Downloaded from www.ajronline.org by 122.183.228.146 on 10/07/15 from IP address 122.183.228.146. Copyright ARRS. For personal use only; all rights reserved
947
Case ‘‘:
f,’.
‘, ‘
*‘
Bronchopulmonary High-Resolution Eric J. Stern,1
W. Richard
Y
,
.‘-,
,t
-.
.-
-:
,,
Sequestration: Dynamic, CT Evidence of Air Trapping
Webb,1
Report
Martha
L. Warnock,2
and
Christopher
Ultrafast,
J. Salmon1
lobe with an air-fluid level, and the patient was treated for presumed
Intralobar bronchopulmonary sequestration is a congenital anomaly that consists of nonfunctioning, abnormal lung tissue that is contained within an otherwise normal lung and has an anomalous systemic blood supply [1 -4]. Although intralobar sequestrations lack normal communications with the tracheobronchial tree, they can be ventilated by collateral air drift or through fistulous bronchial communications that may develop after an episode of infection. An air-containing intralobar sequestration can appear on chest radiographs as an area of hyperlucency, with or without associated visible cysts, or can appear as normal lung [5]. The CT appearances of bronchopulmonary sequestration have recently been reviewed [6], and the presence of lucent or low-attenuation areas of “emphysema” have been emphasized. It has been suggested that the emphysema seen in patients with sequestration results from collateral ventilation and air trapping [7]. We recently had an opportunity to test this hypothesis by using dynamic expiratory, ultrafast, highresolution CT (HRCT) in a patient who subsequently had an intralobar pulmonary sequestration confirmed surgically and
necrotizing
pneumonia.
On conventional
CT, obtained
area
nonsegmental
of abnormally
with contiguous lucent lung
1 -cm collimation, a was visible in the
posterior, medial, right lung base, adjacent and inferior to a homogeneous well-circumscribed soft-tissue density, corresponding to the mass visible on the chest radiograph. The lucent lung suggested the presence of one or more thin-walled, air-containing cysts (Fig. 1A). Aortography abdominal
aorta
venous
drainage
showed an anomalous artery arising from the upper and supplying the region of abnormal right lung. The was
not
clearly
shown.
CT (Imatron C-i 00, Imatron Inc., So. San Francisco, was first performed immediately after the patient’s aortogram Ultrafast
obtained,
with
the
angiographic
catheter
still
in
place
within
CA) was the
anomalous artery that was feeding the sequestration, in order to show the venous drainage of the sequestered lung. After the injection of 8 ml of contrast material, 10 CT scans, with 6-mm collimation, each 100-msec long, were obtained in 6 sec, at a single level through the
atnal
showed drainage
chambers.
opacification
The
“venous
phase”
of this
of the left atrium, indicating
CT
angiogram
pulmonary
venous
of the sequestration.
A series of ultrafast high-resolution CT (HRCT) scans (3-mm collimation, high-spatial-frequency reconstruction algorithm) were ob-
pathologically.
tamed
through
the abnormal
right
lower
lobe at 1-cm
intervals
with
patient supine. These showed numerous, moderately thin-walled, air-containing cysts, 0.5 to 1.0 cm in diameter, that were not visible the
Case
Report
A 1 9-year-old
routine
chest
hyperlucent, before,
a chest
woman
radiograph.
had
a 3-cm,
The surrounding
but no air-containing radiograph
rounded
had shown
cysts
soft-tissue
right lower
were
consolidation
mass
AJR 157:947-949,
November
1991 o361-803x/91/1575-0947
a
on conventional CT. Several larger air-containing cysts, up to 3 cm in diameter, were noted adjacent to the smaller cystic spaces.
Last, two series of dynamic, expiratory, ultrafast HRCT scans were obtained through the middle and lower portions of the sequestration in an attempt to show air trapping within the abnormally lucent
lobe appeared
visible.
Five years
in the right lower
Received May 10, 1991; accepted after revision June 18, 1991. 1 Department of Aadiology, University of California, San Francisco, Department of Pathology, University of California, San Francisco,
2
on
San Francisco, San Francisco,
0 American
Roentgen
CA 941 43-0628. CA 94143-0628. Ray Society
Address
reprint
requests
to E. J. Stern.
Downloaded from www.ajronline.org by 122.183.228.146 on 10/07/15 from IP address 122.183.228.146. Copyright ARRS. For personal use only; all rights reserved
948
STERN
ET
AL.
