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Updates in: Congenital Lung Lesions

Jonathan Durell, Kokila Lakhoo

Department of Pediatric Surgery, Oxford Children’s Hospital, Oxford, United Kingdom

 

Correspondence:

Kokila Lakhoo Department of Paediatric Surgery

Oxford University Hospitals

John Radcliffe Hospital

Headley Way Oxford, United Kingdom OX3 9DU

Tel: +44 1865 234197

Fax: +44 1865 234211

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Abstract

Congenital lesions of the lung comprise a spectrum of pathologies that in current times are detected on the standard antenatal anomaly ultrasound. An understanding of the underlying pathology, its consequences, and the surgical management are essential to the successful management of these children. This manuscript provides information regarding the aetiology, investigation, and management of the spectrum of congenital pulmonary airway malformations and congenital chylothorax.

Keywords: congenital pulmonary airway malformations, pulmonary sequestration, lobar emphysema, bronchogenic cyst, congenital chylothorax

 

Introduction

With the advancements in antenatal ultrasound and increasing sensitivity of detecting congenital lesions, there is abundant literature regarding classification systems and management algorithms. The management of a newborn with a symptomatic congenital lung lesion is well documented with regards to surgical intervention, whereas the management of the asymptomatic lesion can be quite controversial. Congenital cystic lung lesions include congenital pulmonary airway malformations (CPAMs), bronchopulmonary sequestration, congenital lobar emphysema, and bronchogenic cyst. In this paper we aim to discuss these various congenital anomalies, their backgrounds, investigations, and the management. We will also discuss the management of congenital chylothorax.

Congenital pulmonary airway malformation

The congenital pulmonary airway malformation (CPAM) (Fig.1) presents as a multicystic lesion that is usually isolated to one side and within a single lobe. Virtually all CPAMs nowadays are detected on the 20 week antenatal ultrasound. These multicystic lesions represent areas of over-proliferation and dilatation of terminal bronchioles with abnormal development of alveoli. CPAMs do not favour sex, ethnicity, or laterality of lung. There is a reported incidence of between 1 in 8,300 and 1 in 33,000 births [1]. These intra-pulmonary lesions communicate with the trachea-bronchial tree and the blood supply is derived from the normal supply to the surrounding lung tissues.

Figure 1. Left congenital pulmonary airway malformation

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There have been two classifications developed to describe CPAMs. The Stocker classification (Table I) is a histopathological description of the lesion. The lesion is stratified amongst five categories based on cyst size and type of epithelial lining. There is an association between Stocker classification type 1 and type 4 and development of tumours. Type 1 has been linked to bronchoalveolar carcinoma and type 4 associated with pleuropulmonary blastoma [2]. The Adzick classification is based on antenatal ultrasound findings and divides the CPAM into either macocystic (>5mm cysts) or microcystic (<5mm) cysts (Table II). An association exists between the microcystic group and increased risk of development of hydrops fetalis, which portends a poor outcome.

Table 1. Stocker Classification

Type

Histological Features

Prevalence

0

Involvement of all lung lobes, stillborn

< 2%

1

Single or multiple cysts >2 cm, pseudostratified columnar epithelium

60-70%

2

Single or multiple cysts <2 cm, cuboidal or columnar epithelium

15-20%

3

Predominately solid lesions, <0.5 cm cysts, cuboidal epithelium

5 – 10%

4

Large air-filled cysts, flattened epithelial cells

<10%

 

Table 2. Adzick Classification

Type

Ultrasound Features

Prevalence

Macrocystic (Type 1)

Single or multiple cysts >5 mm

58%

Microcystic (Type 2)

Single or multiple cysts <5 mm

42%

 

Once detected on antenatal ultrasound, regular monitoring of the lesion is mandatory due to the potential of fetal comprise secondary to mass effect from an enlarging lesion. Calculating the volume of the CPAM compared to the head circumference can predict an 80% increased risk of developing hydrops fetalis if the ratio is >1.6. When the ratio is less than 1.6, there has been found a survival rate of 94% and < 3% risk of developing hydrops fetalis [3]. Fetal interventions include thoracocentesis, thoracoamniotic shunt, percutaneous laser ablation, and open surgery for those expanding lesions leading to fetal compromise. A review of fetal intervention in CPAM found the fluid within the CPAM rapidly reaccumulated following thoracocentesis, therefore this procedure did not confer a long-term solution and that open fetal surgery resulted in 50% fetal demise [4].

