Airway Foreign Body Imaging

Updated: Aug 03, 2023
  • Author: Henrique M Lederman, MD, PhD; Chief Editor: John Karani, MBBS, FRCR  more...
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Practice Essentials

Historically, airway foreign bodies have been a major cause of morbidity and mortality in the United States, with approximately 500-2000 deaths occurring each year from foreign body aspiration.  According to the National Safety Council, foreign body airway obstruction is the fourth leading cause of unintentional death. The number of button (disc) battery ingestions has increased dramatically worldwide due to their extensive use in watches, calculators, toys, small electronic devices, musical greeting cards, and hearing aids. [1, 2, 3, 4] According to America's Poison Centers, there were 3017 single exposures to disc batteries, with the majority (57%) occurring in children younger than 6 years. [5]  Because of serious potential complications associated with delayed diagnosis, it is important to differentiate coins from button batteries on radiographs. Button batteries may have a double ring or halo sign; however, this sign can be absent with slimmer batteries. [6]

Although foreign body aspiration most frequently occurs in children, it may occur in adults as well. Foreign body aspiration is commonly referred to as a "café coronary" (elderly adults). [7, 8, 9, 10, 11]  Despite advances in radiologic techniques, the diagnosis of foreign body aspiration can be difficult, and bronchoscopy may be required. [9, 10]

Imaging modalities

When foreign body aspiration is suspected, screening radiographic studies include anteroposterior (AP) and lateral imaging of the soft tissues of the neck, inspiratory and expiratory posteroanterior (PA) chest radiographs (CXRs), and lateral radiographs. [12, 13] The potential is great for morbidity and mortality resulting from an aspirated foreign body; hence, if foreign body aspiration is suspected, the appropriate radiographic studies should be performed. [14, 15, 16]  

Although radiopaque foreign bodies are easy to diagnose on radiographs, they represent a minority (16%) of aspirated foreign bodies, and a negative film does not exclude aspiration. With radiolucent foreign bodies, secondary radiographic signs, such as obstructive emphysema, atelectasis, pneumonia, and a mediastinal shift, are present in approximately 72% of cases and aid in diagnosis. [17]

Lateral decubitus chest radiography, fluoroscopy, or both may help in diagnosing foreign body aspiration in patients who are unable to cooperate with inspiratory and expiratory CXRs, such as young pediatric patients. [18, 19, 20, 21, 22, 23]

As a result of the limitations of radiographic studies in the diagnosis of aspirated foreign bodies, all patients in whom the clinical suspicion for aspirated foreign bodies is high should undergo bronchoscopy for definitive diagnosis and treatment. [2, 3, 19, 24, 25, 26]

Although bronchoscopy is considered the standard of care for diagnosis and treatment of foreign body aspiration, a retrospective review of 133 patients assessed for foreign body aspiration found that CT excluded the diagnosis in 49 cases.  Overall in the study, CT had a sensitivity of 100% and a specificity of 98%. [27]

Most foreign bodies are lodged in the bronchial tree, and only a small percentage (around 4%) become stuck in the larynx. Diagnosis of laryngeal foreign bodies, especially if they are small, thin, and radiolucent, remains a challenge. [28]   Typical indirect radiologic signs that are seen when a foreign body reaches the lower airways (eg, unilateral lung hyperinflation, mediastinal shift, and consolidation) are usually not present when the foreign body is lodged in the larynx, and radiographs are almost always normal. Low‐dose multidetector computed tomography (MDCT) is a sensitive technique that can detect radiolucent foreign bodies in the larynx and the tracheobronchial tree. In addition, it can be combined with virtual bronchoscopy (VB), a technique that has 3‐dimensional surface‐rendering and volume‐rendering possibilities, thus providing a view of the internal surface of the airways. Successful identification of laryngeal foreign bodies with MDCT and thin‐slice reconstruction has been reported in cases with uncertain clinical presentation and negative radiographs. [29]

(See the radiographic images below.)

