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C a r d i o p u l m o n a r y I m ag i ng • R e v i e w

Walker et al.
Imaging Pulmonary Infection

Cardiopulmonary Imaging
Review

FOCUS ON:

Imaging Pulmonary Infection:

Classic Signs and Patterns
Christopher M. Walker 1 OBJECTIVE. The purposes of this article are to describe common and uncommon
Gerald F. Abbott 1 imag- ing signs and patterns of pulmonary infections and to discuss their underlying
Reginald E. Greene1 anatomic and pathophysiologic basis.
Jo-Anne O. Shepard1 CONCLUSION. Imaging plays an integral role in the diagnosis and management of sus-
pected pulmonary infections and may reveal useful signs on chest radiographs and CT
Dharshan Vummidi2
scans. Detected early, these signs can often be used to predict the causative agent and
Subba R. Digumarthy 1 pathophysi- ologic mechanism and possibly to optimize patient care.
Walker CM, Abbott GF, Greene RE, Shepard
JO, Vummidi D, Digumarthy SR

ulmonary infections are among

P
Consolidation and Air
the most common infections Bronchogram Sign
encoun- tered in outpatient and Consolidation is an alveolar-filling process
inpatient clinical care. that replaces air within the affected airspac-
According to the
Centers for Disease Control and Prevention, es, increasing in pulmonary attenuation and
in- fluenza and pneumonia were combined as obscuring the margins of adjacent airways
the eighth leading cause of death in the and vessels on radiographs and CT scans [2].
United States in 2011 [1]. Imaging studies are Consolidation is one of the more common
critical for the diagnosis and management of manifestations of pulmonary infection, and
pulmo- nary infections. When the imaging its appearance is variable, dependent on the
manifes- tations of a known disease entity causative organism.
form a consis- tent pattern or characteristic Air-filled bronchi may become visible when
appearance, those manifestations may be surrounded by dense, consolidated lung paren-
regarded as an imaging sign of that disease. chyma and may produce the air bronchogram
Imaging signs by them- selves are sometimes sign (Fig. 1), initially described by Felix
Keywords: abscess, fungus, infection, signs nonspecific and may also be manifestations of Fleischner in 1948 [3, 4]. In normal lung, air-
noninfectious diseases. Various imaging signs filled bron- chi are not apparent on chest
DOI:10.2214/AJR.13.11463
of thoracic infection can be clinically useful, radiographs be- cause they are surrounded by
Received June 26, 2013; accepted after revision sometimes suggesting a specific diagnosis aerated lung pa- renchyma. In a patient with
August 16, 2013. and often narrowing the dif- ferential fever and cough, this sign suggests the
1 diagnosis. Clinical data, such as WBC count, diagnosis of pneumonia. Though the sign is
Department of Radiology, Thoracic Imaging Division,
Massachusetts General Hospital, 55 Fruit St,
results of microbiologic tests, and im- mune most commonly seen with bacterial infection,
Boston, MA 02114. Address correspondence to C. M. status, should be correlated with the im- aging any infection can manifest the air
Walker (walk0060@gmail.com). sign and any additional findings to facili- tate bronchogram sign. Differential diag- nostic
2
an accurate diagnosis. The objectives of this considerations include nonobstructive
Department of Radiology, University of Michigan,
article are to discuss common and uncom- atelectasis, aspiration, and neoplasms, such as
Ann Arbor, MI.
mon signs and findings of pulmonary adenocarcinoma and lymphoma. One can dif-
This article is available for credit. infection at radiography and CT, discuss the ferentiate atelectasis from pneumonia by look-
mechanisms and pathophysiologic factors that ing for direct and indirect signs of volume
AJR 2014; 202:479–492
produce those findings, and highlight several loss, including bronchovascular crowding,
0361–803X/14/2023–479 noninfectious diseases that may present with fissural displacement, mediastinal shift, and
similar findings. This review is divided diaphrag- matic elevation. Detection of the air
© American Roentgen Ray Society into signs that are most commonly seen or broncho- gram sign argues against the
associated with bac- terial, viral, fungal, and presence of a cen- tral obstructing lesion.
parasitic infections.

47 AJR:202, March 2014 AJR:202, March 2014 47

9 9
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Walker
Imaging et al. Infection
Pulmonary