AJA:157,
November
1991
Fig. 1.-A, Conventional CT scan at level of right lung base. A nonsegmental area of hyperlucency is visible. Cystic components of sequestration are poorly seen. B, Dynamic ultrafast high-resolution CT time-density analysis of normal left lung during a forced exhalation. Measurements were acquired from region of interest (ROI) shown. Hounsfield units are on y-axis, time in seconds on x-axis. Note rapid increase in lung density as patient exhales. During exhalation, lung increases in density by approximately 310 H, well within range of normal in patients we have studied. Note that rate of change in density yields a curve that Is convex upward. C, Time-density analysis of multicystic portion of sequestration in right lung, performed during same exhalation and at same level as in B, shows an increase in density as patient exhales, but at a slower rate than ROl in B. Rate of change in density yields a curve that is concave upward, as opposed to convex-upward curve seen in normal lung. Also, increase in lung density (+140 H) is considerably less than in normal left lung. These findings suggest that this area ventilates, but at an abnormally slow rate. D, Time-density analysis from an area of apparently normal lung parenchyma (arrows) adjacent to sequestration also shows a slow and delayed increase in density during exhalation, yielding a curve that is concave upward. Note that this area of lung is qualitatively more lucent than normal anterior right lung. E, Gross pathologic specimen obtained during partial right lower lobectomy shows multicystic honeycomblike lung that represents sequestration. Note normal lung parenchyma (arrow) adjacent to sequestration.
lung.
Ten
scans,
each
with
of 100 rnsec, were obtained in a forced vital capacity maneuver.
a duration
6 sec, as the patient
performed
Time-density
analysis
graphs
and
uation
were
determined
for
values
for each
series
of images.
Selected
and displayed
in the cin#{233}-loop mode
that
during
occurred
tabulated
mean
normal
and
lung
regions
to show
Hounsfield
abnormal also
atten-
lung were
regions
increase
Several
other
areas
of the
seen
in the
sequestration
normal that
contralateral consisted
of small
on
lung. air
no increase
in density
adjacent
to the cystic
the
CT
HACT
findings the
of delayed
and
to be
showed a normal increase
in density
transitional
HRCT,
which
the
suggests
HRCT
Ultrafast done
by using lung
lung
moves
the
had
normal
that
cephalad
diminished
during not
analysis
contralateral through
part
the
exhalation
in density.
obvious
subpleural
cystic
lung, (Figs.
which 1 B-i
on
sequestration.
of the sequestration
scanning
D).
architecture
of the
left lung the
showed
increase
between normal
appeared
inspiration,
bronchovascular
it was
time-density normal
Unexpectedly, which
during
transitional and
exhalation.
sequestration,
obtained
sequestration
This
of
during
scans
region appeared
portion
exhalation.
that was
of lung
normal This
processes
Several areas within the sequestration that contained small cysts showed an increase in attenuation density during exhalation, but this increase was at a delayed rate, and to a lesser degree, than the density
showed
a region dynamic
visualized
the dynamic
cysts
as a control. plane
during
was
Although exhala-
AJA:157,
November
tion,
motion
was
that
the lung
this
to ensure
DYNAMIC
1991
minimal,
and
region
the same. Partial right lower lobectomy pulmonary
Downloaded from www.ajronline.org by 122.183.228.146 on 10/07/15 from IP address 122.183.228.146. Copyright ARRS. For personal use only; all rights reserved
of the x
sequestration specimen.
On
was gross
of which
filled
with
filled
cyst
were
mucin
and
thelium
and
identifiable
which
was performed,
diagnosed
was this
than
1 cm
largest the
rounded
rare
present
represented
lung
viewed
substantially
and an intralobar examination
resected
specimen
(14.0
air-containing
clotted
soft-tissue
cysts,
some
cysts
were
blood.
