3Bronchopulmonary diseases
3.1Introduction
Classification, diagnostic pathways and therapy recommendations relating to congenital malformations of the lung remain subjects of significant ongoing discussion. From the pediatric point of view, Ernst Eber summarizes the actual state of the debate, and his discussion is complemented with a surgical view provided by Mark Davenport. Particularly in terms of minimally invasive procedures, Steven Rothenberg contributes his outstanding experience in this topic.
Ernst Eber
3.2Congenital thoracic malformations
The phrase “congenital thoracic malformation” (CTM) is an umbrella term for a number of developmental abnormalities, including pulmonary parenchymal lesions such as congenital cystic adenomatoid malformation (CCAM), extra- and intralobar bronchopulmonary sequestrations, and congenital lobar and segmental emphysemas as well as less frequent abnormalities such as bronchogenic and foregut duplication cysts [1, 2].
Over time, various classifications and nomenclatures have been proposed, based on the heterogeneous appearances of these malformations. The term “hybrid lesion” refers to a CTM with anatomical and/ or histological overlap between a CCAM and a bronchopulmonary sequestration, e.g. a lesion with an abnormal blood supply and a histological appearance compatible with CCAM. Today it is assumed that CTMs share a common embryological origin and represent a spectrum of abnormalities of fetal lung development with significant overlap [1, 2]. It was proposed that airway obstruction in utero might result in defective lung development, with different patterns of lung malformation according to the level, timing and degree of the obstruction [3]. While there is histological evidence for peripheral bronchial atresia or stenosis to be associated with all types of CTMs, the mode and timing of these incidents are still unclear [4].
The European Surveillance of Congenital Anomalies (EUROCAT), a European network of population-based registries for the epidemiologic surveillance of congenital anomalies, consists of 43 registries in 23 countries and covers approximately 30% of the European birth population. During the last years, the estimated incidence of CCAMs was around 0.9/10,000 live births, or about one quarter of all CTMs [5].
In developed countries, >90% of fetal lung abnormalities are detected in antenatal screening programmes. Many of these lesions will have regressed and some even disappeared on postnatal ultrasound and chest X-ray examination. Nevertheless, all children with antenatally detected CTMs need postnatal evaluation including ultrasound with Doppler, chest X-ray and chest computed tomography (CT) scan with intravenous contrast or magnetic resonance imaging (MRI). These investigations shall characterize the malformation, its vasculature and whether a communication with the tracheobronchial tree is present. To rule out a foregut communication, an esophageal contrast study may be necessary. Further, all children should be evaluated for associated congenital disorders, in particular cardiac anomalies [1].
There is a lack of prospective studies on the natural history of antenatally detected CTMs. Thus, there is an urgent need for both a systematic approach to congenital lung malformations with separate clinical and pathological descriptions and structured prospective observations of the natural history of antenatally detected asymptomatic malformations, to be able to offer relevant counseling to parents in the future.
Further, more studies are needed to resolve the issue of lung growth and lung function both with surgical and non-surgical management. Clearly, the long-term respiratory outcome after surgery to some degree depends on the extent of lung resection. The potential for alveolar growth and hence the ability of children to replace lost lung parenchyma by compensatory lung growth is believed to decrease with age; however, the evidence is scanty and studies have produced conflicting results. To some extent, overexpansion of the residual lung contributes to compensation for volume loss [1, 2].
As regards management of CTMs, this chapter will focus on postnatal life. For reasons of reference, the terms CCAM, bronchopulmonary sequestration, congenital lobar and segmental emphysema, and bronchogenic and foregut duplication cyst will be used.
3.2.1Congenital cystic adenomatoid malformation (CCAM)
A congenital cystic adenomatoid malformation (CCAM) is an abnormality of the terminal respiratory structures, containing no cartilage and consisting of cysts and solid airless tissue with bronchiolar elements. In the majority of cases, a single lobe is affected, with no particular preference for side and a predilection for the basal lobes. Bilateral lesions are uncommon and usually have a poor prognosis [1, 2].
The original Stocker classification distinguished three types (1, 2, and 3): In the “macrocystic type” (1) one or more large cysts predominate (this type may be hard to distinguish from lung cysts); the “microcystic type” (2) consists of numerous small cysts; and the “solid type” (3) is characterized by a mass of airless tissue. Subsequently, Stocker proposed a new name for these lesions – congenital pulmonary airway malformation (CPAM) and also the rarer types 0 and 4: type 0 is a tracheobronchial defect (also known as acinar dysplasia), characterized by firm small lungs with a bronchial airway; type 4 is an entirely alveolar defect at the lung periphery [6, 7]. Of the five types, only types 1, 2 and 4 are cystic, and only types 1, 2 and 3 are adenomatoid. Type 4 shows histological overlap with grade 1 pleuropulmonary blastoma, with the only distinguishing feature being a lack of blastema in CCAM type 4 [2]. Table 3.2.1 summarizes the characteristics of this classification.