Silhouette Sign bronchiolitis, chronic airways (e.g., cystic fibrosis or immune deficiency),
The silhouette sign was initially inflammation diffuse panbronchiolitis, and adenocarcino- ma
described by Felson as a radiographic sign [11]. Aspiration generally results in de-
that enabled the anatomic localization of pendent tree-in-bud opacities predominat-
abnormalities on orthogonal chest ing in the lower lung zones. Cystic fibrosis
radiographs [5]. The silhouette sign should be considered when upper-lung-zone–
describes loss of a normal lung–soft-tissue predominant bronchiectasis, bronchial wall
interface (loss of silhouette) caused by any thickening, mucus plugging, and mosaic at-
pathologic mechanism that re- places or tenuation are seen in combination with tree-
displaces air within the lung pa- renchyma. in-bud opacities. Diffuse panbronchiolitis
The silhouette sign is produced on chest should be considered when diffuse and uni-
radiographs when the loss of inter- face form tree-in-bud opacities are seen in a pa-
occurs between structures in the same tient of East Asian descent. Less commonly,
anatomic plane within an image. This sign the tree-in-bud sign may be a manifestation of
is commonly applied to the interface vascular lesions (so-called vascular tree- in-
between the lungs and the heart, bud), including embolized tumor or for- eign
mediastinum, chest wall, and diaphragm. material, due to the anatomic location of small
Consolidation that ex- tends to the border of arterioles as paired homologous struc- tures
an adjacent soft-tissue structure will that course alongside the small airways in the
obliterate its interface with that structure centrilobular aspect of the secondary
[5]. For example, lingular pneumo- nia pulmonary lobules [8, 12–15] (Fig. 4).
obscures the left-heart border, and mid- dle
lobe pneumonia obscures the right-heart Bulging Fissure Sign
border, because the areas of consolidation The bulging fissure sign represents expan-
and the respective heart borders are in the sive lobar consolidation causing fissural
same anatomic plane (Fig. 2). Conversely, bulging or displacement by copious amounts
with lower lobe pneumonia, the heart bor- of inflammatory exudate within the affected
der is preserved, but the ipsilateral hemidia- parenchyma. Classically associated with right
phragm is frequently obscured (silhouetted). upper lobe consolidation due to Klebsiella
It is important to consider a diagnosis of pneumoniae (Fig. 5), any form of pneumonia
bac- terial pneumonia in a patient with fever can manifest the bulging fissure sign. The
and cough when the silhouette sign is sign is frequently seen in patients with pneu-
detected at chest radiography. Other mococcal pneumonia [16, 17]. The prevalence
diseases that can manifest the silhouette of this sign is decreasing, likely because of
sign include atelecta- sis (segmental or prompt administration of antibiotic therapy to
lobar), aspiration, pleural effusion, and patients with suspected pneumonia [18]. The
tumor [5]. bulging fissure sign is also less com- monly
detected in patients with hospital-ac- quired
Tree-in-Bud Sign Klebsiella pneumonia than in those with
The small airways or terminal bronchioles community-acquired Klebsiella infec- tion
are invisible on CT images because of their [19]. Other diseases that manifest a bulging
small size (< 2 mm) and thin walls (< 0.1 fissure include any space-occupying process
mm). They may become indirectly visible on in the lung, such as pulmonary hem- orrhage,
CT images when filled with mucus, pus, flu- lung abscess, and tumor.
id, or cells, forming impactions that resemble
a budding tree with branching nodular V- Feeding Vessel Sign
and Y-shaped opacities that are referred to The feeding vessel sign is the CT find-
as the tree-in-bud sign [6–9] (Fig. 3). ing of a pulmonary vessel coursing to a dis- tal
Because tree- in-bud opacities form in the pulmonary nodule or mass. This sign was
center of the sec- ondary pulmonary lobule, originally thought to indicate hematogenous
they characteristi- cally spare the subpleural dissemination of disease [20, 21], but when it
lung parenchyma, including that adjacent to was studied on multiplanar reformatted
interlobar fissures. Although initially images, most of the so-called feeding ves- sels
thought to be diagnos- were actually pulmonary veins coursing from
tic of mycobacterial infection, the tree-in- the nodule, and the pulmonary arteries usually
bud sign may be an imaging manifestation of coursed around the nodule [22]. The feeding
various infections caused by bacteria, fungi, vessel sign was initially considered diagnostic
parasites, and viruses [6, 8, 10]. Tree-in-bud of septic emboli (Fig. 6) but has
opacities usually indicate infectious bron-
chiolitis or aspiration but are less common-
ly seen in other conditions, such as follicular
 Walker
Imaging et al. Infection
Pulmonary
come to be recognized as a potential mani-
festation of other conditions, including me-
tastasis, arteriovenous fistula, and
pulmonary vasculitis [23]. Septic emboli
should be con- sidered when the feeding
vessel sign is seen with cavitating and
noncavitating nodules and subpleural
wedge-shaped consolidation. The nodules
usually have basal and peripher- al
predominance and vary in size [24]. Arte-
riovenous fistula is differentiated from septic
emboli by the finding not only of a feeding
artery but also of an enlarged draining vein.

Inhomogeneous Enhancement
Sign and Cavitation
In a patient with pneumonia, the CT de-
tection of inhomogeneous enhancement and
cavitation suggests the presence of necro-
tizing infection [25, 26]. Pulmonary necro-
sis may become evident as hypoenhancing
geographic areas of low lung attenuation
that may be difficult to differentiate from ad-
jacent pleural fluid [25] (Fig. 7). This find-
ing is often seen before frank abscess forma-
tion and is a predictor of a prolonged
hospital course [26]. A cavity is defined as
abnormal lucency within an area of
consolidation with or without an associated
air-fluid level. Cav- itation may be the result
of suppurative or caseous necrosis or lung
infarction. Impor- tantly, cavitation does
not always indicate a lung infection or
abscess. Cavitation can have noninfectious
causes, including malig- nancy, radiation
therapy, and lung infarction [2]. Suppurative
necrosis usually occurs with infection by
Staphylococcus aureus, gram- negative
bacteria, or anaerobes. Caseous ne- crosis is
a characteristic histologic feature of
mycobacterial infection, but cavitation is a
common pathologic and imaging feature of
angioinvasive fungal infections, such as as-
pergillosis and mucormycosis.

