Pediatric Imaging

Which Imaging Study First for a Child with Chest Pain and Suspected Pneumothorax?

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Which Imaging Study First for a Child with Chest Pain and Suspected Pneumothorax?

A 16-year-old, tall, thin male presents to the emergency department with a sudden onset of sharp, right-sided chest pain and shortness of breath. The symptoms began an hour ago during a coughing fit. He denies any trauma. On examination, he is in mild respiratory distress with diminished breath sounds on the right. You suspect a primary spontaneous pneumothorax. The immediate clinical question is which imaging study to order to confirm the diagnosis and guide management. This article provides a detailed workflow for this specific scenario, grounded in the American College of Radiology (ACR) Appropriateness Criteria. For this presentation, the ACR designates Radiography chest as Usually appropriate.

Who Fits This Clinical Scenario for Suspected Pneumothorax or Pneumomediastinum?

This guidance applies to pediatric patients, from infants to adolescents, who present with acute chest pain, with or without associated shortness of breath, where the clinical suspicion points toward extra-alveolar air—specifically a pneumothorax (air in the pleural space) or pneumomediastinum (air in the mediastinum). The presentation is typically non-traumatic.

Key inclusion criteria for this workflow include:

  • Sudden-onset, often pleuritic, chest pain.
  • Clinical signs suggestive of pneumothorax (e.g., diminished breath sounds, hyperresonance to percussion).
  • A history that increases risk, such as forceful coughing or vomiting, an asthma exacerbation, or a tall, thin body habitus in an adolescent male (classic for primary spontaneous pneumothorax).
  • Suspicion of pneumomediastinum, which may present with retrosternal pain, dysphagia, or subcutaneous emphysema (crepitus) in the neck.

It is crucial to distinguish this scenario from others that may present similarly but require a different diagnostic approach. This workflow does not apply if:

  • The pain is clearly localized to the chest wall and is reproducible with palpation. This presentation fits the ACR variant for Chest pain. Limited to the chest wall.
  • The patient has known congenital or acquired heart disease, and the pain is exertional or associated with palpitations. This suggests a cardiac etiology and routes to the variant for Known or suspected cardiac disease.

What Diagnoses Are You Working Up in This Scenario?

When a child presents with symptoms suggestive of a pneumothorax or pneumomediastinum, the initial imaging is intended to confirm the presence of extra-alveolar air and rule out other critical conditions. The differential diagnosis is focused and drives the choice of a rapid, high-yield imaging study.

Spontaneous Pneumothorax is a primary consideration, especially in adolescents. Primary spontaneous pneumothorax occurs without underlying lung disease and is most common in tall, thin males, thought to be due to the rupture of small apical subpleural blebs. Secondary spontaneous pneumothorax occurs in patients with known lung pathology, such as cystic fibrosis or severe asthma.

Pneumomediastinum involves air dissecting into the mediastinum. It is often triggered by a sudden increase in intra-alveolar pressure from a forceful Valsalva maneuver, such as severe coughing, vomiting, or straining. While often benign and self-limiting, it can cause significant retrosternal chest pain and may be associated with subcutaneous emphysema.

Esophageal Rupture (Boerhaave Syndrome) is a rare but life-threatening cause of pneumomediastinum. It typically follows an episode of forceful vomiting and constitutes a surgical emergency. The initial chest radiograph is critical for detecting mediastinal air, which would prompt an urgent workup for this diagnosis.

Tracheobronchial Injury is another rare, non-traumatic cause of pneumomediastinum and pneumothorax. While most common after severe blunt chest trauma, it can occasionally occur with violent coughing spells. Imaging is key to identifying the location and extent of air leak.

Why Is a Chest Radiograph the Recommended First Step for This Presentation?

The ACR designates a standard Radiography chest as Usually appropriate for the initial evaluation of a child with suspected pneumothorax or pneumomediastinum. This recommendation is based on the test’s high diagnostic yield, wide availability, speed, and low radiation dose.

A standard upright, inspiratory posteroanterior (PA) chest radiograph is highly effective for identifying the key findings. For a pneumothorax, the radiologist looks for the visceral pleural line—a thin white line separated from the chest wall by a lucent collection of air that is devoid of lung markings. For a pneumomediastinum, findings include lucent streaks of air outlining mediastinal structures like the heart border, aorta, or trachea, and the “continuous diaphragm sign,” where air under the heart makes the entire diaphragm visible.

The radiation exposure from a pediatric chest radiograph is extremely low (pediatric relative radiation level ☢ <0.03 mSv), aligning with the ALARA (As Low As Reasonably Achievable) principle, which is paramount in pediatric imaging. This dose is a small fraction of the average annual background radiation.

Alternative imaging modalities are rated lower for this initial workup for clear reasons:

  • CT chest without IV contrast is rated Usually not appropriate as a first-line test. While CT is more sensitive for detecting very small pneumothoraces or subtle pneumomediastinum, it is not necessary for the initial diagnosis in a clinically stable patient. Its use should be reserved for cases where the radiograph is equivocal, in the setting of significant trauma, or to evaluate for underlying lung pathology. The radiation dose is substantially higher (pediatric RRL ☢☢☢☢ 3-10 mSv), making it an inappropriate initial choice.
  • US chest is also rated Usually not appropriate. Although point-of-care ultrasound (POCUS) can rapidly detect a pneumothorax by identifying the absence of lung sliding, it is highly operator-dependent. Furthermore, it is less effective for quantifying the size of the pneumothorax and is not reliable for diagnosing pneumomediastinum. The ACR considers radiography the more standardized and comprehensive initial examination.

