Thoracic Koichi
Nishimura,
MD
#{149} Masanori
Kitaichi,
MD
Takateru
Diffuse Panbronchiolitis: High-Resolution CT and Diffuse panbronchiolitis characterized by chronic tation
and
airway
(DPB) airflow
is limiwith
inflammation
bronchiolar lesions. Chest radiographs of patients with DPB usually show small nodular shadows throughout both lungs. The authors investigated the nature and pathogenesis of the radiologic features of DPB by correlating high-resolution computed tomographic (HRCT) findings with histopathologic features. The HRCT images of nine patients with DPB were compared with the observalions made with inflated lung specimens. The HRCT findings of DPB included centrilobularly distributed, small rounded areas of attenuation; branched linear areas of attenuation, contiguous with the small rounded areas; dilated airways with thick walls, also common outside secondary pulmonary lobules; and decreased lung attenuation in peripheral areas due to air trapping caused by bronchiolar narrowing in the subpleural zones. The authors believe that HRCT best demonstrates this characteristic location of small rounded areas of attenuation associated with dilated airways. Index
terms:
Bronchiolitis,
60.219
puted tomography 60.1211 #{149} Lung, 60.795
(CT), high-resolution, CT, 60.1211 #{149}Lung,
Radiology
184:779-785
I
From
1992;
the
Chest
Kyoto University, and the Department
Medicine,
Kyoto
Disease
Research
Com-
#{149}
diseases,
Institute,
Sakyo-ku, Kyoto 606, Japan, of Radiology and Nuclear
University
Hospital,
Kyoto,
Japan. Received September 24, 1991; revision requested November 25; revision received March 9, 1992; accepted April 6. Address reprint requests to K.N. C RSNA, 1992
I
N
1969, (DPB)
Izumi,
#{149}
#{149} Harumi
Correlation Pathologic
diffuse panbronchiolitis was first described
as a disease
MD
characterized
MATERIALS in Japan
clinically
by
cough, expectoration, and physiologically by chronic airflow limitation; and histologically by typical bronchiobar lesions (1,2). the
results
wide tients
survey showed with DPB had
sal sinusitis
of a Japanese
and
that
In
nation-
In our study,
jor
pathologic
the
nosed.
75%
In these cases, there were typical lesions of panbronchiolitis, as described by Kitaichi et ab (4,5), consisting
were
unit
time, it was primarily bronchioles
bronchi
is no doubt findings
high(HRCT)
over
an
aggregate
within
(3-6).
that are
the
present
adjacent
years), Al-
main
and around the bronchiolar walls, it is not known whether the respiratory bronchioles are primarily or secondarily affected. Furthermore, the relationship of DPB to bronchiectasis, if there is any, remains to be elucidated (6). Extensive studies are hampered by the fact that only a few cases of DPB have been reported outside Japan (710). Thurlbeck (11) also suggested that there could be some degree of overlap between those cases diagnosed as DPB in Japan and those cases that are diagnosed as bronchiectasis in North America. Radiographicabby, DPB is characterized by diffuse small nodular shadows involving the lungs and mild to moderate hyperinflation (2,5). Diffuse small nodular shadows are uncommon in bronchiectasis, even in patients with extensive disease (12). However, this finding does occur commonly in various interstitial lung disorders such as sarcoidosis (12,13). It is, therefore, important to distinguish DPB from other disorders with similar abnormalities seen on chest radiographs, especially for Japanese patients.
of foamy
and
bymphoid
walls of respiratory
One man
also
and
who ranged in age from 20 to 66 years, had DPB, which was histologically diag-
Recent studies, however, have shown that DPB causes inflammation and dilatation of not only the bronthere
the findings
radiographs tomographic
scans with the gross appearance, contact radiographs, stereomicroscopic views, and histologic findings of lung specimens. Nine patients (six men and three women),
and
but
METHODS
we correlated
from routine chest resolution computed
(1,2).
though
AND
that most pachronic parana-
nonsmokers (2). At that thought that the disease involved the respiratory
chiobes
MD
Itoh,
of Findings’
chronic dyspnea;
1983,
Radiology
alveolar
but
bronchioles
ducts
was a former the other
of cells
and
alveoli.
smoker eight
(10 pack-
patients
had
never smoked. All patients had chronic expectoration, and six of the nine had mild to moderate dyspnea. Otolaryngobogic examination and radiographs of the head and sinuses showed chronic paranasal function chronic moderate
sinusitis in all cases. Pulmonary tests revealed mild to severe airflow limitation and mild to hypoxemia (Table).
The CT scans T8800
unit
(GE
were
obtained
Medical
on a CT!
Systems,
Milwau-
kee) with 5-mm collimation during breath holding for 9.6 seconds after full inspiration. A high spatial-resolution algorithm (bone
detail
patients.
algorithm)
The
was
used
high-resolution
for
all
images
were
viewed at window bevels appropriate for pulmonary parenchyma (-800 HU; window width, 1,000 HU) and for mediastinum (±0 maximize
HU; window the differences
attenuation, settings
additional were
Recent
also
HRCT
renchymal sections
width, 250 HU). To in regional lung
studies
diseases with
narrower
windo%.
used.
of pulmonary
have
a collimation
19). In the present
involved of 1-2
study,
pathin
mm
(14-
we employed
medium-sized thickness scans of 5-mm collimation, as described by Todo and Herman (20). Identification of lesions with respect essential
to pulmonary for defining
tion. Because included
vascular
on a single
Abbreviations: tis, HRCT
more
vascular images is a centrilobular loca-
DPB =
high-resolution
scan
=
images
are
of medium
diffuse panbronchioliCT.
779
Clinical
and Pulm
Characteristics
Patient/Age
onary
(y)/Sex
Functio
n Tests
iv1
FEy1 (L)
of Patien ts with
DPB
(% pred)
FEV1/FVC (%)
VC (%) 106.2
Pao (torr)
Sputum (mL/d)
1/20/M
2.71
72.8
63.2
79.9
30
2/55/M
0.71 1.01
21.9 63.5
61.7 72.6
47.7 70.6
48.8 70.6
200 20
2.16 1.25
55.8
64.7
70.6
5/47/F
57.1
64.1
81.7
63.0 61.6
10 20
6/45/M
1.59
47.7
58.7
72.0
64.4
7/52/F
1.63
70.0
74.1
89.0
74.6
3/66/F 4/38/M
Histopathologic Diagnosis Open lung biopsy (RML) Autopsy Lobectomy (LLL) due to lung cancer Open lung biopsy (R:S3, S9) Open lung biopsy (L:S1 + 2, 54, S6)
0.92
24.1
37.2
63.1
64.0
150
9/2i/M
2.16
50.3
71.3
74.5
64.5
10
thickness,
we
volume in i second, FVC = forced vital capacity, L = left, LLL = leftlowerlobe, value, R = right, RML = right middle lobe, S = segment, VC = vital capacity.
forced expiratory of predicted
=
percentage
=
preferred
5-mm
to thinner sections. In seven patients,
specimens
tamed
biopsy.
at open
lung
were One
time interval from HRCT to thowas 3-60 days (mean, 30.3 days)
lower lobectomy adenocarcinoma
patients. The was clinically
the was
period observed
patient
died
despite condition
improvement for which
antibiotic formed
therapy. 122 days
for
condition stable
from
patients
and
from
two
radiologist
findings,
was
one
patients. of CT and
macroscopicalby
during were
seg-
from
which
throughout
both
were
between
the HRCT
and
diographs histologic
and the findings
the biopsy
Specimens
were
sites
The lung
chus
with
before
lobe from a lobectomy
a fixative (13).
serially
cut
HRCT
who
fixed,
died
per-
and
polyethyl-
into the brondried
at a constant
of
was
the patient who were inflated by
containing
formaldehyde The
scans
the biopsy
of the patient
lower
ene glycol
sliced
specimens thickness
were (1 cm
ally
less
than
(L:S1
+
2,
of oxygen,
artenalpressure
and contact
raand
and
Figure
2. Patient
strates
centrilobular
9.
