eMedicine Specialties > Emergency Medicine > Pediatric

Pediatrics, Pneumonia

Author: Lakshmi V Atkuri, MD, Assistant Professor, Section of Emergency Medicine, University of Texas Health Science Center at Houston
Coauthor(s): Brent R King, MD, Associate Professor of Emergency Medicine and Pediatrics, University of Texas Health Science Center at Houston; Chair, Department of Emergency Medicine, Memorial Hermann Hospital, Lyndon B Johnson General Hospital
Contributor Information and Disclosures

Updated: May 23, 2006

Introduction

Background

Pneumonia (ICD10: P23.9) is one of several infections of the lower respiratory tract that may be observed in children. The other lower respiratory tract diseases, croup (laryngotracheobronchitis), bronchitis, and bronchiolitis (to which pneumonia is closely related), are beyond the scope of this article and are not discussed further. The World Health Organization (WHO) has defined pneumonia solely on the basis of clinical findings obtained by visual inspection and timing of the respiratory rate.

It is important for the physician to understand that the typical causes and presentations of pneumonia in infants and children are variable, depending upon the child's age and underlying medical condition.

Pathophysiology

Pneumonia results from inflammation of the alveolar space and may compromise air exchange. While often complicating other lower respiratory infections such as bronchiolitis or laryngotracheobronchitis, pneumonia may also occur via hematogenous spread or aspiration. Most commonly, this inflammation is the result of invasion by bacteria, viruses, or fungi, but it can occur as a result of chemical injury.

Four stages of lobar pneumonia have been described. In the stage of congestion (first 24 h), the lung is grossly doughy in consistency, and, microscopically, it is characterized by vascular congestion and alveolar edema. Many bacteria and a few neutrophils are present. The stage of red hepatization (2-3 d), so called because of its similarity to the consistency of liver, is characterized by the presence of many erythrocytes, neutrophils, desquamated epithelial cells, and fibrin within the alveoli. In the stage of gray hepatization (2-3 d), the lung is gray-brown to yellow because of fibrinopurulent exudate, disintegration of red cells, and hemosiderin. The final stage of resolution is characterized by resorption and restoration of the pulmonary architecture. Fibrinous inflammation may extend to and across the pleural space, causing a rub heard by auscultation, and it may lead to resolution or to organization and pleural adhesions.

Bronchopneumonia, a patchy consolidation involving one or more lobes, usually involves the dependent lung zones, a pattern attributable to aspiration of oropharyngeal contents. The neutrophilic exudate is centered in bronchi and bronchioles, with centrifugal spread to the adjacent alveoli.

In interstitial pneumonia, patchy or diffuse inflammation involving the interstitium is characterized by infiltration of lymphocytes, macrophages, and plasma cells. The alveoli do not contain a significant exudate, but protein-rich hyaline membranes similar to those found in adult respiratory distress syndrome (ARDS) may line the alveolar spaces. Bacterial superinfection of viral pneumonia can also produce a mixed pattern of interstitial and alveolar airspace inflammation.

Miliary pneumonia is a term applied to multiple, discrete lesions resulting from the spread of the pathogen to the lungs via the bloodstream. The varying degrees of immunocompromise in miliary tuberculosis, histoplasmosis, and coccidioidomycosis may manifest as granulomas with caseous necrosis to foci of necrosis. Miliary herpesvirus, cytomegalovirus, or varicella-zoster virus infection in severely immunocompromised patients results in numerous acute necrotizing hemorrhagic lesions.

Factors that bypass or inactivate local defenses (eg, tracheostomy tubes, immotile cilia syndrome) predispose the child to pneumonia. The result is loss of surfactant activity with local collapse and consolidation.

Pneumonia may be classified by the causative organism, the anatomic location, or the tissue response.

Frequency

United States

A WHO Child Health Epidemiology Reference Group publication cites the incidence of community-acquired pneumonia among children younger than 5 years in developed countries as approximately 0.026 episodes per child year.

In a recent prospective multicentric study of 154 immunocompetent children with acute community-acquired pneumonia, comprehensive investigation combining microbiologic, serologic, biochemical, and experimental molecular tests were performed and a pathogen was identified in 79% of children. Bacteria accounted for 60%, of which 73% were due to Streptococcus pneumoniae, Mycoplasma pneumoniae, and Chlamydia pneumoniae were detected in 14% and 9%, respectively. Viruses were documented in 45% of children. Notably, 23% of the children had concurrent acute viral and bacterial disease.

In the study, preschool-aged children had as many episodes of atypical bacterial lower respiratory infections as older children. Children with typical bacterial or mixed bacterial/viral infections had the greatest inflammation and disease severity. Multivariable analyses revealed that high temperature (38.4°C) within 72 hours after admission and the presence of pleural effusion were significantly associated with bacterial pneumonia.