Tab. 3.2.1: Classification of congenital pulmonary airway malformations according to Stocker [6, 7].
Clinical features vary extensively. Antenatally, large lesions may compress the ipsilateral lung and via mediastinal shift also the contralateral lung, resulting in lung hypoplasia. Compression of the esophagus may cause polyhydramnios, and the resulting distension of the uterus may induce premature labor. Impairment of venous return and hydrops may lead to fetal or neonatal death. Antenatal assessment of large lesions comprises evaluation by fetal ultrasound, fetal echocardiogram, ultrafast MRI and fetal karyotype. However, in utero therapy is only required in a minority of highly selected fetuses. Proposed interventions include maternal steroid administration, puncture or shunting of macrocystic masses, alcohol embolization or lasering of a feeding vessel, lobectomy via hysterotomy for more solid masses and resection while on placental circulation. A pleural effusion may be treated with a pleuroamniotic shunt. Fetal therapy requires the expertise of a highly skilled multidisciplinary team, and the evidence base for these interventions is relatively poor [1, 7].
However, the majority of fetuses have a good outcome, and an initially large lesion does not necessarily correlate with a poor prognosis; in fact, the growth pattern is unpredictable. Complete postnatal spontaneous resolution of a CCAM occurs very rarely. As diaphragmatic defects may be missed on ultrasound, CCAM and congenital diaphragmatic hernia sometimes are difficult to differentiate, not only antenatally but even in newborns. A correct diagnosis, prerequisite for providing appropriate management and parental counseling, may not be possible despite the use of serial ultrasound scans and MRI [1, 2].
Approximately 10% of neonates will have respiratory distress shortly after birth; they should undergo urgent CT to confirm the nature of the lesion and subsequent emergency surgery. In a recent review, the mortality rate during the neonatal period was suggested to be about 7% [8]. The majority are smaller lesions which are usually asymptomatic in early postnatal life (Fig. 3.2.1).
Fig. 3.2.1: Chest CT of a 10-month-old girl with a CCAM type 2 in the right lower lobe. The malformation was diagnosed antenatally, and the girl was asymptomatic.
If not detected antenatally, the diagnosis of smaller lesions may be delayed until school age, adolescence or even adulthood. However, many of them are diagnosed within the first two years of life, as they are prone to develop infection (pneumonia, lung abscess, empyema). Occasionally, they present later with hemoptysis, pneumothorax due to cyst rupture or high output cardiac failure (if there is a large systemic arterial blood supply) [1, 2, 7, 9].
In addition, there is a clear relationship between CCAM and malignant transformation although the risk of transformation and the overall prevalence are not known. Pleuropulmonary blastoma is a rare aggressive neoplasm with an unfavorable outcome; preschool children are typically affected. Some authors regard pleuropulmonary blastoma as the pulmonary dysontogenetic analog to Wilms’ tumor in the kidney and neuroblastoma in the adrenal gland. Up to 40% of pleuropulmonary blastomas will show cysts, and with the histological overlap between CCAM type 4 and grade 1 pleuropulmonary blastoma there is potential diagnostic confusion [1, 2, 10, 11]. Bronchioloalveolar carcinoma has repeatedly been reported to arise in pre-existing CCAM type 1, and the mean age for this complication appears to be young adulthood. However, bronchioloalveolar carcinoma has also been described in pediatric cases with CCAM, strongly suggesting malignant transformation of underlying CCAM. Evidence suggests that CCAM is a pre-invasive lesion for mucinous bronchioloalveolar carcinoma, and it has been pointed out that lack of growth over many years cannot be entirely trusted as a criterion of benignity [1, 2].
Surgery is the accepted standard of care for symptomatic lesions, and is definitely indicated when a postnatal complication occurs or when antenatal treatment has already been performed [1, 9].
