Ch.7 - Recognizing Pneumonia Flashcards
Segmental pneumonia:
Prototype: staph pneumonia.
Tends to be multifocal, does not have air bronchograms, and can be associated with volume loss because the bronchi are also filled with inflammatory exudate.
Interstitial pneumonia:
Prototype: Viral pneumonia, or PCP.
Tends to involve the airway walls and alveolar septa and may produce, especially early in the course, a fine, reticular pattern in the lungs.
Later in the course, it produces airspace disease.
Round pneumonia:
Prototype (hemophilus):
Usually occurs in children in the lower lobes posteriorly and can resemble a mass, the clue being that masses in children are uncommon.
Cavitary pneumonia:
Prototype: TB.
Has lucent cavities produced by lung necrosis as its hallmark.
Post-primary TB usually involves the upper lobes.
It can spread via a TRANSBRONCHIAL route that can infect the opposite lower lobe or another lobe in the same lung.
Aspiration:
- Can be bland and clear quickly.
- Can be infected and take months to clear.
- May form a chemical pneumonitis which can take weeks to clear.
Pneumonia can be localized by:
Using the silhouette sign + the spine sign as aids.
Pneumonias frequently resolve by:
Breaking up so that they contain patchy areas of newly aerated lung within the confines of the previous pneumonia –> VACUOLIZATION.
When pneumonias may contain air bronchograms?
If the BRONCHI THEMSELVES are NOT filled with inflammatory exudate or fluid.
Air bronchograms are much more likely to be visible when?
The pneumonia involves the CENTRAL portion of the lung near the hilum.
Near the periphery, the bronchi are too SMALL to be visible.
Is an air bronchogram specific for pneumonia?
NO - Anything of fluid or soft tissue density that replaces the normal gas in the airspaces may also produce this sign.
Except for the presence of air bronchograms, airspace pneumonia is usually …?
Homogenous in density.
In some types of pneumonia (ie bronchopneumonia), the BRONCHI, as well as the airspaces, contain inflammatory exudate. This can lead to what?
ATELECTASIS associated with the pneumonia.
To sum up, 6 key sings of pneumonia:
- More OPAQUE than surrounding normal lung.
- Airspace disease –> Margins may be fluffy + indistinct except whee they abut a pleural surface like the interlobar fissures where the margins will be sharp.
- Interstitial pneumonias –> Prominence of interstitial tissues of the lung in the affected area. Disease may spread to ALVEOLI and resemble airspace disease.
- Pneumonias tends to be homogenous in density.
- Lobar pneumonias may contain air bronchograms.
- Segmental pneumonias may be associated with ATELECTASIS in the affected portion of the lung.
5 patterns of appearance of pneumonias:
- Lobar.
- Segmental.
- Interstitial.
- Round.
- Cavitary.
Lobar pneumonias almost always produce … and almost always contain … .
A silhouette sign.
Air bronchograms.
The prototypical bronchopneumonia is caused by?
S.aureus. Many Gram(-) bacteria, such as P.aeruginosa, can produce the same picture.
Patterns that might suggest a causative organism - TB?
Upper lobe cavitary pneumonia with spread to the OPPOSITE LOWER LOBE.
Patterns that might suggest a causative organism - K.pneumoniae?
Upper lobe lobar pneumonia with BULGING INTERLOBAR fissure.
Patterns that might suggest a causative organism - P.aeruginosa or anaerobes?
LOWER lobe CAVITARY pneumonia.
Patterns that might suggest a causative organism - P.jiroveci?
Perihilar interstitial disease OR perihilar airspace disease.
Patterns that might suggest a causative organism - Coccidioides, TB?
Thin-walled upper lobe cavity.
Patterns that might suggest a causative organism - Strep, staph, TB?
Airspace disease with effusion.
Patterns that might suggest a causative organism - Histoplasma, coccidioides, TB?
Diffuse nodules.
Patterns that might suggest a causative organism - Aspergillus (ABPA)?
Soft-tissue, fingerlike shadows in upper lobes.
Patterns that might suggest a causative organism - Cryptococcus?
