This document provides an overview of imaging features of non-bacterial pulmonary infections. It begins by describing the mechanisms of pulmonary infections and then discusses various types of infections including viral, fungal, protozoal and helminthic origins. For each type of infection, examples of specific pathogens are given along with their typical radiographic and CT imaging appearances. Common findings include areas of consolidation, ground-glass opacities, nodules and reticulation. The document emphasizes how imaging can help identify and characterize different pulmonary infections.
2. CONTENTS
• Mechanism of disease in pulmonary infections.
• Different types of non bacterial pulmonary
infections.
• Individual infections with their imaging features.
• Complications of pulmonary infections.
• Summary
• References
3. MECHANISMS OF DISEASE IN
PULMONARY INFECTIONS
• Microorganisms responsible for producing
pneumonia enter the lung and cause infection
by three potential routes:
1. via the tracheo-bronchial tree,
2. via the pulmonary vasculature, or
3. via direct spread from infection in the
mediastinum, chest wall, or upper abdomen.
4. • Non bacterial infections of lung comprises of;
– Viral
– Fungal
– Protozoal
– Helminthic
5. VIRAL PNEUMONIAS
• Usually commences in distal bronchi and
bronchioles as an interstitial process with
destruction of the epithelium, oedema and
lymphocytic infiltration.
• More common in infants and children and less
common in adults (unless
immunocompromised).
6. • Radiological appearances of a viral pneumonia
are very varied, but often include:
– Peribronchial shadowing
– Reticulonodular shadowing
– Patchy or extensive consolidation
7. • Common viruses causing pulmonary infections:
1. Influenza virus
2. Adenovirus
3. Respiratory synctial virus
• Less common viruses causing pulmonary
infections:
1. Epstein Barr Virus
2. Varicella Zooster
3. Herpes Simplex Virus (Type I)
4. Cytomegalovirus (esp. in immunocompromised)
5. New Emerging Viruses (SARS, MERS, H5N1, H1N1,
SARS-COV-2)
8. Influenza Virus:
• Pulmy. infxns are usu.
due to secondary
bacterial infection.
• Ocassionally, a
fulminating H’gic
pneumonia may be seen
with widespread
consolidation
indistinguishable from
noncardiogenic
pulmonary oedema or
ARDS.
9. Adenovirus:
• accounts for 5%–10% of acute respiratory
infections in infants and children.
• less than 1% of respiratory illnesses in adults.
• In children, may result in lobar collapse,
especially of the right upper lobe.
• CT findings:
– patchy bilateral areas of consolidation in a lobular
or segmental distribution.
– bilateral ground-glass opacities with a random
distribution.
10.
11. Respiratory Syncytial Virus:
• Most frequent viral cause of lower respiratory
tract infection in infants.
• CT findings:
– small centrilobular nodules
– airspace consolidation
– ground-glass opacities
– bronchial wall thickening
12.
13. Epstein Barr Virus:
• Infection occurs early in life
• Presents as infectious mononucleosis with the
typical triad of;
– Fever,
– Pharyngitis and
– Lymphadenopathy
• CT findings: similar to those of other viral
pneumonias.
14. Herpes Varicella Zooster:
• More often in adults than in children
• Acute phase of infection shows widespread
nodular shadows up to 1 cm in diameter in
CXR
• Pneumonia will be concurrent with the typical
skin rash clinically.
• Following recovery a small proportion of these
nodules calcify and, if multiple, may produce a
characteristic radiographic appearance.
15.
16. Herpes Simplex Virus (Type I):
• (HSV-1) pneumonia may be a life-threatening
infection seen almost exclusively in immuno-
compromised and/or mechanically ventilated
patients.
• Airspace consolidation, predominantly lobar or
more extensive and always bilateral, or a
mixed airspace and interstitial pattern.
17. • CT findings:
– Patchy, lobular, sub-segmental or segmental
consolidation and ground-glass opacities;
– associated small centri-lobular nodules and tree-
in-bud pattern have been described in patients
infected with herpes simplex virus type 2;
– nodules surrounded by a ‘halo’ of ground-glass
opacity may also occur
18.
19. Cytomegalovirus (CMV):
• CMV pneumonia is a major cause of morbidity
and mortality following hematopoietic stem
cell (HSC) and solid organ transplantation, and
in patients with AIDS in whom CD4 cells are
decreased to fewer than 100 cells/mm3.
• Infection occurs in up to 70% of bone marrow
transplant (BMT) recipients, and
approximately one-third develop CMV
pneumonia.
20. • Chest radiographs:
– focal and diffuse hazy opacification
– multiple small (less than 5 mm) nodules
• CT features:
– lobar consolidation,
– diffuse and focal ground-glass opacities,
– irregular reticular opacities,
– multiple miliary nodules or small nodules with
associated areas of ground-glass attenuation
(‘halo’).