4
HRCT scan demonsmall rounded and
branching linear areas of attenuation with a millimeter pattern. Note that a constant distance (2-3 mm) separates small rounded areas of attenuation (arrows) from the adjacent pleura or pulmonary veins (pv) and that these small rounded areas tend to be located at the end of branching linear areas of attenuation (arrowheads). These HRCT findings are representative of DPB in our series.
and
central
rounded HRCT
areas of attenuation scans were always
in
areas
enclosed by pleura, pubmonary veins, or extrabobubar pulmonary vessels and bronchi (ie, the boundaries of secondary pulmonary
pa-
sessed
as
tients (patients 2 and 6). The major HRCT findings of DPB were small rounded areas of attenuation, branched linear areas of attenua-
were
prominent
gions
(Fig
lion,
graphs of inflated specimens 3,4). Some nodular lesions are seen on stereophotomicrographs
outer
made
in diameter
Small seen on
shadows
in attenuation
was
scans
L
lobules) and were usually separated by a distance of 2-3 mm from these structures. They were, therefore, as-
and
Radiology
hyperinfla-
stereomicroscopic for the inflated
5 mm
ties
#{149}
2,
had unclear borders (Fig 1). Mild to moderate hypermnflation and “tramlines” were also observed. Penbronchial thickening and thin tubular
(21).
comparison
shadows
mild
The chest radiographs of nine patients demonstrated diffuse small nodular infiltrates throughout both lungs. Nodular shadows were gener-
bronchioles
Subsequently,
nodular
lungs.
and then I mm). Contact radiographs of each specimen slice were obtained. Both contact radiographs and sliced specimens were examined with a stereomicroscope
780
+
RESULTS
injection of 10% formalin, with a stereomicroscope,
compared
and
and
and further histologic sections (4 rim) were then made. Stereomicroscopic views and histologic findings at low magnificathe biopsy formed.
small
radio-
tion.
about 1-2 cm thick, presumably large enough to contain secondary pulmonary lobules. Biopsy specimens, inflated and
fixed through were examined
Posteroantenor
lungs
the lung
thoracotomy
obtained.
1. Patient 4. shows diffuse
Figure graph
To obtain patho-
(HI.)
(M.K.) observed
the sites
were in
different
one pathologist
specimens
per-
biopsy specimens three different segments
logic
instilling
=
(L:S1
to thoOne
accident,
An autopsy after HRCT.
five
the left underwent
Pao
56,
a of the
of his respiratory he received intensive
ments in the other a rigorous correlation
tion
S9) Open lung biopsy S9) Open lung biopsy S9)
of before
from HRCT in any case.
of a cerebrovascubar
At thoracotomy,
recorded
(R:S2,
biopsy
and the biopsy procedure; no in chest radiographic find-
ings during racotomy
two
(R:S3, 56)
lung
ob-
lung. The racotomy
both HRCT deterioration
lung biopsy
Open
patient
a left papillary
in these eight these patients
Open
collimation
underwent 3 x 3-cm
obtained
50-100 10
8/30/M
Note.-FEV1 % pred
-
thickened
and
and lung
dilated
bronchi, between
zones.
in two
walls
and
of
dispanithe
inner
being
in
2) (17,22).
centribobular
Such
re-
a centribob-
ubar distribution for small nodules could be confirmed with correlative stereomicrographs
and
photomicro(Figs clearly
September
(Fig
1992
linear areas of attenuation extending from small rounded areas of attenuation on HRCT scans corresponded to dilated bronchioles filled with secretions, which, on stereomicrographs, were most clearly observed in subpleural regions (Fig 4c). Dilatation thickening
of bronchi and are also common
wall in air-
ways outside the secondary pulmonary lobules (Fig 5). However, thickening of extrabobubar bronchial walls observed on the HRCT scans of patient 2 could not be confirmed with lung specimens obtained at autopsy. Intrabronchiab secretions may have contributed to bronchial wall thickening seen on HRCT scans of this patient, in view of the fact that the patient expectorated as much as 200 mL of sputum every day. The outer layer and subpleural zone of the lung were seen as areas of hypoattenuation on the HRCT scans. Attenuation between the central and peripheral parts of the lungs was remarkabby
different.
lung attenuation on narrower (23). Although distinguish a the outer and pleural layer
This
minished attenuation scans of patients with
Figure
3. Patient
linear
areas
crograph (large
4.
scans
of attenuation
of biopsy arrows),
(a) HRCT
at several
in a biopsy
specimens
corresponding
levels
specimen
obtained
from
to small
rounded
demonstrate (area
within
the left lung areas
small
rounded
square).
(b) Stereophotomi-
demonstrates
of attenuation
and branch-
some on
the
nodular
HRCT
lesions
scans.
Note
the dilated peripheral airway filled with secretions (small arrows) and accompanying pulmonary vessel (arrowheads). Because the dilated airways are larger and thicker than the associated pulmonary artery, these structures most likely correspond to the branching linear areas of attenuation observed on the HRCT scans. Bar = 5 mm. A = specimen obtained from the left upper
lobe,
segment
3; B
specimen
=
obtained
from
the
left
lower
lobe,
segment
9. (Fig 3 con-
tinues.)
3b).
on the DPB.
HRCT
DISCUSSION
b. ing
stratified
was best appreciated window settings (Fig 6) it was impossible to clear boundary between inner zones, the subappeared to have a di-
A photomicrograph
(bow-magnifi-
cation view) of the same specimen demonstrates that the nodule is enclosed by pleura and an interbobular septum with a constant separation of approximately 2-3 mm, indicating that (Fig
it is a typical 3c).
centribobular
nodule
Small rounded areas of attenuation on HRCT scans corresponded to nodubar lesions, with an average diameter of about 1 mm, situated adjacent to membranous and respiratory bronchi-
oles
and
lesions and adjacent
alveoli.
Unit
Volume
184
by
recognized
lesions
(Fig
Kitaichi
within
et al (4,5),
these
nodular
3d).
