Keywords pulmonary sequestration - transcatheter arterial embolization - congenital lung malformation
Introduction
Congenital lung malformations (CLMs) comprise an array of lesions, the most common
of which are congenital pulmonary airway malformations (CPAM) and pulmonary sequestrations
(PS). Overall, their incidence has been increasing with published rates ranging from
one in 2,000 to one in 11,000 births.[1 ]
[2 ] The reason for this increase is not clear but is believed to be due in part to increased
neonatal screening ultrasonography. PSs account for up to one-fourth of all lesions.[3 ] The pathognomonic feature of sequestrations that distinguishes them from the more
common CPAM is a systemic arterial supply, usually arising from the aorta. Regardless
of the type of CLM, resection is advocated by many to avoid complications of infection,
pneumothorax, or malignancy.[4 ]
The standard of care for resecting CLMs is complete lobectomy which ensures the entire
lesion is removed. Early resection before symptoms develop is preferred because surgery
at that time carries a lower rate of complications.[5 ] In an effort to avoid the morbidity of lobectomy, authors have attempted segmental
pulmonary resections[1 ] and therapeutic embolization to induce necrosis.[6 ] Widespread use of these less invasive therapies, however, has been limited because
of concerns of incomplete resection or involution.[6 ]
[7 ]
We present the case of a 7-month-old boy treated with a hybrid approach using preoperative
embolization followed by segmentectomy. The embolization clearly demarcated the intralobar
sequestration, thereby aiding intraoperative localization and facilitating complete
resection of only the affected portion of lung.
Case Report
A 3-week-old male was referred to pediatric surgery for evaluation of a congenital
lung lesion. He was born at 37 weeks via cesarean section for breech presentation
with a birthweight of 2.78 kg. After birth, he developed respiratory distress and
was admitted to the neonatal intensive care unit where a chest X-ray demonstrated
multiple cystic lucencies in the right lung field initially concerning for a CPAM.
Prenatal care was limited and it was unknown if the lesion had been previously diagnosed
on ultrasound. He required CPAP for respiratory support which was weaned off on day
1 of life. He was discharged home on day 7 of life to follow up with pediatric surgery.
He presented for surgical consultation at 3 weeks of life. Examination revealed a
well-appearing 3.75 kg infant, with clear breath sounds bilaterally and no evidence
of heart failure. His parents reported no further respiratory symptoms. The computed
tomography (CT) angiogram was obtained which revealed a cystic lung lesion in the
right lower lobe with a large systemic artery originating from the distal thoracic
aorta proximal to the origin of the celiac artery ([Fig. 1 ]). These findings confirmed the diagnosis of a PS. The need for surgery to avoid
complications related to the sequestration was discussed with the infant's parents.
Due to the large size of the systemic feeding vessel, we elected to perform angiographic
embolization preoperatively to reduce the risk of intraoperative bleeding. Ideally,
we would have performed resection at 3 months of age, but the procedure was delayed
until 7 months due to social circumstances beyond our control. During that time, the
infant remained asymptomatic.
Fig. 1 Computed tomography reconstruction demonstrating the vascular anatomy of the pulmonary
sequestration. Feeding artery noted by red arrow.
He was admitted and underwent angiography via right femoral arterial access with interventional
radiology. This demonstrated rapid flow through the feeding artery into the sequestration
with brisk drainage into the right inferior pulmonary vein. Onyx 18 (ethylene vinyl
alcohol, dimethyl sulfoxide) was chosen for embolization because it is a pliable copolymer
that would not interfere with the function of a LigaSure device or endothoracic stapler
during surgery. We used an occlusion balloon to arrest flow within the feeding vessel
so that the brisk arterial flow would not flush the copolymer through the lesion into
the pulmonary vein while it hardened. Following embolization, there was no further
flow through the sequestration; however, there was some flow noted proximally within
the feeding vessel itself ([Fig. 2 ]). We were unable to embolize the entire length of the feeding artery because the
occlusion balloon could not be placed more proximally in the vessel without risking
inadvertent embolization into the aorta. Following this procedure, he was monitored
in the PICU overnight before proceeding with surgery the following day.
