Airspace Diseases I

AIRSPACE DISEASES I

Types of alveolar filling

Features of Airspace diseases ASD• Ground glass opacity: increased density yet not obscuring the blood

vessels on CT• Consolidation: homogenous or heterogenous opacity that obscure

the blood vessels associated with air bronchogram and silhouette sign. Lobar, segmental or patchy, no volume loss, limited by fissures.

Other features include:• Cavity and cysts• Miliary pattern• Mass/nodule• Interstitial pattern• Lymph nodes and pleural effusion/thickening

Silhouette sign

Differentiation between ASD

• Clinical history is very important• Onset of disease: acute or chronic• Acute e.g. pneumonia, pulmonary edema, alveolar hge• Chronic e.g. BAC, lymphoma, cryptogenic organizing pneumonia• Course of disease: rapid progression, slow, rapid resolution• Focal, multi-focal or diffuse• Peripheral or central, upper or lower predilection• Cavitation• Other findings e.g. pleural effusion, cardiac enlargement, lymph

nodes.

BACTERIAL PNEUMONIA Two types• Community acquired e.g. strept, staph, H influenza, TB• Hospital acquired e.g. pseudomonas, proteus, E.coli

• Patients at risk: chronic debilitating disease e.g. DM, immunocompromised, hospitalized

• C/P: acute onset of fever, chills, productive cough, chest pain. Leukocytosis and sputum analysis

• Radiography: ground glass opacity and consolidation + air bronchogram. Other findings depends on type of organism

• CT is indicated in recurrent pneumonia, unresolved pneumonia, Immuno-compromised and to detect complication.

BACTERIAL PNEUMONIA

Streptococcal Pneumonia• Affecting all age groups• Risk factors include chronic illness,

alcoholism, sickle-cell disease, splenectomy

• Radiography: lobar consolidation mostly basal + air bronchogram. Normal lung volume

Parapneumonic effusion

• May produce patchy consolidation if the patient receive ttt

• Complete resolution 2-6 weeks

Staphylococcal Pneumonia• Affecting debilitated patients

• Infection by inhalation or hematogenous e.g. in IV drug abuse and children with central line and indwelling catheter

• Radiography: Mainly patchy multifocal and bilateral opacities. Pleural effusion, empyema, cavitation are common

• In children resolve to pneumatocele

Klebsiella Pneumonia• Freidlander’s bacillus• Radiography: homogenous opacity

similar to strept pneumonia

• Usually affecting the upper lobe and more right sided

• Lung volume is normal or increased with bulging fissure due to excessive exudation

• Cavitation is common, mimics TB

Klebsiella Pneumonia

Legionnaire’s disease• Legionella pneumophila• Patient at risk are debilitated and

smokers. Diarrhea is associated.• Source of infection include water

cooler, air conditioner and showers. Mortality 20%.

• Radiography: solitary or multifocal, mass like, homogeneous opacities, simulating Strep Pneumoniae,

may involve the whole lung and spread to the other lung with small pleural effusion

• Rapid progression may occur lead to shock, renal and respiratory failure

Nocardiosis • Nocardia asteroides• affected patients are immunocompromised, including patients

with AIDS

• Radiography: begins with a focus of pulmonary infection and may disseminate to other organs, notably the brain.

Pulmonary consolidation, either unifocal or multifocal, is the usual

feature

Cavitation, pleural effusion and lymph node enlargement are frequent

Nocardiosis

Gram –ve pneumonia• Most commonly Escherichia coli, Pseudomonas aeruginosa,

Haemophilus influenzae

• Most common cause of nosocomial infection

• They occur with chronic bronchitis, cystic fibrosis and debilitated

• Radiography: patchy consolidation often basal and may be bilateral, random large nodules, tree-in-bud opacities,

ground glass opacity, necrosis, pleural effusion Healing may leave pneumatoceles.