Thompson et al reported annual influenza-associated hospitalizations in the United States by hospital discharge category, discharge type, and age group (Thompson, 2004). After elderly persons, the second highest rates of influenza-associated hospitalizations were in children younger than 5 years. However, the relative risk for an influenza-associated hospitalization relative to death was 270 in this age group compared to 11 in those in the 50-64 years age range.

International

The WHO Child Health Epidemiology Reference Group (Rudan, 2004) data, based on 28 studies, estimated the median global incidence of clinical pneumonia to be 0.28 episodes per child-year. The 25-75% interquartile range was 0.21-0.71. This equates to an annual incidence of 150.7 million new cases, of which 11-20 million (7-13%) are severe enough to require hospital admission. Ninety five percent of all episodes of clinical pneumonia in young children worldwide occur in developing countries.

Mortality/Morbidity

According to the WHOs Global Burden of Disease 2000 Project, lower respiratory infections were the second leading cause of death in children younger than 5 years (about 2.1 million [19.6%]).

• Most children are treated as outpatients and fully recover. However, in young infants and immunocompromised individuals, the death rate is much higher.
• Certain rare infectious agents are associated with a higher death rate.
• In studies of adults with pneumonia, a higher mortality rate is associated with abnormal vital signs, immunodeficiency, and certain organisms.

Race

Pneumonia affects children of all races; however, certain conditions that may predispose to pneumonia have racial predilections. For example, cystic fibrosis is far more common in white children. Children with sickle cell anemia are at increased risk for pneumonia even when compliant with antibiotic prophylaxis and fully immunized.

Age

Pneumonia in the pediatric population is most common in infants and toddlers and least common in adolescents and young adults.

Clinical

History

In children, the etiologic agent, the age of the patient, and underlying illnesses all affect the historical features of the illness.

• Neonates
  • As hospital stays for newborn infants have become shorter and the popularity of freestanding birthing centers has increased, it is possible for some conditions that have traditionally been diagnosed in the newborn nursery, instead, to present in the ED.
  • The infant may present with tachypnea; signs of respiratory distress, such as grunting, flaring, and retractions; lethargy; poor feeding; or irritability. Fever may not be present in newborns; however, hypothermia and temperature instability may be observed.
  • Severely affected infants may be cyanotic.
  • Those infants who are less ill appearing are more likely to have nonspecific complaints, such as irritability or poor feeding.
  • Cough is unusual in the newborn period.
  • Early-onset group B streptococci infection usually presents via ascending perinatal infection as sepsis or pneumonia within the first 24 hours of life. Chlamydia trachomatis pneumonia often exists with conjunctivitis and presents during the second or third week of life.
• Infants
  • After the first month of life, cough is the most common presenting symptom.
  • Infants may have a history of antecedent upper respiratory symptoms.
  • Depending upon the degree of illness, tachypnea, grunting, and retractions may be noted. Vomiting, poor feeding, and irritability are also common.
  • Infants with bacterial pneumonia often are febrile, but those with viral pneumonia or pneumonia caused by atypical organisms may have a low-grade fever or may be afebrile. The child's caretakers may complain that the child is wheezing or has noisy breathing. In many cases, these sounds are actually upper airway noises.
• Toddlers and preschool children
  • A history of an upper respiratory illness before the onset of symptoms is common.
  • Cough is the most common presenting symptom.
  • Vomiting, particularly post-tussive emesis, may be present. Chest pain is common. Abdominal pain or tenderness is not an uncommon symptom of lower lobe pneumonia and chest pain, although this usually represents pleuritic involvement in children with viral syndromes.
  • The presence and degree of fever is dependent upon the organisms involved. Similarly, the symptoms of respiratory compromise may be observed in severe cases.
• Older children and adolescents
  • Atypical organisms, such as Mycoplasma, are more common in these patients.
  • In addition to the symptoms observed in younger children, adolescents may have other constitutional symptoms, such as headache, pleuritic chest pain, and vague abdominal pain. Vomiting, diarrhea, pharyngitis, and otalgia/otitis are other common symptoms.

Physical

Early in the physical examination, it is important to identify and treat respiratory distress, hypoxemia, and hypercarbia. Signs such as grunting, flaring, severe tachypnea, and retractions should prompt the clinician to provide immediate respiratory support. An assessment of oxygen saturation by pulse oximetry should be performed early in the evaluation of all children with respiratory symptoms. When appropriate and available, side-stream capnography may be useful in the evaluation of children with potential respiratory compromise. Severely affected children with respiratory distress not responsive to supplemental oxygen should undergo tracheal intubation.