Inspiratory chest radiograph in a 12-month-old boy Inspiratory chest radiograph in a 12-month-old boy with a 2-month history of wheezing demonstrates moderate hyperlucency and hyperexpansion of the right hemithorax. A mild deviation of the mediastinum toward the left chest is noted. Courtesy of Brit B. Gay, Jr, MD, Radiology Department, Egleston Children's Hospital, Atlanta, Ga.
Expiratory chest radiograph in a 12-month-old boy Expiratory chest radiograph in a 12-month-old boy with a 2-month history of wheezing demonstrates continued hyperlucency and hyperexpansion of the right hemithorax. A greater mediastinal shift is noted toward the left lung field. A corn kernel was removed from the patient's right mainstem bronchus during bronchoscopy. Courtesy of Brit B. Gay, Jr, MD, Radiology Department, Egleston Children's Hospital, Atlanta, Ga.

 

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Radiography

Initial radiographic studies should include AP and lateral views of the soft tissues of the neck, PA radiographs obtained during inspiration and expiration, and lateral images. The depiction of radiopaque foreign bodies is straightforward. Obtaining 2 views of the foreign body helps determine its location and excludes the presence of superimposed multiple foreign bodies. Most foreign bodies are radiolucent; therefore, indirect radiologic findings must often be obtained. [30] Radiolucent tracheal foreign bodies may show signs of an infraglottic opacity or of swelling from airway inflammation on PA and lateral neck radiographs. [31]

If the clinical suspicion is high for foreign body aspiration, bronchoscopy should be performed for definitive diagnosis and treatment. Although diagnosis is often based on history and physical exam, radiographs may be useful in confirming the diagnosis, but they should not be used to exclude the diagnosis, because radiographs are normal in more than 50% of cases of tracheal foreign bodies. [1, 2, 3]

Patients with bronchial foreign bodies may have normal findings on CXRs; however, the affected lung may show hyperaeration (obstructive emphysema) and shifting of the mediastinum away from the affected lung on expiratory CXRs because of the ball-valve effect of the tracheal foreign body (see the images below). In such cases, the patients can inspire air past the foreign body but have difficulty exhaling.

Inspiratory chest radiograph in a 12-month-old boy Inspiratory chest radiograph in a 12-month-old boy with a 2-month history of wheezing demonstrates moderate hyperlucency and hyperexpansion of the right hemithorax. A mild deviation of the mediastinum toward the left chest is noted. Courtesy of Brit B. Gay, Jr, MD, Radiology Department, Egleston Children's Hospital, Atlanta, Ga.
Expiratory chest radiograph in a 12-month-old boy Expiratory chest radiograph in a 12-month-old boy with a 2-month history of wheezing demonstrates continued hyperlucency and hyperexpansion of the right hemithorax. A greater mediastinal shift is noted toward the left lung field. A corn kernel was removed from the patient's right mainstem bronchus during bronchoscopy. Courtesy of Brit B. Gay, Jr, MD, Radiology Department, Egleston Children's Hospital, Atlanta, Ga.

In patients who are unable to cooperate for expiratory imaging (eg, young children), decubitus CXR or fluoroscopy may show hyperaeration and mediastinal shifting. Decubitus CXRs reveal failure of the affected lung to collapse, even if the patient is in the decubitus position (see the image below).

Left lateral decubitus chest radiograph demonstrat Left lateral decubitus chest radiograph demonstrates failure of collapse in an 11-month-old girl with a 2-week history of persistent coughing. A corn kernel was found in the patient's left mainstem bronchus during bronchoscopy. Courtesy of Brit B. Gay, Jr, MD, Radiology Department, Egleston Children's Hospital, Atlanta, Ga.

Images in patients with chronic bronchial foreign bodies may show atelectasis, with a mediastinal shift toward the foreign body and/or recurrent pneumonias in the affected lung segment (see the images below).

Chest radiograph in a 6-year-old boy who complaine Chest radiograph in a 6-year-old boy who complained of chest pain and dysphagia. Complete atelectasis of the left lung is noted, with a mediastinal shift towards the left lung. Courtesy of Brit B. Gay, Jr, MD, Radiology Department, Egleston Children's Hospital, Atlanta, Ga.
Chest radiograph obtained 2 days after a piece of Chest radiograph obtained 2 days after a piece of popcorn was removed from the patient's left mainstem bronchus. Resolution of the atelectasis is complete, and the mediastinum is in its normal position. Courtesy of Brit B. Gay, Jr, MD, Radiology Department, Egleston Children's Hospital, Atlanta, Ga.