This
blood-
mass
seen
on
the
the cysts were lined by airway epi-
cartilage
elements.
in the
subpleural gradually
sequestration
No
However,
blended
the
were
was
pathologic
in diameter;
contained
Histologically,
normal
after the
in this part of the specimen.
parenchyma specimen; lung,
less
contained
slice
primarily of thin-walled
the
represented
chest radiograph.
images
on each
inspection,
8.0 x 2.3 cm) consisted
most
the individual
selected
HRCT
region with (Fig.
bronchus
was
some normal lung of
the
the cystic
resected abnormal
1 E).
Discussion It has been suggested that hyperlucent lung parenchyma seen in association with sequestration is the result of air trapping within the sequestration, within large air-containing cysts, or within the adjacent lung [5-7]. In each of these instances, the air trapping presumably occurs because the abnormal lung parenchyma lacks normal bronchial connections and is aerated collaterally [5, 6]. In a recent review, Ikezoe et al. [6] found the presence of lucent or low-attenuation areas of “emphysema” in six of i 6 patients with an intralobar sequestration. Because of the greater contrast and density resolution of CT, the hyperlucent lung associated with sequestrations is better seen on CT scans than on chest radiographs. However, heretofore CT has not clearly shown the relationship of the lucent areas to either cystic regions of the sequestration or to adjacent lung. Ikezoe et al. [6] were unable to show that areas of Iucency were associated with small air-containing cysts, but HRCT was not performed in any of their cases, and cyst walls may not have been visible. In our case, the areas of lucency on CT corresponded to areas of the sequestration that contained both small and large air cysts, and these lucent areas also were seen in apparently normal lung at end exhalation. The cystic portion of the sequestration that we studied showed a delayed and diminished increase in density during exhalation, best shown by using time-density analysis. These findings suggest that communication with the airway occurred in this case, but that an abnormal egress of air, or air trapping, occurred during rapid exhalation; if no communication were present, no change in density or cyst size would be expected during exhalation. Indeed, in several areas of the sequestration, little or no increase in density was measured during exhalation. Because no normal bronchial connection to the sequestration was seen on pathologic examination, we assume that the ability of some parts of the sequestration to ventilate, albeit at a reduced rate, must be because of the presence of anomalous bronchial connections or fistulas.
OF
SEQUESTRATION
949
These features strongly support the hypothesis of air trapping via collateral pathways as the mechanism for the emphysematous parenchyma associated with intralobar pulmonary sequestrations. It is not clear if a previous or ongoing inflammatory process is a prerequisite for the development of these collateral pathways or emphysematous spaces. For example, in smoking-related pulmonary emphysema, a contributing factor to the formation of emphysematous cysts appears to be inflammatory degradation and disruption of elastic fibers in the alveolar walls [8]. Additionally, a region of apparently normal lung adjacent to the sequestration also showed a delayed and diminished increase in density during exhalation. Although we have no pathologic proof, we speculate that this segment of lung, which exhibited abnormal lucency only during exhalation, also must have been trapping air, either because of the mass effect of the sequestration and compression of the segment’s subtending airway or as a manifestation of inherently abnormal lung parenchyma that was transitional between the sequestration and normal lung, detectable only with this technique. The use of ultrafast CT to define the venous drainage of a sequestration has not been previously reported. Although we do not advocate the use of CT angiography in all such cases, the detection of the venous drainage of the sequestration into the left atrium, shown in this case, makes the diagnosis of intralobar sequestration likely. Extralobar sequestrations usually drain via systemic veins into the right atrium and only rarely empty via pulmonary veins. We conclude that dynamic ultrafast HRCT clearly shows the air trapping that is proposed as a mechanism for the emphysematous changes that occur in association with intralobar sequestrations and that this air trapping occurs both in the sequestration and in adjacent normal-appearing parenchyma. Also, HRCT shows the characteristic multicystic component of pulmonary sequestrations better than conventional CT does, thus aiding in the diagnosis.
REFERENCES 1 . Choplin A, Siegel M. Pulmonary sequestration: six unusual presentations. AJR 1980;1 34:695-700 2. Felker A, Tonkin I. Imaging of pulmonary sequestrations. AJR 1990:154 : 241 -249 3. Paul D, Mueller C. Case report: pulmonary sequestration. J Comput Assist Tomogr 1982:6: 163-1 65 4. Wimbish K, Agha F, Brady T. Bilateral pulmonary sequestration: CT appearance. AJR 1983;140:689-690 5. Felson B. Pulmonary sequestration revisited. Med Radiogr Photogr 1988:64:1-28 6. Ikezoe J, Murayarna 5, Godwin JD, Done SL, Verschakelen JA. Bronchopulmonary sequestration: CT assessment. Radiology 1990:176:375-379 7. Culiner M, Wall C. Collateral ventilation in intralobar pulmonary sequestration. Dis Chest 1965:47:118-122 8. Fukuda Y, Basset F, Soler P. Ferrans VJ, Masugi Y, Crystal AG. Intraluminal fibrosis and elastic fiber degradation lead to lung remodeling in pulmonary Langerhans cell granulomatosis (histiocytosis X). Am J Pathol 1990:137:415-424
947
Case ‘‘:
f,’.