The pathologic basis for branching linear areas of attenuation proved to be widening of the bronchiolar bumen, chronic inflammatory thickening of the bronchiolar presence of intraluminab
wall,
and the secretions
in and around the respiratory bronchialveolar
4b).
these nodules inflammatory
lesions Number
#{149}
as described
(Figs 4, 5). All these findings contribute to the radiopacity of bronchioles that are not normally visualized. A contact radiograph of the inflated and fixed left lower lobe from patient 3 demonstrated some radiopaque nodules, adjacent to the terminal portion of dilated peripheral airways (Fig
oles. Histologically, represent the chronic
and fibrotic membranous
tis,
were
ducts
of panbronchioli3
and
Some
showed
peripheral
focal
narrowing
airways
(Fig
The secondary pulmonary lobule is about 1 cm wide. It is bordered by interbobular septa, pleura, pulmonary veins, or extrabobubar pulmonary yessebs
and
bronchi
(Fig
7) (12,13,24,25).
Pulmonary
arteriolar and bronchiobar structures enter the central portion of the lobule. Bronchioles divide into three to five terminal bronchioles within a lobule. The distance from the first-order respiratory bronchiole to the peripheral almost constant
border
of the
lobule
is
(2-3 mm) (Fig 7) (25). Recent studies with correlation of HRCT and pathologic findings have demonstrated that the entire secondary pulmonary lobule and even intrabobular structures may be appreciated as areas of increased attenuation on HRCT scans in some diseases (1418,21,22).
Furthermore,
Murata
et al
also
(17) reported that the HRCT appearance of pulmonary parenchymab disease can be classified as having a centribobubar, panbobular, bronchovascubar, or peribobular distribution (17). In the present study of nine patients with DPB, small nodular lesions were always observed on both HRCT
5). The
scans
and
inflated
lung
specimens
Radiology
as
781
#{149}
being
(a) separated
pulmonary
from
veins,
the
pleura,
or extrabobular
pub-
monary vessels and bronchi (the boundaries of secondary pulmonary lobules) by approximately 2-3 mm and as being (b) continuous with pubmonary arteries and dilated airways (Figs
3, 7) (17,21,22).
Findings from our HRCT and pathologic correlative studies confirmed that lesions of DPB were typicabby centribobubarby distributed (Figs 3, 7), one of the four major CT distribution patterns described by Murata et al (17). To our knowledge, this is the first comprehensive study of DPB, correlating findings of HRCT scans with those of lung specimens obtamed at thoracotomy or at autopsy. Transbronchial biopsy specimens are generally not appropriate for such a correlative study because they are not barge enough to include secondary pulmonary lobules. Murata et al (17) observed centrilobular increased attenuation on HRCT scans in two patients with bronchopneumonia, one patient with lung abscess, one with cryptococcosis, one with nonspecific granubomatous inflammation, one of three patients with sarcoidosis, and one of five patients with malignant lymphoma. Moore et al (26) reported the CT findings
of pulmonary
histiocytosis
X, in
which many small nodules were distributed in the centers of secondary lobules around small airways with 1.5-mm collimation. In addition, contact radiographs of fixed and sliced lungs, which were excised at autopsy, were used by Itoh et al (27) to prove that small nodules in bronchopneumonia, acinonodose tuberculosis, chronic bronchiolitis, and simple pneumoconiosis
attributable
d.
to fenric
dust were located around terminal or respiratory bronchioles. It is, therefore, possible that centribobular nodules may be observed on HRCT scans of patients with these four diseases. Akira et al (28) reported that small nodules were centribobubarly distributed on HRCT scans of 19 patients with DPB diagnosed clinically and one patient with DPB diagnosed at autopsy.
four
They
CT types:
nodules
connected
linear areas accompanied ductal areas
depicted
small
schematics
nodules, to small
of
small branching
of attenuation, nodules by ring-shaped or small of attenuation, and barge cystic areas of attenuation accompanied by dilated proximal bronchi. Their illustrations were compatible with these findings. They suggested that patients with end-stage DPB may be included in a diagnosis of bronchi782
Radiology
#{149}
C.
(c) Histopathologic view demonstrates a typical centrilobular nodule by pleura (arrows) and interlobular septa (arrowheads), defining its centrilobular location. This specimen was obtained from the same left lower lobe as in Figure 4b. (Hematoxylin-eosin stain; original magnification, x 10.) (d) Histopathologic view shows two unit lesions of panbronchiolitis. There are aggregates of foamy and lymphoid cells within the walls of respiratory bronchioles (arrows). This specimen was obtained from the same left upper lobe as in Figure 4b. (Hematoxylin-eosin stain; original magnification, x40.) Figure enclosed
3 (continued).
ectasis. However, knowledge, it has
to the best of our been questionable
whether the appearance of these small nodules was followed by dibatation of the airways. To clarify the relation between the small nodules and dilated
airways
in DPB,
prospective
long-term studies are necessary. AUra et al (28) included the correlation of CT and pathologic findings from a lung excised at autopsy of one patient, which demonstrated that DPB lesions were situated around respiratory bronchioles. However,
although tubular structures were observed on both HRCT scans and contact radiographs, the small nodules were not clearly observed in patients with advanced disease. Nakata
study diseases,
vanced tasis,
et
ab (29),
in
on pulmonary reported
another
HRCT
parenchymab two
cases
of ad-
DPB: one involved bronchiecand the other had generalized
bulbous changes. The latter was never observed in the
finding present
study.
Some
authors
(24,25)
recognized, September
1992
pattern likely
on HRCT represented
scans within
are
most secondary
pulmonary lobules (Figs 2, 4). Moreover, Murata et ab (22) described the visualization of pulmonary central arterioles within secondary pubmonary lobules with HRCT. It is possible that the branched linear areas of attenuation seen on HRCT scans in patients with DPB may correspond to both dilated peripheral airways and pulmonary arteries. However, in view of the fact that stereomicrographs and contact radiographs (Figs 3-5) reveabed that dilated airways were a larger caliber than that of the accompanying pulmonary arteries, we presume that branched linear areas of attenuation on HRCT scans are attnibutable primarily to dilated, secretionfilled airways. Dilatation of bronchioles was apparent in most of the lung specimens obtained either at autopsy or bobectomy (Figs 3-5). A number of dilated airways were also demonstrated on HRCT scans. Our correlative study showed that dilated airways filled with intraluminab secretions may account for the observed branching and linear areas of attenuation on HRCT scans (Fig 4a, 4c) and for bronchial wall thickening (Fig 5a) in the more central portion of the lung. The batter finding is the CT equivalent of tramlines on the chest radiograph. Generally, tramlines observed on chest radiographs
may
also
intrabronchial seen in patient It is possible is secondary to
further
caused
2 (Fig
by
as were 5).
that airway bronchiobar
occurring in the lesions. However, sarily mean that
will always bronchiolar pathologic
be
secretions,
dilatation narrowing of nodular
vicinity this does dilatation
not necesof airways
result from widespread narrowing. The CT and findings from our study
emphasize
the
need
for
inves-
relation between DPB and bronchiectasis (6). Murata et ab (23) used positron tigating
the
emission
C.
