The term “pneumonia” refers to any disease that causes an inflammation of the lung tissue. Pneumonia is a very common respiratory condition that affects the air sacs within the lungs. Left untreated, it can result in a host of complications. One of these complications is known as consolidation of the lung, which is essentially solidication o hardening of the otherwise elastic lung tissue.
Reasons for Pneumonia
Infections of the respiratory tract are the most common causes of pneumonia. Among the infectious causes of pneumonia, bacterial infections account for the majority of the cases. Viral and fungal pathogens are also capable of causing pneumonia. In addition, pneumonia can also be caused by noninfectious conditions, such as injury to the lung caused by mechanical or chemical trauma.
Left untreated, pneumonia due to non-infectious causes can be as serious as pneumonia due to infectious causes. Young children and elderly patients are commonly affected by pneumonia, especially after contracting respiratory tract infections. People with systemic infections (such as HIV) or chronic debilitating conditions are also at a higher risk of developing pneumonia.
Read more on pneumonia.
Damage to the Lungs
The extent of lung tissue affected in pneumonia varies on a case-to-case basis. Pneumonia may affect either a small part of the lung (a lobe or a segment) or the whole lung tissue. Significant damage usually occurs to the epithelial lining of the alveoli (air sacs) in the lungs. This type of damage to the lung tissue is technically referred to as diffuse alveolar damage (abbreviated as DAD).
Damage to the alveolar lining affects the normal gas exchange processes in the lungs. Left untreated, the condition may eventually result in death. One of the complications of influenza, bronchitis and tracheitis is bronchopneumonia. This condition is characterized by significant inflammation of the lower respiratory tract. However, the majority of the lung tissue remains unaffected.
In some cases of pneumonia, the septum separating the alveoli get affected. Such a condition is referred to as interstitial pneumonia. A variety of causes have been attributed to interstitial pneumonia, including chemicals, infections, immune disorders and impaired healing processes. In some cases, the exact cause of interstitial pneumonia may not be known (idiopathic interstitial pneumonia).
Types of Pneumonia
Based on factors such as causative agent, extent of lung tissue damage and source of the causative agent, pneumonia can be classified into the following types:
- Causative agent: Chemical, noninfectious, and infectious pneumonia.
- Affected area: Interstitial, lobar, and bronchopneumonia.
- Source of cause: Hospital-acquired pneumonia, community-acquired pneumonia, ventilator-acquired pneumonia, healthcare-acquired pneumonia, and nursing home-acquired pneumonia.
- Infectious agent: Viral, fungal, bacterial and atypical pneumonia.
What happens in pneumonia?
Infections (especially bacterial infections) are the most common contributors to the development of pneumonia. The causative pathogens can reach the lung tissue through multiple routes. The most common route of infection is the respiratory tract (through inhalation). However, pathogens can also reach the lung tissue through the bloodstream or from an infection present in adjacent tissues.
The arrival of pathogens in the lung tissue results in damage to the epithelial cells lining the alveoli and the capillaries that lie within the alveolar septa. The increase in vascular permeability caused by microvascular injury results in alveolar edema as the cells, proteins and fluids from the blood seep into the interstitial tissue spaces. The exudates eventually leak into the alveoli.
As the infection spreads to the neighboring alveoli, more and more lung tissue becomes congested with vascular exudates and cellular debris. When a large area of the lung gets congested, the condition is referred to as consolidated lung. Pneumonia results in impaired gaseous exchange within the lungs.
Read more on effusion.
Accumulation of vascular exudates reduces the surface area of the lung that is capable of carrying out gaseous exchange between the blood and the air. This results in a decrease in the concentration of oxygen (technically referred to as hypoxia) and an increase in the concentration of carbon dioxide in the blood (technically referred to as hypercapnia).
Left untreated, pneumonia can affect the entire lung tissue in one or both the lungs. This can be fatal. However, the condition is treatable. In otherwise healthy patients, the consolidated lung exudate can get cleaned out through macrophage consumption, cough, digestion and resorption.
What is Pneumonia Lung Consolidation?
Lung consolidation refers to a condition in which the air spaces within the lungs get filled up with liquid or solid material. This solidification of the lung tissue is also referred to as pulmonary consolidation. Inflammation caused by pneumonia is the most common cause of pulmonary consolidation.
Lung consolidation in pneumonia is characterized by the accumulation of capillary exudates (including cellular debris and blood cells) within the alveoli. The extent of consolidation may vary from small patches affecting only a few lobules to widespread solidification of entire lobes of the lungs.
Even though lung consolidation is commonly associated with pneumonia, other factors such as edema, pus accumulation, and lung collapse (technically referred to as atelectasis) can also cause solidification of the lung tissue. Consolidation of lung may also be caused by accumulation of fluid and solid material within the space the surrounds the lungs. This can severely affect the capacity of the lung for expansion, resulting in insufficient gas exchange.
Symptoms of Lung Consolidation
Lung consolidation is characterized by the following signs and symptoms:
- Difficulty in breathing
- Shortness of breath
- Noisy breathing or breathing accompanied by abnormal breathing sounds.
- Cyanosis or pallor
- Dull note upon chest percussion
- Reduced expansion of chest on one side
- Vocal resonance
- X-rays may show opaque areas in the lung tissue
Causes of Lung Consolidation
The most common cause of lung consolidation is pneumonia. Both infectious and non-infectious pneumonia can result in lung consolidation. In case of infectious pneumonia, lung consolidation is usually seen in the middle or later stages of the disease.
Depending on the type of pathogen responsible for the pneumonia, radiological features of the consolidated lungs may vary. Examples of lung infections that can result in consolidation include ascariasis, actinomycosis, aspergillosis, cryptococcosis, blastomycosis, syphilis, and hydatid cyst.
Aspiration pneumonia is a type of non-infectious pneumonia that is caused when some foreign material enters the lungs and damages the lung parenchyma. Pulmonary edema, collapsed lung (atelectasis), and lung tumors are other causes of consolidated lungs.