‘, ‘
*‘
Bronchopulmonary High-Resolution Eric J. Stern,1
W. Richard
Y
,
.‘-,
,t
-.
.-
-:
,,
Sequestration: Dynamic, CT Evidence of Air Trapping
Webb,1
Report
Martha
L. Warnock,2
and
Christopher
Ultrafast,
J. Salmon1
lobe with an air-fluid level, and the patient was treated for presumed
Intralobar bronchopulmonary sequestration is a congenital anomaly that consists of nonfunctioning, abnormal lung tissue that is contained within an otherwise normal lung and has an anomalous systemic blood supply [1 -4]. Although intralobar sequestrations lack normal communications with the tracheobronchial tree, they can be ventilated by collateral air drift or through fistulous bronchial communications that may develop after an episode of infection. An air-containing intralobar sequestration can appear on chest radiographs as an area of hyperlucency, with or without associated visible cysts, or can appear as normal lung [5]. The CT appearances of bronchopulmonary sequestration have recently been reviewed [6], and the presence of lucent or low-attenuation areas of “emphysema” have been emphasized. It has been suggested that the emphysema seen in patients with sequestration results from collateral ventilation and air trapping [7]. We recently had an opportunity to test this hypothesis by using dynamic expiratory, ultrafast, highresolution CT (HRCT) in a patient who subsequently had an intralobar pulmonary sequestration confirmed surgically and
necrotizing
pneumonia.
On conventional
CT, obtained
area
nonsegmental
of abnormally
with contiguous lucent lung
1 -cm collimation, a was visible in the
posterior, medial, right lung base, adjacent and inferior to a homogeneous well-circumscribed soft-tissue density, corresponding to the mass visible on the chest radiograph. The lucent lung suggested the presence of one or more thin-walled, air-containing cysts (Fig. 1A). Aortography abdominal
aorta
venous
drainage
showed an anomalous artery arising from the upper and supplying the region of abnormal right lung. The was
not
clearly
shown.
CT (Imatron C-i 00, Imatron Inc., So. San Francisco, was first performed immediately after the patient’s aortogram Ultrafast
obtained,
with
the
angiographic
catheter
still
in
place
within
CA) was the
anomalous artery that was feeding the sequestration, in order to show the venous drainage of the sequestered lung. After the injection of 8 ml of contrast material, 10 CT scans, with 6-mm collimation, each 100-msec long, were obtained in 6 sec, at a single level through the
atnal
showed drainage
chambers.
opacification
The
“venous
phase”
of this
of the left atrium, indicating
CT
angiogram
pulmonary
venous
of the sequestration.
A series of ultrafast high-resolution CT (HRCT) scans (3-mm collimation, high-spatial-frequency reconstruction algorithm) were ob-
pathologically.
tamed
through
the abnormal
right
lower
lobe at 1-cm
intervals
with
patient supine. These showed numerous, moderately thin-walled, air-containing cysts, 0.5 to 1.0 cm in diameter, that were not visible the
Case
Report
A 1 9-year-old
routine
chest
hyperlucent, before,
a chest
woman
radiograph.
had
a 3-cm,
The surrounding
but no air-containing radiograph
rounded
had shown
cysts
soft-tissue
right lower
were
consolidation
mass
AJR 157:947-949,
November
1991 o361-803x/91/1575-0947
a
on conventional CT. Several larger air-containing cysts, up to 3 cm in diameter, were noted adjacent to the smaller cystic spaces.
Last, two series of dynamic, expiratory, ultrafast HRCT scans were obtained through the middle and lower portions of the sequestration in an attempt to show air trapping within the abnormally lucent
lobe appeared
visible.
Five years
in the right lower
Received May 10, 1991; accepted after revision June 18, 1991. 1 Department of Aadiology, University of California, San Francisco, Department of Pathology, University of California, San Francisco,
2
on
San Francisco, San Francisco,
0 American
Roentgen
CA 941 43-0628. CA 94143-0628. Ray Society
Address
reprint
requests
to E. J. Stern.
Downloaded from www.ajronline.org by 122.183.228.146 on 10/07/15 from IP address 122.183.228.146. Copyright ARRS. For personal use only; all rights reserved
948
STERN
ET
AL.