The main reasons for surgical management of asymptomatic lesions are (1) to prevent complications such as infection, bleeding, pneumothorax, sudden respiratory compromise and malignancy, (2) to reduce post-operative complications (compared to emergency surgery) and (3) to encourage compensatory lung growth (which may be better after early, rather than delayed, surgery). Based on the evidence available today, a weak recommendation can be given to resect asymptomatic cystic CTMs [1, 7, 9]. While a clear recommendation for the timing of surgery cannot be given at present, most surgeons opt for excision of the lesion during the first year of life, and many around the first birthday [1, 7]. Expert pathology review of the excised specimen is essential, and genetic analysis should be considered where appropriate. Of note, in a rather large series of antenatally detected, asymptomatic cystic malformations almost a quarter had histological evidence of infection whether they ultimately turned out to have CCAM, bronchopulmonary sequestration, or a hybrid lesion; almost 3% showed malignancy [12].
Surgery for asymptomatic lesions is controversial, but needs to be balanced against risks of radiation (serial imaging with CT scans with a not insubstantial risk of later cancer), general anesthesia (or sedation), equally important the potential loss to follow-up, and the risk of malignancy. As yet, MRI does not appear to be sufficiently detailed to replace CT in this field [1, 2, 7].
Whether surgery is performed or not, patients with CCAMs should be followed-up into adulthood with standardized protocols. A multi-disciplinary approach to the management of these lesions is of great importance.
3.2.2Sequestration
The reported incidence of bronchopulmonary sequestrations ranges between 1% and 6% of all CTMs. Sequestrations are lesions predominantly comprising solid, nonfunctioning bronchopulmonary tissue, typically with no bronchial communication and aberrant blood supply via systemic arteries (from the lower thoracic or upper abdominal aorta or one of its major branches). They usually drain their venous blood normally into the left atrium; occasionally, venous drainage may also be abnormal to the right atrium, inferior caval vein or the azygos system. Depending on their appearances, sequestrations are commonly divided into intralobar and extralobar types. Intralobar sequestrations are lesions embedded in normal parenchyma, covered by visceral pleura in continuity with the normal lung. Extralobar sequestrations are invariably solid, have their own separate pleural covering maintaining complete anatomical separation of the mass from the rest of the lung, and are usually located beneath the left lower lobe. About two-thirds of all sequestrations are located in the posterior basal segment of the left lower lobe, and the lesions usually occupy a lung segment or less (Fig. 3.2.2).
Fig. 3.2.2: Chest X-ray of a 6-month-old girl with an extralobar bronchopulmonary sequestration in the left lower lobe. The malformation was diagnosed antenatally, and the girl was asymptomatic.
In addition, a number of reports described ectopic (intra- or subdiaphragmatic) locations. Especially extralobar sequestrations may be found in association with diaphragmatic hernias or other malformations [1, 2, 7].
The lesions may contain cysts, and – as mentioned above – hybrid malformations with coexisting features of CCAM type 2 are seen in up to 60% of cases (Fig. 3.2.3a and b).
Fig. 3.2.3a: Chest X-ray of a 10-month-old girl with a hybrid lesion in the left lower lobe. The malformation caused a shift of the mediastinum to the right, and the girl presented with mild tachypnea.
Fig. 3.2.3b: Angiography of a 10-month-old girl (same patient as in Fig. 3.2.3a) with a hybrid lesion in the left lower lobe, showing a large aberrant artery originating from the abdominal aorta.
In a large series of extralobar sequestrations, half (23/46) of the cases were associated with a coexistent CCAM, all of them type 2 lesions on histologic examination [1].
Antenatally, sequestrations present with increased echogenicity on ultrasound or increased signal intensity on MRI, similar to CCAM type 3 lesions. Differentiation between a bronchopulmonary sequestration and a CCAM is usually made on the basis of a separate blood supply; however, CCAMs can also have a separate blood supply. Antenatally, sequestrations appear to have a favorable outlook. A few will present with hydrothorax and pleural effusion, requiring in utero drainage. Many sequestrations show a decrease in size over time, and some even completely disappear on serial antenatal ultrasound scans. As for CCAMS, it is imperative to search for these malformations by CT or MRI angiography, even when they are undetectable on postnatal ultrasound and chest radiograph examinations [1, 2, 7]. Sequestrations have a variety of imaging appearances, including a consolidation, a mass or a cystic or multicystic lesion. Extralobar sequestrations are almost always airless, sharply defined and homogeneous.
In the majority of infants, a sequestration remains asymptomatic until infection develops. Recurrent localized pneumonitis, with fever and occasionally purulent sputum or hemoptysis, may develop at any age from infancy to adulthood, more frequently with increasing age and in patients with intralobar sequestrations. The malformation may also be found incidentally on a chest radiograph. The size of abnormal arteries and veins, and thus blood flow through the malformation may be considerable. As a consequence, a sequestration – functioning hemodynamically as a systemic arteriovenous malformation – may cause cardiovascular symptoms or even lead to cardiac failure. Bronchopulmonary sequestrations rarely have been linked with malignancy in adulthood (almost always but not exclusively intralobar sequestrations); speculatively, these tumors developed in hybrid lesions [1, 2].