Svedstrom and colleagues studied the accuracy of CXRs in the diagnosis of tracheobronchial foreign bodies and found that the diagnostic accuracy, sensitivity, and specificity of CXRs were 67%, 68%, and 67%, respectively. According to the authors, these results show that CXRs alone are neither sensitive nor specific enough to exclude tracheobronchial foreign bodies. They found that of the 34 patients from whom a foreign body was removed, preoperative CXRs showed airtrapping in 50%, atelectasis in 12%, and signs of infection in 18%. Normal CXR findings were obtained in 24% of patients who had endoscopically verified airway foreign bodies. [32]

In their study of patients with laryngotracheal foreign bodies, Esclamado and colleagues reported that 92% of neck radiographs showed an infraglottic density or swelling and therefore suggested that PA and lateral neck radiographs should be part of the radiographic workup when foreign body aspiration is a concern. [31] In contrast, 58% of the patients in their study who had laryngotracheal foreign bodies had normal CXR findings.

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Computed Tomography

As a result of its greater contrast resolution, computed tomography (CT) scanning has been used to demonstrate airway foreign bodies that are radiolucent on plain radiographs. [33, 34, 1]  Many authors recommend using narrow windows when imaging the thorax, to decrease the likelihood of missing a foreign body. [35, 36]  Chest CT scan has demonstrated a high sensitivity  of 94%. When compared with chest radiography, plain chest CT scan can have advantages of shorter examination time and finer image detail to detect location, size, and shape of airway foreign bodies. [37, 38, 39]  

In addition to providing plain radiographic findings, such as hyperlucency, atelectasis, and lobar consolidation, CT scans can depict the foreign body within the lumen of the tracheobronchial tree and the 3-dimensional position of the foreign body within the thorax. [33, 40, 41]

Current state-of-the-art helical multidetector-row CT scanners may improve the sensitivity of radiologic evaluation in patients who are unable to cooperate for inspiration and expiration radiography. The use of low-dose mutidetector CT and virtual bronchoscopy (VB) may help detect the foreign body. These scanners may be useful with young children and with adults suffering from an altered level of consciousness. [42]

In a retrospective analysis of 200 children evaluated for foreign body aspiration at a tertiary referral center, the negative predictive value (NPV) of CT was 99.2%, and the positive predictive value (PPV) was 83.8%. [43]   The use of CT with multiplanar reconstruction in suspected foreign body aspiration may be useful to decrease the number of negative bronchoscopies. [44]

In a study of tracheal foreign bodies in children by Shen et al, 359 of 382 patients (95.5%) showed a high-density shadow in the tracheal/bronchial lumen by multislice spiral CT (MSCT). [38]

If CT scans demonstrate signs of foreign body aspiration, the patient should undergo bronchoscopy for definitive diagnosis and treatment. No further radiologic study is indicated.

Any process that causes obstruction or narrowing of the airway lumen can produce signs similar those of foreign body aspiration. Examples include neoplastic disease, granulomatous disease, bronchial stenosis, and a mucus plug.

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Magnetic Resonance Imaging

The use of magnetic resonance imaging (MRI) in identifying aspirated peanuts has been reported. [42, 45, 46, 47] Using T1-weighted images, the presence of peanuts can be demonstrated via the direct depiction of the high signal intensity emitted by their fat content surrounded by low-intensity lung tissue. Imaizumi and colleagues reported that peanuts can be clearly distinguished from the surrounding areas of granulation and atelectasis because of their hyperintensity on T1-weighted images. [48]

The advantages of MRI include its noninvasive nature and the lack of radiation exposure from this modality. MRI also offers high-resolution multiplanar images of soft tissue.The disadvantages of MRI include its cost, the long data-acquisition time, the need for sedation in some patients, and the necessity to remove all metallic devices from patients. [45]

As with all imaging modalities, if clinical suspicion of an airway foreign body remains high, bronchoscopy should be performed for definitive diagnosis and treatment.

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