Pulmonary Malformations

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INTRODUCTION

Congenital lung abnormalities are uncommon and diverse in their presentations. Congenital lobar over- inflation (CLO), otherwise known as congenital lobar emphysema, is among the most common of the con- genital lung anomalies. It is characterized by air trap- ping and overdistension of one or more lobes which are otherwise anatomically normal. This distension causes compression of adjacent normal lung paren- chyma and can result in mediastinal shift and cardi- orespiratory compromise. CLO is believed to result most commonly from structural deficiency or ab- sence of supportive cartilage in the affected lobar bronchus, thereby causing expiratory collapse of the conducting airway with impedance to expiratory flow. CLO is most often seen in the Caucasian popu- lation with a male preponderance of two or three to one. It is most common in the left upper lobe (40–50%), with other sites affected less frequently:

right middle lobe 30–40%, right upper lobe 20%, and lower lobes 1%. Approximately half of the patients develop respiratory distress within the newborn pe- riod while the remainder present up to 4 to 6 months of age or later. Presenting signs are those of respira- tory embarrassment, including dyspnea, tachypnea, agitation and wheezing.

Congenital cystic adenomatoid malformations (CCAM) are a rare group of cystic lobar hamartoma- tous lesions, represent up to 50–70% of the broncho- pulmonary foregut malformations in some reports.

The lesions are generally large, firm, multicystic masses that are composed of terminal respiratory structures, usually bronchiolar in origin.

Since the advent of routine ultrasound in obstetric practice, the majority of cystic lung lesions are now discovered prenatally in many institutions. Serial ultrasonographic examinations may demonstrate shrinkage or even spontaneous resolution in up to 40% of fetal CCAMs. After birth, some neonates demonstrate tachypnea, dyspnea, cyanosis or im- pending respiratory failure. Of the remainder, most will present within the first years of life with recur- rent or persistent respiratory infections, pulmonary abscesses, reactive airway disease or failure to thrive.

As for all bronchopulmonary foregut malformations,

the plain chest radiograph is the best initial diagnos- tic test in the neonate.

Pulmonary sequestrations make up 10–30% of the cystic bronchopulmonary foregut malformations.

They are classified according to whether the seques- tration resides within the visceral pleura of the nor- mal lung (intralobar sequestration) or is invested by its own visceral pleura (extralobar sequestration). In both types of pulmonary sequestration, however, there is no bronchial communication between the se- questrum and the normal tracheobronchial tree. In addition, the malformation receives its blood supply from aberrant systemic arterial vessels.

Intralobar sequestrations make up about 50–70%

of the pulmonary sequestrations and most common- ly involve the posterior and basal segments of the left lower lobe. The arterial supply is usually derived from aberrant branches of the descending thoracic aorta, although occasionally intercostal, brachioce- phalic, or abdominal aortic aberrant vessels are en- countered. Venous drainage is usually via the asso- ciated pulmonary vein. Extralobar sequestrations are completely separated from the normal lung and in- vested by an individual pleura. They are completely separate from the functional airways. They are found in the left lower chest most commonly, but may occur anywhere. Rarely, subdiaphragmatic locations are re- ported. A 3:1 male predominance is reported in most series for extralobar sequestrations. These sequestra- tions also derive arterial blood supply from the de- scending aorta, with up to 20% having an aberrant vessel traversing the diaphragm.

Patients with intralobar sequestration will typical- ly present with pulmonary infections due to abnor- mal air-space connections with inadequate drainage, or from compressive atelectasis of adjacent paren- chyma. Extralobar sequestrations, on the other hand, are frequently seen on prenatal ultrasound.

Congenital lung cysts comprise up to one-third of

bronchopulmonary foregut malformations in some

reports. The most common of these lesions are bron-

chogenic cysts. Bronchogenic cysts arise from the

trachea, bronchus or other conducting airways but

have usually lost their connection with the parent

Brian T. Sweeney, Keith T. Oldham

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Brian T. Sweeney, Keith T. Oldham 108

Lung surgery in children is generally similar to that in adults except that the diminutive size, the associat- ed lesions, and the unique pathologic entities require certain special considerations. Lobectomy can be performed by conventional thoracotomy or video- assisted thoracosocpy.

Lobectomy is the procedure of choice for the treat- ment of congenital lobar emphysema, CCAM, intra- lobar sequestrations and some parenchymal lung cysts. The patient is positioned in the lateral decubit- us position, with the upper arm extended and placed over the head. Rolled towels and other positioning devices may be placed in order to optimize stabiliza- tion and exposure of the operative field.

Optimal exposure is gained by transverse or oblique incision over the fourth or fifth intercostal space, below and lateral to the nipple to avoid cos- metic and functional damage to the breast tissue.

There should be some space between the tip of the scapula and the posterior extent of the incision. This becomes important during closure of the muscle layers, especially if the incision must be extended posterolaterally. Underlying muscle and subcutane- ous tissue is divided along the line of incision by elec- trocautery. To limit postoperative morbidity, it is de- sirable and usually possible to employ a muscle spar- ing approach. This affords adequate exposure yet avoids division of the serratus anterior and chest wall musculature other than the latissimus dorsi. The scapula is elevated off the chest wall by retractor to gain exposure, and palpation is used to count the ribs to the correct interspace. In most situations in in- fants, the highest palpable rib is the second. General- ly, the fourth interspace is used for a lobectomy al- though the fifth can be used effectively as well.

