Pneumonia - Diagnosis

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Lung Biopsy. In very severe cases of pneumonia or when the diagnosis is unclear, particularly in patients with a damaged immune system, a lung biopsy may be required. A lung biopsy involves taking some tissue from the lungs and examining it under a microscope.

Lung Tap. This procedure typically uses a needle inserted between the ribs to draw fluid out of the lung for analysis. It is known by a number of names, including:

• Lung aspiration
• Lung puncture
• Thoracic puncture
• Transthoracic needle aspiration
• Percutaneous needle aspiration
• Needle aspiration

It is a very old procedure that is not done often anymore, because it is invasive and poses a slight risk for collapsed lung. Some experts argue, however, that a lung tap is more accurate than other methods for identifying bacteria, and the risk it poses is slight. Given the increase in resistant bacteria, they believe its use should be reconsidered in young people.

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An infectious disease specialist may need to be consulted in severe or difficult cases.

Ruling Out Other Disorders that Cause Coughing or Affect the Lung

Common Causes of Persistent Coughing. Persistent coughing is nearly always temporary and harmless when other symptoms, such as fever, are not present. The four most common causes of persistent coughing are:

• Asthma
• Chronic bronchitis
• Gastroesophageal reflux disease (GERD)
• Postnasal drip

Other common causes of chronic cough include heavy smoking or the use of heart drugs known as ACE inhibitors.

Acute Bronchitis. Acute bronchitis is an infection in the passages that carry air from the throat to the lung. The infection causes a cough that produces phlegm. Acute bronchitis is almost always caused by a virus and usually clears up on its own within a few days. In some cases, acute bronchitis caused by a cold can last for several weeks.

Chronic Bronchitis. Chronic bronchitis causes shortness of breath and is often accompanied by infection, mucus production, and coughing, but it is a long-term and irreversible condition. The same bacteria and viruses that cause pneumonia can cause an infection in patients with chronic bronchitis. However, infections involve only the airways leading to the lungs, and not the lung tissue itself. The two disorders may share the same symptoms, such as:

• Coughing
• Fatigue
• Fever
• Sputum production

There are significant differences between chronic bronchitis and pneumonia:

• Patients with bronchitis are less likely to have wheezing, shortness of breath, chills, very high fevers, and other signs of severe illness.
• Those with pneumonia often cough up heavy sputum, which may contain blood.
• X-rays of patients with pneumonia show inflammation and other changes in the lung tissue that are not seen in patients with chronic bronchitis.

Asthma. In asthma, the cough is accompanied by wheezing and occurs mostly at night or during activity. Fever is rarely present (unless the patient also has an infection). Asthma symptoms from occupational causes can lead to persistent coughing, which is usually worse during the work week. Tests -- the methacholine inhalation challenge and pulmonary function studies -- may be effective in diagnosing asthma.

Other Disorders that Affect the Lung. Many conditions mimic pneumonia, particularly in hospitalized patients. They include:

• Acute respiratory distress syndrome (ARDS)
• Atelectasis, a collapse of lung tissue
• Bronchiectasis, an irreversible widening of the airways that is usually associated with birth defects, chronic sinus or bronchial infection, or blockage
• Heart failure (if it affects the left side of the heart, fluid build-up can occur in the lungs and cause persistent cough, shortness of breath, and wheezing)
• Interstitial pulmonary fibrosis, a non-infectious inflammation of the lung that causes damage and scarring
• Lung cancer
• Severe allergic reactions, such as reactions to drugs
• Tuberculosis

Ruling Out Causes in Children. Important causes of coughing in children at different ages include:

• Asthma
• Sinusitis in children 18 months - 6 years

Review Date: 04/13/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).