 Introduction/Background Pneumonia is one of the most common acute infections and the single greatest infectious cause of death in children worldwide, accounting for 16% of all deaths in children under 5 years of age [1,2]. Properly recognizing, diagnosing, and treating pneumonia and its complications are of vital importance. Pneumonia can be defined clinically as the presence of fever and/or acute respiratory symptoms [3-5]. However, the clinical symptoms often lack sensitivity and specificity for the diagnosis of pneumonia [5]. Imaging plays a limited role in uncomplicated pneumonia and is primarily reserved for diagnosis of pneumonia in more severe presentations, including significant respiratory distress, hypoxemia, failed antibiotic therapy, or for suspected complications [3,6]. Resolution of radiographic findings may lag behind the clinical presentation [3,7], and imaging is not specific for the causative organism [6]. Community-acquired pneumonia in children is defined as the presence of signs and symptoms of pneumonia in a previously healthy child caused by an infection acquired outside of the hospital [3]. Hospital-acquired pneumonia is most commonly defined as pneumonia that develops after 48 hours of hospitalization that was not present at the time of admission [10]. Hospital-acquired pneumonia is the second most common nosocomial infection after bloodstream infections, and the most common of all infections acquired in intensive care units [10]. Ventilator-associated pneumonia is a subset of hospital-acquired pneumonia that occurs in mechanically ventilated children and can affect up to 12% of ventilated children [11]. A diagnosis of hospital- acquired pneumonia is based upon a new or progressive lung infiltrate along with clinical evidence that the infiltrate is of infectious origin, which includes the new onset of fever, purulent sputum, and leukocytosis [10]. The frequency of complicated pneumonia is rising [6,12].
Pneumonia in the Immunocompetent Child.  Introduction/Background Pneumonia is one of the most common acute infections and the single greatest infectious cause of death in children worldwide, accounting for 16% of all deaths in children under 5 years of age [1,2]. Properly recognizing, diagnosing, and treating pneumonia and its complications are of vital importance. Pneumonia can be defined clinically as the presence of fever and/or acute respiratory symptoms [3-5]. However, the clinical symptoms often lack sensitivity and specificity for the diagnosis of pneumonia [5]. Imaging plays a limited role in uncomplicated pneumonia and is primarily reserved for diagnosis of pneumonia in more severe presentations, including significant respiratory distress, hypoxemia, failed antibiotic therapy, or for suspected complications [3,6]. Resolution of radiographic findings may lag behind the clinical presentation [3,7], and imaging is not specific for the causative organism [6]. Community-acquired pneumonia in children is defined as the presence of signs and symptoms of pneumonia in a previously healthy child caused by an infection acquired outside of the hospital [3]. Hospital-acquired pneumonia is most commonly defined as pneumonia that develops after 48 hours of hospitalization that was not present at the time of admission [10]. Hospital-acquired pneumonia is the second most common nosocomial infection after bloodstream infections, and the most common of all infections acquired in intensive care units [10]. Ventilator-associated pneumonia is a subset of hospital-acquired pneumonia that occurs in mechanically ventilated children and can affect up to 12% of ventilated children [11]. A diagnosis of hospital- acquired pneumonia is based upon a new or progressive lung infiltrate along with clinical evidence that the infiltrate is of infectious origin, which includes the new onset of fever, purulent sputum, and leukocytosis [10]. The frequency of complicated pneumonia is rising [6,12].