21.
22. NEW EMERGING VIRUSES
HUMAN METAPNEUMOVIRUS (hMNV):
• Recently identified RNA virus, genus
Metapneumovirus.
• usually associated with upper airway disease,
lower airway bronchitis and bronchiolitis,
influenza like syndrome and pneumonia.
• CT findings:
– patchy areas of ground-glass attenuation,
– small nodules and multifocal areas of
consolidation in a bilateral asymmetric distribution
23. SEVERE ACUTE RESPIRATORY
SYNDROME
• Caused by coronavirus (SARS-CoV-1)
• First detected China in late 2002.
• IP: 2-10 days
• Early systemic symptoms within 2 to 7 days of
dry cough or shortness of breath,
• Development of radiographically confirmed
pneumonia by day 7 to 10 and
lymphocytopenia in many cases.
24. • CT features:
– unilateral or bilateral ground-glass opacities,
– focal unilateral or bilateral areas of consolidation
or a mixture of both.
– In the areas of ground-glass opacification,
thickening of the intralobular interstitium or
interlobular septa may be present.
– If marked septal thickening occurs, a ‘crazy paving’
appearance results.
25.
26. MIDDLE EAST RESPIRATORY
SYNDROME (MERS):
• Caused by a coronavirus (MERS-CoV).
• Most patients develop a severe acute
respiratory illness with symptoms of cough,
fever and dyspnoea, with a high case fatality
rate of 30%–40%.
• CXR:
– Pulmonary opacities and consolidation, with a
peripheral predominance in the mid and lower
lung zones in the initial stages of the illness.
– As the disease progresses, parenchymal
abnormalities may spread to the central areas and
become diffuse.
27. • CT findings:
– ground-glass opacities, consolidation, interlobular
thickening and pleural effusion (early stages).
– centrilobular nodules, a ‘crazy-paving’ pattern,
obliterative bronchiolitis, peribronchial air
trapping and organising pneumonia (later stages).
28.
29. AVIAN FLU (H5N1):
• Subtype of the influenza A virus
• Case fatality rate> 60%.
• CXR: multifocal consolidation.
• CT findings: focal, multifocal or diffuse GGOs
or areas of consolidation.
• Pseudocavitation, pneumatocele formation,
lymphadenopathy and centrilobular nodules
often seen.
30.
31. SWINE INFLUENZA (H1N1):
• Declared a pandemic in 2011.
• Virus continues to spread globally but its
virulence is not greater than that observed
with seasonal influenza.
• CT findings:
– U/L or B/L GGOs with/out associated focal or
multifocal areas of consolidation.
– Predominant peribronchovascular and subpleural
distribution, resembling organising pneumonia .
32.
33. COVID-19 (CORONAVIRUS DISEASE 2019)
• Causative agent: SARS-CoV-2
• Is currently a WHO declared pandemic.
• As of December 7 2020, over 67 million
people had been infected globally with over
1.5 million deaths.
• Many people with infection are asymptomatic.
• Symptoms and signs are non-specific but in
symptomatic individuals most commonly
include:
34. – fever (85-90%)
– cough (65-70%) with sputum in 30-35%
– smell and taste disturbances (50%) 12
– fatigue (35-40%)
– shortness of breath (15-20%)
35. Radiographic features
• The primary findings of COVID-19 are those
of atypical or organizing pneumonia.
• Up to 18% of cases demonstrate normal chest
x-rays or CT when mild/early in the disease
course.
• Bilateral and/or multilobar involvement is
common, more often with a lower zone
distribution.
36. • Plain radiograph
– patchy or
diffuse airspace
opacities,
whether consolidatio
n or ground-glass
opacity.
– pleural effusion is
rare.
37. CT:
• The primary findings on CT in adults have
been reported as:
– ground-glass opacities (GGO)
– crazy paving appearance (GGOs with inter-/intra-
lobular septal thickening)
– air space consolidation
– bronchovascular thickening in the lesion
– traction bronchiectasis
38.
39. FUNGAL INFECTION
• Fungi involved in pulmonary infections are;
1. Pathogenic fungi
• can infect any host
• coccidioidomycosis, blastomycosis and
histoplasmosis
2. Saprophytic fungi
• infect only immunocompromised hosts
• PCP, candidiasis, mucormycosis and
aspergillosis.
44. CANDIDIASIS
• Common fungal pneumonia in
immunocompromised patients.
• CT findings:
– Multiple bilateral nodular opacities,
– Often associated with areas of consolidation and
ground-glass opacity.
– Less commonly pleural effusion, thickening of the
bronchial walls and cavitation.
45. PNEUMOCYSTIS JIROVECI
• P. jiroveci (formerly Pneumocystis carinii) is a
opportunistic fungus causing pneumonia in
immunocompromised individuals.