Air-Fluid Level Sign

In a patient with pneumonia, detection of
an air-fluid level on chest radiographs or
CT images suggests the presence of a lung
ab- scess or empyema with bronchopleural
fis- tula. The former typically requires
medi- cal treatment with antibiotics, and the
latter usually requires insertion of a chest
tube for drainage. Lung abscess is most
commonly associated with aspiration
pneumonia and septic pulmonary emboli.
Common causative organisms include
anaerobes, Staphylococcus aureus, and
Klebsiella pneumoniae. Lung ab- scess is
associated with increased morbidity and
mortality. Prompt detection at imaging
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studies may improve patient care, enabling nant effusions (Fig. 10), hemothorax, and se- parenchyma seen as outer consolidation or
clinicians to treat patients with an appropri- quelae of previous talc pleurodesis, lobecto- ground-glass opacity [42].
ate course of antibiotic therapy [27]. my, or pneumonectomy. Hemothorax usually
Detection of an air-fluid level at chest has associated heterogeneously high attenua-
radi- ography should prompt evaluation of its tion, and talc pleurodesis has attenuation
loca- tion as being in the lung parenchyma or sim- ilar to that of calcium and is often
with- in the pleural space. A lung abscess clumped.
with an air-fluid level can be differentiated
from em- pyema with bronchopleural fistula Halo Sign
by mea- surement and comparison of the The halo sign is the CT finding of a
lengths of the visualized air-fluid level on periph- eral rim of ground-glass opacity
orthogonal chest radiographs. Because of the surrounding a pulmonary nodule or mass [2,
charac- teristic spherical shape of a lung 32]. When detected in a febrile patient with
abscess, an associated air-fluid level neutrope- nia, this sign is highly suggestive
typically has equal lengths on of angio- invasive Aspergillus infection
posteroanterior and lateral chest radiographs [32–34] (Fig.
(Fig. 8). By contrast, empyema typically 11). The ground-glass opacity represents
forms lenticular collections of pleu- ral hemorrhage surrounding infarcted lung and
fluid, and an associated air-fluid level is caused by vascular invasion by the fungus
(e.g., bronchopleural fistula) usually exhibits [35]. The halo sign is typically seen early in
length disparity when compared on postero- the course of the infection. In a group of 25
anterior and lateral chest radiographs. In ad- patients with invasive Aspergillus infection,
dition, both entities typically display a differ- the halo sign was seen in 24 patients on day
ence in the angle of their interface with an 0 and was detected in only 19% of patients
adjacent pleural surface. A lung abscess usu- by day 14, highlighting the importance of
ally forms an acute angle when it intersects per- forming CT early in the course of a
with an adjacent pleural surface, and its wall suspect- ed fungal infection [36]. In a large
is often thick and irregular. By contrast, em- group of immunocompromised patients with
pyema typically forms obtuse angles along Asper- gillus infection, Greene and
its interface with adjacent pleura and usu- colleagues [37] found that patients in whom
ally has smooth, thin, enhancing walls [28, the halo sign was visualized at CT had
29]. Other differential diagnostic consider- improved surviv- al and response to
ations for an intrathoracic air-fluid level in- antifungal treatment com- pared with those
clude hemorrhage into a cavity, lung cancer, without the halo sign at CT. Differential
and metastatic disease. considerations for the halo sign include
other infections, such as mucormy- cosis
Split-Pleura Sign and Candida (Fig. 12), Pseudomonas,
Normal visceral and parietal pleura are in- herpes simplex virus, and cytomegalovirus
distinguishable on CT images. In the presence infections, and other causes, such as Wegen-
of an exudative pleural effusion with locula- er granulomatosis, hemorrhagic metastasis,
tion, inflammatory changes may thicken both and Kaposi sarcoma [38, 39].
the visceral and parietal pleura that surround
the fluid collection and may become evident Air Crescent Sign of Angioinvasive
as the split-pleura sign, suggesting the pres- Aspergillus Infection
ence of empyema [28, 30]. A loculated effu- The air crescent sign is the CT finding of
sion may have an atypical chest radiographic a crescentic collection of air that separates a
appearance when located within a fissure. nodule or mass from the wall of a surround-
The split-pleura sign may be seen in ing cavity [2]. This sign is seen in two types
combination with the air-fluid level sign of Aspergillus infection: angioinvasive and
when a broncho- pleural fistula occurs within mycetoma [40]. In angioinvasive
empyema. Aspergillus infection, the sign is caused by
Empyema should be considered when a parenchymal cavitation, typically occurs 2
patient presents with fever, cough, and chest weeks after de- tection of the initial
pain and CT shows the split-pleura sign. In a radiographic abnormal- ity, and coincides
series of 58 patients with empyema, the split- with the return of neutro- phil function (Fig.
pleura sign was seen in 68% [30] (Fig. 9). 13). The air crescent sign is suggestive of a
The split-pleura sign is not specific for favorable patient prognosis [41]. The
empyema but rather indicates the presence of intracavitary nodule represents ne- crotic,
an exuda- tive effusion [31]. Other important retracted lung tissue that is separated from
causes of this sign include parapneumonic peripheral viable but hemorrhagic lung
and malig-
48 AJR:202, March 2014 AJR:202, March 2014 48
1 1
 Air Crescent or Monad Sign be recognized, however, as occurring in
of Mycetoma many other condi-
The air crescent sign of mycetoma, also re-
ferred to as the Monad sign, is seen in an im-
munocompetent host with preexisting cystic
or cavitary lung disease, usually from tuber-
culosis or sarcoidosis [42]. The fungal ball or
mycetoma develops within a preexisting lung
cavity and may exhibit gravity dependence
(Fig. 14). The mycetoma is composed of fun-
gal hyphae, mucus, and cellular debris. My-
cetomas can cause hemoptysis. The treatment
options include surgical resection, bronchial
artery embolization, and instillation of anti-
fungal agents into the cavity [40]. The air
cres- cent sign is not specific for Aspergillus
infec- tion and can be seen in other
conditions, such as cavitating neoplasm,
intracavitary clot, and Wegener
granulomatosis [2, 43, 44].

Finger-in-Glove Sign
The finger-in-glove sign is the chest radio-
graphic finding of tubular and branching
tubu- lar opacities that appear to emanate
from the hila, said to resemble gloved fingers
[45, 46]. The tubular opacities represent
dilated bronchi impacted with mucus. The CT
finger-in-glove sign is branching
endobronchial opacities that course alongside
neighboring pulmonary ar- teries. The
finding is classically associated with
allergic bronchopulmonary aspergillosis
(ABPA), seen in persons with asthma and pa-
tients with cystic fibrosis (Fig. 15), but may
also occur as an imaging manifestation of en-
dobronchial tumor (Fig. 16), bronchial
atresia, cystic fibrosis, and postinflammatory
bronchi- ectasis [45–47]. Bronchoscopy may
be nec- essary to exclude endobronchial
tumor as the cause of the finger-in-glove
sign.
The tubular opacities that occur in ABPA
result from hyphal masses and mucoid im-
paction and typically affect the upper lobes.
In 19–28% of cases, the endobronchial
opac- ities in ABPA may be calcified or
hyperatten- uating on unenhanced CT
images (Fig. 15), probably because of the
presence of calcium salts, metals, and
desiccated mucus [47–50].

Crazy-Paving Sign
The crazy-paving sign is the CT finding
of a combination of ground-glass opacity
and smooth interlobular septal thickening
that re- sembles a masonry pattern used in
walkways [2]. The crazy-paving sign was
originally de- scribed as a characteristic CT
pattern detect- ed in patients with pulmonary
alveolar pro- teinosis. The sign has come to