Fig. 2 Pre- and postembolization angiogram demonstrating cessation of flow through the pulmonary
sequestration.
Thoracoscopy was performed via a standard three-port approach with the infant in the
left lateral decubitus position. Upon entry, the large systemic feeding artery itself
was not thrombosed. However, the embolized portion of sequestered lung was clearly
demarcated and appeared dark purple compared with the surrounding, well-perfused pink
lung parenchyma. The inferior pulmonary ligament was mobilized allowing complete visualization
of the embolized tissue within the right lower lobe. We had initially planned to perform
lobectomy, but after this mobilization, it was clear that the lesion was peripheral
and could be fully excised with a nonanatomical segmentectomy. The feeding vessel
was mobilized circumferentially and divided using a LigaSure device. The lung parenchyma
was similarly divided taking care to include a margin of well-perfused lung around
the sequestration. A 16 Fr chest tube was placed and the lung re-expanded with no
air leak noted. He was extubated and transferred to the surgical ward without complication.
His chest tube was removed on postoperative day 1, and he was discharged on postoperative
day 2.
The infant was seen in follow-up 2 weeks after surgery. His parents reported that
his activity level was back to normal and denied pain or respiratory symptoms. Final
pathology of the specimen confirmed an intralobar PS.
Discussion
Lobectomy is currently the gold standard for the treatment of CLMs. Increasingly,
this is performed thoracoscopically, with excellent results reported in infants.[8 ] Some authors have advocated observation of these lesions with resection only performed
for children that develop pneumonia or other symptoms. A recent meta-analysis compared
these approaches for 168 children, 70 of whom had early surgery and 98 of whom were
observed and had delayed surgery only after symptoms developed. Of the 98 patients
treated expectantly, 64.3% developed symptoms and underwent surgery. The morbidity
of resection in this symptomatic group was 31.8%, compared with 10% in the 70 patients
who elected to have early resection.[5 ] Because of this difference in complications, many surgeons advocate for early lobectomy
as the standard of care.
Advocates of the resection of asymptomatic lesions also cite a risk of malignant degeneration
of CLMs. There is no high quality data quantifying this risk in part due to a lack
of life-long follow-up of children with unresected lesions. In addition, many lesions
are resected, so it is unknown whether they would ultimately progress to malignancy.
Proponents of resection for the prevention of malignancy cite an association of pleuropulmonary
blastoma (PPB) with cystic lung lesions. One series of 129 CLMs found that PPB occurred
in 2% of lesions previously diagnosed as CPAMs.[9 ] Conversely, 66% of all PPBs occur within cystic lung lesions.[10 ]
In an effort to reduce the morbidity of lobectomy, authors have reported various lung-preserving
techniques including segmental resection or embolization alone to induce necrosis
and involution. A segmentectomy preserves healthy and functioning lung parenchyma;
however, it is difficult to ensure all abnormal lung tissue is removed. Bagrodia et
al compared segmentectomy with lobectomy by reporting 45 infants undergoing surgery
for CLMs (19 segmentectomy and 26 lobectomy).[1 ] They found no difference in surgical complications, but a considerably shorter length
of stay after segmentectomy (2 vs. 7 days). No patient developed recurrent symptoms
or had residual disease on chest X-ray over a median follow-up of 9 months (range:
0–97 months). These successful results, however, are not universal. A recent meta-analysis
of 328 cases (268 lobectomy and 60 segmentectomy) reported that 15% of patients treated
with segmentectomy had residual lesions, compared with 0% of those undergoing lobectomy.[7 ] This highlights the difficulty of ensuring complete resection of all abnormal tissue
when performing segmentectomy.