As for CCAMs, surgery is the accepted standard of care for symptomatic sequestrations, and is indicated if antenatal treatment has already been performed or when a postnatal complication arises [1, 9].
Because the exact incidence of complications and the natural history of bronchopulmonary sequestrations are largely unknown, it is difficult to give an evidence-based argument for the treatment of antenatally diagnosed, asymptomatic sequestrations. Some authors believe that asymptomatic children with non-cystic sequestration may be followed up expectantly. Others advocate resection of all bronchopulmonary sequestrations because of the risks of complications (infection, hemorrhage and malignancy); in particular, resection of intra- and subdiaphragmatic bronchopulmonary sequestrations was suggested to rule out a tumor. As extralobar sequestrations appear to have a lower risk of developing complications than intralobar ones, their management is even more controversial [1, 9]. In any case, the risks of complications of the malformation itself must be weighed against the risks of surgical morbidity. Unfortunately, reasonable risk estimates are difficult to obtain from the literature. However, with the high frequency of hybrid lesions and the apparently low morbidity with modern surgical techniques, elective surgery might be the preferable strategy in children with an antenatally detected and postnatally verified lesion. In addition, the cost : benefit ratio of repeated CT scans with significant radiation exposure, as well as of office visits, needs to be considered.
As an alternative to surgery, embolization of the systemic feeding artery has been used in children with bronchopulmonary sequestrations [13, 14]. It was suggested that particularly infants with sequestrations who present with congestive heart failure might benefit from embolization alone or in combination with subsequent surgical resection. However, general anesthesia is also needed, embolization may not be as adequate as complete resection of the lesion, and long-term results are lacking. Thus, it appears that embolization cannot be recommended as sole treatment modality [1, 7, 14].
3.2.3Congenital lobar and segmental emphysema
Congenital lobar emphysema (CLE) is characterized by hyperinflation of one or (rarely) more lobes, usually as a consequence of bronchial obstruction with a valve mechanism; localized malformations and/ or deficiencies of bronchial cartilage, valvelike mucosal folds, and extrinsic bronchial compression all have been described as causes. Approximately half of the lesions are located in the left upper lobe; right upper lobe and middle lobe are less frequently affected. CLE often is associated with congenital heart disease [1, 2].
Recently, a sub-type of congenital parenchymal lung pathology, termed congenital segmental emphysema (CSE), has been described. CSE is characterized by postnatal evolution from an initially solid segmental appearance to a hyperlucent and hyperinflated segment. Other authors prefer the term “peripheral bronchial atresia” for the apparently same entity [15]. Bronchial atresia, the most likely underlying and often hidden pathology, is found within a spectrum of antenatally diagnosed lung lesions, such as CCAMs, bronchopulmonary sequestrations, hybrid lesions and CLEs. Further, CLE specimens may show both cystic adenomatoid and polyalveolar changes [4].
A polyalveolar lobe with an increased number of normally expanded alveoli per acinus may also cause radiologic “overinflation” and thus resemble CLE. The affected lobe, usually the left upper, is enlarged and air-filled, and clinically resembles CLE. The etiology is obscure but some authors speculate that the two morphological patterns classic hyperexpansion and polyalveolar lobe might be related to different outcomes of a putative lesion during lung development, depending on the timing of this lesion [1, 2].
Complications of CLE are mostly mechanical, and the lesion uncommonly causes symptoms outside the neonatal period; further, there is hardly any evidence for malignancy occurring in this lesion. CLE tends to compress the surrounding lung tissue and to displace the mediastinum, and thus to present early with respiratory distress (Fig. 3.2.4).
Fig. 3.2.4: Chest X-ray of a 3-month-old boy with congenital lobar emphysema of the right upper lobe. The malformation compressed the surrounding lung tissue and caused a shift of the mediastinum to the left, and the boy presented early with respiratory distress.
While the majority of patients present within the first weeks or months of life, a coincidental detection of the malformation may occur at any age. As the antenatal ultrasound appearance of CLE is relatively inconspicuous, this malformation is not readily diagnosed before birth. Postnatally, a chest radiograph and/or a chest CT scan are generally diagnostic. Flexible bronchoscopy may reveal the cause of bronchial obstruction [1, 2]. CLE may be misdiagnosed as pneumothorax, and patients with severe respiratory distress frequently undergo chest tube drainage.
