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Variable radio-opacity of a metallic foreign body
  1. M D Weller,
  2. C A Ayshford
  1. Department of Otolaryngology, Heartlands Hospital, Birmingham, UK
  1. Correspondence to:
 Mr M D Weller
 Department of Otolaryngology, Heartlands Hospital, Birmingham, UK; wellermjblueyonder.co.uk

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A 10 year old boy was seen in the accident and emergency department giving a history of swallowing the metal disc that makes up part of the ring pull from a steel soft drinks can. He could feel it stuck in his throat, at the level of the cricoid, and it was uncomfortable to swallow. He was otherwise completely fit and well. Examination was unremarkable.

A plain AP radiograph of the neck was obtained (fig 1), with clear views to the level of the third thoracic vertebra, which was normal, and the patient reviewed. In view of the persistent symptoms, and the definite history, a lateral radiograph of the neck was performed (fig 2). This showed a radio-opaque object at the level of the first thoracic vertebra.

Figure 1

 Plain AP radiograph of the neck.

Figure 2

 Lateral radiograph of the neck.

A referral to the ENT surgeons was made, oesophagoscopy performed under general anaesthetic, and the foreign body removed. The child made a full, uneventful recovery.

DISCUSSION

There have been discussions in the medical literature previously regarding the most appropriate investigations for swallowed foreign bodies in children in the accident and emergency setting. Important factors to consider are that sharp or potentially caustic foreign bodies (such as watch batteries) should be removed, but that smooth, non-obstructing foreign bodies may be allowed to pass the length of the digestive tract without surgical intervention. It is important to remember that the narrowest parts of the gastrointestinal tract, and therefore the most likely points for obstruction to occur, are at the cricopharyngeal sphincter, the upper third of the oesophagus as it passes over the arch of the aorta and the gastro-oesophageal junction. Objects that have passed into the stomach are unlikely to impact elsewhere in the intestinal tract.

The textbooks in both ENT and accident and emergency medicine suggest that for a history of a potentially radio-opaque swallowed foreign body that has become lodged, radiographs should be obtained of the chest, abdomen, and neck (in that order) until the foreign body is seen.1,2 In a child this can be achieved in a single film. The orientation of discoid foreign bodies such as coins varies depending on their impaction in the oesophagus or trachea. In the oesophagus they will appear as a round disc on an AP film, and in the trachea they will appear side on as a bar.

The radio-opacity of various objects has been investigated previously, and it is known that ring pulls from aluminium drinks cans are radiolucent.1 Most soft drinks cans these days seem to be made from steel. In the reported case, the steel disc was not seen on the AP view, but is seen on the lateral view. This prompted a radiograph to assess whether this was actually the case (fig 3). It is clearly shown that the steel disc is visible radiographically only when viewed from the side. This is because of the increased thickness of metal when viewed from the side.

Figure 3

 Photographs and radiographs of a steel disc from a drinks can in different positions.

CONCLUSIONS

How should a suspected foreign body in the oesophagus be investigated? There seems to be a case for obtaining both AP and lateral radiographs. This would be beneficial not only for the reasons of variable radio-opacity dependent upon orientation as listed above, but also to give a better idea of anatomical location. The disadvantage of this however would be the increased radiation exposure.

There have been unusual cases reported previously where multiple radiographs have been suggested. In particular, a case reported in 1993 in which a single coin was seen in the oesophagus on the AP radiograph, which was removed endoscopically.3 A second look in the oesophagus to check for abrasion revealed a second, smaller coin that had been located either anteriorly or posteriorly to the fist and therefore not seen on AP radiography. They would have been seen as two separate coins on lateral radiography. This case, and the suggestions made by the authors to perform multiple radiographic investigations in all cases, sparked a series of letters on the subject covering the above points. Nine years later there still seems to be no consensus opinion.

Another method of investigation to consider is the use of portable metal detectors to localise the position of metallic foreign bodies. A randomised controlled study from Canada published in 2000 reported a 100% accuracy in the diagnosis of metallic foreign bodies that had been accidentally ingested.4 The difficulty with this method of investigation is that in the author’s experience there are only a minority of departments that have access to a portable metal detector.

Clinically it can be very difficult for a patient to locate precisely where a foreign body lies in the oesophagus. All cases should therefore be treated with caution and investigations tailored to suit the particular case and the department in which the case presents.

REFERENCES

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