Will a glass foreign body be visible on an x-ray?

Glass Foreign Body Visibility on X-Ray

Glass is inconsistently visible on radiographs, particularly if fragments are small or obscured by adjacent bone, but most glass foreign bodies can be detected with standard x-ray imaging. 1

Detection Characteristics of Glass on Radiography

• Glass is radiodense and can be detected on x-rays, unlike truly radiolucent materials such as wood, plastic, and rubber. 1
• Detection rates vary significantly by fragment size: 2.0-mm glass fragments show 99% detection, 1.0-mm fragments show 83% detection, and 0.5-mm fragments show only 61% detection on standard two-view radiographs. 2
• In clinical practice, glass foreign bodies were radiographically detected in 25 out of 26 patients (96%), with almost all glass foreign bodies being detectable when proper technique is used. 3

Key Factors Affecting Detection

Fragment size is the primary limiting factor for radiographic detection, with 0.5- to 2.0-mm fragments representing a "limited detection" size range. 2

• Small fragments may be missed on x-ray, especially if obscured by adjacent osseous structures. 1
• Two-view radiography (posteroanterior and lateral) is appropriate and cost-effective for screening purposes, with no statistically significant benefit from adding oblique views. 2

When X-Ray is Negative but Glass is Suspected

If radiographs are negative but a glass foreign body is still suspected based on history and examination, ultrasound is the imaging modality of choice, with 95% sensitivity for foreign body detection. 1, 4

Alternative Imaging Options:

• CT is superior to radiography, being 5-15 times more sensitive for detecting foreign bodies. 1, 4
• Glass appears moderately hyperdense on CT (at least 2000 Hounsfield units), making it readily distinguishable from soft tissue. 1
• CT can detect glass fragments as small as 0.01 mm³ for high-density glass types. 5
• Ultrasound shows all foreign bodies as hyperechoic with posterior acoustic shadowing and can provide real-time guidance for removal. 1, 4

Clinical Pitfalls to Avoid

• Never rely solely on negative radiographs to exclude glass foreign bodies, especially for small fragments or those in anatomically complex areas. 1
• Glass foreign bodies were overlooked in 9 patients who had previous examinations limited to inspection and probing without radiographic evaluation. 3
• Retained glass can trigger granulomatous reactions and subsequent soft tissue infections including cellulitis, abscess formation, or sinus tracts. 4, 6

Practical Algorithm

1. Obtain radiographs first (multiple views) for any suspected glass foreign body. 1, 4
2. If glass is visualized on x-ray, proceed with removal planning.
3. If x-ray is negative but clinical suspicion remains high (visible wound track, palpable fragment, or mechanism suggesting retained glass), obtain ultrasound immediately. 1, 4
4. Consider CT if ultrasound is unavailable or if precise localization relative to critical structures is needed before removal. 1, 4