For many years, surgical removal of the affected part of the lung (lobectomy or segmental lung resection) was the standard recommended treatment. More recently, several authors have advocated a conservative approach on the basis of CLE cases in whom symptoms gradually resolved (Fig. 3.2.5).
Fig. 3.2.5: Chest X-ray of a 4-year-old boy (same patient as in Fig. 3.2.4) with congenital lobar emphysema of the right upper lobe. Mild hyperinflation of the right upper lobe and no shift of the mediastinum; at this time, the boy was asymptomatic.
Thus, a number of pediatric pulmonologists now tend towards a trial of supportive treatment and observation instead of resorting to surgery immediately after diagnosis; surgical intervention may be reserved for children who do not improve or who present as newborns with very severe respiratory distress [1, 9, 16].
While conservative treatment in mildly to moderately symptomatic children with CLE appears to be appropriate, it calls for a close follow-up to ensure that there are no adverse outcomes with an expectant, non-surgical approach. In an old and small study, normal growth rate of functional lung tissue was reported for both children after surgical resection of CLE and children in whom CLE had been managed conservatively. Thus, it appears that growth of the remaining lung is not hampered by a non-resected cystic lesion, or space-occupying hyperinflated lobe. Since then, successful long-term expectant management has been repeatedly reported [16]. However, further data on long-term follow-up courses are clearly desirable, especially in the light of the finding that CLE specimens may show cystic adenomatoid changes [4].
3.2.4Bronchogenic and foregut duplication cysts
Bronchogenic cysts originate from defective development of the large airways (trachea or bronchi) and share their origin with foregut duplication cysts; their prevalence is unknown. They are thick-walled (containing smooth muscle, and occasionally cartilage) cysts, and are lined by respiratory epithelium [2]. Bronchogenic cysts are usually single and sometimes quite large malformations; most of them are located in the paratracheal or carinal region thus presenting as mediastinal cysts, but intrapulmonary forms may also be seen (Figs. 3.2.6 and 3.2.7).
Fig. 3.2.6: Chest X-ray of a 1.5-year-old girl with a bronchogenic cyst projecting from the mediastinum. The typically rounded paratracheal mass with uniform density was found incidentally, and the girl was asymptomatic.
Fig. 3.2.7: Chest X-ray of a 7-year-old girl with an intrapulmonary bronchogenic cyst in the left lung. The lesion was found incidentally, and the girl was asymptomatic.
Foregut duplication cysts may be found in the posterior mediastinum. Apart from gut tissue, they may also contain neural elements and may be associated with vertebral malformations [1].
With wide-spread use of antenatal ultrasound, today these cysts are often detected before birth. Many cysts are asymptomatic and thus may be found incidentally on a chest radiograph. Bronchogenic cysts may be obstructive to neighboring structures (e.g. esophagus) and in case of airway compression may lead to cough, wheeze, dyspnea or even respiratory distress. Radiographic findings are variable, ranging from a rounded mass projecting from the mediastinum and with uniform density similar to that of the cardiac shadow to hyperinflation or atelectasis of a lobe or an entire lung. Air-fluid levels may be seen when the lesion communicates with the tracheobronchial tree. Chest CT or MRI usually permit to confirm the nature of the lesion [1].
Secondary infection of a cyst is a frequent complication and may cause acute distension with exacerbation of symptoms. In addition, peptic ulceration may develop in cysts containing gastric mucosa. As a serious complication, malignant transformation has been described leading to squamous cell carcinoma or bronchioloalveolar carcinoma from the lining epithelial cells to leiomyosarcoma from the wall, typically during adulthood [1, 2].
There is good evidence to recommend surgical resection of symptomatic bronchogenic cysts. In contrast, the evidence for conservative management of asymptomatic cysts is very limited. Both the high risk of developing typical cyst-related complications and the small risk of malignant transformation may justify removal of the lesion even in asymptomatic patients, as surgery can usually be performed without significant loss of functional lung tissue, and with virtually zero mortality and an acceptable rate of morbidity [1, 9, 17].
Steven Rothenberg
3.2.5VATS in congenital thoracic malformations
There are numerous indications requiring pulmonary lobe resections in infants and children, but the majority are for the broad spectrum of bronchopulmonary malformations that present in early infancy and childhood. These include bronchogenic cysts, bronchopulmonary sequestrations, congenital pulmonary airway malformation (CPAM) and congenital lobar emphysema (CLE) [18]. These lesions may be detected by prenatal ultrasound, present as acute respiratory distress in the newborn period, or may remain undiagnosed and asymptomatic until later in life.
