Is pulmonary infiltrate the same as pneumonia (PNA)?

From the Guidelines

No, pulmonary infiltrate is not the same as pneumonia (PNA), though they are related. Pulmonary infiltrate is a radiological finding that appears as an opacity or density on chest imaging, indicating abnormal substances accumulating in the lungs. While pneumonia commonly causes pulmonary infiltrates, many other conditions can also produce this radiological finding, including pulmonary edema, hemorrhage, cancer, inflammatory disorders like sarcoidosis, and atelectasis. Pneumonia specifically refers to an infection-induced inflammation of the lung tissue, typically caused by bacteria, viruses, or fungi, and is characterized by symptoms such as fever, cough, sputum production, and shortness of breath, along with infiltrates on imaging. The distinction matters clinically because treatment approaches differ significantly depending on the underlying cause of the infiltrate. When pulmonary infiltrates are identified on imaging, further diagnostic evaluation is usually needed to determine whether pneumonia or another condition is responsible before appropriate treatment can be initiated, as emphasized by the guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia 1.

Key Considerations

• The presence of a new or progressive radiographic infiltrate plus at least two of three clinical features (fever greater than 38 C, leukocytosis or leukopenia, and purulent secretions) represents the most accurate combination of criteria for starting empiric antibiotic therapy 1.
• A chest radiograph is required for the routine evaluation of patients who are likely to have pneumonia, to establish the diagnosis and to aid in differentiating CAP from other common causes of cough and fever, such as acute bronchitis 1.
• The diagnosis of pneumonia is based on the presence of select clinical features and is supported by imaging of the lung, usually by chest radiography, with the gold standard for the diagnosis of pneumonia being a chest radiograph 1.
• The clinical strategy emphasizes prompt empiric therapy for all patients suspected of having HAP, with the selection of initial antibiotic therapy based on risk factors for specific pathogens, modified by knowledge of local patterns of antibiotic resistance and organism prevalence 1.

Diagnostic Approach

• When evaluating a patient with suspected pneumonia, it is crucial to consider the clinical context, including the presence of fever, cough, sputum production, and shortness of breath, in addition to the radiographic findings 1.
• Further diagnostic evaluation, such as microbiological studies and imaging, may be necessary to determine the underlying cause of the pulmonary infiltrate and to guide treatment decisions 1.
• The use of clinical criteria, such as the CPIS score, can help in the diagnosis of ventilator-associated pneumonia, but should be interpreted in the context of the patient's overall clinical presentation 1.

Treatment Implications

• The treatment approach for pulmonary infiltrates depends on the underlying cause, with pneumonia requiring antibiotic therapy, while other conditions may require different treatments, such as diuretics for pulmonary edema or anticoagulation for pulmonary embolism 1.
• Delaying appropriate antibiotic therapy for pneumonia can lead to increased mortality, emphasizing the importance of prompt empiric therapy for patients suspected of having HAP 1.

From the Research

Definition and Difference

• Pulmonary infiltrate and pneumonia (PNA) are related but not exactly the same thing. Pulmonary infiltrate refers to the accumulation of cells, fluid, or other substances in the lungs, which can be caused by various factors, including infections, injuries, or diseases 2, 3.
• Pneumonia, on the other hand, is a specific type of infection that inflames the air sacs in the lungs, which can be caused by bacteria, viruses, or fungi 4, 5.

Causes of Pulmonary Infiltrate

• Pulmonary infiltrates can be caused by non-infectious factors such as pulmonary embolic disease, congestive heart failure (CHF), acute respiratory distress syndrome (ARDS), pulmonary hemorrhage, and pulmonary drug reactions 2, 3.
• In patients with acute leukemia, pulmonary infiltrates can be caused by leukemic infiltration of the lungs, pulmonary hemorrhage, and/or edema, diffuse alveolar damage, viral pneumonia, and rarely transfusion-related acute lung injury (TRALI) or the differentiation syndrome 5.

Diagnosis and Differentiation

• The diagnosis of pulmonary infiltrate and pneumonia requires a thorough medical history, physical examination, radiologic pattern of the infiltrates, and timing of their appearance in relation to the start of antileukemic therapy 5.
• Initial symptoms in pulmonary embolism differ from those in pneumonia, with dyspnea and/or pleuritic chest pain being more common in pulmonary embolism, while fever, chills, and/or cough are more common in pneumonia 6.
• C-reactive protein and body temperature are significantly higher, and pulmonary infiltrates are more common in pneumonia compared to pulmonary embolism 6.