48 AJR:202, March 2014 AJR:202, March 2014 48

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tions, including infection (e.g., Pneumocystis differentiated from those with a cen- trilobular nodules are evenly spaced and do not
jiroveci pneumonia, influenza, and infections trilobular or perilymphatic distribution. come into contact with adjacent pleural
by other organisms) [51, 52]. In Cen- surfaces. Perilymphatic nodules are distribut-
Pneumocystis pneumonia, the histologic ed along peribronchovascular structures, the
features that pro- duce the crazy-paving subpleural lung, and along interlobular sep- ta.
pattern are alveolar exudates containing the Random nodules forming the miliary pat- tern
infective organisms and cellular infiltration are distributed uniformly throughout the lungs,
or edema in the alveo- lar walls and and those in the periphery may come into
interlobular septa [52, 53]. An- cillary contact with a pleural surface [61, 62].
clinical or radiographic features sug- gestive Noninfectious causes of the miliary pattern
of Pneumocystis pneumonia include a include metastatic disease, IV injected for-
history of immunosuppression, imaging eign material, and rarely sarcoidosis [62, 63].
findings of pulmonary cysts, and the occur-
rence of secondary spontaneous pneumotho- Reverse Halo and Bird’s Nest Signs
rax [54] (Fig. 17). The reverse halo sign is the CT finding of
Differential diagnostic considerations for peripheral consolidation surrounding a cen-
the crazy-paving sign can be categorized tral area of ground-glass opacity [64]. As-
according to the typical time course of the sociated irregular and intersecting areas of
suspected diseases (Fig. 18). Diseases char- stranding or irregular lines may be present
acterized by an acute time course include within the area of ground-glass opacity and
pulmonary edema, pulmonary hemorrhage, become evident as the bird’s nest sign [65]
and infection. Those with a more chronic (Fig. 21). These signs are suggestive of in-
course include pulmonary alveolar proteino- vasive fungal infection (e.g., angioinvasive
sis, pulmonary adenocarcinoma, and lipoid Aspergillus infection or mucormycosis) in
pneumonia [52, 55]. susceptible patient populations [66]. Major
predisposing factors for fungal infection in-
Grape-Skin Sign clude stem cell or solid organ transplant, he-
The grape-skin sign is the radiographic or matologic malignancy, diabetic ketoacidosis,
CT finding of a very thin-walled cavitary and a depressed immune system. Imaging fea-
le- sion that develops in lung parenchyma tures that favor mucormycosis over Aspergillus
pre- viously affected by consolidation or infection in a neutropenic patient are detec-
lung granulomas that have undergone tion of the reverse halo or bird’s nest sign,
central ca- seous necrosis [56]. As multiplicity of pulmonary nodules (> 10), and
classically described, the grape-skin sign is development of infection despite vori-
a solitary finding of a thin-walled cavity conazole prophylaxis [66–68]. The reverse
with central lucency that has been halo and bird’s nest signs are not specific for
associated with chronic pulmonary invasive fungal infection and may also be
coccidioidomycosis infection [57, 58] seen in other conditions, including crypto-
(Fig. genic organizing pneumonia, bacterial pneu-
19). Over time the lesion may deflate, or it monia, paracoccidioidomycosis, tuberculo-
may rupture into the pleural space, the result sis, sarcoidosis, Wegener granulomatosis, and
being pneumothorax [56, 59]. The differen- pulmonary infarction [64, 68–73].
tial diagnosis of this finding includes other
solitary cavitary or cystic lesions, such as Meniscus, Cumbo, and Water Lily
re- activation tuberculosis infection, Signs of Echinococcal Infection
pneumato- cele, neoplasm (e.g., primary Pulmonary hydatid disease is a zoonotic
lung cancer or metastasis), and other fungal parasitic infection caused by the larval stage of
infections. Echinococcus tapeworms [74]. This ge- nus of
worms is endemic in Alaska, South America,
Miliary Pattern the Mediterranean region, Africa, and
The miliary pattern consists of multiple Australia. Humans can serve as interme- diate
small (< 3 mm) pulmonary nodules of hosts after contact with a definitive host (e.g.,
similar size that are randomly distributed dog or wolf) or after consuming con-
throughout both lungs [2]. This pattern taminated vegetables or water [74]. The lung is
implies hematog- enous dissemination of the second most common organ involved, after
disease and is clas- sically associated with the liver, and is infected by either hema-
tuberculosis but can also be seen with other togenous or direct transdiaphragmatic spread
infections, such as histoplasmosis and from the liver [74–76].
coccidioidomycosis, par- ticularly in
immunocompromised individuals [60] (Fig.
20). Random pulmonary nodules must be
 The hydatid cyst is composed of three lay-
ers: an outer protective barrier consisting
of modified host cells, called the pericyst; a
middle acellular laminated membrane, called
the ectocyst; and an inner germinal layer that
produces scolices, hydatid fluid, daughter
vesicles, and daughter cysts, called the en-
docyst [74, 75, 77]. The meniscus, Cumbo,
and water lily signs are all seen with pulmo-
nary echinococcal infection [74–78]. These
signs are caused by air dissecting between
the cyst layers, which are initially indistin-
guishable on CT images because the cysts
are fluid filled (Fig. 22). With bronchial
erosion, air dissects between the outer
pericyst and ectocyst to produce the
meniscus sign (Fig.
23). Some radiologists believe that the me-
niscus sign is suggestive of impending cyst
rupture [76, 77]. As it accumulates further,
air penetrates the endocyst layer and causes
the Cumbo sign, which comprises an air-flu-
id level in the endocyst and a meniscus sign
(Fig. 23). Finally, the endocyst layer collaps-
es and floats on fluid, forming the water lily
sign (Fig. 24).