Treatment may vary somewhat depending on the time of diagnosis and the presentation, but in most cases complete lobar resection is the desired therapy. Minimally invasive techniques now allow these procedures to be done with much less pain and morbidity and avoid the long-term consequence of a thoracotomy in an infant or small child.
Thoracoscopic lobectomy can be one of the most technically demanding procedures performed by a pediatric surgeon. The ability to first correctly identify vital structures to both the affected lobe and those going to areas needing to be preserved, and then safely secure the large pulmonary vessels, and a general lack of adequate lung case volume for most pediatric surgical trainees make these procedures even more difficult to adopt. However, a strict adherence to certain principals and a full understanding of pulmonary anatomy can help in assuring that these procedures are done safely and correctly. The basics of a thoracoscopic approach (or VATS) [19] and the most important points are emphasized here.
Technique
The procedures are performed with the patient in a lateral decubitus position and in most cases single-lung ventilation, obtained by mainstem intubation of the contralateral side is desired. In cases where single-lung ventilation could not be achieved, CO2 insufflation alone is usually adequate to achieve lung collapse, but the anesthetist needs to take care not to increase inspiratory pressures and inflate the lung especially during critical aspect of the dissection. In general, bronchial blockers are not necessary, and often attempts to place them can take excessive time and are often unsuccessful or the blocker becomes dislodged during the procedure. Most infants and children with bronchopulmonary malformations tolerate single lung ventilation without any problem.
The room is set up to facilitate an anterior approach (Fig. 3.2.8a). This is used because there is more space from the anterior chest wall to the lung hilum, then from a posterior approach, as is typical with an open thoracotomy. The surgeon and assistant are at the patient’s front with the monitor at the patient’s back. The chest is first insufflated with CO2 using a veress needle to help collapse the lung and avoid injury of the parenchyma with a trocar. Three trocars are used in almost all cases. The first port is placed between the posterior and mid axillary line in the fifth or sixth interspace. This placement allows determination of the position of the major fissure and evaluation of the lung parenchyma. The most common error is to place this port to far posterior. This forces the surgeon to look back on his instruments while working in the anterior portion of the fissure or the anterior hilum. This is extremely difficult as it forces the surgeon to work in a paradox (against the camera). The more anterior position avoids this and allows the surgeon to look down on his instruments for the majority of the procedure. The position of the fissure should dictate the placement of the other ports. The working ports are placed in the anterior axillary line above and below the camera port (Fig. 3.2.8b).
Three valved ports, ranging from 3 to 5 mm, are used in most cases. A fourth port can be added for retraction if necessary but is rarely needed. In the majority of cases vessel sealing technology is used to handle the pulmonary vessels, especially in small infants. A bipolar sealing device in a 3-mm curved dissector design (JustRight Surgical, Louisville, Co.) is our preferred device. In larger patients (>20 Kg) the 5 mm Ligasure (Medtronic, Boulder, Co.) is used. These devices are preferred because it can be used to dissect out the vessels and obtain adequate vessel length. Two separate seals, a minimum of 3 to 5 mm apart are then created (Fig. 3.2.9a). If there is not adequate length of the vessel to achieve two separate seals, the surgeon can simply dissect into the lung parenchyma to get adequate length. The vessel is then partially divided with scissors between the seals to insure both seals are secure and there is no bleeding, before the vessel is completely divided and retracts (Fig. 3.2.9b). If there is any evidence of bleeding from the partially cut lumen the surgeon still has control and can regrasp and reseal the vessel. The same device and technique can also be used to seal and divide the lung parenchyma in cases of an incomplete fissure, resulting in an air and water tight seal of the lung.
Fig. 3.2.8: (a) Room set up thoracoscopic lobectomy. (b) Trocar placement for a right-sided lobectomy. The camera port is in the mid-axillary line one interspace below and anterior to the tip of the scapula.
Each lobe is approached relatively the same. The branches of pulmonary artery to the affected lobe are dissected out, sealed and divided first, often at the segmental level. In general the pulmonary vein is then similarly treated, and then lastly the bronchus. For the last few years, in lower lobectomies, the bronchus was divided prior to the vein because this yielded excellent exposure of the trunk of the inferior pulmonary vein, facilitating safe isolation and division. A chest tube is left in all cases of lobar resection.
Fig. 3.2.9: (a) Applying the distal seal to the segmental artery to the pulmonary artery with a 3-mm sealer. The proximal seal is already in place. (b) Cutting the vessel part way to insure both seals are competent before the vessel is completely divided.
In larger patients (generally those over 20 kg), an endoscopic stapler can also be used to secure some or all of the major pulmonary vessels. There is also now a 5-mm stapler (Justright Surgical) which can be used to take the main pulmonary vascular trunks in infants under 15 kg.
