An Approach to Pneumonias 1. Lobar Pneumonias A lobe, or lobes, are consolidated
Radiological criteria for calling a shadow in CXR as consolidation are: 1.Lobar or Segmental Density The density should either correspond to lobe or segment of Lung. 2.Air Bronchogram presence of air bronchogram would confirm that it is an alveolar process. 3.No Loss of Lung Volume In early stages of consolidation the volume of lung increases. In later stages there can be some amount of loss of lung volume due to secretions obstructing airways. As a general rule there is no significant loss of lung volume in consolidation Consolidation
The silhouette sign : An intra-thoracic radio-opacity, if in anatomic contact with a border of heart or aorta, will obscure that border. An intra-thoracic lesion not anatomically contiguous with a border or a normal structure will not obliterate that border.
In the case of middle lobe disease (collapse), the right heart margin is lost.
Right lower lobe pneumonia will blur the diaphragm on the right side. The right heart margin remains distinct. The view shows air in the bronchi of the consolidated lobe and beginning abcess formation.
• Haziness in the right mid lung field. •Right heart margin slightly hazy with intact silhouette of right diaphragm •Middle lobe density in lateral •No significant loss of lung volume in lateral •Air bronchogram in lateral
• Density in the left upper lung field •Loss of silhouette of left heart margin •Density in the projection of LUL in lateral view •Air bronchogram in PA view •No significant loss of lung volume
• Haziness in the left lower lung field •Blunting of left costophrenic angle •Loss of silhouette of left heart margin •Density in the projection of lingula in lateral view •Air bronchogram in lateral •No significant loss of lung volume
One whole lobe is consolidated with decreased crepitation. The size of the affected lobe is normal. However, the color is dark red. The cut surface may ooze fluid, which may be hemorrhagic or purulent. Airways of the affected lobe may contain pus. This gross photograph of a cut lung shows consolidation and discoloration of most of the lower lobe .
This low power photomicrograph shows many alveolar spaces filled with inflammatory infiltrate. This high power photomicrograph shows the infiltrate to be composed of neutrophils. Note that the alveolar septa are relatively normal. After complete resolution, the underlying lung architecture is preserved.
Lobar Pneumonia : Most common causes for lobar pneumonia are: 1.Pneumococcus 2.Mycoplasma 3.Gram negative organisms 4.Legionella
<ul><li>Bronchopneumonias pneumonia that is localized, often to the bronchioles and surrounding alveoli </li></ul>
• Histopathology •Patchy distribution in and around small airways •Dense acute inflammatory exudate of PMNs, fibrin and blood in bronchi, bronchioles and adjacent alveoli. •FOCAL destruction of alveolar walls (you can see normal parenchyma in other areas adjacent) Bronchopneumonias
Comparison of bronchopneumonia vs. lobar pneumonia bronchopneumonia Lobar pneumonia
Most common causes for bronchopneumonia are: 1.Streptococcus 2.Viral 3.Staph Some selected bronchopneumonias follow...
Bilateral bronchopneumonia (which lobes, eager young minds?)
Bronchopneumonia is a very common form of pneumonia. It presents differently from lobar pneumonia on the chest film. Lobar pneumonia tends to start at the periphery and involve a single lobe of the lung. However, bronchopneumonia starts centrally in the bronchi and may cause peripheral consolidation which is due either to infection or to atelectasis. Thus, a bronchopneumonia tends to be bilateral. There is associated peribronchial thickening and there are patchy areas of consolidation which involve both lungs. This consolidation is asymmetrical. It may involve a segment of the RUL and another in the lingula. The commonest organism to cause bronchopneumonia is staph aureus. Bronchopneumonias are also very common in children.
This case shows a woman with bronchopneumonia. Note that there is bilateral patchy consolidation with obliteration of the apex of the heart and portions of the right and left diaphragm on the PA view. Areas of increased density can be seen in the right upper lobe, right lower lobe and in the left lower lobe. These should represent areas of consolidation.
