Introduction

Pneumonia is a common condition with significant morbidity and mortality. It is estimated to be responsible for approximately three million childhood deaths per year, most of which occur in developing countries.¹ Even in developed countries, pneumonia remains a major cause of acute morbidity and one of the most common reasons for paediatric hospital admissions.² The incidence of pneumonia is approximately 40 per 1000 children per year in those under five years of age, and 15 per 1000 children per year in 5–14-year-olds.^3–5

In spite of how common it is, there is no single clinical or radiological definition that is widely accepted for pneumonia. It is investigated with a range of tests, the usefulness of which is known to be incomplete, and it is then often treated without knowledge of the aetiology. Fortunately, most children recover completely with empiric treatment.

Definition

There are various definitions that can be used for pneumonia. From a pathological point of view, it is defined as inflammation or infection of the lung parenchyma. In the clinical setting, the diagnosis is typically made on the basis of a constellation of clinical features, including fever, cough, tachypnoea and auscultatory findings, and confirmed by radiographic changes.

Aetiology

In the majority of cases of childhood pneumonia, the causative pathogen is not identified. Blood cultures are positive in under 5% of cases of pneumonia.^5–7 Transthoracic lung aspiration yields a cause in up to 69% of cases,^8,9 but is invasive. It is difficult to obtain adequate sputum for microscopy and culture in young children. Other indirect methods of identifying a cause, such as serology or immunofluorescence and culture of nasopharyngeal aspirates are neither sensitive nor specific.

Although an alveolar or lobar infiltrate on chest X-ray is considered by some to be suggestive of bacterial infection, chest X-ray changes cannot reliably predict aetiology.^9,10 Nor is any radiological pattern pathognomonic for viral or Mycoplasma pneumoniae infection.

Age is the best predictor of aetiology of pneumonia. In neonates, where bacterial causes predominate, Group B streptococci and Escherichia coli are the most common pathogens. Viruses, particularly respiratory syncytial virus (RSV), parainfluenza, influenza, metapneumovirus and adenovirus, are the most common cause overall, particularly in young children. The occurrence of recent local outbreaks and the clinical pattern may give a clue to the likely causative virus. These viruses appear to be responsible for approximately 40% of cases of community-acquired pneumonia in children who are hospitalised, particularly in those under 2 years of age, whereas Streptococcus pneumoniae is responsible for 27% to 44% of cases of community-acquired pneumonia.¹¹ Up to 40% of infections are mixed.⁵ Infection with Mycoplasma pneumoniae and Chlamydia pneumoniae is usually considered to cause pneumonia in children of school age and in older patients, although more recent studies suggest that preschool-aged children have as many episodes of atypical bacterial pneumonia as older children.¹¹ Staphylococcal and Group A streptococcal pneumonia are uncommon, but should be considered in children who are severely unwell with invasive disease. These infections are more likely to be seen in indigenous and Pacific Islander children. More recently, infections with community-acquired multiresistant Staphylococcus aureus (CAMRSA) have emerged. CAMRSA results in a necrotising fulminant pneumonia with increased morbidity and mortality.

Gram-negative pneumonia is uncommon in children; non-typeable Haemophilus influenzae is mainly seen in children with underlying lung disease, such as cystic fibrosis and bronchiectasis.

The presence of a pleural effusion does not necessarily indicate more severe disease – Strep. pneumoniae remains the most common bacterial cause, with or without effusion.

Clinical findings

Pneumonia should be considered in any infant or child presenting with fever, cough, difficulty breathing, tachypnoea, increased work of breathing (nasal flaring, lower chest indrawing or recession), and auscultatory findings consistent with consolidation or effusion. However, the auscultatory findings may be unreliable in young children, particularly in those under 1 year. Infants may present with symptoms not obviously related to a lower respiratory tract infection, such as lethargy, vomiting, poor feeding, grunting, or poor perfusion. Children less than 3 months of age may present with apnoea. Tachypnoea is the most sensitive and specific sign¹² and may be the only clue in some children. Auscultatory findings, including asymmetrical breath sounds, crackles and bronchial breathing are less predictive. The presence of coryza or wheeze (particularly bilateral) suggests that bacterial pneumonia is unlikely.^6,13 Pneumonia located in the apex of the lung may present with neck pain and be confused with meningitis, whilst basal pneumonia may cause abdominal pain, suggestive of an acute abdomen. Conversely, an infant with grunting respirations may give the initial impression of an intra-abdominal problem.