Figure uation.
diograph
4. Patient Some
3.
linear
(a) HRCT areas
of specimen
are
scans
show
continuous
(1-mm-thick
slice)
small
rounded
with
dilated
from
the left lower
and branching
airways
linear
(arrowheads).
lobe reveals
areas
of atten-
(b) Contact
several
ra-
radiopaque
nodules. Note the dilated peripheral airways (arrows) and some nodules (arrowheads) near the extreme end of the stenotic airway (arrows). These correspond to small rounded and branching linear areas of attenuation on the HRCT scan. Bar = 1 cm. (c) Stereophotomicrograph shows dilated bronchioles filled with secretions in the subpleural area (arrows), which corresponds to the branching linear areas of attenuation on the HRCT scan. Bar = 1 cm.
from bronchographic and pathologic correlation, that airways with a miblimeter pattern within secondary pub-
Volume
184
Number
#{149}
3
monary chiobes.
tenuation
lobules Therefore,
are terminal
branching
linear
bronareas
of at-
in a millimeter
tomography
with
radioac-
tive nitrogen and CT attenuation numbers to point out that hyperinflation of the lung exists in the outer and peripheral zones in patients with DPB; however, these cases were not histologically present study,
difference tween the
confirmed. In the we demonstrated
histologically (Fig 6). Such a stratified
tilation
may
a
in lung attenuation beouter and inner zones in proved cases of DPB impairment
correspond
imaging of the cortex the lungs. Although
of yen-
to differential and medulla Gurney (30)
of pro-
Radiology
#{149}
783
a.
b.
C.
Figure
5. Patient and intralobular lung shows that eas of attenuation airway is dilated
2. (a) HRCT scans demonstrate dilatation of airways and bronchial wall thickening (arrows) proximal to secondary lobules small rounded and branching linear areas of attenuation (arrowhead). (b) Contact radiograph of the inflated and fixed right the intralobular and extralobular peripheral airways are dilated and stenotic. These are equivalent to the branching linear arand the dilated peripheral airways on the HRCT scan. Bar = 5 mm. (c) Stereophotomicrograph shows that the peripheral and stenotic in the vicinity of a small nodular lesion (arrowheads). Arrows = peripheral direction, bar = 5 mm.
posed logic
structural between
several differences
and physiothe cortex
and the medulla, the relative flation seen in DPB is probably
hyperincaused
by multiple foci of narrowing portions of peripheral airways. opsy and autopsy specimens,
along In bisome
peripheral adjacent
airways appeared stenotic to macroscopic nodular be-
sions
(Figs
and
frequency
airways central
4, 5). A greater
number
of stenotic
in the region,
outer where
peripheral
zone versus the large airways
predominate, probably account for the stratified appearance of lung attenuation seen in patients with DPB. In conclusion, HRCT is superior to chest radiography in demonstrating lesions of DPB, small nodules, dilated airways, and regional differences in
attenuation tion). lesion
(ie, relative
Although is never
the seen
hyperinfla-
location of a DPB on a routine chest
radiograph, the characteristic lobular distribution of these is clearly
observed
on
HRCT
scans.
be recognized but it is diffi-
cult
outer
zones. 784
In contrast, Radiology
#{149}
the
HRCT
inner
6. Patient
8.
CT scans
show
lower
lung
attenuation
in the outer
zones
than
in the
zones.
centrinodules
Hyperinflation can with chest radiography, to appreciate
Figure
and
scans
inner
can
demonstrate tion on the
the relative hyperinflatransverse section of the
lungs
a minimal
with
summation
fect. Consequently, HRCT be useful in differentiating
ef-
appears to DPB from
other graphic
Our
diseases
with
a similar
radio-
appearance.
HRCT
and
pathologic
tech-
niques may be useful as a model for the investigation of other pulmonary
September
1992
15.
16.
Bergin C, Roggli V, Coblentz C, Chiles C. The secondary pulmonary lobule: normal and abnormal CT appearances. AJR 1988; 151:21-25. Webb ER. High-resolution CT of the lung parenchyma. Radiol Clin North Am 1989;
27:1085-1097. 17.
Murata K, Khan nary parenchymal high-resolution
A, Herman PG. Pulmodisease: evaluation with CT. Radiology 1989; 170:
629-635. 18. -
Airway Artery
Pulmonary
Vein
Interlobular
5m
DPB. Each secondary and bronchial course along
ondary
lobule is indicated
structures enter the the interlobular septa.
pulmonary
infiltrative
Pulmonary
Figure 7. Schematic of centrilobular nodules ure on the left is derived from serial sections right indicates the location of the centrilobular
lobules.
Most
19.
Septum
and dilated peripheral airways of normal inflated lung, whereas nodules and dilated peripheral
by a different
type of shading.
central portion of the lobule. Nodular lesions are centrally
intralobular
and
extralobular
in DPB. The figthe one on the airways in
Pulmonary
arterial
Conversely, situated
pulmonary within these
bronchioles
are dilated
21.
with 22.
ular distribution eases. #{149}
pattern
Acknowledgment:
for
We thank
other
dis-
disorders. 746.
Elsevier,
M, Nishimura
6.
panbronchiolotis. In: Sharma OP, diseases in the tropics. New York: 1991; 479-509. Izumi T. Diffuse panbronchiolitis. 1991; 100:596-597. Desai SJ, Gephardt GN, Stoller JK. panbronchiolitis preceding ulcerative
tis. Chest 8.
Poletti Spiga served
741-
1988;
Kitaichi
Om P. Sharma, Medical in pre-
Amsterdam:
5.
7.
MD (University of Southern California, Center, Los Angeles), for his assistance paring the manuscript.
K, Izumi
T.
Yamanaka A, Saiki 5, Tamura Problems in chronic obstructive disease, with special reference panbronchiolitis. Naika 1969;
5, Saito K. pulmonary to diffuse 23:442-451.
Diffuse coli-
1989; 95:1342-1344.
10.
Uapanese]
2.
3.
4.
Homma
H, Yamanaka
A, Tanimoto
chiolitis from the view point of differential diagnosis. In: Grassi C, Rizzato G, Pozzi E, eds.
Sarcoidosis
and
other
granulomatous
Y, Kudoh
F.
5, Maeda
Analysis
H, Suzaki
of HLA antigens
11.
12. 13.
14.
forms of bronchied. Pathology of Thieme, 1988; 526-
D, Gamsu
G.
Normal
eased isolated lungs: high-resolution Radiology 1988; 166:81-87.
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Philadel-
phia: Saunders, 1973. Heitzman ER. The lung: radiologicpathologic correlations. 2nd ed. St Louis: Mosby, 1984. Webb WR, Stein MG, Finkbeiner WE, Im
JG, Lynch
25.
State of the art: of chronic diffuse II. Am Rev Respir
Todo G, Herman
High-resolution
PG.
computed tomography of the pig lung. Invest Radiol 1986; 21:689-696. Itoh H, Todo G, Murata K, et al. Recent progress of chest imaging. In: Hayaishi 0, Torizuka K, eds. Biomedical imaging. New York: Academic Press, 1986; 249-271. Murata K, Itoh H, Todo G, et al. Centrilobular lesions of the lung: demonstration by high-resolution CT and pathological correlation. Radiology 1986; 161:641-645.
Murata
K, Itoh H, Senda
M, et al.
Strati-
Reid L, Simon G. The peripheral pattern in the normal bronchogram and its relation to peripheral pulmonary anatomy. Thorax 1958; 13:103-109. Reid L. The secondary lobule in the adult human lung, with special reference to its appearance in bronchograms. Thorax 1958;
26.