Burrow Sign of Paragonimiasis

Paragonimiasis is a zoonotic parasitic in-
fection caused by lung flukes [79]. Humans
serve as a definitive host when they ingest
raw or improperly cooked crab or crayfish
[76]. Paragonimus westermani and
Paragonimus kellicotti are the two
pathogens endemic to Asia and North
America, respectively. They produce
similar imaging findings in the tho- rax
[79–83].
The chest CT findings reflect the life
cycle of the parasite. The second form of the
imma- ture organism lives in the crab or
crayfish. Af- ter ingestion by a mammal, the
parasite pen- etrates through the small bowel
to enter the peritoneal cavity, where it incites
an inflam- matory reaction. Several weeks
later, the or- ganism migrates through the
diaphragm to en- ter the pleural space. After
finding mates, the parasites burrow through
the visceral pleura into the lung parenchyma,
where they produce cysts that contain eggs.
The eggs are extrud- ed into bronchioles and
expectorated by the infected mammal to
complete the life cycle [79]. The burrow sign
is a linear track extend- ing from the pleural
surface or hemidiaphragm to a cavitary or
cystic pulmonary nodule. The linear track
represents the path followed by the worms
within the lung, and the cavitary or cystic
pulmonary nodule contains both the adult
worms and their eggs (Fig. 25). There is
often associated pleural effusion, omental fat
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stranding, and anterior cardiophrenic and in- sequential change with antituberculous 11. Li Ng Y, Hwang D, Patsios D, Weisbrod G. Tree-
ternal mammary lymphadenopathy. Patients therapy. Radiology 1993; 186:653–660 in-bud pattern on thoracic CT due to pulmonary
occasionally present with pneumothorax [79– intravascular metastases from pancreatic adeno-
83]. Recognizing the linear burrow track is carcinoma. J Thorac Imaging 2009; 24:150–151
the key to differentiating this entity from 12. Franquet T, Giménez A, Prats R, Rodríguez-Arias
others, such as malignancy, fungal infection, JM, Rodríguez C. Thrombotic microangiopathy of
and tu- berculosis [80–83]. pulmonary tumors: a vascular cause of tree-in-bud
pattern on CT. AJR 2002; 179:897–899
Conclusion 13. Bendeck SE, Leung AN, Berry GJ, Daniel D,
Imaging plays an important role in the di- Ruoss SJ. Cellulose granulomatosis presenting as
agnosis of suspected pulmonary infection centrilobular nodules: CT and histologic find- ings.
and may reveal useful signs at chest radiog- AJR 2001; 177:1151–1153
raphy and CT. Signs such as the water lily 14. Tack D, Nollevaux MC, Gevenois PA. Tree-in-
and burrow signs almost always indicate a bud pattern in neoplastic pulmonary emboli. AJR
specific infection, whereas findings such as 2001; 176:1421–1422
the split-pleura sign often suggest a specif- 15. Shepard JA, Moore EH, Templeton PA, McLoud
ic diagnosis of empyema in the clinical set- TC. Pulmonary intravascular tumor emboli: di-
ting of pneumonia. Several signs, such as lated and beaded peripheral pulmonary arteries at
the halo and reverse halo signs, may indicate CT. Radiology 1993; 187:797–801
po- tentially serious fungal infections in an 16. Francis JB, Francis PB. Bulging (sagging) fissure
im- munocompromised patient. Imaging sign in Hemophilus influenzae lobar pneumonia.
signs of lung abscess, such the an air-fluid South Med J 1978; 71:1452–1453
level sign in a cavity, may also be predictive 17. Felson B, Rosenberg LS, Hamburger M. Roent-
of progno- sis and guide duration of therapy. gen findings in acute Friedländer’s pneumonia.
Radiology 1949; 53:559–565
References 18. Korvick JA, Hackett AK, Yu VL, Muder RR.
1. Hoyert DL, Xu J. Deaths: preliminary data Klebsiella pneumonia in the modern era: clinico-
for radiographic correlations. South Med J 1991;
2011. Natl Vital Stat Rep 2012; 61:1–51 84:200–204
2. Hansell DM, Bankier AA, MacMahon H, 19. Rafat C, Fihman V, Ricard JD. A 51-year-old
McLoud TC, Müller NL, Remy J. Fleischner So- man presenting with shock and lower-lobe con-
ciety: glossary of terms for thoracic imaging. solidation with interlobar bulging fissure. Chest
Ra- diology 2008; 246:697–722 2013; 143:1167–1169
3. Fleischner FG. The visible bronchial tree; a 20. Kuhlman JE, Fishman EK, Teigen C. Pulmonary
roent- gen sign in pneumonic and other septic emboli: diagnosis with CT. Radiology
pulmonary con- solidations. Radiology 1948; 1990; 174:211–213
50:184–189 21. Huang RM, Naidich DP, Lubat E, Schinella R,
4. Fleischner FG. Der sichtbare Bronchialbaum, ein Garay SM, McCauley DI. Septic pulmonary em-
differentialdiagnostisches Symptom im Röntgen- boli: CT-radiographic correlation. AJR 1989;
bild der Pneumonia. Fortschr Geb 153:41–45
Rontgenstr 22. Dodd JD, Souza CA, Müller NL. High-resolution
1927; 36:319–323 MDCT of pulmonary septic embolism: evaluation
5. Felson B, Felson H. Localization of intrathoracic of the feeding vessel sign. AJR 2006; 187:623–
lesions by means of the postero-anterior roent- 629
genogram; the silhouette sign. Radiology 1950; 23. Milne EN, Zerhouni EA. Blood supply of pulmo-
55:363–374 nary metastases. J Thorac Imaging 1987; 2:15–23
6. Verma N, Chung JH, Mohammed TL. Tree-in- 24. Han D, Lee KS, Franquet T, et al. Thrombotic
bud sign. J Thorac Imaging 2012; 27:W27 and nonthrombotic pulmonary arterial embo- lism:
7. Eisenhuber E. The tree-in-bud sign. spectrum of imaging findings. Radio- Graphics
Radiology
2003; 23:1521–1539
2002; 222:771–772
25. Ketai L, Jordan K, Marom EM. Imaging infec-
8. Rossi SE, Franquet T, Volpacchio M, Giménez
tion. Clin Chest Med 2008; 29:77–105
A, Aguilar G. Tree-in-bud pattern at thin-section
26. Donnelly LF, Klosterman LA. Pneumonia in
CT of the lungs: radiologic-pathologic overview.
children: decreased parenchymal contrast en-
Ra- dioGraphics 2005; 25:789–801
hancement—CT sign of intense illness and im-
9. Collins J, Blankenbaker D, Stern EJ. CT patterns
pending cavitary necrosis. Radiology 1997; 205:
of bronchiolar disease: what is “tree-in-bud”?
817–820
AJR 1998; 171:365–370
27. Hirshberg B, Sklair-Levi M, Nir-Paz R, Ben-Sira
10. Im JG, Itoh H, Shim YS, et al. Pulmonary tuber-
culosis: CT findings—early active disease and
 L, Krivoruk V, Kramer MR. Factors predicting ses from opportunistic fungi: radiologic-
mortality of patients with lung abscess. Chest patholog- ic correlation. RadioGraphics 1995;
1999; 115:746– 15:271–286
750
28. Kuhlman JE, Singha NK. Complex disease of
the pleural space: radiographic and CT
evaluation. RadioGraphics 1997; 17:63–79
29. Kuhlman JE. Complex disease of the pleural
space: the 10 questions most frequently asked of
the radiologist—new approaches to their
answers with CT and MR imaging.
RadioGraphics 1997;
17:1043–
1050
30. Stark DD, Federle MP, Goodman PC, Podrasky
AE, Webb WR. Differentiating lung abscess and
empyema: radiography and computed tomogra-
phy. AJR 1983; 141:163–167
31. Aquino SL, Webb WR, Gushiken BJ. Pleural
ex- udates and transudates: diagnosis with
contrast- enhanced CT. Radiology 1994;
192:803–808
32. Pinto PS. The CT halo sign. Radiology 2004;
230:109–110
33. Kuhlman JE, Fishman EK, Siegelman SS. Inva-
sive pulmonary aspergillosis in acute leukemia:
characteristic findings on CT, the CT halo sign,
and the role of CT in early diagnosis. Radiology
1985; 157:611–
614
34. Kuhlman JE, Fishman EK, Burch PA, Karp JE,
Zerhouni EA, Siegelman SS. Invasive
pulmonary aspergillosis in acute leukemia: the
contribution of CT to early diagnosis and
aggressive manage- ment. Chest 1987; 92:95–99
35. Won HJ, Lee KS, Cheon JE, et al. Invasive pul-
monary aspergillosis: prediction at thin-section
CT in patients with neutropenia—a prospective
study. Radiology 1998; 208:777–782
36. Caillot D, Couaillier JF, Bernard A, et al. In-
creasing volume and changing characteristics of
invasive pulmonary aspergillosis on sequential
thoracic computed tomography scans in patients
with neutropenia. J Clin Oncol 2001; 19:253–
259
37. Greene RE, Schlamm HT, Oestmann JW, et al.
Imaging findings in acute invasive pulmonary
aspergillosis: clinical significance of the halo
sign. Clin Infect Dis 2007; 44:373–379
38. Primack SL, Hartman TE, Lee KS, Müller NL.
Pulmonary nodules and the CT halo sign. Radi-
ology 1994; 190:513–515
39. Jamadar DA, Kazerooni EA, Daly BD, White CS,
Gross BH. Pulmonary zygomycosis: CT appear-
ance. J Comput Assist Tomogr 1995; 19:733–738
40. Buckingham SJ, Hansell DM. Aspergillus in the
lung: diverse and coincident forms. Eur Radiol
2003; 13:1786–
1800
41. Abramson S. The air crescent sign. Radiology
2001; 218:230–232
42. McAdams HP, Rosado-de-Christenson ML, Tem-
pleton PA, Lesar M, Moran CA. Thoracic myco-
Downloaded from www.ajronline.org by 103.105.29.29 on 09/21/20 from IP address 103.105.29.29. Copyright ARRS. For