Gram –ve pneumonia

ATYPICAL PNEUMONIAS• Acute inflammatory changes centered within the alveolar wall and

interstitium• So called interstitial pneumonia

• Lack of alveolar exudation

• Minor clinical symptoms ---- major radiological features

Organisms:• Mycoplasma pneumoniae• Viral e.g. influenza virus, respiratory syncytial virus, adenovirus

Mycoplasma• Lack rigid cell wall though not

affected by Abs acting on cell wall synthesis

• Most common non bacterial cause of community acquired pneumonia

• Earliest radiological appearance is fine reticulonodular infiltration followed by segmental or lobar consolidation, usually unilateral

• Complications include meningoencephalitis

VIRAL PNEUMONIA• Common in infants and children • Adults affected if immunocompromised• Pneumonia starts in distal bronchi and bronchioles as an interstitial

process followed by inflammation of alveoli and terminal bronchioles hemorrhagic exudates

• Radiography: peribronchial shadowing, reticulonodular shadowing and patchy or extensive consolidation. Lung is usually overinflated

• Organisms: Influenza virus A and B: scattered homogeneous opacities that

rapidly become bilateral, extensive, confluent

• Measles: disease of childhood, radiography shows widespread reticular shadows and diffuse ill defined nodules,

mediastinal and hilar adenopathy

• Varicella: more frequently in adults than in children through reactivation, predisposing factors include lymphoma, pregnancy, or steroid therapy. Pulmonary involvement follows the skin rash by 1–6 days.

Widespread 5–10 mm in diameter poorly marginated nodules or acinar opacities, which may become confluent.

In resolution, numerous small irregular calcified nodules.

• CMV: occurs in bone marrow and solid organ transplantation, Focal and diffuse hazy opacification and multiple small (less than 5 mm)

nodules, CT reveals small centrilobar nodules and ground-glass or homogeneous

consolidation generally in a symmetric and bilateral distribution.

VIRAL PNEUMONIA

Tuberculosis• Mycobacterium tuberculosis• People at risk are children, immunocompromised and immigrants

• Predisposing factors: HIV infection, DM, alcoholism, silicosis, malignancy, immunocompromised from a variety of causes, living in closed institutions

• C/P: night fever, night sweat, loss of weight, loss of appetite

• Course of disease Primary T.B Post primary (Secondary) T.B

Primary T.B• Most cases are subclinical• Infection occurs at lower lobe (high perfusion), subpleural as focus

of consolidation (Ghon’s focus) which spread to lymphatic regional lymphadenopathy, subpleural location lead to small pleural effusion

Fate:• Good immunity resolution leaving calcific focus• Bad immunity further consolidation and cavitation similar to

post primary T.B, rupture of cavity into pleural space give rise to pneumothorax, pleural effusion or empyema, erosion of bronchus leads to scattered bronchopneumonia, erosion of pulmonary vessel leads to miliary T.B

• Enlarged LNs may cause distal collapse or hyperinflation

Primary T.B

Post primary TB• Either reactivation or reinfection• Mainly involve the subapical parts of upper lobe and apical

segments of lower lobes• Starts as focus of inflammation patchy, nodular and bilateral

consolidation enlarge, coalesce and caseate cavity surrounded by satellite small cavities, may be bilateral.

The cavity is traversed by artery and bronchus Erosion of the artery leads to miliary T.B Erosion of the bronchus leads to T.B bronchopneumonia• No LNs unless the patient has HIV• Healing by fibrosis and volume loss. Fibrosis obliterate the cavity

and calcification may occur. The trachea is pulled towards the affected side Hilum are pulled upwards

Post primary TB• Chronic cavity may be colonized by aspergillus forming mycetoma

• TB bronchopneumonia appears as nodular or patchy areas of consolidation

• Miliary T.B appears as 1-2 mm nodules scattered throughout both lungs, they may enlarge and coalesce

• Pleural effusion may occur with post primary TB and may progress to empyema. Healing leads to pleural thickening and calcification

• Bilateral apical pleural thickening indicates healed TB

Post primary T.B

Non tuberculous mycobaterial infection• 1-3 % of mycobacterial infection• Caused by M. avium–intracellulare complex (MAC) or MAI• Predisposing factors: debilitating disease, immunocompromised,

chronic airflow obstruction, previous pulmonary tuberculosis, silicosis and following lung transplantation