On the lateral view portions of the left and right hemidiaphragm are incompletely seen and there is increased density in the region of the middle lobe. Additionally, the major fissure is very prominent and consolidation can be seen adjacent to this fissure on the lateral view. This likely represents a consolidation in the right upper lobe. This appearance is typical for a bronchopneumonia. Usually there is discrete peribronchial cuffing in the hilar region as well. We do not see this on these films .
This next patient had a head and neck cancer (notice bilateral apical fibrosis secondary to radiation therapy) and developed a lung abscess in the left lower lobe superior segment secondary to aspiration pneumonia. The first film shows an infiltrate in the left lower lobe extending from the hilum to the retrocardiac and midlung zones. The midlung zone opacity is more prominent and has a more or less rounded, but poorly marginated contour suggesting the possibility of an abscess.
A film taken 8 days later shows a large lucency replacing the opacity in the midlung zone. This occurs when the abscess communicates with an airway. An air fluid level is seen in the cavity. The surrounding infiltrates have improved. This case illustrates a classic location of lung abscess and aspiration pneumonia, the superior segment of either lower lobe. Patients with swallowing difficulty and impaired consciousness are particularly susceptible.
One last bronchopneumonia: this is an aspiration pneumonia such as we commonly see in the ICU following drug O.D.
Okay, we’ve done lobar pneumonias, and bronchopneumonias. Now, how about: 3. Necrotizing Pneumonias
Most common causes for Necrotizing pneumonia are: •Staphylococcal •Anaerobic infection •Gram negative organisms
But this one was caused by pneumococcus ...which lobe?
Acute fire-eater pneumonia in a 21-year-old man who had aspirated petroleum during a performance. Posteroanterior chest radiograph shows ill-defined nodular areas of increased opacity in both lower lobes (arrows).
Caveat Ultissimo Magnum Alertorum! All that is round is not a round pneumonia!
Here is a viral, interstitial pneumonia with some extension into the alveolar spaces (more about this later)
It’s helpful to think histologically when looking at chest films of pneumonia: Here is normal lung
Lobar Pneumonia Remember that bacteria (as a rule of thumb) elicit a neutrophilic inflammatory response. Here you can see the alveolar air spaces are full of PMNs as well of exsanguinated RBCs. It shouldn't surprise you then that hemoptysis (coughing up blood) can be a symptom of pneumonia. Notice that the interstitial space is left relatively normal.
Lobar Pneumonia PMNs only live for 2 or 3 days. So (although you may not be able to make the distinction at this magnification) macrophages have replaced the PMNs. At the same time, the alveolar exudate has become fibrotic. This complication of lobar pneumonia is called "organizing pneumonia."
Interstitial Pneumonia Viral pneumonias manifest themselves in the interstitium rather than the alveolar air spaces. Notice that the interstitial space is greatly expanded with lymphocytes while the alveolar spaces are relatively normal. Does it make sense to you that viral pneumonias are usually less problematic than bacterial pneumonias? A common complication of viral pneumonia, however, is a secondary bacterial superinfection.
And then the chest film gets more confusing, and the patient, sicker:
Really advanced stuff: •With viral pneumonias, chest radiographic findings usually are nonspecific-they cause an interstitial infiltrate, but some features are characteristic of individual viruses. •HSV can produce focal lesions on chest x-ray that begin as small nodules in the periphery. As the disease progresses, the nodules coalesce to form extensive infiltrates. Usually see this in newborns, or in immunocompromised patients.
.•In influenza pneumonia, radiographic findings are similar to those described for other respiratory viral infections. Perihilar and peribronchial infiltrates occur commonly, while progression to diffuse interstitial infiltrates is observed with severe disease. Other findings of influenza pneumonia include hyperexpansion of the lungs, subsegmental atelectasis of multiple lobes, and lobar atelectasis, particularly of the right-upper or right-middle lobe
.•In CMV pneumonia, chest radiographs show interstitial infiltrates predominantly in the lower lobes. Advancement to diffuse interstitial infiltrates is observed in patients with organ transplant.