Spontaneous resolution of these lesions has been reported; therefore a post-natal chest CT scan is performed to investigate the persistence and anatomic relations of the antenatal diagnosed CPAM. It has been shown that the chest x-ray is only 61% sensitive in detecting persistent lesions, whereas chest CT was 100% sensitive [5] There are multiple opinions throughout literature and differing protocols between institutions regarding the timing of post-natal imaging. Our local policy is to perform a chest CT at 1 month of age without a general anaesthetic (feed and wrap technique) with clinical assessment and discussion with parents by 2 months of age. If surgical intervention is deemed appropriate, this is performed at 3 to 6 months of age.

The recommendation of surgical intervention by 6 months of age in the asymptomatic child has been determined to be safe, well tolerated, there is a decreased risk of developing infection within the CPAM, and more time allowed for compensatory lung growth compared to performing the surgery at a later time in childhood [5].

In the symptomatic newborn with an antenatal diagnosis of CPAM, an emergency chest CT should be performed to delineate the size and anatomy of the lesion and a segmentectomy, lobectomy, or pneumonectomy should be performed, as per the CT and inter-operative findings.

The main area of controversy in the management of CPAMs is in what to do with the asymptomatic child with a proven lesion. The reasoning behind conservative management is that there is a lack of knowledge about natural history of these lesions due to the absence of prospective studies determining the outcome of conservatively managed CPAMs. There is also the argument that the risk of malignancy is low and that with long term follow up those children predisposed to eventually having a surgical intervention can be identified and the risks of operating on every child can be averted [6]. Recently, there has been advocated the use of screening for DICER1 germline gene mutations because of its association with pleuropulmonary blastoma, with the reasoning that a child with a negative mutation screen, no family history, and absence of multifocal or bilateral disease can be kept safely under observation [7].

The counter argument to this reasoning is that there is a risk of developing recurrent infections (pneumonia / lung abscess / empyema) and, albeit a low risk, may develop carcinoma within the lesion. There have been reports of bronchoalveolar carcinoma, pleuropulmonary blastoma, and rhabdomyosarcoma occurring within CPAMs [8]. Also, there has been reported a significantly longer procedure time and increased intra-operative blood loss when performing CPAM excision following pneumonia [8].

The approach to surgical intervention can be open via thoracotomy or using minimally invasive techniques in thoracoscopy. There have been published multiple case series and a meta-analysis to determine whether open or minimally invasive resection of CPAMs has better outcomes. Within individual case series, it was determined that although the length of procedure is longer there were similar overall complication rates, shorter intensive care stay, shorter duration of chest drain, and shorter hospital stay. The meta-analysis concluded that thoracoscopy was safe, feasible, and that there were no significant differences in length of procedure or complication rate. It also found that there was a shorter length of hospital stay and shorter duration of chest drain [9].

Bronchopulmonary sequestration

A bronchopulmonary sequestration (BPS) (Fig. 2) is a mass of lung tissue that is found in isolation from the surrounding lung and has no connection to the trachea-bronchial tree. BPS accounts for up to around 6 percent of all congenital pulmonary lung malformations [10] and is typically diagnosed on antenatal ultrasound and can be difficult to distinguish from a CPAM unless the arterial blood supply is traced. Although the venous drainage of these lesions may share the same vessels as the surrounding lung, the arterial blood is derived from a systemic source. In most cases the arterial blood is derived from the thoracic or abdominal aorta; however, the blood can be supplied from the subclavian, mammary, renal, splenic, or pulmonary arteries. This lesion is thought to derive from an accessory lung bud and is an embryologic developmental anomaly. BPS can be anatomically categorised as either intralobar (75%) or extralobar (25%). Intralobar BPS is located within normal lung tissue and lacks a visceral pleura, whereas extralobar BPS is located outside the normal lung and has its own visceral pleura [11].