What’s Next After the Chest Radiograph? Downstream Workflow

The results of the initial chest radiograph directly guide the subsequent clinical pathway. The downstream workflow depends on whether the study is positive, negative, or indeterminate, as well as the patient’s clinical stability.

If the radiograph is positive for a pneumothorax:

  • Small Pneumothorax: If the pneumothorax is small (often defined as <2-3 cm from the chest wall at the apex) and the patient is clinically stable with normal vital signs, management is typically conservative. This may involve observation, supplemental oxygen (which can increase the rate of resorption), and serial chest radiographs to ensure it is not enlarging.
  • Large or Tension Pneumothorax: A large pneumothorax or any pneumothorax causing hemodynamic instability (tension physiology) is a medical emergency. The imaging finding triggers immediate procedural intervention, such as needle decompression followed by chest tube placement, to re-expand the lung.

If the radiograph is positive for pneumomediastinum:

  • Management is usually supportive and focused on treating the underlying cause (e.g., asthma). The primary concern is ruling out a life-threatening etiology like esophageal or tracheobronchial rupture. If the history is highly suggestive (e.g., severe vomiting followed by pain), a contrast esophagram may be necessary.

If the radiograph is negative:

  • If the initial chest radiograph is negative but the patient’s symptoms persist or worsen, the clinical team should reconsider the differential diagnosis. The pain may be musculoskeletal, cardiac, or related to another etiology. This may prompt a shift to a different ACR workflow, such as the one for chest wall pain or suspected cardiac disease.

Pitfalls to Avoid (and When to Get Help)

In the workup of a suspected pediatric pneumothorax, several common pitfalls can delay diagnosis or lead to unnecessary testing. Awareness of these can improve patient care.

  • Missing a subtle pneumothorax: A small apical pneumothorax can be difficult to see. Systematically trace the lung markings to the periphery and specifically look for the thin visceral pleural line at the apices.
  • Overlooking signs of pneumomediastinum: This diagnosis can be subtle on a radiograph. Look carefully for air tracking along the heart borders or great vessels and into the soft tissues of the neck.
  • Mistaking a skin fold for a pneumothorax: A skin fold can create a line that mimics the visceral pleura. A key differentiator is that a skin fold line is often thicker and can be traced extending beyond the boundary of the thoracic cavity.
  • Prematurely ordering a CT scan: Resist the urge to order a CT as the initial test. The chest radiograph is sufficient for diagnosis in the vast majority of cases and avoids significant radiation exposure.

Escalation is critical if you suspect a tension pneumothorax based on clinical signs (e.g., hypotension, tracheal deviation, severe respiratory distress, unilateral absence of breath sounds). Do not delay life-saving intervention like needle decompression for imaging confirmation.

Related ACR Topics and Tools

This article focuses on a single clinical variant. For a comprehensive overview of imaging for all pediatric chest pain scenarios, from musculoskeletal pain to suspected pulmonary embolism, please consult our parent guide. Additional GigHz tools can help you apply these criteria in your daily practice.

Frequently Asked Questions

Is an expiratory chest radiograph helpful for a suspected pneumothorax in a child?

The ACR rates decubitus and expiratory views as ‘Usually not appropriate.’ While an expiratory film can occasionally make a small apical pneumothorax more conspicuous, it rarely changes clinical management, is often difficult to obtain correctly in a child in respiratory distress, and effectively doubles the radiation exposure. A standard upright inspiratory view is the recommended initial study.

In this scenario, when should I consider a CT scan instead of a plain radiograph?

A CT scan is not a first-line test for suspected spontaneous pneumothorax or pneumomediastinum. You should consider a CT if the initial radiograph is negative or equivocal but your clinical suspicion remains very high, if there is a history of significant trauma, or to evaluate for underlying lung pathology (like bullous disease) in cases of recurrent pneumothorax. It is also used to better characterize a pneumomediastinum if an esophageal or airway rupture is a primary concern.

Can I use ultrasound to diagnose a pneumothorax in a child?

Point-of-care ultrasound (POCUS) is a rapid, radiation-free tool that can detect a pneumothorax by looking for the absence of ‘lung sliding.’ However, the ACR considers it ‘Usually not appropriate’ as the standard initial diagnostic test for this scenario. This is likely due to its high operator dependency and its limitations in quantifying the size of the pneumothorax or reliably detecting pneumomediastinum. A chest radiograph remains the standard of care for initial diagnosis.

What’s the clinical difference between a pneumothorax and a pneumomediastinum presentation?

Both can cause acute chest pain and shortness of breath. Pneumothorax pain is typically sharp, pleuritic (worse with inspiration), and localized to one side of the chest. Pneumomediastinum pain is more often described as retrosternal and constant. A key clinical sign highly suggestive of pneumomediastinum is subcutaneous emphysema (a crackling feeling, or crepitus) in the neck or upper chest. A ‘crunching’ sound heard over the heart during auscultation (Hamman’s sign) is classic but rarely found.

How significant is the radiation risk from a single chest X-ray for a child?

The radiation dose from a single pediatric chest radiograph is very low. The ACR estimates the pediatric relative radiation level at less than 0.03 mSv, which is a small fraction of the 3 mSv of natural background radiation an average person is exposed to each year. The clinical benefit of accurately and quickly diagnosing a potentially life-threatening condition like a pneumothorax far outweighs this minimal radiation risk.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026