AJA:157,
November
1991
Fig. 1.-A, Conventional CT scan at level of right lung base. A nonsegmental area of hyperlucency is visible. Cystic components of sequestration are poorly seen. B, Dynamic ultrafast high-resolution CT time-density analysis of normal left lung during a forced exhalation. Measurements were acquired from region of interest (ROI) shown. Hounsfield units are on y-axis, time in seconds on x-axis. Note rapid increase in lung density as patient exhales. During exhalation, lung increases in density by approximately 310 H, well within range of normal in patients we have studied. Note that rate of change in density yields a curve that Is convex upward. C, Time-density analysis of multicystic portion of sequestration in right lung, performed during same exhalation and at same level as in B, shows an increase in density as patient exhales, but at a slower rate than ROl in B. Rate of change in density yields a curve that is concave upward, as opposed to convex-upward curve seen in normal lung. Also, increase in lung density (+140 H) is considerably less than in normal left lung. These findings suggest that this area ventilates, but at an abnormally slow rate. D, Time-density analysis from an area of apparently normal lung parenchyma (arrows) adjacent to sequestration also shows a slow and delayed increase in density during exhalation, yielding a curve that is concave upward. Note that this area of lung is qualitatively more lucent than normal anterior right lung. E, Gross pathologic specimen obtained during partial right lower lobectomy shows multicystic honeycomblike lung that represents sequestration. Note normal lung parenchyma (arrow) adjacent to sequestration.
lung.
Ten
scans,
each
with
of 100 rnsec, were obtained in a forced vital capacity maneuver.
a duration
6 sec, as the patient
performed
Time-density
analysis
graphs
and
uation
were
determined
for
values
for each
series
of images.
Selected
and displayed
in the cin#{233}-loop mode
that
during
occurred
tabulated
mean
normal
and
lung
regions
to show
Hounsfield
abnormal also
atten-
lung were
regions
increase
Several
other
areas
of the
seen
in the
sequestration
normal that
contralateral consisted
of small
on
lung. air
no increase
in density
adjacent
to the cystic
the
CT
HACT
findings the
of delayed
and
to be
showed a normal increase
in density
transitional
HRCT,
which
the
suggests
HRCT
Ultrafast done
by using lung
lung
moves
the
had
normal
that
cephalad
diminished
during not
analysis
contralateral through
part
the
exhalation
in density.
obvious
subpleural
cystic
lung, (Figs.
which 1 B-i
on
sequestration.
of the sequestration
scanning
D).
architecture
of the
left lung the
showed
increase
between normal
appeared
inspiration,
bronchovascular
it was
time-density normal
Unexpectedly, which
during
transitional and
exhalation.
sequestration,
obtained
sequestration
This
of
during
scans
region appeared
portion
exhalation.
that was
of lung
normal This
processes
Several areas within the sequestration that contained small cysts showed an increase in attenuation density during exhalation, but this increase was at a delayed rate, and to a lesser degree, than the density
showed
a region dynamic
visualized
the dynamic
cysts
as a control. plane
during
was
Although exhala-
AJA:157,
November
tion,
motion
was
that
the lung
this
to ensure
DYNAMIC
1991
minimal,
and
region
the same. Partial right lower lobectomy pulmonary
Downloaded from www.ajronline.org by 122.183.228.146 on 10/07/15 from IP address 122.183.228.146. Copyright ARRS. For personal use only; all rights reserved
of the x
sequestration specimen.
On
was gross
of which
filled
with
filled
cyst
were
mucin
and
thelium
and
identifiable
which
was performed,
diagnosed
was this
than
1 cm
largest the
rounded
rare
present
represented
lung
viewed
substantially
and an intralobar examination
resected
specimen
(14.0
air-containing
clotted
soft-tissue
cysts,
some
cysts
were
blood.
This
blood-
mass
seen
on
the
the cysts were lined by airway epi-
cartilage
elements.
in the
subpleural gradually
sequestration
No
However,
blended
the
were
was
pathologic
in diameter;
contained
Histologically,
normal
after the
in this part of the specimen.
parenchyma specimen; lung,
less
contained
slice
primarily of thin-walled
the
represented
chest radiograph.
images
on each
inspection,
8.0 x 2.3 cm) consisted
most
the individual
selected
HRCT
region with (Fig.