The bronchus to the affected lobe is dissected in a similar fashion to the artery and isolated. In infants under 10–15 kg, the 5-mm stapler is used to seal the bronchus (Fig. 3.2.10), if this is not available 5-mm clips or suture can be used. In larger patients a 12-mm endoscopic stapler was used.
If there are large space-occupying cysts, these are first “collapsed” using the vessel sealer. The cystic areas of the lung is grasped, and energy is applied. This causes the cyst to involute, creating more intrathoracic space and improving the surgeon’s ability to manipulate the lung and identify important structures.
Fig. 3.2.10: Applying a 5-mm stapler to the bronchus of the left lower lobe in a 4-kg infant.
Discussion
Thoracoscopic lobectomy in children for congenital cystic lung disease is now an accepted and well-described technique [20–24]. Most authors agree on the relative merits of a thoracoscopic approach, including less pain, shorter hospital stay, and decreased long-term morbidity, including chest wall deformity, shoulder girdle weakness, and scoliosis [25]. Despite this general consensus, the adoption of this technique and surgeons’ comfort with the approach remain relatively low. We believe there are three main reasons for this. First, the average trainee in general surgery and pediatric surgery fellowship receives very little open or endoscopic thoracic training. Experience with lung biopsy, empyema, and mediastinal masses is usually adequate, but exposure to complex lung resections maybe limited. This lack of volume results in a decreased familiarity with pulmonary anatomy. Using a thoracoscopic approach further compounds this, as the surgeon can no longer put his or her hand in the chest cavity to palpate the structures and identify the anatomy.
One of the most difficult aspects of these cases is when the fissure is incomplete and the pulmonary vessels are not readily visible. We have found that using the tissue- sealing technology to dissect and divide the parenchyma of an incomplete fissure is the safest way to approach this. The fissure is approached layer by layer until the pulmonary artery is visualized. Using the vessel sealer results in limited bleeding and air leak.
Understanding the anatomic relationships for each lobe using this anterior approach are critical to success. The three-dimensional relationships of the vessels and bronchi to each lobe, which cannot always be seen in the two- dimensional view of the scope are important to understand. It is often helpful to have a senior surgeon with significant thoracic experience available for consultation, even if they don’t have significant thoracoscopic experience. The third major issue was standardizing the management of the pulmonary vessels.
Early in our experience we learned that thoracoscopic suture ligation of each individual vessel was difficult and time consuming. The small working space, difficulty in achieving traction and countertraction to obtain adequate vessel length while suturing, and the technical demands of tying a secure knot made this process laborious. We do not favor endoscopic clips for most vessels because of the risk of dislodging them during the extensive tissue manipulation necessary during a lobectomy.
Therefore, early on we adopted vessel sealing as a way to safely mange the pulmonary vessels [26]. The initial 5-mm sealing device used could manage a vessel up to 7 mm in diameter and was an adequate tissue dissector. The 3-mm sealing device now available can seal vessels up to 5 mm and works well as a dissector, especially in the smaller chest cavities of infants. It is more than adequate for most pulmonary vessels in children under 10 kg and for segmental branches in larger children. A key to using vessel-sealing technology effectively is to make proximal and distal seals on the vessel approximately 3–5 mm apart. Using scissors, a partial cut is made to determine that the seals are secure and that there is no bleeding once the lumen is entered. Once the vessel is partially divided and no bleeding is seen, the vessel can be completely divided. The benefit of the technique described is the opportunity to reseal the vessel before the vessel retracts and control is lost.
Because of the relatively large nature of the pulmonary vessels and the limited space in the chest cavity, it takes very little blood to obscure the operative field and force conversion to an open thoracotomy. For this reason, we have avoided any energy devices that seal and divide the vessel in one step, because if the seal fails the ability to salvage the situation is minimal. We have had only one conversion to open for bleeding since adopting this technique. That was a clear technical complication by the surgeon on a large sequestration vessel. A second vessel lying behind the first was not seen and was inadvertently cut while dividing the first vessel that was sealed.
For bronchus management we initially cut and then suture the bronchus using polydioxanone suture in smaller patients. This can be time consuming and technically demanding. We discovered that in most patients <10 kg the bronchus could be occluded using 5-mm endoscopic clips. If the lobar bronchus is too large, then distal dissection allows for a segmental bronchus to be taken. This decreases the size of the remaining main trunk. For example, the superior segment bronchus in a lower lobectomy can be occluded separately, and then the trunk to the basal segments can be taken with a second clip. In larger patients we used the 12-mm endoscopic linear staplers. However, because of the variations in anatomy and the close proximity of the bronchus to the other lobes, extreme care must be taken to avoid compromising the other bronchi. Therefore, if there is any question the bronchus to the target lobe should be divided sharply and sutured close. There is now new 5-mm stapling technology that better fits in the chest cavity of infants and children and should eliminate the use of clips and larger staplers in these smaller patients.