• Classical findings: diffuse bilateral interstitial
infiltrates in a perihilar distribution
• CT: perihilar GGOs, occasionally combined with
focal consolidation, with a patchy or
geographical distribution.
46.
47. MUCORMYCOSIS
• Opportunistic fungal infection
• Lobar or multi-lobar areas of consolidation
and solitary or multiple pulmonary nodules
and masses; associated cavitation is found in
26% to 40% of cases.
• Air-crescent sign, highly suggestive of an
invasive fungal infection, can be identified in
5% to 12.5% of cases.
• CT features are non-specific.
48. CRYPTOCOCCOSIS
• Caused by inhaling spores of Cryptococcus
neoformans (found in soil and in bird
droppings).
• Mostly asymptomatic and the pulmonary
lesions heal spontaneously.
• Common pulmonary infection in AIDS patients
with CD4 counts below 100 cells/mm3 .
49. • Radiographic manifestation: pulmonary
masses(5 mm to very large size),
homogeneous segmental or lobar
opacifications, and miliary, reticular or
reticulonodular interstitial patterns.
• May show a halo similar to an invasive
Aspergillus lesion, which may eventually
cavitate.
50.
51. HISTOPLASMOSIS
• Caused by Histoplasma capsulatum (fungus
found in moist soil and in bird or bat excreta).
• Diffuse nodular opacities of variable sizes
(ranging from <3mm to >3cm) or areas of
consolidation can be seen.
• Hilar and mediastinal lymph nodes are
frequently enlarged.
52. • Chronic pulmonary histoplasmosis
radiologically resembles post-primary
tuberculosis, with upper lobe contraction,
calcification and cavitation.
• Uncommon late manifestation of
histoplasmosis is a fibrosing mediastinitis.
53.
54. • Other fungal infections not common in our
part of world;
– Coccidioidomycosis
– Paracoccidioidomycosis (South American
Blastomycosis)
– North American Blastomycosis
55. PROTOZOAL INFECTIONS
AMEBIASIS:
• Caused by Entamoeba histolytica.
• Usually secondary to liver involvement.
• Lungs: second m/c extra-intestinal site of
amoebic involvement after the liver.
• Pleuropulmonary amoebiasis is a significant
complication of amoebic liver abscess.
56. • Right-sided abnormalities are found in 86% of
cases and consists of hemidiaphragmatic
elevation, pleural effusion or empyema and/or
thickening and plate-like atelectasis.
• If communication with a major bronchus
occurs, haemoptysis can develop, containing
the ‘anchovy paste’ pus coming from the
amoebic abscess.
57.
58. MALARIA:
• Transmitted by the bite of Anopheles
mosquito.
• Caused by s Plasmodium vivax, P. falciparum
(deadliest), P. malariae and P. ovale.
• ARDS is the most common lung manifestation.
• Septal thickenings, pleural effusions and
airspace consolidations are seen on HRCT and
are consistent with noncardiogenic pulmonary
oedema.
59.
60. TRYPANOSOMIASIS:
• Also known as Chagas disease
• Caused by Trypanosoma cruzi.
• Acquired through the bite of a triatomine insect.
• Acute phase is usually asymptomatic but can
present with febrile illness with facial or palpebral
oedema and acute myocarditis.
• A nodular lesion or furuncle, usually called
chagoma, can appear at the site of inoculation.
61. • Chronic manifestations include
cardiomyopathy, bundle branch blocks,
complete atrioventricular block and
ventricular aneurysms.
• Late gastrointestinal compromise is caused by
damage to neurones of the myenteric plexus,
with achalasia, megaoesophagus and
megacolon.
63. HELMINTHIC INFECTIONS
NEMATODES
ASCARIASIS:
• Most common parasitic infections, affecting 1.3
billion people worldwide.
• Transmitted by faeco-oral route.
• Main signs and symptoms are those of Loeffler
syndrome, characterised by cough, fever,
expectoration and eosinophilia.
• Chest radiography and CT may show patchy
acinar opacities, usu. b/l and migratory.
64. STRONGYLOIDIASIS:
• Caused by Strongyloides stercoralis.
• S. stercoralis filariform larvae invade the lungs
and small intestine through the skin from the
soil.
• Main imaging findings include ill-defined,
patchy, migratory airspace consolidation.
65.
66. TOXOCARIASIS:
• Caused by the larvae of Toxocara canis.
• In humans, the larvae do not develop into
adult worms but migrate through host tissues
(so called visceral larva migrans).
• Cl/f: peripheral eosinophilia, abdominal pain,
hepatosplenomegaly, fever and
hypergammaglobulinaemia.
• CT findings: GGOs, solid nodules, areas of
consolidation and linear opacities
67. Fig. Toxocariasis.
A 14-year-old male
patient with cough,
fever, tachypnoea and
weight loss in the last
10 days. (A)
Posteroanterior chest
radiograph and (B)
chest CT show a
diffuse micronodular
pattern. (Courtesy Dr.
