmonary arteries and veins are identified and controlled in similar fashion.
The bronchus to the affected lobe is taken last using clips, staplers, or ligatures.
A chest tube is left in place to help with lung re-expansion and to evacuate pleural fluid.
A newborn with a prenatally diagnosed lung malformation was born several hours ago. She appears to be in no respiratory distress and has a normal physical exam. What are the next steps?
This patient can be discharged in 24–48 hours.
Plain film radiographs of the chest are often performed as a baseline study.
However, even if the plain film is completely normal, a chest CT is indicated because of the low sensitivity of plain films.
Most referral centers do not perform a chest CT until a child is at least 2 months old in order to obtain the best images for preoperative planning purposes.
MRI avoids the ionizing radiation of CT, but is not the preferred imaging modality because it requires sedation to minimize motion artifacts and gives inferior resolution of the lung parenchyma.
A four-month old healthy child with a small, asymptomatic CPAM on CT comes to your office. Would you recommend surgical resection? If so, why and when would this be performed? If not, why not?
Although there are no well-designed, prospective studies on the natural history of CPAMs, early surgical resection of a CPAM has been the preferred management strategy in the USA.
The median age at resection is about 5–6 months of age.
The rationale for prophylactic lung resection is to prevent pneumonia and other complications.
Earlier resection has also been embraced since the resection may be easier given that subclinical infection and inflammation have yet to occur.
Early resection may also allow for maximal compensatory lung growth.
Other pediatric surgeons cite a small, but defined risk for malignant degeneration.
Finally, the optimal frequency and best imaging approach to monitor unresected CPAMs has not been defined.
Opponents of early surgical resection argue that the risk of pneumonia in selected CPAMs may be as low as 5%.
Since some lesions may regress and most may never become symptomatic, it may be difficult to justify performing an operation that can have its own complications, including massive hemorrhage and prolonged air leak.
Moreover, the cancer risk is believed to be very small, especially in prenatally diagnosed lesions.
There are also concerns about the possible long- term neurotoxic effects of anesthesia in younger children.
What is pleuropulmonary blastoma?
Pleuropulmonary blastoma (PPB) is a rare malignant primary cancer of the lung.
Type 1 PPB presents at a mean age of about 9 months and can be confused with macrocystic CPAM by chest CT.
As a result, many surgeons strongly urge resec- tion of all CPAMs for fear of inadvertently observing PPB.
The treatment of PPB involves a gross total resection and chemotherapy.
Roughly a third of PPB lesions are associated with the DICER1 mutation, a gene defect with increased susceptibility to ovarian and kidney tumors.
—
Another argument that supports resection of asymptomatic lesions is the coexistence of malignancy in a CPAM or malignant degeneration of a CPAM lesion.
The exact incidence of lung cancer associated with CPAM is not known, but some studies showed that up to 5% of CPAM lesions may contain malignant elements.
A lesion that may be difficult to differentiate from CPAM is pleuropulmonary blastoma (PPB), as shown in the case depicted in Figures 9.12 through 9.14.
This patient was a baby girl who had a small, wedge-shaped, fluid-filled mass identified on 21-week fetal ultrasound.
At 31 weeks, it appeared bi-lobed, but had not increased much in size, as shown in Figure 9.12.
The patient had no symptoms at birth or after.
The chest x-ray at 2 days of age showed nonspecific haziness in the left upper lobe but, at 2 weeks, demonstrated an impressive air-filled cyst with mediastinal shift. A CT scan demonstrated large, dominant, peripheral cysts, a finding typical of PPB on imaging.
The patient underwent early left upper lobectomy, with the findings noted on Figure 9.13.
A type I PPB was confirmed on pathology, as shown in Figure 9.14. The large cystic areas were lined by alveolar and respiratory epithelium overlying a loose to dense fibrous stroma, containing primitive small cells in a cambium-like layer beneath the epithelium.
Of note, many pathologists now consider all Stocker type 4 CPAMs to be PPB, until proved otherwise.
The patient was followed closely and has done well, with no further lesions identified on 7-year follow-up.
The patient also underwent screening of her kidney and spleen for synchronous lesions, as well as genetic consultation and testing for DICER-1 mutation, all of which were negative.
This is the most favorable presentation of PPB.
Patients who present later with type II (cystic and solid) and type III (solid) PPB typically require adjuvant chemotherapy and have less favorable prognoses.
There is strong evidence that type I PPB will progress over time to types II or III.
Sherif
What is the best operative approach for an asymptomatic congenital lung malformation in an infant?
There remains debate on the best operative approach.
The traditional operative approach in infants is an open (thoracotomy) incision, which is safe, well-tolerated, and associated with a three-day hospital stay.
A muscle-sparing approach has been adopted by many pediatric surgeons to help minimize musculoskeletal morbidity, including scoliosis.
More recently, minimally invasive (thoracoscopic) approaches have gained traction since they result in smaller scars and obviate the need for an epidural catheter to attain good postoperative pain control.
However, thoracoscopic surgery necessitates effective lung isolation, is associated with a relatively steep learning curve despite ongoing refinements in surgical instrumentation, and has generally longer operative times.
Hospital lengths of stay are similar or only marginally shorter after thoracoscopic resection [5].
Is there a role for segmentectomy or wedge resection in the surgical man- agement of CPAM?
Yes, there is a small and limited role for lung preserving resections in selected patients with lung malformations.
Routine use of segmental or wedge resections has generally been discouraged because of increased risk of parenchymal leak from the cut surface of the lung as well as concerns regarding leaving residual disease behind.
However, those with bilateral disease (1–2%) or CPAMs involving multiple lobes on the same side might benefit from segmental or wedge resection.
Those with lung function that is already compromised (e.g., bronchopulmonary dysplasia) may also be ideal candidates.
How do you manage a child with an intralobar BPS?
Children with intralobar BPS are at increased risk for pneumonia and high-output cardiac failure because of chronic shunting of blood through a large systemic feeding artery.
For these reasons, surgical resection is indicated.
How do you manage a child with a small extralobar BPS?
The management of small extralobar BPS lesions is controversial given that they are not contiguous with the native lung and therefore less likely to become infected.
Opinions on management vary amongst pediatric surgeons and range from observation to catheter embolization to thoracoscopic resection.
What are the histologic features of bronchogenic cysts? How would you manage a child with an asymptomatic bronchogenic cyst identified by CT scan?
Bronchogenic cysts contain cartilage and ciliated columnar epithelium.
Most should be excised before complications (e.g., airway obstruction, abscess) ensue.
If complete surgical excision is not possible without causing damage to adjacent mediastinal structures, then other options include sclerotherapy or de-epithelialization.
Criteria for cystic adenomatoid malformation (CCAM) type III is:
A. Multiple larger cysts greater than 5 cm.
B. Multiple larger cysts greater than 3 cm.
C. Multiple larger cysts greater than 2 cm.
D. Multiple cysts smaller than 2 cm.
E. Multiple cysts smaller than 0.5 cm.
E
In type III cystic adenomatoid malformation the entire lobe is infiltrated with bronchiole-like structure usually smaller than 0.5 cm in diameter.
Syed/MCQ