43. Bard R, Hassani N. Crescent sign in pulmonary 57. Chong S, Lee KS, Yi CA, Chung MJ, Kim TS, 70. Gasparetto EL, Escuissato DL, Davaus T, et al.
hematoma. Respiration 1975; 32:247–251 Han J. Pulmonary fungal infection: imaging find- Reversed halo sign in pulmonary paracoccidioi-
44. Cubillo-Herguera E, McAlister WH. The pulmo- ings in immunocompetent and immunocompro- domycosis. AJR 2005; 184:1932–1934
nary meniscus sign in a case of bronchogenic car- mised patients. Eur J Radiol 2006; 59:371–383 71. Marchiori E, Grando RD, Simões Dos Santos CE,
cinoma. Radiology 1969; 92:1299–1300 58. Kim KI, Leung AN, Flint JD, Müller NL. Chron- et al. Pulmonary tuberculosis associated with the
45. Nguyen ET. The gloved finger sign. Radiology ic pulmonary coccidioidomycosis: computed to- reversed halo sign on high-resolution CT. Br J Ra-
2003; 227:453–454 mographic and pathologic findings in 18 patients. diol 2010; 83:e58–e60
46. Mintzer RA, Neiman HL, Reeder MM. Mucoid im- Can Assoc Radiol J 1998; 49:401–407 72. Marchiori E, Zanetti G, Mano CM, Hochhegger
paction of a bronchus. JAMA 1978; 240:1397–1398 59. McAdams HP, Rosado-de-Christenson ML, Lesar B, Irion KL. The reversed halo sign: another atyp-
47. Agarwal R, Aggarwal AN, Gupta D. High-attenu- M, Templeton PA, Moran CA. Thoracic mycoses ical manifestation of sarcoidosis. Korean J Radiol
ation mucus in allergic bronchopulmonary asper- from endemic fungi: radiologic-pathologic correla- 2010; 11:251–252
gillosis: another cause of diffuse high-attenuation tion. RadioGraphics 1995; 15:255–270 73. Mango VL, Naidich DP, Godoy MC. Reversed
pulmonary abnormality. AJR 2006; 186:904 60. Burrill J, Williams CJ, Bain G, Conder G, Hine halo sign after radiofrequency ablation of a lung
48. Agarwal R, Gupta D, Aggarwal AN, Saxena AK, AL, Misra RR. Tuberculosis: a radiologic review. nodule. J Thorac Imaging 2011; 26:W150–W152
Chakrabarti A, Jindal SK. Clinical significance of RadioGraphics 2007; 27:1255–1273 74. Pedrosa I, Saíz A, Arrazola J, Ferreirós J, Pedrosa
hyperattenuating mucoid impaction in allergic 61. Gruden JF, Webb WR, Naidich DP, McGuinness CS. Hydatid disease: radiologic and pathologic
bronchopulmonary aspergillosis: an analysis of G. Multinodular disease: anatomic localization at features and complications. RadioGraphics 2000;
155 patients. Chest 2007; 132:1183–1190 thin-section CT—multireader evaluation of a 20:795–817
49. Logan PM, Müller NL. High-attenuation mucous simple algorithm. Radiology 1999; 210:711–720 75. Polat P, Kantarci M, Alper F, Suma S, Koruyucu
plugging in allergic bronchopulmonary aspergil- 62. Lee KS, Kim TS, Han J, et al. Diffuse micronodu- MB, Okur A. Hydatid disease from head to toe.
losis. Can Assoc Radiol J 1996; 47:374–377 lar lung disease: HRCT and pathologic findings. J RadioGraphics 2003; 23:475–494
50. Agarwal R. High attenuation mucoid impaction in Comput Assist Tomogr 1999; 23:99–106 76. Martínez S, Restrepo CS, Carrillo JA, et al. Tho-
allergic bronchopulmonary aspergillosis. World J 63. Koyama T, Ueda H, Togashi K, Umeoka S, Kata- racic manifestations of tropical parasitic infec-
Radiol 2010; 2:41–43 oka M, Nagai S. Radiologic manifestations of sar- tions: a pictorial review. RadioGraphics 2005;
51. Murch CR, Carr DH. Computed tomography ap- coidosis in various organs. RadioGraphics 2004; 25:135–155
pearances of pulmonary alveolar proteinosis. Clin 24:87–104 77. Balikian JP, Mudarris FF. Hydatid disease of the
Radiol 1989; 40:240–243 64. Walker CM, Mohammed TL, Chung JH. Re- lungs: a roentgenologic study of 50 cases. Am J
52. Rossi SE, Erasmus JJ, Volpacchio M, Franquet T, versed halo sign. J Thorac Imaging 2011; 26:W80 Roent-
genol Radium Ther Nucl Med 1974; 122:692–707
Castiglioni T, McAdams HP. “Crazy-paving” pattern 65. Vogl TJ, Hinrichs T, Jacobi V, Böhme A, Hoelzer D. 78. McPhail JL, Arora TS. Intrathoracic hydatid dis-
at thin-section CT of the lungs: radiologic-patho- Computed tomographic appearance of pulmonary ease. Dis Chest 1967; 52:772–781
logic overview. RadioGraphics 2003; 23:1509–1519 mucormycosis [in German]. Rofo 2000; 172:604–608 79. Procop GW. North American paragonimiasis
53. Marchiori E, Müller NL, Soares Souza A, Escuis- 66. Georgiadou SP, Sipsas NV, Marom EM, Kontoyi- (caused by Paragonimus kellicotti) in the context
sato DL, Gasparetto EL, Franquet T. Pulmonary annis DP. The diagnostic value of halo and reversed of global paragonimiasis. Clin Microbiol Rev
disease in patients with AIDS: high-resolution CT halo signs for invasive mold infections in compro- 2009; 22:415–446
and pathologic findings. AJR 2005; 184:757–764 mised hosts. Clin Infect Dis 2011; 52:1144–1155 80. Henry TS, Lane MA, Weil GJ, Bailey TC, Bhalla
54. Kanne JP, Yandow DR, Meyer CA. Pneumocystis 67. Chamilos G, Marom EM, Lewis RE, Lionakis MS, S. Chest CT features of North American para-
jiroveci pneumonia: high-resolution CT findings Kontoyiannis DP. Predictors of pulmonary zygomy- gonimiasis. AJR 2012; 198:1076–1083
in patients with and without HIV infection. AJR cosis versus invasive pulmonary aspergillosis in 81. Im JG, Whang HY, Kim WS, Han MC, Shim YS,
2012; 198:[web]W555–W561 patients with cancer. Clin Infect Dis 2005; 41:60–66 Cho SY. Pleuropulmonary paragonimiasis: radio-
55. Franquet T, Giménez A, Bordes R, Rodríguez- 68. Chung JH, Godwin JD, Chien JW, Pipavath SJ. logic findings in 71 patients. AJR 1992; 159:39–43
Arias JM, Castella J. The crazy-paving pattern in Case 160: pulmonary mucormycosis. Radiology 82. Kim TS, Han J, Shim SS, et al. Pleuropulmonary
exogenous lipoid pneumonia: CT-pathologic cor- 2010; 256:667–670 paragonimiasis: CT findings in 31 patients. AJR
relation. AJR 1998; 170:315–317 69. Kim SJ, Lee KS, Ryu YH, et al. Reversed halo 2005; 185:616–621
56. McGahan JP, Graves DS, Palmer PE, Stadalnik sign on high-resolution CT of cryptogenic orga- 83. Im JG, Kong Y, Shin YM, et al. Pulmonary para-
RC, Dublin AB. Classic and contemporary imaging nizing pneumonia: diagnostic implications. AJR gonimiasis: clinical and experimental studies.
of coccidioidomycosis. AJR 1981; 136:393–404 2003; 180:1251–1254 RadioGraphics 1993; 13:575–586