The benefits of thoracoscopic surgery are clear and have been well documented previously. We also favor earlier resection of prenatally diagnosed lesions before they become infected or the patients become symptomatic. We have documented our experience with infants <10 kg and showed that these procedures had shorter operative times, lower complication rates and shorter hospital stays [27]. In older infants, there can be significant adenopathy and inflammation in the fissures and around the pulmonary artery, making identification and safe division of these vessels much more difficult. These procedures are technically easier in infants at or near 5 kg despite the smaller working space as evidenced by the shorter operative times in this group when performed as compared with older patients. The length of stay (LOS) in this group is also shorter. Some are concerned with issues regarding hypercapnia, cerebral hypoxemia and hypoperfusion during anesthesia in these smaller infants. However, this has not been an issue in our experience or in large series reported from Stanford and The Children’s Hospital of Philadelphia.
Many authors have clearly documented the issues involved with trying to operate on these lung lesions using thoracoscopy once the infant has already had a clinical chest infection. They document a higher complication rate in those patients who were diagnosed after a chest infection and underwent a thoracoscopic lobectomy compared with those diagnosed prenatally and operated on prior to any clinical infections. Garrett-Cox et al [28] found that 83% of patients converted to open surgery had a previous chest infection. These and other studies demonstrate that 30%–40% of patients with bronchopulmonary malformations will develop significant pulmonary infections during their lives; thus we prefer to remove these lesions before they become symptomatic to avoid a more complicated surgery.
For those who argue for conservative nonoperative management of these lesions in asymptomatic patients, despite the high incidence of infection, we have seen two cases of unsuspected pulmonary blastomai. We feel the risks of recurrent infection and possible malignancy outweigh the risks of intervention if a thoracoscopic approach is used in an institution with a large experience in these procedures.
Mark Davenport
Comment
This chapter offers an insight into a multiplicity of congenital intrathoracic pathology areas stretching from intrauterine life to adolescence from the perspective of the earliest years of the twenty-first century. There are things which have changed and some which have remained the same. There has been a fashion for an all-enveloping title for all these things – congenital thoracic malformation (CTM) or congenital pulmonary airway malformation (CPAM); indeed that they are all interlinked in some way [29]. While this gives the sense that there may be common progenitors there are enough dissimilarities within each pathological sector to retain clinical nomenclature – e.g. sequestrations (ICD 9th 748.5) are clinically, observationally, radiologically distinct from the cystic adenomatoid malformation (CCAM) (ICD 9th – 748.4) and this should still be the discerning clinician’s focus.
A major therapeutic advance are maternal steroids (usually betamethasone) which can influence outcome in fetuses with significant CCAM (both macro and microcystic) with remarkable effect. The Philadelphia group recently reported an updated experience (n = 43) with both single shot and repeated steroid courses in fetuses with large macrocystic CCAM at risk of or actually with hydrops [30]. Over 80% showed a diminution in lesion size and as a consequence an increase in survival proportions and a clear decrease in the need for fetal lung resection.
The debate over resection or intervention for the asymptomatic lesion still carries on with verve and vigor, certainly within the UK and Europe if not the USA. Our original meta-analysis showed that about 3% of asymptomatic lesions would develop symptoms within infancy and that elective surgery was safer and less prone to complications than emergency surgery [8]. Having decided to remove a lung lesion then the next question will be how and it is clear that many surgeons have adopted thoracoscopic techniques to do this. In the USA, around 50% of lung resections are now minimally invasive (Fig. 3.2.11) [31]. However, as a large multi-institutional study recently showed it is still not easy, not quick and the actual benefits in terms of reducing hospital stay have not been proven [32].
One of the perceived advantages of early resection is to minimise the risk posed from neoplastic change. While the magnitude of this risk is still unknown there have been some developments in the understanding of causation. The commonest neoplasm, bronchioloalveolar carcinoma (BAC), exists in two forms either mucinous (mBAC) or non-mucinous (nmBAC) and the corresponding cells of origin appear to be a mucus-producing glandular cell and a type II pneumocyte or Club (formerly Clara) cell respectively [32]. The development of BAC in Type 1 CCAM has been associated with an underlying K-ras point mutation [33].