• In RSV, chest radiographs show bilateral interstitial or patchy infiltrates. Lobar consolidation and pleural effusions are present in 25% and 5% of cases, respectively. Here’s an infant with RSV pneumonia:
• In PIV, chest radiographs may reveal findings ranging from focal infection to diffuse interstitial infiltrates or diffuse mixed alveolar-interstitial infiltrates consistent with acute lung injury
.•In varicella pneumonia, radiographic findings are diffuse, fluffy, reticular or nodular infiltrates that can be rapidly progressive. Pleural effusion and peripheral adenopathy can occur. Radiographic abnormalities are more prominent during the peak of the rash and resolve rapidly with clinical improvement. Long-term respiratory sequelae are infrequent in survivors, although small, diffusely scattered, punctate lung calcifications may persist on chest films An early varicella pneumonia
.•Hantavirus infection may result in normal chest radiograph findings during early disease. This is followed by signs of interstitial edema, Kerley B lines, peribronchial cuffing, and indistinct hila. Progression to the pulmonary edema phase over the subsequent 48 hours is indicated by centrally located dense alveolar infiltrates unlike the more peripheral infiltrates of adult respiratory distress syndrome from other causes. With further progression, pleural effusions also may develop.
Bronchopneumonias pneumonia that is localized, often to the bronchioles and surrounding alveoli Most common causes for bronchopneumonia are: 1.Streptococcus 2.Viral 3.Staph
Bilateral bronchopneumonias- note the patchy consolidation
Segmental Pneumonias involve part of one lobe, i.e. are “sub-lobar” Most common causes for segmental pneumonia are: 1.Post obstructive 2.Aspiration
A patient with aspiration pneumonia If the organism necrotizes tissue, this could develop into a necrotizing segmental pneumonia, aka lung abscess
Necrotizing pneumonias ‘eat’ away at the lung parenchyma because of the causative organism’s propensity for doing so. They may start as lobar, segmental, or bronchopneumonias. ¿Claro?
Most common causes for Necrotizing pneumonia are: •Staphylococcal •Anaerobic infection •Gram negative organisms
These pneumonias, as well as the round pneumonias we just saw, involve the alveolar spaces in a more or less focal manner, as opposed to the diffuse alveolar pneumonias seen with CMV and pneumocystis
...and here is blood SLE-microangiitis leading to Pulmonary hemorrhage
And another patient with diffuse alveolar hemorrhage, in this case a marrow transplant patient with no platelets
Finally, the alveolar spaces may not be infected all, at least not initially, as with most viral (interstitial) pneumonias
Finally, we should talk about Bronchiolitis obliterans organizing pneumonia or: BOOP
Patients with BOOP are usually between the ages of 40-70, and present with a history of dry cough and SOB of two weeks to two months in duration. These symptoms persist despite antibiotic therapy. On auscultation of the lungs late inspiratory crackles are heard. The patient often has an elevated ESR, and PFTs demonstrate a decreased diffusion capacity and a restrictive pattern (diminished FC and TLC with a normal FEV/FV ratio). The etiology of BOOP may be idiopathic or secondary to viral illness (RSV, adenovirus), collagen vascular disease, (RA, SLE), caustic inhalation (sulfur dioxide, chlorine), heart-lung transplant and chronic aspiration..
The diagnosis is made histologically, via open lung biopsy since transbronchial biopsy frequently yields inadequate tissue specimens. Fibrous plugs and granulation tissue are present within terminal bronchioles as well as alveolar ducts and alveoli. In addition, perivascular mononuclear cell infiltrates are also seen. The interstitium is commonly involved, distinguishing BOOP from pulmonary fibrosis. The most common chest x-ray finding is bilateral, patchy subpleural air-space opacities (69%), which can mimic lung masses. Pleural effusions and cavitations are rare. Similar radiographic appearances are typical for eosinophilic pneumonia, PE, septic emboli, bronchoalveolar carcinoma, metastatic disease and sarcoidosis