(Figures start on next page)

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Fig. 1—49-year-old man with left lower lobe pneumonia. Example of air Fig. 2—4-year-old girl with lingular pneumonia. Example of silhouette sign.
bronchogram sign. Posteroanterior radiograph (left) and coronal CT image Posteroanterior radiographs show normal interface (right) and loss of normal
(right) show left lower lobe consolidation and air bronchogram sign (arrows). interface of lung and left-heart border (left), thus localizing abnormality to
lingula.

Fig. 3—45-year-old man with reactivation tuberculosis. Example of tree-in-

bud sign. Photograph (top) shows budding tree. Axial CT image (bottom) shows
numerous V- and Y-shaped tree-in-bud opacities.
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Fig. 4—40-year-old man after IV injection of crushed Fig. 5—75-year-old man with alcoholism and Klebsiella pneumonia. Example of bulging fissure sign.
morphine sulfate tablets. Example of tree-in-bud Posteroanterior (left) and lateral (right) radiographs show right upper lobe consolidation causing
sign. Axial maximum-intensity-projection image inferior bulging of minor fissure (black arrows), posterior bulging of major fissure (white arrow), and
shows diffuse vascular tree-in-bud opacities and inferomedial displacement of bronchus intermedius (asterisk).
dilated main pulmonary arteries. Similar findings
involved
all aspects of both lungs. Infectious bronchiolitis or
aspiration is unlikely to result in such diffuse
bilateral distribution of tree-in-bud opacities, and
other conditions, such as diffuse panbronchiolitis
and injection of foreign material, as in this case,
should be considered as alternative diagnoses.

Fig. 6—45-year-old man with septic emboli. Example of feeding vessel sign. Fig. 7—55-year-old man with necrotizing aspiration
Coronal CT image shows septic pulmonary emboli manifesting themselves as pneumonia. Example of inhomogeneous
peripheral solid and cavitary pulmonary nodules of varying sizes. Many enhancement. Axial contrast-enhanced CT image
nodules exhibit feeding vessel sign (arrows). shows heterogeneously enhancing right lower lobe
consolidation (arrows) suspicious for early
pulmonary necrosis. Also present are foci of air
(arrowheads) representing early abscess formation
and small loculated right pleural effusion (asterisks).
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A B
Fig. 8—35-year-old man with Staphylococcus aureus pneumonia forming lung abscess. Example of air-fluid level sign.
A, Posteroanterior (left) and lateral (right) radiographs show right lower lobe cavity with air-fluid level (arrows) of equal length on both orthogonal views. Thick, irregular
wall typical of lung abscess is evident.
B, Axial CT image shows parenchymal location of right lower lobe cavity with air-fluid level, irregular internal contours, and associated bronchus (arrow) coursing to lesion.

