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Pediatrics, Pneumonia: Differential Diagnoses & Workup
Updated: Jul 24, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Differential Diagnoses
| Acute Respiratory Distress Syndrome | Pneumonia, Aspiration |
| Asthma | Pneumonia, Bacterial |
| Bronchiolitis | Pneumonia, Empyema and Abscess |
| Bronchitis | Pneumonia, Immunocompromised |
| Foreign Body Aspiration | Pneumonia, Mycoplasma |
| Pediatrics, Respiratory Distress
Syndrome | Smoke Inhalation |
| Pertussis |
Workup
Laboratory Studies
Very few laboratory studies are particularly useful in the evaluation of the child with pneumonia.
- Although it is true that many of the etiologic organisms may be identified by culture or immunofluorescent antibody techniques, in practice, these are too costly and time consuming for routine use. Furthermore, the results of such tests are rarely available in less than several hours, thus making them even less useful to the emergency clinician.
- Complete blood count
- In cases of pneumococcal pneumonia, the WBC count is often elevated.
- Prior to widespread pneumococcal immunization, Bachur et al observed that approximately 25% of febrile children with a WBC count >20,000/mm3, but without lower respiratory tract findings on examination, had radiographic pneumonia (termed occult pneumonia).18
- Although blood testing was obtained less frequently in the post-Prevnar era, recent studies by the same group demonstrated that leukocytosis was still associated with occult pneumonia.19,20
- Cultures
- Bacteremia is rarely associated with pneumonia in children, and blood culture is not routinely required in immunocompetent children.21
- Blood cultures should be obtained when the patient is critically ill, immunocompromised, or has persistent symptoms. Additionally, blood cultures are useful in patients with high fever and large areas of consolidation—mostly to make a microbiologic diagnosis.
- Sputum cultures should be reserved for unusual cases or very ill patients.
- Sputum Gram stain
- In the cooperative older child with a productive cough, a sputum Gram stain may be obtained.
- In order to be useful, the specimen must contain less than 10 epithelial cells and more than 25 WBC per high-powered field. Very few children are able to cooperate with such a test.
- Consideration should be given for rapid viral testing in young infants with simple infiltrates.
Imaging Studies
- The criterion standard test for the diagnosis of pneumonia is a 2-view plain chest radiograph. However, when chest radiographs are subjected to blinded readings, they may not differentiate between viral disease and bacterial disease.
A, Anteroposterior radiograph of a child with a left lower lobe infiltrate. B, Lateral radiograph of the same child with a left lower lobe infiltrate.
Anteroposterior radiograph of a child with a round pneumonia.
A, Anteroposterior radiograph of a child with presumptive viral pneumonia. B, Lateral radiograph of the same child with presumptive viral pneumonia.
- Although unilateral and/or lobar infiltrates are often seen in bacterial pneumonia, several studies have found that the pattern of radiologic features could not accurately distinguish a bacterial etiology from a viral etiology.22,23
- In contrast, a large Finnish series concluded that an alveolar (equivalent to a lobar) infiltrate is an insensitive but reasonably specific indication of bacterial infection.24
- At either extreme (from typical bronchiolitis with scattered infiltrates to dense lobar pneumonia with a large pleural effusion), the level of diagnostic certainty provided by radiologic findings increases.
- For M pneumoniae, 3 radiographic patterns may be observed: (1) peribronchial and perivascular interstitial infiltrates, (2) patchy consolidations, and (3) homogeneous acinar consolidations like ground-glass.25 The lower fields of the lungs are most often affected, and enlargement of the hilar glands is common.
- In viral pneumonias, 4 common radiographic findings were detected: parahilar peribronchial infiltrates, hyperexpansion, segmental or lobar atelectasis, and hilar adenopathy.26
- Although no radiographic findings are specific for C pneumoniae, a combination of the clinical and radiographic findings strongly suggests the diagnosis before laboratory diagnosis is available. In a study of 125 cases of Chlamydia pneumonia, Radkowski et al demonstrated that most chest films showed bilateral hyperexpansion and diffuse infiltrates with a variety of radiographic patterns including interstitial, reticular nodular, atelectasis, coalescence, and bronchopneumonia. Pleural effusion and lobar consolidation were not seen.27
- Round pneumonia on chest radiographs should raise suspicion for a bacterial etiology, particularly Streptococcus pneumoniae and Staphylococcus aureus.
Other Tests
- On occasion, it may be prudent to perform skin testing for tuberculosis, particularly if high risk for exposure.
- Cold agglutinins
- In the young child or school-aged child with pneumonia, particularly the patient with a gradual onset of symptoms and a prodrome consisting of headache and abdominal symptoms, a bedside cold agglutinins test may help confirm the clinical suspicion of mycoplasmal infection.
- This test is easily performed by placing a small amount of blood in a specimen tube containing anticoagulant and inserting this into a cup filled with ice water. After a few minutes in the cold water, the tube is held up to the light, tilted slightly, and slowly rotated. Small clumps of red blood cells coating the tube are indicative of a positive test result.
- Unfortunately, this test is positive in only half the cases of mycoplasmal infection and is not very specific.
- Urine latex agglutination test: Although antigen detection assays for S pneumoniae lack a high specificity in children, Neuman and Harper observed that 76% of febrile children with a lobar infiltrate on chest radiograph had a positive rapid urine antigen assay.28
Procedures
- When a child has a significant pleural effusion identified on chest radiograph, a thoracentesis should be performed. A lateral decubitus radiograph may be obtained to determine whether the thoracic fluid is free-flowing. Ultrasonography or fluoroscopy may be useful to aid in placement of a traditional or pigtail thoracostomy tube for small-to-moderate–sized effusions.
- Fluid recovered from the pleural space should be sent for Gram stain and culture, along with pH, glucose, protein, and lactate dehydrogenase (LDH).
- If the thoracentesis reveals an empyema, a thoracostomy tube may be required.
More on Pediatrics, Pneumonia |
| Overview: Pediatrics, Pneumonia |
 Differential Diagnoses & Workup: Pediatrics, Pneumonia |
| Treatment & Medication: Pediatrics, Pneumonia |
| Follow-up: Pediatrics, Pneumonia |
| Multimedia: Pediatrics, Pneumonia |
| References |
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References
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Further Reading
Keywords
pneumonia in children, symptoms of pneumonia in children, treatment of pneumonia in children, bacterial pneumonia, respiratory syncytial virus, RSV, lower respiratory tract infection, empiric antibiotics, interstitial pneumonia, miliary pneumonia, lobar pneumonia, bronchopneumonia, dyspnea, hypoxemia
