Anticough Logo

Pneumonia

This article is about human pneumonia.

Part 1 : Symptoms and Diagnosis
Part 2 : Pathophysiology and Types of Pneumonia
Part 3 : Treatment, Complications, Prognosis & Mortality, Prevention, Epidemiology, History

Part 1

Pneumonia is an illness of the lungs and respiratory system in which the alveoli (microscopic air-filled sacs of the lung responsible for absorbing oxygen from the atmosphere) become inflamed and flooded with fluid. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites. Pneumonia may also occur from chemical or physical injury to the lungs, or indirectly due to another medical illness, such as lung cancer or alcohol abuse.

Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing. Diagnostic tools include x-rays and examination of the sputum. Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics.

Pneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically ill. Vaccines to prevent certain types of pneumonia are available. The prognosis for an individual depends on the type of pneumonia, the appropriate treatment, any complications, and the person's underlying health.

Symptoms

Pneumonia fills the lung's alveoli with fluid, keeping oxygen from reaching the bloodstream. The alveolus on the left is normal, while the alveolus on the right is full of fluid from pneumonia.
Pneumonia fills the lung's alveoli with fluid, keeping oxygen from reaching the bloodstream. The alveolus on the left is normal, while the alveolus on the right is full of fluid from pneumonia.

People with infectious pneumonia often have a cough that produces greenish or yellow sputum and a high fever that may be accompanied by shaking chills. Shortness of breath is also common, as is pleuritic chest pain, a sharp or stabbing pain, either felt or worse during deep breaths or coughs. People with pneumonia may cough up blood, experience headaches, or develop sweaty and clammy skin. Other symptoms may include loss of appetite, fatigue, blueness of the skin, nausea, vomiting, mood swings, and joint pains or muscle aches. Less common forms of pneumonia can cause a variety of other symptoms. For instance, pneumonia caused by Legionella may cause abdominal pain and diarrhea, while pneumonia caused by tuberculosis or Pneumocystis may cause only weight loss and night sweats. In elderly people the manifestations of pneumonia may not be typical. Instead, they may develop new or worsening confusion or may experience unsteadiness leading to falls. Infants with pneumonia may have many of the symptoms above, but in many cases, they are simply sleepy or have decreased appetite.

Diagnosis

To diagnose pneumonia, health care providers rely on a patient's symptoms and findings from physical examination. Information from a chest X-ray, blood tests, and sputum cultures may also be helpful. The chest X-ray is typically used for diagnosis in hospitals and some clinics with X-ray facilities. However, in a community setting (general practice), pneumonia is usually diagnosed based on symptoms and physical examination alone. Diagnosing pneumonia can be difficult in some people, especially those who have other illnesses. Occasionally a chest CT scan or other tests may be needed to distinguish pneumonia from other illnesses.

Physical examination

Individuals with symptoms of pneumonia need medical evaluation. Physical examination by a health care provider may reveal fever or sometimes low body temperature, an increased respiratory rate, low blood pressure, a fast heart rate, or a low oxygen saturation, which is the amount of oxygen in the blood as indicated by either pulse oximetry or blood gas analysis. People who are struggling to breathe, confused, or who have cyanosis (blue-tinged skin) require immediate attention.

Pneumonia as seen on chest x-ray.  A: Normal chest x-ray. B: Abnormal chest x-ray with shadowing from pneumonia in the right lung (left side of image).
Pneumonia as seen on chest x-ray. A: Normal chest x-ray. B: Abnormal chest x-ray with shadowing from pneumonia in the right lung (left side of image).

Listening to the lungs with a stethoscope (auscultation) can reveal several things. A lack of normal breath sounds, the presence of crackling sounds (rales), or increased loudness of whispered speech (whispered pectoriloquy) can identify areas of the lung that are stiff and full of fluid, called "consolidation." The examiner may also feel the way the chest expands (palpation) and tap the chest wall (percussion) to further localize consolidation. The examiner may also palpate for increased vibration of the chest when speaking (tactile fremitus).

Chest X-rays, sputum cultures and other tests

An important test for detecting pneumonia in unclear situations is a chest x-ray. Chest x-rays can reveal areas of opacity (seen as white) which represent consolidation. Pneumonia is not always seen on x-rays, either because the disease is only in its initial stages, or because it involves a part of the lung not easily seen by x-ray. In some cases, chest CT (computed tomography) can reveal pneumonia that is not seen on chest x-ray. X-rays can be misleading, because other problems, like lung scarring and congestive heart failure, can mimic pneumonia on x-ray.  Chest x-rays are also used to evaluate for complications of pneumonia.

If an individual is not getting better with antibiotics, or if the health care provider has concerns about the diagnosis, a culture of the person's sputum may be requested. Sputum cultures generally take at least two to three days, so they are mainly used to confirm that the infection is sensitive to an antibiotic that has already been started. A blood sample may similarly be cultured to look for infection in the blood (blood culture). Any bacteria identified are then tested to see which antibiotics will be most effective.

A complete blood count may show a high white blood cell count, indicating the presence of an infection or inflammation. In some people with immune system problems, the white blood cell count may appear deceptively normal. Blood tests may be used to evaluate kidney function (important when prescribing certain antibiotics) or to look for low blood sodium. Low blood sodium in pneumonia is thought to be due to extra anti-diuretic hormone produced when the lungs are diseased (SIADH). Specific blood serology tests for other bacteria (Mycoplasma, Legionella and Chlamydophila) and a urine test for Legionella antigen are available. Respiratory secretions can also be tested for the presence of viruses such as influenza, respiratory syncytial virus, and adenovirus.

Part 2 >