Dante Escuissato,
Curitiba, Brazil.)
68. CESTODES
ECHINOCOCCOSIS (HYDATID DISEASE):
• Caused by the larval forms of Echinococcus
granulosus (most common), E. multilocularis
and E. vogeli.
• Hydatid cyst has been reported in almost all
human tissues and organs but most commonly
in liver and lungs.
• Usually solitary but may be multiple and/or
bilateral in 10% of cases.
69. • May be ruptured (two-thirds) or unruptured
(one-third) at the time of presentation.
• The hydatid is a parasitic echinococcal cyst
consisting of three layers: an adventitia
formed of compressed host tissue, a middle
layer of friable ectocyst and an inner germinal
layer from which is produced large numbers of
scolices which are the heads of developing
worms.
70. • Radiological findings in patients with
unruptured pulmonary cysts are one or more
homogeneous, roughly spherical or oval,
sharply demarcated lesions with mass effect.
• Cysts may rupture into the pleura or bronchi.
• Following rupture into a bronchus an air–fluid
level may appear or the ectocyst may separate
from the adventitia so that a double-walled
cyst may be seen.
71. • If the inner layers are disrupted, a complex
cavitary lesion results with one or more of the
following radiographic features:
– an air-fluid level,
– a floating memb. (water lily sign/camalote sign) ,
– an essentially dry cyst with crumpled membranes
lying at its bottom (rising sun sign, serpent sign)
– cyst with all its contents expectorated (empty cyst
sign).
72. Fig. 5.45 Ruptured Hydatid Cyst. A 65-year-old male shepherd with abrupt onset of
expectoration and pruritus. Close-up view of the right upper lung shows a cystic lesion
surrounded by a parenchymal consolidation due to a massive aspiration of intracystic
content. Note a rounded opacity immediately above the fluid level (‘water lily’ sign)
(arrows).
73.
74. • Secondary infection of a hydatid cyst may
produce a lung abscess with or without
surrounding lung opacity.
• Rupture into the pleural space causes an
effusion or, if there is airway communication,
a hydropneumothorax.
75. CYSTICERCOSIS:
• Caused by larval stage of the pork tapeworm
Taenia solium.
• Disseminated cysticercosis mainly involves the
CNS and, occasionally, heart, lung, striated
muscles and subcutaneous tissue.
• Subcutaneous cysticercosis presents as small,
moveable, painless nodules, usually in the
arms or chest.
76. • CT may depict cystic lesions, commonly with a
hyperdense central nodule, which represents
the parasite head, called the scolex.
• Pulmonary cysticercosis mimics many other
diseases presenting with nodules, cavitary
lesions and pleural effusion.
• If association of chest wall and cardiac
muscles lesions is seen, cysticercosis should
be the first diagnosis to be considered.
77.
78. TREMATODES
PARAGONIMIASIS:
• Caused by a fluke (Paragonimus westermani).
• Infestations are acquired from eating raw or
incompletely cooked fresh water crabs and
crayfish.
• Radiological changes tend to be bilateral,
including a mixture of consolidation, nodules
and band, tubular and ring opacities.
79. • In the lower lobes, parenchymal changes
mimic bronchiectasis, and in the upper lobes,
tuberculosis.
• The constellation of focal pleural thickening
and subpleural linear opacities leading to a
necrotic peripheral pulmonary nodule is
another frequent CT finding of paragonimiasis.
80. SCHISTOSOMIASIS:
• Caused by Schistosoma.
• Chronic granulomatous inflammation can
result in arteriolitis obliterans, pulmonary
hypertension and cor pulmonale.
• Formation of a pulmonary artery aneurysm is
a common complication.
• should be suspected in native populations and
travellers with pulmonary arterial
hypertension coming from endemic regions.
81. Fig. 5.46 Schistosomiasis. A 41-year-old man with schistosomiasis and pulmonary hypertension.
(A) Anteroposterior chest radiograph shows a significant enlargement of the main pulmonary
artery (arrows). Descending aorta is also seen (arrowhead). (B) Close-up view of a contrast-
enhanced CT shows a huge dilatation of the main pulmonary artery (arrows). Note an eccentric
filling defect along the posterior margin of the descending aorta with a peripheral calcification
(arrowhead).
82. (C) A 3D external volume rendering is also useful to
show the pulmonary artery dilatation (arrows).
88. REFERENCES
• Grainger & Allison’s Diagnostic Radiology- A
Textbook of Medical Imaging-7th Edition.
• Textbook of Radiology and Imaging, David
Sutton, 7th Edition.
• Brant and Helm’s Fundamentals of Diagnostic
Radiology, 5th Edition.
• Radiopedia.org