Other authors have attempted to use embolization alone to induce necrosis and involution
of lung malformations. This method can only be used to treat PSs because it requires
their characteristic systemic arterial supply but has the potential to eliminate the
need for resection entirely. Cho et al compared 73 children, 42 of whom were managed
with embolization alone, and 31 with surgical resection.[6 ] Of the children treated with embolization, only three had complete regression, leaving
39 with residual lesions. In addition, four children (9.5%) had complications related
to the embolization including two that developed postprocedural sepsis, one who developed
a renal abscess secondary to a thrombus, and another with distal embolization of a
coil into the iliac artery. Due to the high rate of incomplete regression and procedural
complications, the authors concluded that thoracoscopic resection is preferred over
embolization alone for the treatment of PSs
The novel method we present here is a hybrid approach that addresses the challenge
of incomplete resection that has hindered widespread adoption of lung-preserving surgery
for CLMs. We had initially performed the embolization to reduce the risk of intraoperative
bleeding from the feeding artery given its large caliber. Due to the technical challenges
encountered during the embolization, however, the feeding artery remained patent.
The realization that preoperative embolization might be a solution to the problem
of incomplete resection arose from this apparent failure, by having the unanticipated
consequence of clearly demarcating the lesion from the surrounding normal lung tissue.
We therefore do not advocate embolization for the purpose of bleeding control, rather
for its potential to facilitate more limited pulmonary resection in infants with PSs.
This approach has limitations that should be addressed. Because two separate procedures
are required, the child is subjected to two general anesthetics, the potential for
complications from both procedures and additional radiation resulting from fluoroscopy
during embolization. There are only a limited number of small studies reporting the
rates of complications from embolization of PS in children, with overall complications
ranging from 9.5 to 20%.[6 ]
[11 ]
[12 ] The rates of distal embolization, concern for which was a primary contributor to
our inability to fully embolize the feeding artery, range from 2.4 to 6.3%.[6 ]
[11 ] The combined risks of embolization and sublobar resection will become clearer and
potentially decrease with increasing experience with this technique. It is also possible
that in the future both procedures could be performed under a single anesthetic with
embolization followed immediately by resection. While CT angiography (CTA) is widely
practiced for preoperative evaluation of CLMs, it carries a risk of ionizing radiation.[13 ] Because embolization also requires radiation, magnetic resonance angiography (MRA)
could replace CTA to reduce a child's overall radiation exposure if preoperative embolization
is planned. MRA, however, often requires anesthesia, so this potential benefit would
need to be weighed against the risks of undergoing an additional general anesthetic
early in infancy.
As utilizing this technique requires a systemic arterial supply, its application is
limited to PSs, which make up only a subset of CLMs. In addition, there is unlikely
to be any significant benefit of preoperative embolization of extralobar sequestrations
as these lesions are entirely separate from the normal lung and therefore easily identifiable
intraoperatively.
Finally, this report is of a single patient with limited follow-up so the long-term
risks and benefits of this hybrid approach are unclear. The IDEAL Collaboration has
established recommendations for the development and implementation of new surgical
innovations.[14 ]
[15 ] Stage 1 (IDEA) includes a first description of a new technique in humans. This can
occur after extensive preoperative planning or due to unforeseen intraoperative circumstances
as in our case. Following this, new techniques must be modified, refined, and operator
learning curves overcome with experience in an increasing number of cases prior to
more widespread use (Stage 2a-Development, Stage 2b-Exploration). It is not until
this second stage of development and exploration that long-term outcomes can be assessed.
Conclusion
We have presented a hybrid approach to the treatment of a PS that used preoperative
embolization followed by sublobar resection to preserve lung parenchyma while ensuring
adequate resection of the lesion. As a first description, this report should be considered
primarily one of technical feasibility. We believe the technical success of this hybrid
approach is promising and warrants further investigation in a larger cohort of children
to better quantify its risks and potential for success.
