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Myths in Emergency Medicine: The Metal Detector for Ingested Coins?

May, Natalie MBCHB, MPHE

doi: 10.1097/01.EEM.0000526105.48943.61
Myths in Emergency Medicine

Dr. May is a specialist in emergency medicine with paediatric emergency medicine in the UK and a registrar in prehospital emergency medicine in Sydney, Australia. She writes regularly for http://StEmlynsblog.org. Follow her on Twitter @_NMay, and read her past articles at http://bit.ly/EMN-MythsinEM.

Ingestion or insertion of a foreign body is a common reason for children to present to the emergency department. Coin ingestion, observed or suspected, is seen fairly often: One UK ED reported 484 cases over seven years. (Emerg Med J 2013;30[2]:1572.) Coins are the usual culprits when it comes to foreign bodies and pediatric patients, reflecting their easy accessibility and apparent attractiveness to children. (Am J Emerg Med 2004:22[5]:335; Pediatr Emerg Care 2005;21[9]:582; Med Teach 2012;34[6]:510; Ann Otol Rhinol Laryngol 1991;100[4]:320.) Standard practice is to x-ray these patients if we suspect that a coin might have been ingested, but what if a radiation-free alternative was available?

This is where the humble metal detector comes in.

Several EDs around the world have compared metal detectors with radiographs for identifying intra-oesophageal coins; some papers looked at whether the metal detector could reliably indicate the presence of a coin and others at identifying the location because intraesophageal impaction is what really concerns us. These papers used “above the nipple line” or “above the xiphisternum” as the anatomical landmark.

Some methodological inconsistencies exist among the papers, but the sensitivity is pretty good. The Seikel paper trained users on metal detectors, and yielded impressive sensitivity and negative predictive value with corresponding 95% confidence intervals.

Should we use the metal detector for all patients? A few caveats are important to consider. The patient should be completely asymptomatic at presentation and assessment; symptomatic patients are more likely to have impacted objects. We must also be certain that the object is not a high-risk ingestion, such as a button battery, two or more magnets, or a lead-containing object. These situations might necessitate urgent removal, and the metal detector will not distinguish the object with the same accuracy as radiographs. The patient also should have no anatomical factor that might increase the risk of impaction, such as previous oesophageal surgery.

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Not Sensitive Enough?

What happens to the coins we miss? Where metal detector assessment is uncertain, we should default to radiographs, but remember that not every patient has a coin to find. Nafousi, et al., employed watchful waiting for coins identified as being in the esophagus using serial x-ray assessment, and found that 90 percent passed into the stomach spontaneously within 18 hours. (Emerg Med J 2013;30[2]:1572.) Their paper also provides an estimate of coins actually in the esophagus—just 13 percent of presentations.

It might be reassuring to note that Miller, et al., looked at “chronic” foreign bodies, and found that 50 percent of those with esophageal coins present for more than two weeks had hallmarks of esophageal damage, which were considered serious complications. Remembering, though, that by now we are talking about a small proportion of our original population of possible ingestions. (Int J Pediatr Otorhinolaryngol 2004;68[3]:265.) Ramlakhan, et al., looked at complication rates following the introduction of their metal detector protocol, and found “no significant adverse outcomes for any of the patients in the study for a minimum of 9 months after the last presentation used in the data collection.” (Emerg Med J 2006;23[6]:456.)

Perhaps it's time to consider introducing the metal detector along with a departmental protocol for its use, careful safety-netting, and operator training to reduce the time these patients spend in our EDs and the radiation to which they are exposed.

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