Figure 2. Right bronchopulmonary sequestration

10.3.3 2

The majority of extralobar BPS is found within the thorax, however they can also be found below the diaphragm. Most often these lesions present as respiratory distress within the first month of life, however they can also present as chronic cough, recurrent infection, and abdominal pain in later childhood. Majority of these lesions will be associated with another development anomaly such as congenital diaphragmatic hernia, CPAM, congenital lobar emphysema, bronchogenic cysts, and cardiac anomalies [12].

Intralobar BPS usually presents as recurrent pneumonia throughout childhood. There is a predilection for affect the medial and posterior basal segments of the lower lung lobes and the arterial supply is typically derived from the lower thoracic or upper abdominal aorta. Bronchopulmonary sequestrations appear as a defined homogenous mass on postnatal ultrasound. Antenatal ultrasound may demonstrate either a small lesion or a lesion that occupies a significant proportion of the hemithorax. The mass effect from the lesion can lead to development of hydrops fetalis. Much the same as CPAMs, postnatal imaging should be performed to confirm the persistent postnatal presence of the lesion. Unfortunately, no one modality of imaging supplies all the necessary information a surgeon requires prior to excision of this lesion. Doppler ultrasound can map the blood supply of the lesion but cannot provide detailed anatomical information, whereas CT can provide the anatomical information but is not ideal for mapping the venous and arterial vessels. Magnetic resonance has the capability of mapping the blood supply to and from the lesion but requires a general anaesthetic and is lacking in defining thin-wall cysts and emphysematous changes. Therefore a combination of these imaging modalities may be necessary prior to planning an operative intervention [12]. The symptomatic lesion requires excision. The excision of an extralobar BPS is thought to be a relatively easier procedure as the tissue mass is enveloped within its own pleura and therefore the tissue planes are easier to dissect from the affected lobe. Intralobar BPS tends to be more difficult following infection due to the destruction of tissue planes and, therefore, often a lobectomy is necessary to confidently excise the lesion [13]. Again, as with CPAMs, there is controversy with the management of the asymptomatic, antenatally diagnosed BPS. The controversy lies in the natural history of these lesions. Some surgeons elect to follow the lesion with serial follow ups, whereas others prefer to excise the lesions due to risk of overt haemorrhage and infection. Aside from either open or minimally invasive options for treatment, there is emerging the third option of interventional radiology. Through the use of various devices and substances, the feeding vessel is occluded with the theory that the lesion should involute.

Congenital lobar emphysema

Congenital lobar emphysema (CLE) (Fig. 3), also known as congenital lobar overinflation, is a condition in which there is air-trapping and hyperinflation of one or more pulmonary lobes. Half of cases of CLE have no identifiable underlying cause, whereas in 50% the anomaly can be attributed to either an intrinsic or extrinsic pathology. The intrinsic pathologies leading to air-trapping may include dysplastic or deficient bronchial cartilage, inspissated mucous, mucosal proliferation, or bronchial occlusion from either torsion or atresia. Extrinsic causes produce CLE by compression of the bronchi by entities such as blood vessels, lymph nodes, cysts, polyalveolar lung, or focal pulmonary hypoplasia [14].

Figure 3. Congenital lobar emphysema/overinflation

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Presentation of the child with CLE can include neonatal respiratory distress, simple or tension pneumothorax, wheeze, or atelectasis. CLE may also be an incidental finding on chest x-ray performed for other reasons in the asymptomatic patient. The surgeon must always be cautious in mis-interpreting the CLE as a pneumothorax and placing a chest drain into the lesion. Management of the patient with CLE is dependent upon symptoms. In the symptomatic patient, intervention to treat the either intrinsic or extrinsic underlying pathology can be curative, with often a lobectomy being required. In the asymptomatic or mildly symptomatic patient, the child can be treated expectantly [12].

Bronchogenic cyst

Bronchogenic cysts represent an anomaly of bronchial budding within the embryonic foregut. They are usually single, unilocular cysts filled with fluid or mucous and found principally within the mediastinum, although they may occur within the lung parenchyma, pleura, or diaphragm [15]. The bronchogenic cyst is typically lined with pseudostratified ciliated columnar respiratory epithelium and contains hyaline cartilage and there is no communication with the tracheobronchial tree.