12 Figure 12.1–12.2 structure. They are usually simple, and contain mu-

cus; however, air-fluid levels and infection may be seen if there is continuity with the tracheobronchial tree. In contrast to sequestrations, bronchogenic cysts have a normal bronchial blood supply. Al- though bronchogenic cysts may reside anywhere in the respiratory tract, including paravertebral, para- oesophageal, subcarinal and cervical areas, the ma- jority are found in the lung parenchyma or mediasti- num.

Some patients with bronchogenic cysts are asymptomatic. Of those with symptoms, the most common presentations are wheezing, tachypnea or dyspnea, all related to compression of the adjacent conducting airway with partial obstruction.

Plain radiograph of the chest will usually demon- strate the pathology of the congenital malformation of the lung. In most infants and children with con- genital malformations of the lung additional imaging is required. Ultrasound with Doppler, computed to- mography scan with contrast, or magnetic resonance imaging provide good anatomical details and dem- onstrate relationship to the neighbouring structures.

Treatment of congenital malformations of the

lung is usually by lobectomy of the affected lobe,

which is very well tolerated in the infant population.

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Figure 12.1

Figure 12.2

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Figure 12.3, 12.4

The incision is then continued with electrocautery just superior to the lower rib of the selected intercos- tal space to avoid damage to the neurovascular bun- dle that runs along the inferior border of each rib.

Care must be taken when entering the pleura to avoid

injury to the lung parenchyma beneath. A rib spread- er is then placed to facilitate retraction. The incision may then be continued anteriorly or posteriorly from inside the chest if further exposure is needed.

12 Figure 12.5

The following technique and illustrations are de- scribed for left upper lobectomy, however, the princi- ples are the same for any lobe resection. Gentle later-

al and inferior traction on the lobe exposes the hi-

lum. The visceral pleura is carefully incised circumfe-

rentially, exposing the hilar structures.

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Figure 12.3

Aorta Lt. main pulmonary artery

Lt. lung Lt. main pulmonary vein

Phrenic nerve

Figure 12.5

Figure 12.4

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Figure 12.6, 12.7

Meticulous dissection reveals the left main pulmo- nary artery as it courses under the aortic arch and crosses the left upper lobe bronchus. Nearby struc- tures to be noted are the left phrenic nerve anterio- medially along the mediastinum, and the recurrent laryngeal nerve branching from the vagus under the aortic arch. A review of segmental anatomy of the lung describes four main arterial branches supplying the left upper lobe, however this can be variable.

These are individually encircled, ligated and divided.

This is typically done with heavy silk and using dou- ble proximal ligatures. The bronchial blood supply travelling with the left upper lobe bronchus is like- wise identified and ligated. Attention is then directed to the left upper lobe venous drainage. Again, indi- vidual branches are circumferentially dissected and ligated using the same approach as for the arterial circulation.

12 Figure 12.8

The bronchus is then clamped and divided. Closure of the bronchial stump with commercial surgical sta- pling devices is appropriate in older children; howev- er, size and other technical limitations make this un- desirable in infants where a simple sewn closure is best. Air leaks may be identified for suture repair by filling the chest with warm saline coincident with in- flation of the residual lobe by the anaesthesiologist.

The inferior pulmonary ligament should be divided at this time to facilitate expansion of the left lower

lobe, or it may be done early in the dissection to facil-

itate exposure. The superior and inferior pulmonary

vein sometimes have a common stem outside the

pericardium, which if unrecognized, may necessitate

total pneumonectomy. A chest tube is placed within

the pleura for drainage, and the wound is closed in

anatomical layers using absorbable suture. Post-op-

eratively, drains can be removed early, provided no

air leak is demonstrable.

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Artery branches of the left upper lobe Left upper lobe bronchus

Left pulmonary artery

Figure 12.6

Left vein branches of the left upper lobe

Figure 12.7

Figure 12.8

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CONCLUSION

Lung surgery in neonates and infants is generally similar to that in adults except that the diminutive size, the associated lesions and the unique patholog- ic entities require certain special considerations. Of course, the smaller the child, the more care must be taken in order to avoid technical injury. As with all

lung surgery, technical problems may result in seri- ous and irreversible consequences. Collaboration with paediatric anaesthesiologists familiar with the unique circumstances of paediatric chest surgery is essential.

12 SELECTED BIBLIOGRAPHY

Black TL (2003) Pulmonary sequestration and congenital cystic adenomatoid malformation. In: Ziegler MM, Azizkhan RG, Weber TR (eds) Operative pediatric surgery. McGraw- Hill, New York, pp 445–454

Adzick NS, Harrison MR, Crombleholme TM et al (1998) Fetal lung lesions: management and outcome. Am J Obstet Gyne- col 179 : 884–889

Albanese CT, Sydorak RM, Tsau K (2003) Thoracoscopic lobectomy for prenatally diagnosed lung lesions. J Pediatr Surg 38 : 553–555

Lo, HP, Oldham KT (2003) Congenital malformations of the lung. In: Puri P (ed) Newborn surgery. Arnold, London, pp 295–307

Oldham KT (1997) Lung. In: Oldham KT (ed) Surgery of infants and children: scientific principles and practice. Lip- pincott-Raven, Philadelphia