Moore ADA, Godwin JD, MUller NL, et al. Pulmonary histiocytosis X: comparison of radiographic and CT findings. Radiology 1989; 172:249-254.
27.
Itoh H, Tokunaga
28.
diologic-pathologic correlations of small lung nodules with special reference to peribronchiolar nodules. AJR 1978; 130: 223-231. Akira M, Kitatani F, Yong-Sik L, et al. Dif-
H,
Special WM,
the lung. New York: 529. Felson B. Chest roentgenology.
I. Am Rev Respir
48-53.
in
patients with diffuse panbronchiolitis. Am Rev Respir Dis 1990; 141:1459-1462. Randhawa P. Hoagland MH, Yousem SA. Diffuse panbronchiolitis in North America:
Thurlbeck WM. olitis. In: Thurlbeck
lung disease.
Dis 1990; 142:1206-1215. Muller NL, Miller RR. computed tomography infiltrative lung disease. Dis 1990; 142:1440-1448.
13:110-115.
report of three cases and review of the literature. AmJ Surg Pathol 1991; 15:43-47.
5, et al.
Diffuse panbronchiolitis: a disease of the transitional zone of the lung. Chest 1983; 83:63-69. Maeda M, Saiki 5, Yamanaka A. Serial section analysis of the lesions in diffuse panbronchiolitis. Acta PatholJpn 1987; 37: 693-704. Kitaichi M. Pathology of diffuse panbron-
Sugiyama
State of the art: of chronic diffuse
fled impairment of pulmonary ventilation in “diffuse panbronchiolitis”: PET and CT studies. J Comput Assist Tomogr 1989; 13: 24.
Chest
V. Patelli M, Poletti G, Bertanti T, L. Diffuse panbronchiolitis obin an Italian. Chest 1990; 98:515-
Takaku
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Diffuse ed. Lung Dekker,
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References 1.
20.
veins sec-
secretions.
parenchymal diseases. Findings from the present study confirmed the centribobular distribution of DPB lesions. A similar CT-pathologic correlation could be used to describe a centribob-
Muller NL, Miller RR. computed tomography
fuse
29.
30.
panbronchiolitis:
5, Asamoto
H, et al.
evaluation
Ra-
with
high-resolution CT. Radiology 1988; 168: 433-438. Nakata H, Kimoto T, Nakayama T, et al. Diffuse peripheral lung disease: evaluation by high-resolution computed tomography. Radiology 1985; 157:181-185. Gurney JW. Cross-sectional physiology of the lung. Radiology 1991; 178:1-10.
and disCT.
Radiology
#{149} 785
Nishimura,
MD
#{149} Masanori
Kitaichi,
MD
Takateru
Diffuse Panbronchiolitis: High-Resolution CT and Diffuse panbronchiolitis characterized by chronic tation
and
airway
(DPB) airflow
is limiwith
inflammation
bronchiolar lesions. Chest radiographs of patients with DPB usually show small nodular shadows throughout both lungs. The authors investigated the nature and pathogenesis of the radiologic features of DPB by correlating high-resolution computed tomographic (HRCT) findings with histopathologic features. The HRCT images of nine patients with DPB were compared with the observalions made with inflated lung specimens. The HRCT findings of DPB included centrilobularly distributed, small rounded areas of attenuation; branched linear areas of attenuation, contiguous with the small rounded areas; dilated airways with thick walls, also common outside secondary pulmonary lobules; and decreased lung attenuation in peripheral areas due to air trapping caused by bronchiolar narrowing in the subpleural zones. The authors believe that HRCT best demonstrates this characteristic location of small rounded areas of attenuation associated with dilated airways. Index
terms:
Bronchiolitis,
60.219
puted tomography 60.1211 #{149} Lung, 60.795
(CT), high-resolution, CT, 60.1211 #{149}Lung,
Radiology
184:779-785
I
From
1992;
the
Chest
Kyoto University, and the Department
Medicine,
Kyoto
Disease
Research
Com-
#{149}
diseases,
Institute,
Sakyo-ku, Kyoto 606, Japan, of Radiology and Nuclear
University
Hospital,
Kyoto,
Japan. Received September 24, 1991; revision requested November 25; revision received March 9, 1992; accepted April 6. Address reprint requests to K.N. C RSNA, 1992
I
N
1969, (DPB)
Izumi,
#{149}
#{149} Harumi
Correlation Pathologic
diffuse panbronchiolitis was first described
as a disease
MD
characterized
MATERIALS in Japan
clinically
by
cough, expectoration, and physiologically by chronic airflow limitation; and histologically by typical bronchiobar lesions (1,2). the
results
wide tients
survey showed with DPB had
sal sinusitis
of a Japanese
and
that
In
nation-
In our study,
jor
pathologic
the
nosed.
75%
In these cases, there were typical lesions of panbronchiolitis, as described by Kitaichi et ab (4,5), consisting
were
unit
time, it was primarily bronchioles
bronchi
is no doubt findings
high(HRCT)
over
an
aggregate
within
(3-6).
that are
the
present
adjacent
years), Al-
main
and around the bronchiolar walls, it is not known whether the respiratory bronchioles are primarily or secondarily affected. Furthermore, the relationship of DPB to bronchiectasis, if there is any, remains to be elucidated (6). Extensive studies are hampered by the fact that only a few cases of DPB have been reported outside Japan (710). Thurlbeck (11) also suggested that there could be some degree of overlap between those cases diagnosed as DPB in Japan and those cases that are diagnosed as bronchiectasis in North America. Radiographicabby, DPB is characterized by diffuse small nodular shadows involving the lungs and mild to moderate hyperinflation (2,5). Diffuse small nodular shadows are uncommon in bronchiectasis, even in patients with extensive disease (12). However, this finding does occur commonly in various interstitial lung disorders such as sarcoidosis (12,13). It is, therefore, important to distinguish DPB from other disorders with similar abnormalities seen on chest radiographs, especially for Japanese patients.
of foamy
and
bymphoid
walls of respiratory
One man
also
and
who ranged in age from 20 to 66 years, had DPB, which was histologically diag-
Recent studies, however, have shown that DPB causes inflammation and dilatation of not only the bronthere
the findings
radiographs tomographic
scans with the gross appearance, contact radiographs, stereomicroscopic views, and histologic findings of lung specimens. Nine patients (six men and three women),
and
but
METHODS
we correlated
from routine chest resolution computed
(1,2).
though
AND
that most pachronic parana-
nonsmokers (2). At that thought that the disease involved the respiratory
chiobes
MD
Itoh,
of Findings’
chronic dyspnea;
1983,
Radiology
alveolar
but
bronchioles
ducts
was a former the other
of cells
and
alveoli.
smoker eight
(10 pack-
patients
had
never smoked. All patients had chronic expectoration, and six of the nine had mild to moderate dyspnea. Otolaryngobogic examination and radiographs of the head and sinuses showed chronic paranasal function chronic moderate
sinusitis in all cases. Pulmonary tests revealed mild to severe airflow limitation and mild to hypoxemia (Table).
The CT scans T8800
unit
(GE
were
obtained
Medical
on a CT!