• Clinically resembles post primary TB but not radiologically • Radiography: appears as multiple nodules, showing no specific

lobar predilection and bronchiectasis particularly in the lingula and right middle lobe

• CT has identified a similar pattern with easier detection of bronchiectasis. HRCT demonstrates small centrilobular nodules, small airway or bronchiolar ectasia and tree-in-bud opacities

Non tuberculous mycobaterial infection

Fungal infection

Histoplasmosis• Histoplasma capsulatum• Inhalation of soil or dust contaminated with bat or bird excreta

Endemic in south america• Infection may be subclinical• Radiography: multiple poorly defined nodules approximately 5–10

mm in diameter. Hilar and mediastinal lymph nodes are frequently enlarged.

Chronic pulmonary histoplasmosis radiologically resembles post-primary tuberculosis, with upper lobe contraction, calcification and cavitation.

Occasionally a solitary, well defined nodule may form, calcify and is then termed a histoplasmoma with target appearance.

Fibrosing mediastinitis may develop and can lead to constriction of the airways, superior vena cava, pulmonary arteries and pulmonary veins. CT is helpful in demonstrating complications

Histoplasmosis

Aspergillosis• Aspergillus fumigatus Four clinical forms• Aspergilloma (mycetoma): colonization on preexisting cavity (TB

or sarcoid). Mobile mass within cavity and air crescent sign. DD: blood clot, hydatid, cavitary neoplasm• Semi-invasive: mild immunocompromised and preexisting lung

disease. Radiography: heterogeneous opacities are followed by an

enlarging, thick-walled cavity which develops over a period of weeks

• Invasive: immunocompromised. Appear as one or more rounded poorly marginated fluffy areas of homogeneous opacification with or without air bronchogram. They may cavitate with the formation of an air crescent.

CT may reveal ground-glass haloes around the nodules from invasion of blood vessels (hemorrhagic nodules)

• Allergic bronchopulmonary ABPA: hypersensitivity reaction which occurs in the major airways.

The most common cause of pulmonary eosinophilia in UK Radiography: non-segmental areas of opacity most common in the

upper lobes,

branching thick tubular opacities due to bronchi distended with mucus and fungus give rise to “finger in glove” appearance, and occasionally pulmonary cavitation.

Bronchial wall thickening with “tramlines” and “ring” formation indicates bronchiectasis.

The lungs are often overinflated, while late in the disease there may be volume loss due to fibrosis.

Mycetoma

Invasive aspergillosis

Pulmonary complications in HIV• Opportunistic infection occurs when CD4 cell below 200• Normally CD4 T-helper cells 800-1200 /microliter

• < 400 kaposi sarcoma, TB• < 200 candidiasis, histoplasmosis, PCP• <50 AIDs related lymphoma

• People at risk are IV drug abusers, homosexual, blood transfusion

Pulmonary complications in HIV• Pneumocystis carinii pneumonia (PCP): bilateral ground-glass

infiltrates without effusion/adenopathy or bilateral perihilar interstitial infiltrates, frequently associated with pneumatoceles, apical predominance (in patients on prophylactic aerosolized pentamidine)

• Cryptococcosis (cryptococcus neoformans): segmental infiltrate with pulmonary nodules, pleural effusion and LNs , Brain/meningeal affection

• Histoplasmosis: diffuse nodular/miliary pattern• Nocardiosis: cavitating pneumonia• CMV: bilateral focal nodules, infiltrates

Pulmonary complications in HIV• Toxoplasmosis (toxoplasma gondii): coarse interstitial and nodular

pattern. Indistinguishable from PCP

• Kaposi sarcoma: numerous fluffy ill-defined nodules/asymmetric clusters in a vague perihilar distribution, interlobular septal thickening and pleural effusion and lymph nodes

• AIDS-related lymphoma: NHL, primary extra nodal, pleural effusion, solitary/multiple well-defined pulmonary nodules, diffuse bilateral reticulonodular heterogeneous opacities, hilar/mediastinal adenopathy

• AIDS related complex ARC: generalized lymphadenopathy

Miliary

Airspace Diseases I

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