Solitary pulmonary nodule.
Patterns that might suggest a causative organism - Aspergillus?
Spherical soft-tissue mass in a thin-walled upper lobe cavity.
Features of ROUND pneumonia?
Sphrerically shaped pneumonia usually seen in the LOWER LOBES of CHILDREN that may resemble a mass.
Why air bronchograms are usually NOT present in segmental bronchopneumonias?
Unlike lobar pneumonias, segmentral bronchopneumonias produce exudate that FILLS the bronchi.
3 prototypes for interstitial pneumonia:
- Viral pneumonia.
- M.pneumoniae.
- Pneumocystis pneumonias in AIDS.
PCP classically presents as?
A perihilar, reticular interstitial pneumonia OR as airspace disease that may mimic the central distribution pattern of PULMONARY EDEMA.
PCP - Other imaging features:
- Unilateral airspace disease or widespread, patchy airspace disease, are LESS COMMON.
- Usually NO PLEURAL EFFUSIONS + NO HILAR ADENOPATHY.
Usual location of the round pneumonias?
Almost always POSTERIOR in the lungs, usually in the LOWER LOBES.
Round pneumonias - Causative agents:
- H.flu.
- Strep.
- S.pneumoniae.
… may be the ONLY MANIFESTATION of primary TB in children.
UNILATERAL HILAR ADENOPATHY.
Cavity in reactivation TB:
Thin-walled + smooth inner margin + no air-fluid level.
Reactivation TB almost always affects?
The apical or posterior segments of the UPPER lobes or the SUPERIOR segments of the LOWER lobes.
–> BILATERAL UPPER LOBE DISEASE is very common.
What important clue should make us think of TB infection?
TRANSBRONCHIAL SPREAD –> From one upper lobe to the opposite lower lobe or to another lobe in the lung.
Healing of reactivation TB occurs with?
Fibrosis + retraction.
Miliary TB - Small nodules?
When first visible, the small nodules measure only about 1mm in size.
They can grow 2-3mm if untreated.
When miliary TB is treated …?
Clearing is usually rapid. Seldom if ever heals with residual calcification.
Other infectious agents that produce cavitary disease?
- Staph pneumonia –> Thin-walled pneumatoceles.
- S.pneumoniae.
- K.pneumoniae.
- Coccidiomycosis.
3 patterns of acute aspiration:
- Bland gastric acid or water.
- Infected aspirate (aspiration pneumonia).
- Unneutralized stomach acid (chemical pneumonitis).
Aspiration with bland gastric acid or water - Characteristics?
Rapidly appearing and rapidly clearing AIRSPACE disease in dependent lobe (s).
NOT A PNEUMONIA.
Aspiration with infected aspirate - Characteristics:
- Usually LOWER lobes.
- Frequently cavitates.
- May take MONTHS to clear.
Aspiration with unneutralized stomach acid (chemical pneumonitis) - Characteristics:
Almost immediate appearance of dependent airspace disease that frequently becomes secondarily infected.
Aspiration of bland (neutralized) gastric juices or water - How long to clear?
Classically remains for 1 day or 2 before clearing through RESORPTION.
Mendelson syndrome?
Aspiration of unneutralized stomach acid.
Is it possible to localize the pneumonia using ONLY the FRONTAL RADIOGRAPH?
Frequently, yes - By analyzing which structure’s edges are obscured by the disease (i.e. the silhouette sign).
Ascending aorta no longer visible - Disease location?
Right upper lobe.
Right heart border no longer visible - Disease location?
Right middle lobe.
Right hemidiaphragm no longer visible - Disease location?
Right lower lobe.
Descending aorta no longer visible - Disease location?
Left upper or lower lobe.
Left heart border no longer visible - Disease location?
Lingula of left upper lobe.
Left hemidiaphragm no longer visible - Disease location?
Left lower lobe.
The spine sign usually indicates?
LOWER LOBE PNEUMONIA.
Lobar pneumonia:
Prototype: pneumococcal pneumonia.
Tends to be homogenous, occupies most or all of a lobe, has air bronchograms centrally and produces the silhouette sign.
