Lobar pneumonia is a form of

pneumonia Pneumonia is an Inflammation, inflammatory condition of the lung primarily affecting the small air sacs known as Pulmonary alveolus, alveoli. Symptoms typically include some combination of Cough#Classification, productive or dry cough, ches ...

characterized by inflammatory exudate within the intra-alveolar space resulting in consolidation that affects a large and continuous area of the lobe of a lung. It is one of three anatomic classifications of pneumonia (the other being

bronchopneumonia Bronchopneumonia is a subtype of pneumonia. It is the acute inflammation of the Bronchus, bronchi, accompanied by inflamed patches in the nearby lobules of the lungs. citing: Webster's New World College Dictionary, Fifth Edition, Copyright 2014 ...

and

atypical pneumonia Atypical pneumonia, also known as walking pneumonia, is any type of pneumonia not caused by one of the pathogens most commonly associated with the disease. Its clinical presentation contrasts to that of "typical" pneumonia. A variety of microorga ...

). In children round pneumonia develops instead because the

pores of Kohn The pores of Kohn (also known as interalveolar connections or alveolar pores) are discrete holes in alveolar wall, walls of adjacent Pulmonary alveolus, alveoli. Cuboidal type II alveolar cells, which produce Pulmonary surfactant, surfactant, usuall ...

which allow the lobar spread of infection are underdeveloped.

Pathophysiology

The invading organism starts multiplying, thereby releasing toxins that cause inflammation and edema of the lung parenchyma. This leads to the accumulation of cellular debris within the lungs. This leads to consolidation or solidification, terms used for macroscopic or radiologic appearance of the lungs affected by pneumonia. Bacterial pneumonia is mainly classified into lobar and diffuse depending on the degree of lung irritation or damage.

Stages

Lobar pneumonia usually has an acute progression. Classically, the disease has four stages: * Congestion in the first 24 hours: This stage is characterized histologically by vascular engorgement, intra-alveolar fluid, and small numbers of neutrophils, often numerous

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

. Grossly, the

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

is heavy and hyperemic. * Red hepatization or consolidation: Vascular congestion persists, with extravasation of red blood cells into alveolar spaces, along with increased numbers of

neutrophil Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in differe ...

s and

fibrin Fibrin (also called Factor Ia) is a fibrous protein, fibrous, non-globular protein involved in the Coagulation, clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerization, polymerize. ...

. The filling of air spaces by the exudate leads to a gross appearance of solidification, or consolidation, of the alveolar

parenchyma upright=1.6, Lung parenchyma showing damage due to large subpleural bullae. Parenchyma () is the bulk of functional substance in an animal organ such as the brain or lungs, or a structure such as a tumour. In zoology, it is the tissue that ...

. This appearance has been likened to that of the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

, hence the term "hepatization". * Grey hepatization: Red blood cells disintegrate, with the persistence of neutrophils and fibrin. The alveoli still appear consolidated, but grossly the color is paler and the cut surface is drier. This is when death typically occurs in severe cases. * Resolution (complete recovery): The exudate is digested by enzymatic activity, and cleared by

macrophage Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...

s or by cough mechanism. Enzymes produced by neutrophils will liquefy exudates, and this will either be coughed up in sputum or drained via lymph.

In children

The openings between the alveoli known as the

, and the collateral airways of the

canals of Lambert Collateral ventilation is a back-up system of alveolar ventilation that can bypass the normal route of airflow when airways are restricted or obstructed. The pathways involved include those between adjacent alveoli (pores of Kohn), between bronchio ...

, are undeveloped in children. The spread of infection that would otherwise occur is prevented and can result in round pneumonia, most commonly caused by '' S. pneumoniae''. This clinically presents with an initial mild respiratory infection, followed by

fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...

. On

imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to create, preserve, or duplicate images. ...

it presents as an opaque pulmonary consolidation which is unusually round and can resemble a lung mass. However, it quickly resolves with antibiotics.

Diagnosis

The most common organisms which cause lobar pneumonia are ''

Streptococcus pneumoniae ''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, hemolysis (microbiology), alpha-hemolytic member of the genus ''Streptococcus''. ''S. pneumoniae'' cells are usually found in pairs (diplococci) and do not f ...

'', also called pneumococcus, ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, Motility, non-motile, Coccobacillus, coccobacillary, facultative anaerobic organism, facultatively anaerobic, Capnophile, capnophili ...

'' and ''

Moraxella catarrhalis ''Moraxella catarrhalis'' is a fastidious, nonmotile, Gram-negative, aerobic, oxidase-positive diplococcus that can cause infections of the respiratory system, middle ear, eye, central nervous system, and joints of humans. It causes the in ...

''. ''

Mycobacterium tuberculosis ''Mycobacterium tuberculosis'' (M. tb), also known as Koch's bacillus, is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. First discovered in 1882 by Robert Koch, ''M. tuberculosis'' ha ...

'', the tubercle bacillus, may also cause lobar pneumonia if pulmonary

tuberculosis Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

is not treated promptly. Other organisms that cause lobar pneumonia are

Legionella pneumophila ''Legionella pneumophila'', the primary causative agent for Legionnaires' disease, Legionnaire's disease, is an Aerobic organism, aerobic, pleomorphic, Flagellum, flagellated, non-spore-forming, Gram-negative bacteria, Gram-negative bacterium. ' ...

and

Klebsiella pneumoniae ''Klebsiella pneumoniae'' is a Gram-negative, non-motile, encapsulated, lactose- fermenting, facultative anaerobic, rod-shaped bacterium. It appears as a mucoid lactose fermenter on MacConkey agar. Although found in the normal flora of the mo ...

. Like other types of pneumonia, lobar pneumonia can present as community-acquired, in immune-suppressed patients, or as a nosocomial infection. However, most causative organisms are of the community-acquired type. Pathological specimens to be obtained for investigations include: # Sputum for culture, AAFBS, and gram stain # Blood for full hemogram/complete blood count, ESR, and other acute phase reactants # Procalcitonin test, more specific On a posteroanterior and lateral

chest radiograph A chest radiograph, chest X-ray (CXR), or chest film is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are the most common film taken in medicine. L ...

, an entire lobe will be radiopaque, which is indicative of lobar pneumonia. File:X-ray of lobar pneumonia.jpg,

Chest radiograph A chest radiograph, chest X-ray (CXR), or chest film is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are the most common film taken in medicine. L ...

of a lobar pneumonia, affecting the right middle lobe. File:CT of lobar pneumonia.jpg,

CT scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

of the same case. Identifying the infectious organism (or other cause) is an important part of modern treatment of pneumonia. The anatomical patterns of distribution can be associated with certain organisms, and can help in selection of an antibiotic while waiting for the pathogen to be cultured.

References

External links

* {{Respiratory pathology Pneumonia