The presentation of pneumococcal pneumonia is generally abrupt, whilst M. pneumoniae and viral infections more often present with a more indolent course, less fever, and other symptoms such as malaise, headache, arthralgia and rash.

Investigations

Posteroanterior chest X-rays are generally used to confirm pneumonia where there is clinical suspicion. However, they need not be performed routinely in older children with mild disease where the diagnosis may be made clinically. They are particularly important for confirming the diagnosis of pneumonia in children less than 5 years of age who present with fever and tachypnoea, unless classical features of bronchiolitis are present. Lateral X-rays do not confer much additional information in most cases.

Although, it is not possible to reliably predict aetiology or differentiate bacterial from viral pneumonia on chest X-ray, pneumococcal pneumonia typically presents with a lobar infiltrate or round pneumonia. Pneumatoceles, abscesses and cavities are associated most frequently with staphylococcal pneumonia but they are also seen in pneumonias caused by other bacteria. Bronchopneumonia is more typical of viral or other aetiology.

Large effusions may be difficult to differentiate from empyema. In some cases, ultrasound may be helpful in determining whether loculations are present.

Radiological changes lag behind clinical signs, and may persist for 4–6 weeks. Follow-up chest X-rays are unnecessary in most cases of uncomplicated pneumonia, but should be considered if symptoms and signs are persistent following treatment.

Most other investigations to determine microbiological aetiology are not particularly helpful in the emergency department setting to dictate immediate medical management. Rapid viral antigen tests, such as direct immunofluorescence assay for RSV and other respiratory viruses on nasopharyngeal aspirates, do not usually alter management. However, they may inform infection control strategies for young children admitted to hospital. Many respiratory pathogens may be identified using molecular methods, such as polymerase chain reaction (PCR) analysis of respiratory secretions.

Management

Patients should be stabilised as necessary with high-flow oxygen and fluid resuscitation. Many children will not require any specific treatment. Most children who are not too unwell and have lobar consolidation on chest X-ray can be managed as outpatients with oral amoxicillin 25 mg kg⁻¹ (up to 1 g) three-times daily for 7 days. Children under 1 year of age, and those who are more unwell or hypoxic may require inpatient management (Table 6.5.1) and treatment with intravenous benzylpenicillin 50 mg kg^–1 (up to 1.2 g) 6-hourly. Infants less than 3 months of age should also be given intravenous gentamicin 7.5 mg kg^–1 daily.

Antibiotic resistance among pneumococci is becoming more common. However, there is no difference in outcome between cases caused by susceptible and resistant strains, and amoxicillin or benzylpenicillin remains the treatment of choice.^14,15 The use of third-generation cephalosporins provides no additional benefit over these penicillins. They should be reserved for severe pneumonia where it may be important to cover beta-lactamase producers and Gram-negative bacteria.

Children presenting with coryza, wheeze, diffuse crackles and minimal chest X-ray changes may have viral pneumonitis. Admission may be necessary for supportive care, but antibiotics should be withheld. A trial of inhaled bronchodilator therapy may be useful in children who appear to have significant associated bronchospasm. A macrolide antibiotic, such as oral roxithromycin 4 mg kg^–1 (up to 150 mg) twice daily for 7 days, should be considered for those with suspected M. pneumoniae infection.

Only children who are severely unwell require broader-spectrum antibiotics to include cover for Staph. aureus and Gram-negative bacteria: flucloxacillin 50 mg kg^–1 intravenously (IV) (up to 2 g) 6-hourly plus cefotaxime 50 mg kg^–1 IV 6-hourly. In settings or populations where CAMRSA is more prevalent, vancomycin 10–15 mg kg^–1 per dose 6-hourly should be added.

A short course (3 days) of antibiotic therapy is as effective as a longer treatment (5 days) for non-severe pneumonia in children under 5 years of age.¹⁶

Complications

A child who remains very unwell and febrile after 48 hours of parenteral treatment should be reassessed for the possibility of empyema or, more rarely, lung abscess. In these cases, input from infectious diseases and respiratory specialists is advised.

Prevention

The introduction of conjugate H. influenzae type b (Hib) and Strep. pneumoniae vaccines into the routine immunisation schedule in many countries has led to a reduction in the burden of pneumonia caused by these two organisms.¹⁷

Conclusion

Pneumonia is a common illness in children. Viruses are the most common cause, and many children will not require any specific treatment. Strep. pneumoniae remains the most common bacterial cause, and amoxicillin remains the antibiotic treatment of choice.¹⁸