Chapter 96
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CHAPTER <strong>96</strong> ■ Thoracic Surgery: Surgical Considerations 1651<br />
Pulmonary Sequestration<br />
These lesions are also referred to as bronchopulmonary<br />
sequestrations (BPSs). They classically have anomalous arterial<br />
and pulmonary or systemic venous blood supply and do not<br />
formally communicate with the normal tracheobronchial tree. The<br />
former arterial vessels which arise from the thoracic (85–90%) or<br />
abdominal aorta (10–15%) can be very large, resulting in a large<br />
arteriovenous shunt and possible high-output cardiac failure;<br />
moreover, these vessels, if not properly ligated and divided at the<br />
time of surgical resection, can result in major intraoperative<br />
hemorrhage and can occasionally retract into the subdiaphragmatic<br />
space (if they originate from the abdominal aorta).<br />
There are two types of BPS, intralobar BPS and extralobar BPS.<br />
They differ based on their location within the lung parenchyma;<br />
intralobar BPS, which is more common (making up 90% of BPS),<br />
lies within the parenchyma of the lobe and indirectly communicates<br />
with the adjacent normal lung parenchyma via the<br />
pores of Kohn; these pores create an opportunity for infection of<br />
the BPS. Extralobar BPS is separate from the adjacent lung<br />
parenchyma and is invested with its own visceral pleura but does<br />
similarly have systemic arterial and pulmonary or systemic blood<br />
supplies. As such, it rarely becomes infected but is at risk for<br />
creating an arteriovenous shunt, causing high-output cardiac<br />
failure. Unlike intralobar BPS, extralobar BPS is associated with<br />
congenital diaphragmatic hernias and can be anatomically located<br />
in the thorax (more commonly on the left side) or the subdiaphragmatic<br />
space.<br />
BPS lesions can be imaged with transthoracic ultrasound, chest<br />
CT scan, or MRI. These lesions tend to occur more in the lower<br />
portion of the chest; they are differentiated from other congenital<br />
lesions by identification of a lung mass with an adjacent large<br />
arterial vessel which can be followed to the aorta. Preoperative<br />
indications for surgical resection of intralobar and extralobar BPS<br />
include recurrent pulmonary infection, congestive heart failure,<br />
or resection for diagnosis of a paraspinal mass (to differentiate if<br />
from a neoplasm as a neurogenic tumor). As with CCAM/CPAM,<br />
they can be resected via open or thoracoscopic techniques and<br />
authors have noted equal success with resection of these lesions<br />
with minimal access techniques. 52 Intraoperative considerations<br />
include the rare risk of major hemorrhage if the arterial blood<br />
vessel if not properly ligated; moreover, approximately 15% of BAS<br />
lesions will have more than one arterial blood vessel which can be<br />
inadvertently missed leading to unanticipated blood loss. 51<br />
Congenital Lobar Emphysema<br />
Congenital lobar emphysema (CLE) has multiple etiologies that<br />
lead to overdistention (air trapping) of the lobe of lung, resulting<br />
in compression of adjacent normal lung parenchyma. Some have<br />
implicated the embryologic absence of cartilage in the involved<br />
bronchus, leading to a ball-valve effect of progressive over inflation<br />
of the lung tissue, and others have implicated the polyalveolar lobe<br />
syndrome, which involves the development of abnormally high<br />
numbers of alveoli, leading to gigantic alveolar units. 51 Clinically,<br />
these children present with respiratory symptoms such as<br />
tachypnea; some of these symptoms will resolve with time averting<br />
the need for surgery. Optimal diagnostic imaging is achieved with<br />
a chest CT scan; the upper and middle lobes are most commonly<br />
involved. Figure <strong>96</strong>–14 illustrates a child with left-sided CLE on<br />
CT scan. Bronchoscopy can also be used to identify abnormal areas<br />
Figure <strong>96</strong>-14. Computed tomography scan (axial) of a child<br />
with left-sided, posterior congenital lobar emphysema with<br />
compression of adjacent normal lung parenchyma.<br />
of absent cartilage in the tracheobronchial tree. Intraoperative<br />
complications can occur at the time of induction of anesthesia,<br />
because positive pressure ventilation can cause acute over<br />
distention of the lobe involved with CLE. Strong consideration<br />
should be given to an anesthetic based on spontaneous ventilation<br />
and the surgeon should be in the operating room at the time of<br />
induction in case an emergent thoracotomy is required to relieve<br />
compression of adjacent intrathoracic structures.<br />
Bronchogenic Cysts<br />
Bronchogenic cysts are noncommunicating cystic structures<br />
adjacent to the tracheobronchial tree which usually exist at the<br />
level of the carina or main stem bronchi. They lack normal<br />
alveolar structures but do contain a ciliated columnar epithelial<br />
lining that produces mucus; as the cyst collects mucus, it<br />
extrinsically compressed the adjacent normal bronchial structures.<br />
Although this compression can cause air trapping, resulting in a<br />
clinical picture of CLE, many of these cysts are asymptomatic at<br />
diagnosis and are only noted incidentally on diagnostic chest<br />
imaging. Preoperative indications include surgical excision of the<br />
cysts to address respiratory compromise, to prevent infection of<br />
the cyst, to prevent the unusual occurrence of acute hemorrhage<br />
into the cyst causing acute extrinsic compression of the trachea,<br />
and to prevent the rare case of adenocarcinoma. These patients<br />
are often ideal candidates for a thoracoscopic approach for<br />
resection of the cyst, provided that the ipsilateral lung is not<br />
over inflated. Many authors have demonstrated the benefit of<br />
thoracoscopic resection over open thoracotomy. 53–55 The<br />
complication of injuring the adjacent airway at the time of<br />
resection is now lessened as it is recognized that the entire cyst<br />
wall need not be resected to achieve a low recurrence rate, if the<br />
remaining mucosal lining is cauterized.