Background
Pneumonia is considered a major healthcare and economic problem with a considerable effect on morbidity and mortality worldwide. The incidence of community-acquired pneumonia has remained constant over the last few decades affecting 3–5 people per 1000 person-years, predominantly among the young and elderly. Even if discharged, patients are still at risk of returning to Emergency Departments (EDs) or clinics and being readmitted with more severe disease. Pneumonia is also an important health-care related complication: it is the second most common type of nosocomial infection and has the highest mortality. Due to this high burden, physicians with patients suspected of pneumonia are constantly challenged to determine if the clinical syndrome is pneumonia rather than alternative diagnosis.
The diagnosis of pneumonia is made by a constellation of suggestive clinical features such as tachypnea, fever, and respiratory rales or reduced breath sounds on auscultation; and, the presence of consolidation or opacification in a chest radiograph (CXR) or in computerized tomography (CT) scan of the chest. CXR is the main imaging approach in many settings; however, limitations for its use exist. For example, radiation exposure precludes CXR use in pregnant women. Moreover, it is frequently troublesome to acquire both posteroanterior and laterolateral projections in hospitalized patients, especially among the critically-ill. Finally, CXR can be a time consuming procedure and its interpretation has high inter-observer variability among radiologists. Chest CT scan, considered the gold-standard imaging approach for pneumonia, has its own limitations: it is expensive; impractical, especially in the critically-ill; and, has higher radiation exposure than CXR.
Use of lung ultrasound (LUS) has long been limited to the diagnosis of pleural effusions, thoracentesis and biopsy-guided procedures; however, it has recently been shown to be highly effective in evaluating pulmonary conditions such as pneumonia and pneumothorax. The use of LUS has gained popularity in intensive care units (ICUs) and EDs in the last decade, and has become increasingly recognized as a potentially useful diagnostic approach for community-acquired pneumonia. We sought to summarize the existing evidence in published literature and characterize the diagnostic accuracy of LUS for pneumonia in adults.