Affiliations: Heybeliada Chest Diseases and Thoracic Surgery Center
Georgetown University Medical Center
Correspondence to: Attila Saygı, MD, Ataturk Caddesi Sehit Ilhan, Sokak Demircan Apt No. 8/4, Sahrayicedia, Kadikoy, Istanbul 81300, Turkey; e-mail: email@example.com
To the Editor:
I read with interest the case of intralobar pulmonary
sequestration (ILS) that appeared in the June 2000 issue of
CHEST as a Roentgenogram of the Month.1
The development of ILS, one of the most interesting developmental
pulmonary abnormalities, has not been elucidated yet. I do not agree
with the comments of the authors on this case regarding the etiology as
being both acquired and congenital in the same patient. The quite rare
and large aberrant systemic artery originating from the left
circumflex coronary artery and reaching the left lower lobe is proof
enough that this case is congenital in origin. In the study of Stocker
and Makzak,2 arteries from the thoracic aorta branching
into the visceral pleura traversing the ligamentum pulmonale have been
found to be anatomically present, and, depending only on that
criterion, it was claimed that a chronically infected lesion
obstructing a bronchus and occluding the pulmonary artery could cause
acquired ILS by means of systemic arterial parasitization from aortic
arteries traversing the ligamentum pulmonale.
The following factors are in favor of this hypothesis: no ILS case
among 42,000 infants < 2 months of age3; normal
pulmonary venous drainage; the rarity of ILS in lobes other than the
lower lobes (pulmonary ligament arteries do not exist in the upper
lobes); and fewer ILS cases with other abnormalities when compared to
extralobar sequestration (ELS) cases.2–3 But this
hypothesis cannot explain patients with both ILS and ELS, patients with
ILS who have gut fistulas, accompanying congenital malformations with
an incidence of 14%, bilateral sequestrations of the same or different
types, ILS patients with upper lobe localization, or cases of ILS in
neonates.4–17 Besides this, it is clear in this case that
there is no need for the acquired neovascularization (parasitization
from aortic arteries) of sequestrated lung tissue that has already been
supplied by an artery large enough and is unquestionably congenital in
The wheel theory of Clements et al18 seems to
be more acceptable in explaining the development of congenital
bronchopulmonary malformations. According to Clements et
al,18 ILS and ELS have similar origins.
If the patient with ILS whose case was presented by Lewis and
Tsou1 had been operated on and, thus, had had ILS
histopathologically confirmed (eg, bronchial obstruction,
occlusion of the pulmonary artery, or a type of pleural envelope
lesion), collateral vessels originating from the aortic arch and
reaching the lesion could have been claimed to be acquired originally
because of neovascularization secondary to chronic infection. This case
is congenital in origin because of the abnormal artery
originating from the circumflex artery.
In addition, ELS is frequently localized in the left lower lobe, just
between the lobe and the diaphragm in its own pleural envelope. The
type of pleural envelope in the lesion (IL-EL) cannot be detected by CT
scanning alone but requires histopathologic verification. The venous
drainage in this case also has not been clearly identified. Pulmonary
venous drainage is characteristic in patients with ILS. When the
diagnosis is uncertain, surgery is the rule in
Two other limitations of this case are the discordance with the
acquired ILS hypothesis of Stocker and Makzak,2 in that
arteries do not reach the lesion via the ligamentum pulmonale, and the
lack of a bronchologic study. There are ILS cases with communication to
the tracheobronchial tree or cases in which inflammatory changes occur
in adjacent bronchi.19In this case, the patient has a
history of bronchitis of quite a long duration. Collateral arteries
from the aortic arch to the lesion are not proof enough that the lesion
was acquired. Besides, by means of collateral ventilation, the
sequestrated portion of the lung in patients with ILS can be ventilated
and infected.20 The above-mentioned sequential events do
not necessarily mean that ILS is acquired as a result of
I believe that this case of sequestration is congenital in origin, and,
with respect to the above-mentioned reasons, it will not be objective
to define the etiology of this case as both congenital and acquired
unless further investigations concerning venous drainage, type of
pleural envelope of the lesion, and aortic vessels to the lesion, as
well as bronchologic studies, are performed.
We appreciate Dr. Attila Saygi’s interest and comments
regarding our Roentgenogram of the Month in June 2000 demonstrating
sequestration.1 Briefly, our patient was a 66-year-old
Chinese man with a long history of recurrent bronchitis/chest
infections who resided at high altitude and who traveled to Washington,
DC for evaluation of his dyspnea. We discovered a left lower lobe
infiltrate by plain chest radiography, a large aberrant artery arising
from the left circumflex artery leading to the left lower lobe, and
multiple collateral vessels arising from the aortic arch also
traversing to the left lower lobe. We believe that this case represents
an intralobar sequestration of both congenital and acquired etiology.
Although it is somewhat difficult to fully ascertain Dr. Saygi’s
arguments, it appears that he disagrees with our conclusion that there
was both a congenital and acquired origin of the abnormal vasculature.
He proposes that the aberrant circumflex artery as well as the multiple
collaterals from the aortic arch are congenital in origin, primarily
citing the theory of Clements and Warner2–3 regarding
congenital acquisition of intralobar pulmonary sequestration.
As stated in our earlier discussion, there is undoubtedly a debate in
the literature regarding the etiology of intralobar sequestrations as
congenital or acquired anomalies. There are compelling theories that
argue in favor of the acquired origin of intralobar
sequestration4–5 and also those in favor of the congenital
theory.2–3 Stocker and colleagues4–5 argue
that there are small systemic arteries in the pulmonary ligament that
can be parasitized to supply an infected region of the lung when the
pulmonary artery supply is compromised. Livingston et al6
also argue that chronically infected lung tissue can lead to
neovascularization from high-pressure systemic circulation. We concede
that in our patient the region of the abnormal lung was already being
supplied by a high-pressure systemic artery originating from the
circumflex artery, rather than from the low-pressure pulmonary artery
as in normal anatomy. Also, in our patient there was no evidence of
compromise of the aberrant circumflex vessel. We believe that the
chronic infection, inflammation, and fibrosis that originated from the
underlying sequestered lung tissue and then from recurrent infection
led to neovascularization in the form of multiple collaterals arising
from the aortic arch. We argue that arterial vasculature from
congenital and acquired origins can coexist in a sequestration within
the same patient.
This patient’s symptoms spontaneously improved after his arrival in
Washington, DC, and he quickly returned to his homeland. Therefore, we
were unable to perform further diagnostic studies or therapeutic
interventions, such as determining the venous drainage, or performing
bronchoscopy or bronchography, or thoracic surgery to accurately define
the pleural envelope. Had we been able to perform some of these
additional studies, in the very least, we would have obtained more data
regarding this unusual case of sequestration.
We agree that the pathogenic theory of intralobar sequestration remains
a controversial issue.
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