Review article
The role of lung ultrasound in the diagnosis and follow-up of community-acquired pneumonia

https://doi.org/10.1016/j.ejim.2012.01.003Get rights and content

Abstract

CAP may be diagnosed and followed up by lung sonography (LUS), a technique that shows excellent sensitivity and specificity that is at least comparable with that of chest X-ray in two planes. LUS may be performed with any abdomen-sonography device. Therefore, LUS is a readily available diagnostic tool that does not involve radiation exposure and has wide applications especially in situations where X-ray is not available and/or not applicable. An X-ray or CT of the chest should be performed in cases of negative lung sonography and if other differential diagnoses or complications are suspected.

Introduction

Lower respiratory tract infections are a major healthcare and economic problem with a considerable impact on morbidity and mortality. Among such infections, community-acquired pneumonia (CAP) is the seventh leading cause of death overall and the most common cause of death from infectious diseases in the United States [1]. The annual incidence rate of CAP is 6/1000 in the 18–39 age groups and 34/1000 in people aged 75 years and over. Between 20 and 40% of CAP patients require hospitalization, and, of these, 5–10% are admitted to an intensive care unit (ICU). Due to the burden of CAP on morbidity and mortality, healthcare providers must adopt practices focused on improving outcomes. One of the most important challenges in the management of pneumonia is correct and early diagnosis.

Section snippets

What are current problems in diagnosing pneumonia?

Based on the latest European Respiratory Society guidelines, CAP is defined as an acute illness with signs or symptoms compatible with a respiratory tract infection supported by X-ray findings of new lung infiltrates [2]. There is a strong consensus among international societies that a chest X-ray should be performed in all patients who are admitted to hospital with suspected pneumonia [2], [3], [4].

Although chest X-ray is widely recognized as a crucial step in the diagnosis of pneumonia, this

How is lung ultrasound performed in patients with suspected pneumonia?

LUS is becoming a widely used imaging technique in several settings. It can be performed with any abdomen-sonography device. Selection of the most suitable probe is critical: vascular probes have the highest resolution in superficial layers, but make artifact identification harder. Convex or microconvex probes (3.5–5 MHz) are the best suited to diagnosing pneumonia by lung ultrasonography. Fine regulation of the sonographer's parameters is not strictly required. Of these parameters, focus can be

Is lung ultrasound helpful in the diagnosis and follow-up of pneumonia?

In most cases, pneumonia affects the peripheral lung tissue. Due to the inflammatory defence reaction of the host against pathogenic microorganisms the peripheral airways and alveoli are flooded by a neutrophil-rich exudate. As a consequence, air is evacuated from the affected tissue, allowing sonographic evaluation if the lesion extends up to the pleura.

Is lung ultrasound better than CXR and/or CT?

In a large multicentre trial [17] baseline results (including unequivocal results) showed that pneumonia was correctly diagnosed by LUS in 211 of 229 cases (92.1%) and by X-ray in 199 of 229 cases (86.9%) (Table 3).

On the other hand, CAP was correctly ruled out by LUS in 127 of 133 patients (95.5%) and by X-ray in 122 of 133 patients (91.7%). X-ray detected 14 cases of CAP that were missed by LUS, whereas 26 cases of LUS-detected CAP were missed by X-ray (Table 3).

In the same study, LUS and

Use in children/pediatric population

CAP is a common disease in the pediatric population with 40 cases annually per 1.000 children under 5 years in Europe and North America. Pneumonia in children may present with fever, cough and tachypnea and hospitalization is often required. Up to 50% of hospitalized pneumonia cases are complicated by parapneumonic effusion, pulmonary necrosis and empyema.

X-ray is currently recommended as the first imaging step for diagnosing pneumonia in children. However, several studies have been performed

What are the future implications of lung ultrasound in pneumonia?

To date no comparisons of the sonomorphology of CAP, hospital acquired pneumonia and ventilator-associated pneumonia have been made, although their sonomorphology may differ. Co-morbidity such as heart failure or pulmonary edema and antibiotic therapy may also influence sonographic features. During the course of pneumonia, the air bronchogram became less pronounced in 79 of 314 patients (23%) [16]. Therefore, in cases of pneumonic lesions under antibiotic therapy, lung cancer, which do not

Learning points

  • CAP may be diagnosed and followed up by lung sonography.

  • Lung sonography shows an excellent sensitivity and specificity that is at least comparable with that of chest X-ray in two planes.

  • Lung sonography may be performed with any abdomen-sonography device.

  • Lung sonography is a readily available diagnostic tool that does not involve radiation exposure and has wide applications especially in situations where X-ray is not available and/or not applicable.

  • An X-ray or CT of the chest should be performed

Conflict of interest statement

All authors assert that there are no conflicts of interest, financial or otherwise, pertaining to this study.

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