Systems,
Milwau-
kee) with 5-mm collimation during breath holding for 9.6 seconds after full inspiration. A high spatial-resolution algorithm (bone
detail
patients.
algorithm)
The
was
used
high-resolution
for
all
images
were
viewed at window bevels appropriate for pulmonary parenchyma (-800 HU; window width, 1,000 HU) and for mediastinum (±0 maximize
HU; window the differences
attenuation, settings
additional were
Recent
also
HRCT
renchymal sections
width, 250 HU). To in regional lung
studies
diseases with
narrower
windo%.
used.
of pulmonary
have
a collimation
19). In the present
involved of 1-2
study,
pathin
mm
(14-
we employed
medium-sized thickness scans of 5-mm collimation, as described by Todo and Herman (20). Identification of lesions with respect essential
to pulmonary for defining
tion. Because included
vascular
on a single
Abbreviations: tis, HRCT
more
vascular images is a centrilobular loca-
DPB =
high-resolution
scan
=
images
are
of medium
diffuse panbronchioliCT.
779
Clinical
and Pulm
Characteristics
Patient/Age
onary
(y)/Sex
Functio
n Tests
iv1
FEy1 (L)
of Patien ts with
DPB
(% pred)
FEV1/FVC (%)
VC (%) 106.2
Pao (torr)
Sputum (mL/d)
1/20/M
2.71
72.8
63.2
79.9
30
2/55/M
0.71 1.01
21.9 63.5
61.7 72.6
47.7 70.6
48.8 70.6
200 20
2.16 1.25
55.8
64.7
70.6
5/47/F
57.1
64.1
81.7
63.0 61.6
10 20
6/45/M
1.59
47.7
58.7
72.0
64.4
7/52/F
1.63
70.0
74.1
89.0
74.6
3/66/F 4/38/M
Histopathologic Diagnosis Open lung biopsy (RML) Autopsy Lobectomy (LLL) due to lung cancer Open lung biopsy (R:S3, S9) Open lung biopsy (L:S1 + 2, 54, S6)
0.92
24.1
37.2
63.1
64.0
150
9/2i/M
2.16
50.3
71.3
74.5
64.5
10
thickness,
we
volume in i second, FVC = forced vital capacity, L = left, LLL = leftlowerlobe, value, R = right, RML = right middle lobe, S = segment, VC = vital capacity.
forced expiratory of predicted
=
percentage
=
preferred
5-mm
to thinner sections. In seven patients,
specimens
tamed
biopsy.
at open
lung
were One
time interval from HRCT to thowas 3-60 days (mean, 30.3 days)
lower lobectomy adenocarcinoma
patients. The was clinically
the was
period observed
patient
died
despite condition
improvement for which
antibiotic formed
therapy. 122 days
for
condition stable
from
patients
and
from
two
radiologist
findings,
was
one
patients. of CT and
macroscopicalby
during were
seg-
from
which
throughout
both
were
between
the HRCT
and
diographs histologic
and the findings
the biopsy
Specimens
were
sites
The lung
chus
with
before
lobe from a lobectomy
a fixative (13).
serially
cut
HRCT
who
fixed,
died
per-
and
polyethyl-
into the brondried
at a constant
of
was
the patient who were inflated by
containing
formaldehyde The
scans
the biopsy
of the patient
lower
ene glycol
sliced
specimens thickness
were (1 cm
ally
less
than
(L:S1
+
2,
of oxygen,
artenalpressure
and contact
raand
and
Figure
2. Patient
strates
centrilobular
9.
4
HRCT scan demonsmall rounded and
branching linear areas of attenuation with a millimeter pattern. Note that a constant distance (2-3 mm) separates small rounded areas of attenuation (arrows) from the adjacent pleura or pulmonary veins (pv) and that these small rounded areas tend to be located at the end of branching linear areas of attenuation (arrowheads). These HRCT findings are representative of DPB in our series.
and
central
rounded HRCT
areas of attenuation scans were always
in
areas
enclosed by pleura, pubmonary veins, or extrabobubar pulmonary vessels and bronchi (ie, the boundaries of secondary pulmonary
pa-
sessed
as
tients (patients 2 and 6). The major HRCT findings of DPB were small rounded areas of attenuation, branched linear areas of attenua-
were
prominent
gions
(Fig
lion,
graphs of inflated specimens 3,4). Some nodular lesions are seen on stereophotomicrographs
outer
made
in diameter
Small seen on
shadows
in attenuation
was
scans
L
lobules) and were usually separated by a distance of 2-3 mm from these structures. They were, therefore, as-
and
Radiology
hyperinfla-
stereomicroscopic for the inflated
5 mm
ties
#{149}
2,
had unclear borders (Fig 1). Mild to moderate hypermnflation and “tramlines” were also observed. Penbronchial thickening and thin tubular
(21).
comparison
shadows
mild
The chest radiographs of nine patients demonstrated diffuse small nodular infiltrates throughout both lungs. Nodular shadows were gener-
bronchioles
Subsequently,
nodular
lungs.
and then I mm). Contact radiographs of each specimen slice were obtained. Both contact radiographs and sliced specimens were examined with a stereomicroscope
780
+
RESULTS
injection of 10% formalin, with a stereomicroscope,
compared
and
and
and further histologic sections (4 rim) were then made. Stereomicroscopic views and histologic findings at low magnificathe biopsy formed.
small
radio-
tion.
about 1-2 cm thick, presumably large enough to contain secondary pulmonary lobules. Biopsy specimens, inflated and
fixed through were examined
Posteroantenor
lungs
the lung
thoracotomy
obtained.
1. Patient 4. shows diffuse
Figure graph
To obtain patho-
(HI.)
(M.K.) observed
the sites
were in
different
one pathologist
specimens
per-
biopsy specimens three different segments
logic
instilling
=
(L:S1
to thoOne
accident,
An autopsy after HRCT.
five
the left underwent
Pao
56,
a of the
of his respiratory he received intensive
ments in the other a rigorous correlation
tion
S9) Open lung biopsy S9) Open lung biopsy S9)
of before
from HRCT in any case.
of a cerebrovascubar
At thoracotomy,
recorded
(R:S2,
biopsy
and the biopsy procedure; no in chest radiographic find-
ings during racotomy
two
(R:S3, 56)
lung
ob-
lung. The racotomy
both HRCT deterioration
lung biopsy
Open
patient
a left papillary
in these eight these patients
Open
collimation
underwent 3 x 3-cm
obtained
50-100 10
8/30/M
Note.-FEV1 % pred
-
thickened
and
and lung
dilated
bronchi, between
zones.
in two
walls
and
of
dispanithe
inner
being
in
2) (17,22).
centribobular
Such
re-
a centribob-
ubar distribution for small nodules could be confirmed with correlative stereomicrographs
and
photomicro(Figs clearly
September
(Fig
1992
linear areas of attenuation extending from small rounded areas of attenuation on HRCT scans corresponded to dilated bronchioles filled with secretions, which, on stereomicrographs, were most clearly observed in subpleural regions (Fig 4c). Dilatation thickening
of bronchi and are also common
wall in air-
ways outside the secondary pulmonary lobules (Fig 5). However, thickening of extrabobubar bronchial walls observed on the HRCT scans of patient 2 could not be confirmed with lung specimens obtained at autopsy. Intrabronchiab secretions may have contributed to bronchial wall thickening seen on HRCT scans of this patient, in view of the fact that the patient expectorated as much as 200 mL of sputum every day. The outer layer and subpleural zone of the lung were seen as areas of hypoattenuation on the HRCT scans. Attenuation between the central and peripheral parts of the lungs was remarkabby
different.
lung attenuation on narrower (23). Although distinguish a the outer and pleural layer
This
minished attenuation scans of patients with
Figure
3. Patient
linear
areas
crograph (large
4.
scans
of attenuation
of biopsy arrows),
(a) HRCT
at several
in a biopsy
specimens
corresponding
levels
specimen
obtained
from
to small
rounded
demonstrate (area
within
the left lung areas
small
rounded
square).