Fig. 9—48-year-old woman with empyema. Example of split-pleura sign. Axial (left) Fig. 10—65-year-old man with malignant pleural effusion. Example of split-pleura
and sagittal (right) contrast-enhanced CT images show thickened visceral sign. Axial (left) and sagittal (right) contrast-enhanced CT images show
(arrowhead) and parietal (white arrows) pleura separated from their normal state of thickening of visceral (arrowheads) and parietal (arrows) pleura with associated
apposition (i.e., split) to surround loculated empyema. Adjacent atelectasis is evident effusion. Split-pleura sign only indicates presence of exudative effusion and must
in right lower lobe. Split-pleura sign is not specific for empyema but rather indicates be
presence of exudative effusion. Chest tube is incompletely visible (black arrows). correlated with clinical findings and thoracentesis to establish accurate diagnosis.
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Fig. 11—35-year-old man with fever, neutropenia, and angioinvasive Fig. 12—47-year-old man with disseminated candidiasis. Example of halo
Aspergillus infection. Example of halo sign. Posteroanterior radiograph and sign. Axial CT image shows multiple bilateral pulmonary nodules with
axial CT image show right upper lobe mass with peripheral ground-glass surrounding ground-glass opacity.
opacity (arrows) constituting halo sign.

Fig. 13—38-year-old man with angioinvasive Aspergillus infection. Example Fig. 14—65-year-old woman with intracavitary mycetoma. Example of air
of air crescent sign. Axial (left) and coronal (right) CT images show air crescent or Monad sign. Axial supine (left) and prone (right) CT images show
crescent sign (arrows), which occurs in immunocompromised patients with gravity dependence of fungal ball (mycetoma). Air crescent sign of mycetoma
recovering occurs in immunocompetent patients. Fungus ball develops within preexisting
neutrophil levels. Intracavitary nodule (asterisks) represents necrotic lung cavity, usually in association with tuberculosis or sarcoidosis.
tissue.
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Fig. 15—25-year-old
woman with allergic
bronchopulmonary
aspergillosis (ABPA).
Example of finger-in-
glove sign.
A, Posteroanterior
radiograph shows
branching tubular
opacities (arrows)
emanating from both hila.
B, Unenhanced axial
(left) and oblique sagittal
(right) CT images show
branching tubular
opacities (arrows)
with high attenuation.
Opacities in ABPA are
composed of hyphal
masses, and mucoid
impaction and may be
calcified on CT images in
as many as 28% of cases.

A B

Fig. 16—63-year-old man with squamous cell lung cancer. Example of finger-in- Fig. 17—24-year-old man with HIV infection and
glove sign. Posteroanterior radiograph (top left) and corresponding coronal (top Pneumocystis pneumonia. Example of crazy-paving
right) and axial (bottom) CT images show branching tubular opacity (arrows) in sign. Axial CT image shows diffuse ground-glass
right upper lobe. Proximal portion of branching opacity was FDG avid (not opacity with areas of superimposed interlobular
shown) and represented tumor, whereas rest of opacity represented mucoid septal thickening (combination that forms crazy-
impaction in dilated bronchus. paving pattern) and multiple thin-walled cysts. In
HIV-positive patient with dyspnea, findings are most
consistent with Pneumocystis pneumonia.
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Fig. 18—CT scans show crazy-paving sign in patients with various disorders. Differential diagnostic
considerations are influenced by patient’s clinical presentation and disease course. In patients with acute
symptoms, crazy-paving sign may represent pulmonary edema, pulmonary hemorrhage, or infection. In
patients with chronic symptoms, crazy-paving sign may represent lipoid pneumonia, lung cancer, or pulmonary
alveolar proteinosis (PAP).

Fig. 19—55-year-old man with chronic Fig. 20—29-year-old man with AIDS (CD4 count,
coccidioidomycosis infection. Example of grape-skin 10/μL) and disseminated histoplasmosis. Example
sign. Posteroanterior radiograph shows thin-walled of miliary pattern. Axial CT image shows multiple
grape-skin cyst (arrows). Axial CT image (inset) small pulmonary nodules distributed uniformly
shows that over time cavity may deflate and acquire throughout both lungs. Some nodules are in contact
slightly thicker wall. with major fissure and subpleural lung and have no
relation to secondary pulmonary lobules. Differential
considerations for randomly distributed pulmonary
nodules include miliary infection (e.g., tuberculosis,
histoplasmosis), metastatic disease, and rarely
sarcoidosis.
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Fig. 21—44-year-old man with febrile neutropenia and pulmonary mucormycosis.

Example of reverse halo and bird’s nest signs. Axial (left) and coronal (right) CT
images show peripheral rim of consolidation (arrows) surrounding central
ground- glass opacity, reticulation, and nodularity. This appearance has been
likened
to bird’s nest and reverse halo. Early diagnosis of mucormycosis pneumonia is
imperative because standard voriconazole therapy is not effective for
treatment. (Courtesy of Chou S, University of Washington, Seattle, WA)

Fig. 22—Drawings show normal hydatid cyst and meniscus, Cumbo, and water lily signs. (Courtesy of Loomis
S, REMS Media Services, Mass General Imaging, Boston, MA)

49 AJR:202, March 2014 AJR:202, March 2014 49

1 1
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Fig. 23—49-year-old man with pulmonary hydatid disease. Example of meniscus Fig. 24—27-year-old woman with pulmonary hydatid
(left) and Cumbo (right) signs. Chest CT images show air between pericyst and disease. Example of water lily sign. Posteroanterior
ectocyst layers (arrows) consistent with meniscus sign. Air-fluid level in radiograph shows large right lower lobe thick-
endocyst (arrowhead) in combination with meniscus sign forms Cumbo sign. walled cavity with lobulated air–soft-tissue
(Courtesy of Rossi S, Centro de Diagnostico Dr Enrique Rossi, Buenos Aires, interface representing floating endocyst (arrow).
Argentina) Coronal
CT image (inset) from earlier examination shows
unruptured cyst.

A B
Fig. 25—32-year-old man with North American paragonimiasis after ingestion of raw crayfish. Example of burrow sign. (Courtesy of
Henry T, Emory University, Atlanta, GA)
A, Axial CT images in soft-tissue (left) and lung (right) windows shows linear burrow track (arrows) extending from thickened pleura
to pulmonary nodule.
B, Axial CT image shows long linear burrow track (arrow) in right upper lobe and small pneumothorax.

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