• The examination of patients not in respiratory distress should begin with observation. "Shirt off, lights on" is a good phrase for this process. The examiner should simply observe the patient's respiratory effort and count the respirations for a full minute. This procedure will allow for the identification of subtle signs of respiratory embarrassment and other important findings, such as splinting. In infants, observation should include an attempt at feeding, unless the baby has extreme tachypnea. The baby who is doing well at rest may decompensate during feeding.
• Auscultation is perhaps the most important portion of the examination of the child with respiratory symptoms. The examination often is very difficult in infants and young children for several reasons.
  • Babies and young children often cry during the physical examination making accurate auscultation difficult. When young infants cry, it usually is because they are uncomfortable. They may, for example, be hungry or may find the stethoscope or the examiner's hand to be cold. The best chance of success lies in prewarming hands and instruments and in using a pacifier to quiet the infant. The opportunity to listen to a sleeping infant should never be lost.
  • Older infants and toddlers may cry because they are ill or uncomfortable, but, most often, they have stranger anxiety. For these children, it is best to spend a few minutes with the parents in the child's presence. If the child sees that the parent trusts the examining physician then he or she may be more willing to let the examiner approach. A small toy may help to gain the child's trust. Any part of the examination using instruments should be deferred as long as possible, because the child may find the medical equipment frightening. Occasionally, if the child is allowed to hold the stethoscope for a few minutes, it becomes less frightening. Even under the best of circumstances, it is difficult to examine a toddler. If the child is asleep when the physician begins the evaluation, auscultation should be performed early.
  • It is not unusual for children with respiratory symptoms to have a concomitant upper respiratory infection with copious upper airway secretions. This creates another potential problem, transmission of upper airway sounds. In many cases, the sounds created by upper airway secretions can almost obscure true breath sounds and lead to erroneous diagnoses. In young children, there is no effective way to remove these secretions without causing crying. If doubt exists as to the etiology of sounds heard through the stethoscope, the examiner should listen to the lung fields and then hold the stethoscope near the child's nose. If the sounds from both locations are approximately the same, the likely source of the abnormal breath sounds is the upper airway.
  • Even when the infant or young child is quiet and has a clear upper airway, the child's normal physiology may make the examination difficult. The minute ventilation is the product of the respiratory rate and tidal volume. In young children, respiratory rate makes a very large contribution to the overall minute ventilation. In other words, babies take many shallow breaths as opposed to a few deep ones. Therefore, a subtle finding, particularly one at the pulmonary bases, can be missed. In order to create a few deeper breaths, the examiner need only apply gentle pressure to the chest or abdomen near the end of exhalation. This will force a bit more air out of the chest and allow expiratory noises, such as wheezing, to become more apparent. Additionally, the subsequent inspiration will be somewhat deeper, allowing fine crackles to be noted.
  • The sine qua non for this disease has always been the presence of crackles (formerly called rales). Focal crackles in a febrile child without underlying lung disease is pneumonia until proven otherwise. However, not all children with pneumonia have crackles.
  • Other examination findings suggestive of pneumonia include focal wheezing or whistling sounds and decreased breath sounds in one lung field.
  • Similarly, certain more diffuse lung infections may result in generalized crackles or wheezing.
• Percussion may reveal important information. Occasionally, a child presents with a high fever and cough but without osculatory findings suggestive of pneumonia. In such cases, percussion often helps to identify an area of consolidation.
• Pneumonia may occur as a part of another generalized process. Therefore, signs and symptoms suggestive of other disease processes, such as rashes and pharyngitis, should be sought during the examination.

Causes

Pathogens implicated in pneumonia vary with the age of the pediatric patient, the underlying patient-specific risk factors, immunization status, and seasonality.