(b) Stereophotomi-
demonstrates
of attenuation
and branch-
some on
the
nodular
HRCT
lesions
scans.
Note
the dilated peripheral airway filled with secretions (small arrows) and accompanying pulmonary vessel (arrowheads). Because the dilated airways are larger and thicker than the associated pulmonary artery, these structures most likely correspond to the branching linear areas of attenuation observed on the HRCT scans. Bar = 5 mm. A = specimen obtained from the left upper
lobe,
segment
3; B
specimen
=
obtained
from
the
left
lower
lobe,
segment
9. (Fig 3 con-
tinues.)
3b).
on the DPB.
HRCT
DISCUSSION
b. ing
stratified
was best appreciated window settings (Fig 6) it was impossible to clear boundary between inner zones, the subappeared to have a di-
A photomicrograph
(bow-magnifi-
cation view) of the same specimen demonstrates that the nodule is enclosed by pleura and an interbobular septum with a constant separation of approximately 2-3 mm, indicating that (Fig
it is a typical 3c).
centribobular
nodule
Small rounded areas of attenuation on HRCT scans corresponded to nodubar lesions, with an average diameter of about 1 mm, situated adjacent to membranous and respiratory bronchi-
oles
and
lesions and adjacent
alveoli.
Unit
Volume
184
by
recognized
lesions
(Fig
Kitaichi
within
et al (4,5),
these
nodular
3d).
The pathologic basis for branching linear areas of attenuation proved to be widening of the bronchiolar bumen, chronic inflammatory thickening of the bronchiolar presence of intraluminab
wall,
and the secretions
in and around the respiratory bronchialveolar
4b).
these nodules inflammatory
lesions Number
#{149}
as described
(Figs 4, 5). All these findings contribute to the radiopacity of bronchioles that are not normally visualized. A contact radiograph of the inflated and fixed left lower lobe from patient 3 demonstrated some radiopaque nodules, adjacent to the terminal portion of dilated peripheral airways (Fig
oles. Histologically, represent the chronic
and fibrotic membranous
tis,
were
ducts
of panbronchioli3
and
Some
showed
peripheral
focal
narrowing
airways
(Fig
The secondary pulmonary lobule is about 1 cm wide. It is bordered by interbobular septa, pleura, pulmonary veins, or extrabobubar pulmonary yessebs
and
bronchi
(Fig
7) (12,13,24,25).
Pulmonary
arteriolar and bronchiobar structures enter the central portion of the lobule. Bronchioles divide into three to five terminal bronchioles within a lobule. The distance from the first-order respiratory bronchiole to the peripheral almost constant
border
of the
lobule
is
(2-3 mm) (Fig 7) (25). Recent studies with correlation of HRCT and pathologic findings have demonstrated that the entire secondary pulmonary lobule and even intrabobular structures may be appreciated as areas of increased attenuation on HRCT scans in some diseases (1418,21,22).
Furthermore,
Murata
et al
also
(17) reported that the HRCT appearance of pulmonary parenchymab disease can be classified as having a centribobubar, panbobular, bronchovascubar, or peribobular distribution (17). In the present study of nine patients with DPB, small nodular lesions were always observed on both HRCT
5). The
scans
and
inflated
lung
specimens
Radiology
as
781
#{149}
being
(a) separated
pulmonary
from
veins,
the
pleura,
or extrabobular
pub-
monary vessels and bronchi (the boundaries of secondary pulmonary lobules) by approximately 2-3 mm and as being (b) continuous with pubmonary arteries and dilated airways (Figs
3, 7) (17,21,22).
Findings from our HRCT and pathologic correlative studies confirmed that lesions of DPB were typicabby centribobubarby distributed (Figs 3, 7), one of the four major CT distribution patterns described by Murata et al (17). To our knowledge, this is the first comprehensive study of DPB, correlating findings of HRCT scans with those of lung specimens obtamed at thoracotomy or at autopsy. Transbronchial biopsy specimens are generally not appropriate for such a correlative study because they are not barge enough to include secondary pulmonary lobules. Murata et al (17) observed centrilobular increased attenuation on HRCT scans in two patients with bronchopneumonia, one patient with lung abscess, one with cryptococcosis, one with nonspecific granubomatous inflammation, one of three patients with sarcoidosis, and one of five patients with malignant lymphoma. Moore et al (26) reported the CT findings
of pulmonary
histiocytosis
X, in
which many small nodules were distributed in the centers of secondary lobules around small airways with 1.5-mm collimation. In addition, contact radiographs of fixed and sliced lungs, which were excised at autopsy, were used by Itoh et al (27) to prove that small nodules in bronchopneumonia, acinonodose tuberculosis, chronic bronchiolitis, and simple pneumoconiosis
attributable
d.
to fenric
dust were located around terminal or respiratory bronchioles. It is, therefore, possible that centribobular nodules may be observed on HRCT scans of patients with these four diseases. Akira et al (28) reported that small nodules were centribobubarly distributed on HRCT scans of 19 patients with DPB diagnosed clinically and one patient with DPB diagnosed at autopsy.
four
They
CT types:
nodules
connected
linear areas accompanied ductal areas
depicted
small
schematics
nodules, to small
of
small branching
of attenuation, nodules by ring-shaped or small of attenuation, and barge cystic areas of attenuation accompanied by dilated proximal bronchi. Their illustrations were compatible with these findings. They suggested that patients with end-stage DPB may be included in a diagnosis of bronchi782
Radiology
#{149}
C.
(c) Histopathologic view demonstrates a typical centrilobular nodule by pleura (arrows) and interlobular septa (arrowheads), defining its centrilobular location. This specimen was obtained from the same left lower lobe as in Figure 4b. (Hematoxylin-eosin stain; original magnification, x 10.) (d) Histopathologic view shows two unit lesions of panbronchiolitis. There are aggregates of foamy and lymphoid cells within the walls of respiratory bronchioles (arrows). This specimen was obtained from the same left upper lobe as in Figure 4b. (Hematoxylin-eosin stain; original magnification, x40.) Figure enclosed
3 (continued).
ectasis. However, knowledge, it has
to the best of our been questionable
whether the appearance of these small nodules was followed by dibatation of the airways. To clarify the relation between the small nodules and dilated
airways
in DPB,
prospective
long-term studies are necessary. AUra et al (28) included the correlation of CT and pathologic findings from a lung excised at autopsy of one patient, which demonstrated that DPB lesions were situated around respiratory bronchioles. However,
although tubular structures were observed on both HRCT scans and contact radiographs, the small nodules were not clearly observed in patients with advanced disease. Nakata
study diseases,
vanced tasis,
et
ab (29),
in
on pulmonary reported
another
HRCT
parenchymab two
cases
of ad-
DPB: one involved bronchiecand the other had generalized
bulbous changes. The latter was never observed in the
finding present
study.