Unless detected on antenatal ultrasound, the bronchogenic cyst typically presents in early adulthood with symptoms such as infection or mass effect from the cyst, respiratory distress, dyspnoea, recurrent pneumonia, lobar emphysema, haemorrhage, or dysphagia. Investigations to diagnose this lesion are dependent upon the presentation of the patient and may often include chest x-ray, CT scan, and barium swallow. There is an extensive list of differential diagnoses when encountered with a solitary thoracic cyst. These include pericardial cyst, cystic hygroma / lymphangioma, neurenteric cyst, meningocoele, oesophageal duplication cyst, thyroid colloid cyst, and thymic cyst, abscess, and metastasis [12].

Although the bronchogenic cyst may run an indolent course through childhood, it is recommended the cyst undergoes surgical intervention through surgical resection, enucleation, or lobectomy. This recommendation comes from the adult cardiothoracic experience of complications related to the bronchogenic cyst. A large series published fistulisation, ulcerations of the cyst wall, haemorrhage, infection, and secondary bronchial atresia as the complications encountered [16]. There have also been published cases of rhabomyosarcoma, pulmonary blastoma, and malignant mesenchymoma occurring in bronchogenic cysts [17].

Congenital chylothorax

Congenital chylothorax is defined as accumulation of lymphatic fluid within the pleural cavity. Although this is rare in the neonatal period, it is the most common cause of pleural effusion at this age. There is an estimated incidence of 1 in 7,000 to 1 in 10,000, there tends to be a male preponderance, and fluid accumulation on the right side is more common. Although once thought to occur secondary to obstetric trauma, visualisation of chylothoraces on antenatal scans has disproved this theory. With most cases being idiopathic, there has been noted to be an association with Down, Turner, Gorham-Stout, Yellow nail, and Noonan syndromes, and X-linked myotubular myopathy. Congenital chylothorax is postulated to be due to thoracic duct atresia or congenital fistulae secondary to failure of lymphatic channels to connect with the main lymphatic network thereby resulting in a generalized pleural loss of chyle. There is a reported mortality in upwards of 60% [18].

Following birth, 50% of babies have symptoms within the first 24 hours and 75% will be symptomatic by the end of the first week. Those presenting later will have signs of muscle wasting, weight loss, and malnutrition. There is also immunological compromise due to hypogammaglobulinemia and lymphopenia [19].

When detected antenatally, transabdominal fetal thoracocentesis and thoraco-amniotic shunts can be utilised to prevent the pulmonary hypoplasia resulting from mass effect. There are a variety of postnatal treatment options for the persistent congenital chylothorax. As the baby may develop respiratory compromise soon after birth from mass effect of the pleural fluid, respiratory support and decompression with a chest drain is of utmost importance. To decrease the flow of lymph, a formula of medium-chain triglycerides (MCT) is provided. MCT bypasses intestinal lymphatic absorption and is instead absorbed directly into the portal venous system. The drawback of long-term MCT formula is the risk of deficiency of essential long-chain fatty acids. Replacement of albumin and globulin loss and the prevention of infections are also key to successful management. These conservative measures are trialled for 6 weeks prior to contemplating surgical intervention. The use of octreotide has been published with mixed success. The action of octreotide to decrease lymph flow is uncertain but it has been hypothesized that it causes mild vasoconstriction of splanchnic vessels and hepatic venous flow. This leads to reduction in gastric, pancreatic and intestinal secretions as well as intestinal absorption, which collectively reduces the flow of chyle. The conclusion of a recent Cochrane review found insufficient evidence to recommend its routine use in refractory cases of chylothorax [20]. Surgical interventions such as pleurodesis, thoracic duct ligation and pleural peritoneal shunts are usually reserved for the most refractory of cases. Pleurodesis can be achieved through manual abrasion or chemically with talc, doxycycline, betadine or bleomycin.

Conclusion

The pathologies presented in this paper were provided to give an overview of congenital anomalies present within the chest and current methods of investigation and management. Congenital pulmonary airway malformations represent a spectrum of pathology that has an incompletely understood aetiology and pathophysiology. The management of symptomatic children is universally agreed; however, the management of the asymptomatic child is a topic of much debate. The surgeon must take into account the risk versus benefit of potential complications and malignancy in determining whether they will adopt a pro-intervention mentality or support a more conservative approach to managing these lesions. Congenital chylothorax is also a pathology that can be difficult to manage, especially when it is refractory to the initial treatment strategies.

 

 

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