• Newborns and infants
  • In the neonate, pathogens that may infect the infant via the maternal genital tract include group B streptococci, Escherichia coli and other fecal coliforms, and C trachomatis.
    • Group B streptococci most often is transmitted to the fetus in utero, usually as a result of colonization of the mother's vagina and cervix by the organism.
    • Affected infants commonly present within the first few hours after birth, but if infection is acquired during the delivery, the presentation may be delayed for a day or two.
    • The usual presenting symptoms include tachypnea, hypoxemia, and signs of respiratory distress.
    • Physical examination reveals diffuse fine crackles and the chest x-ray may demonstrate a ground glass appearance and air bronchograms.
  • Newborns also may be affected by the bacteria and viruses that cause infections in older infants and children. Risk factors for infection include older siblings, group day care, and lack of immunization, particularly against pertussis.
  • In the young infant, 1-3 months of age, continued concern about perinatally acquired pathogens mentioned above as well as the unusual Listeria monocytogenes remains. However, most pneumonia in this age group is community acquired and involves S pneumoniae, Staphylococcus aureus, and Haemophilus influenzae.
    • Although the young unimmunized or incompletely immunized infant remains at theoretical risk for H influenzae and pneumococcal disease, herd immunity gained from widespread immunization of the population has been generally protective.
    • Most lower respiratory disease in the young infant occurs during the respiratory virus season and may be viral in origin along with bronchiolitis. Beyond the newborn period, viruses cause most lower respiratory tract infections in infants. The most common agents are the parainfluenza viruses, influenza virus, adenovirus, and respiratory syncytial virus (RSV). The latter organism can be particularly dangerous to former premature infants and to those babies with underlying lung disease.
  • Atypical organisms also cause infections in infants. Of these, C trachomatis, Ureaplasma urealyticum, cytomegalovirus, and Pneumocystis carinii (PCP) are the most common. Pneumocystis infects virtually all humans in early infancy; however, it causes severe symptoms only in debilitated or immunocompromised patients.
  • Bordetella pertussis may affect infants. Only 80% of fully immunized children are protected against pertussis and that immunity to this disease wanes in late adolescence. Since infants have not completed the vaccination series and because adults are a potential reservoir for infection, both groups are at risk.
  • S pneumoniae is by far the most common bacterial pathogen in this age group. In a recent study to evaluate the effectiveness of heptavalent pneumococcal conjugate vaccine in children younger than 5 years for prevention of pneumonia, Black et al showed a 32.2% reduction in the first year of life and a 23.4% reduction between 1-2 years, but only a 9.1% reduction in children older than 2 years. Underimmunized infants may also be infected by H influenzae.
  • Infection with S aureus is currently on the increase and complicated by lung abscess, parapneumonic effusions, and empyema (Mishaan, 2005).
• Young children
  • Viruses usually infect toddlers and preschoolers. The usual culprits are those previously discussed.
  • Children in this age group are also at risk for infection by M pneumoniae. Pneumococcus is by far the most common bacterial cause of pneumonia, although the lungs may be secondarily infected as a part of other generalized infections (eg, meningococcemia).
• Older children and adolescents
  • M pneumoniae is a frequent cause of pneumonia among older children and adolescents.
  • C pneumoniae can cause pneumonia along with a variety of other symptoms.
  • Older adolescents may have lost their immunity to pertussis and may become infected by this organism. Unlike the whooping cough in infants, pertussis in older patients usually causes a paroxysmal cough, which persists for more than 3 weeks and may last up to 3 months.
  • Bacterial pneumonia in this age group most often is caused by Pneumococcus species.
  • Histoplasma capsulatum, which is found in nitrate rich soil, usually is acquired as a result of inhalation of spores. Chicken coops and other bird roosts and decaying wood are oft-cited sources. The infection is usually asymptomatic; however, infants and young children are at risk for symptomatic infection, which may cause respiratory distress and hypoxemia.
  • Blastomyces dermatitides is a dimorphic yeast, which is found in certain geographic locations, most notably the Ohio and Mississippi River valleys. As with histoplasmosis, blastomycosis is acquired by inhalation of spores. Although 3 distinct forms of infection exist, the most common is acute pneumonia, which most often resolves without treatment.
  • Cryptococcus neoformans is a common infection among pigeon breeders, but it is unusual in other immunocompetent individuals. It may occur in as many as 5-10% of patients with AIDS. In immunocompetent patients, this organism causes no symptoms or a mild pneumonia and requires no treatment.
  • Mycobacterial pneumonia has recently been noted with increasing frequency in some inner city areas. Children in homeless shelters and group homes and those with household contacts are at particular risk. Similarly, the diagnosis must be considered in immunocompromised children.
• RSV is a common cause of viral lung infections. Serious infections with this organism usually occur in infants with underlying lung disease.
• The herpesviruses rarely may cause pneumonia. In infants, the usual agent is herpes simplex and, in older children, pneumonia may complicate common varicella infections.
• Influenza A is a less common pathogen.
• Legionella species is not an important pathogen in the pediatric population and is almost never observed in immunocompetent children.
• Children with cystic fibrosis may be infected with various organisms such as S aureus, Pseudomonas aeruginosa, Burkholderia cepacia, and other multidrug-resistant organisms.
• Not all pneumonia is caused by infectious agents. Children who have severe gastroesophageal reflux may develop chemical pneumonitis secondary to recurrent aspiration. Inhalation of certain chemicals or smoke may cause pulmonary inflammation.

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