Some
authors
(24,25)
recognized, September
1992
pattern likely
on HRCT represented
scans within
are
most secondary
pulmonary lobules (Figs 2, 4). Moreover, Murata et ab (22) described the visualization of pulmonary central arterioles within secondary pubmonary lobules with HRCT. It is possible that the branched linear areas of attenuation seen on HRCT scans in patients with DPB may correspond to both dilated peripheral airways and pulmonary arteries. However, in view of the fact that stereomicrographs and contact radiographs (Figs 3-5) reveabed that dilated airways were a larger caliber than that of the accompanying pulmonary arteries, we presume that branched linear areas of attenuation on HRCT scans are attnibutable primarily to dilated, secretionfilled airways. Dilatation of bronchioles was apparent in most of the lung specimens obtained either at autopsy or bobectomy (Figs 3-5). A number of dilated airways were also demonstrated on HRCT scans. Our correlative study showed that dilated airways filled with intraluminab secretions may account for the observed branching and linear areas of attenuation on HRCT scans (Fig 4a, 4c) and for bronchial wall thickening (Fig 5a) in the more central portion of the lung. The batter finding is the CT equivalent of tramlines on the chest radiograph. Generally, tramlines observed on chest radiographs
may
also
intrabronchial seen in patient It is possible is secondary to
further
caused
2 (Fig
by
as were 5).
that airway bronchiobar
occurring in the lesions. However, sarily mean that
will always bronchiolar pathologic
be
secretions,
dilatation narrowing of nodular
vicinity this does dilatation
not necesof airways
result from widespread narrowing. The CT and findings from our study
emphasize
the
need
for
inves-
relation between DPB and bronchiectasis (6). Murata et ab (23) used positron tigating
the
emission
C.
Figure uation.
diograph
4. Patient Some
3.
linear
(a) HRCT areas
of specimen
are
scans
show
continuous
(1-mm-thick
slice)
small
rounded
with
dilated
from
the left lower
and branching
airways
linear
(arrowheads).
lobe reveals
areas
of atten-
(b) Contact
several
ra-
radiopaque
nodules. Note the dilated peripheral airways (arrows) and some nodules (arrowheads) near the extreme end of the stenotic airway (arrows). These correspond to small rounded and branching linear areas of attenuation on the HRCT scan. Bar = 1 cm. (c) Stereophotomicrograph shows dilated bronchioles filled with secretions in the subpleural area (arrows), which corresponds to the branching linear areas of attenuation on the HRCT scan. Bar = 1 cm.
from bronchographic and pathologic correlation, that airways with a miblimeter pattern within secondary pub-
Volume
184
Number
#{149}
3
monary chiobes.
tenuation
lobules Therefore,
are terminal
branching
linear
bronareas
of at-
in a millimeter
tomography
with
radioac-
tive nitrogen and CT attenuation numbers to point out that hyperinflation of the lung exists in the outer and peripheral zones in patients with DPB; however, these cases were not histologically present study,
difference tween the
confirmed. In the we demonstrated
histologically (Fig 6). Such a stratified
tilation
may
a
in lung attenuation beouter and inner zones in proved cases of DPB impairment
correspond
imaging of the cortex the lungs. Although
of yen-
to differential and medulla Gurney (30)
of pro-
Radiology
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783
a.
b.
C.
Figure
5. Patient and intralobular lung shows that eas of attenuation airway is dilated
2. (a) HRCT scans demonstrate dilatation of airways and bronchial wall thickening (arrows) proximal to secondary lobules small rounded and branching linear areas of attenuation (arrowhead). (b) Contact radiograph of the inflated and fixed right the intralobular and extralobular peripheral airways are dilated and stenotic. These are equivalent to the branching linear arand the dilated peripheral airways on the HRCT scan. Bar = 5 mm. (c) Stereophotomicrograph shows that the peripheral and stenotic in the vicinity of a small nodular lesion (arrowheads). Arrows = peripheral direction, bar = 5 mm.
posed logic
structural between
several differences
and physiothe cortex
and the medulla, the relative flation seen in DPB is probably
hyperincaused
by multiple foci of narrowing portions of peripheral airways. opsy and autopsy specimens,
along In bisome
peripheral adjacent
airways appeared stenotic to macroscopic nodular be-
sions
(Figs
and
frequency
airways central
4, 5). A greater
number
of stenotic
in the region,
outer where
peripheral
zone versus the large airways
predominate, probably account for the stratified appearance of lung attenuation seen in patients with DPB. In conclusion, HRCT is superior to chest radiography in demonstrating lesions of DPB, small nodules, dilated airways, and regional differences in
attenuation tion). lesion
(ie, relative
Although is never
the seen
hyperinfla-
location of a DPB on a routine chest
radiograph, the characteristic lobular distribution of these is clearly
observed
on
HRCT
scans.
be recognized but it is diffi-
cult
outer
zones. 784
In contrast, Radiology
#{149}
the
HRCT
inner
6. Patient
8.
CT scans
show
lower
lung
attenuation
in the outer
zones
than
in the
zones.
centrinodules
Hyperinflation can with chest radiography, to appreciate
Figure
and
scans
inner
can
demonstrate tion on the
the relative hyperinflatransverse section of the
lungs
a minimal
with
summation
fect. Consequently, HRCT be useful in differentiating
ef-
appears to DPB from
other graphic
Our
diseases
with
a similar
radio-
appearance.
HRCT
and
pathologic
tech-
niques may be useful as a model for the investigation of other pulmonary
September
1992
15.
16.
Bergin C, Roggli V, Coblentz C, Chiles C. The secondary pulmonary lobule: normal and abnormal CT appearances. AJR 1988; 151:21-25. Webb ER. High-resolution CT of the lung parenchyma. Radiol Clin North Am 1989;
27:1085-1097. 17.
Murata K, Khan nary parenchymal high-resolution
A, Herman PG. Pulmodisease: evaluation with CT. Radiology 1989; 170:
629-635. 18. -
Airway Artery
Pulmonary
Vein
Interlobular
5m
DPB. Each secondary and bronchial course along
ondary
lobule is indicated
structures enter the the interlobular septa.
pulmonary
infiltrative
Pulmonary
Figure 7. Schematic of centrilobular nodules ure on the left is derived from serial sections right indicates the location of the centrilobular
lobules.
Most
19.
Septum
and dilated peripheral airways of normal inflated lung, whereas nodules and dilated peripheral
by a different
type of shading.
central portion of the lobule. Nodular lesions are centrally
intralobular
and
extralobular
in DPB. The figthe one on the airways in
Pulmonary
arterial
Conversely, situated
pulmonary within these
bronchioles
are dilated
21.
with 22.
ular distribution eases. #{149}
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