bronchus
was
some normal lung of
the
the cystic
resected abnormal
1 E).
Discussion It has been suggested that hyperlucent lung parenchyma seen in association with sequestration is the result of air trapping within the sequestration, within large air-containing cysts, or within the adjacent lung [5-7]. In each of these instances, the air trapping presumably occurs because the abnormal lung parenchyma lacks normal bronchial connections and is aerated collaterally [5, 6]. In a recent review, Ikezoe et al. [6] found the presence of lucent or low-attenuation areas of “emphysema” in six of i 6 patients with an intralobar sequestration. Because of the greater contrast and density resolution of CT, the hyperlucent lung associated with sequestrations is better seen on CT scans than on chest radiographs. However, heretofore CT has not clearly shown the relationship of the lucent areas to either cystic regions of the sequestration or to adjacent lung. Ikezoe et al. [6] were unable to show that areas of Iucency were associated with small air-containing cysts, but HRCT was not performed in any of their cases, and cyst walls may not have been visible. In our case, the areas of lucency on CT corresponded to areas of the sequestration that contained both small and large air cysts, and these lucent areas also were seen in apparently normal lung at end exhalation. The cystic portion of the sequestration that we studied showed a delayed and diminished increase in density during exhalation, best shown by using time-density analysis. These findings suggest that communication with the airway occurred in this case, but that an abnormal egress of air, or air trapping, occurred during rapid exhalation; if no communication were present, no change in density or cyst size would be expected during exhalation. Indeed, in several areas of the sequestration, little or no increase in density was measured during exhalation. Because no normal bronchial connection to the sequestration was seen on pathologic examination, we assume that the ability of some parts of the sequestration to ventilate, albeit at a reduced rate, must be because of the presence of anomalous bronchial connections or fistulas.
OF
SEQUESTRATION
949
These features strongly support the hypothesis of air trapping via collateral pathways as the mechanism for the emphysematous parenchyma associated with intralobar pulmonary sequestrations. It is not clear if a previous or ongoing inflammatory process is a prerequisite for the development of these collateral pathways or emphysematous spaces. For example, in smoking-related pulmonary emphysema, a contributing factor to the formation of emphysematous cysts appears to be inflammatory degradation and disruption of elastic fibers in the alveolar walls [8]. Additionally, a region of apparently normal lung adjacent to the sequestration also showed a delayed and diminished increase in density during exhalation. Although we have no pathologic proof, we speculate that this segment of lung, which exhibited abnormal lucency only during exhalation, also must have been trapping air, either because of the mass effect of the sequestration and compression of the segment’s subtending airway or as a manifestation of inherently abnormal lung parenchyma that was transitional between the sequestration and normal lung, detectable only with this technique. The use of ultrafast CT to define the venous drainage of a sequestration has not been previously reported. Although we do not advocate the use of CT angiography in all such cases, the detection of the venous drainage of the sequestration into the left atrium, shown in this case, makes the diagnosis of intralobar sequestration likely. Extralobar sequestrations usually drain via systemic veins into the right atrium and only rarely empty via pulmonary veins. We conclude that dynamic ultrafast HRCT clearly shows the air trapping that is proposed as a mechanism for the emphysematous changes that occur in association with intralobar sequestrations and that this air trapping occurs both in the sequestration and in adjacent normal-appearing parenchyma. Also, HRCT shows the characteristic multicystic component of pulmonary sequestrations better than conventional CT does, thus aiding in the diagnosis.
REFERENCES 1 . Choplin A, Siegel M. Pulmonary sequestration: six unusual presentations. AJR 1980;1 34:695-700 2. Felker A, Tonkin I. Imaging of pulmonary sequestrations. AJR 1990:154 : 241 -249 3. Paul D, Mueller C. Case report: pulmonary sequestration. J Comput Assist Tomogr 1982:6: 163-1 65 4. Wimbish K, Agha F, Brady T. Bilateral pulmonary sequestration: CT appearance. AJR 1983;140:689-690 5. Felson B. Pulmonary sequestration revisited. Med Radiogr Photogr 1988:64:1-28 6. Ikezoe J, Murayarna 5, Godwin JD, Done SL, Verschakelen JA. Bronchopulmonary sequestration: CT assessment. Radiology 1990:176:375-379 7. Culiner M, Wall C. Collateral ventilation in intralobar pulmonary sequestration. Dis Chest 1965:47:118-122 8. Fukuda Y, Basset F, Soler P. Ferrans VJ, Masugi Y, Crystal AG. Intraluminal fibrosis and elastic fiber degradation lead to lung remodeling in pulmonary Langerhans cell granulomatosis (histiocytosis X). Am J Pathol 1990:137:415-424
