Abstract

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Coins are frequently ingested by young children in the UK. X-Radiographs have been considered as the gold standard of detecting any swallowed metal foreign bodies in order to ascertain subsequent management. The cost of radiographs, high proportion of normal radiographs and potential long term hazards11 of ionising radiation has led some investigators to look for alternative first line diagnostic tests.
A hand held metal detector is an obvious alternative both potentially cheap and effective without the hazard of radiation. This review looks at the relevant literature in order to determine whether or not a metal detector is a suitable alternative with a good specificity and sensitivity.

Introduction

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Coins are frequently ingested by young children in the UK. X-Radiographs have been considered as the gold standard of detecting any swallowed metal foreign bodies in order to ascertain subsequent management. The cost of radiographs, high proportion of normal radiographs and potential long term hazards11 of ionising radiation has led some investigators to look for alternative first line diagnostic tests.
A hand held metal detector is an obvious alternative both potentially cheap and effective without the hazard of radiation. This review looks at the relevant literature in order to determine whether or not a metal detector is a suitable alternative with a good specificity and sensitivity.

Methods

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Search Strategy
The following databases on WebSPIRS from SilverPlatter Information N.V were searched1. Medline (1990-2002), Embase (1988-2002), PsycInfo (1990-2002), Serfile (2002), ASSIA for Health (1987-2002), AMED (1995-2002), CINAHL (1982-2002), HMIC, BNI Plus. The Cochrane Database of reviews was accessed via the University of Liverpool website2. To obtain journals, I checked the library catalogues at the Royal Liverpool Hospital, the University of Liverpool Harold Cohen Library, Liverpool John Moores library, Alder Hey Hospital, the Liverpool Medical Institute and the British Library in London.
My aim was to identify any relevant RCTs, prospective studies, meta-analyses or reviews which focused on metal detectors and ingested foreign bodies. Non-specific titles were initially included i.e. if the title referred to metal detectors in general. Free-text terms and MeSH terms chosen from the index of aditus were used. Terms were subsequently crossed with each other. Other limits included the English language.
The articles that were found were mainly from Medline1 as the other databases were either irrelevant or repeat citations from Medline. The titles and abstracts were closely looked at and determined whether or not they were truly relevant to the dissertation. I discarded any trials not relating to ingested foreign bodies. I also looked at the references of papers and obtained any which were relevant.
Guidelines from NICE3 were sought but not found. The website for best evidence in Accident and emergency was also looked at but there were no relevant articles.
From the searches 7 papers were found. Of which 6 were relevant. Further papers were identified from the references and ordered. 5 prospective studies were identified, 1 controlled trial using a model and 7 case studies. No reviews were found.

Review

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Initially concentrating on the five prospective studies found, an assessment was carried out based upon adapted published quality criteria-4-7. The assessment of papers can be seen in table 2.

Discussion

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The vast majority of ingested foreign bodies will follow a benign course with no significant complications; there have been cases of problems with retained objects in the oesophagus including perforation, airway obstruction and fistulae16-19. Children may be unreliable historians and many reporters suggest a radiograph to be done on every child with a history of foreign body ingestion20. Radiographs offer the Gold standard of diagnostic tests in this area and are highly specific, very available and offer immediate feedback. The disadvantages include the use of ionising radiation (which although realistically is negligible9,11 remains a cause of concern to mothers and fathers, we also do not know any long term effects), the logistics, the time to complete the test and the overall cost.
This however may be unnecessary especially with the combined fact of the high specificity and sensitivity a hand held metal detector offers and the relatively uncomplicated course of ingested FBs. The device uses the potential risk of radiation, it is also small, convenient and easy to use. Its cheapness is also a key issue; the cost of the entire equipment for a whole year can be recovered with the saving of one or two roentographs9.
A flow diagram of when to use the metal detector must therefore be drawn up, taking into account the issue of location, and the issue of any subsequent follow up. Combining suggestions from the papers13,10 and the algorithm in another15 a proposed flow chart is shown in fig 1.
One of the few problems that exist with the metal detector is that there is difficulty detecting metal objects less than 1 cm. The localisation can also be ambiguous at times meaning that coins identified in the epigastrium via metal detector must be classified as being in the chest as opposed to the abdomen. The other issue arises if the child swallows a non-radio-opaque metal for example aluminium? In this scenario the metal detector acts as safety net.
From the literature it seems that hand held metal detectors are viable alternatives to an X-Radiograph. If the history of a metal object ingestion is definite then a metal detector may even supercede the gold standard of X-Rays. If a patient is asymptomatic and a metal foreign body is detected below the oesophagus then the child should be discharged with the possibility of a follow up appointment in 1 week or if complications such as abdominal pain, vomiting, diarrhoea, blood in stool or pyrexia develop. If symptomatic then X-Radiograph should be done immediately with a view to subsequent invasive management.
Even though a large number of databases were searched, the specificity hoped for was not achieved. Ingested foreign coins could be expressed in various ways and a complete search would have taken more time. A possible hand search of relevant articles and databases with grey literature would have enhanced the search results. The authors of key papers could also have been approached via email along with inclusion of perhaps any unpublished data. Limits inflicted upon the size of this project may have led to a reduced number of articles appraised.

Conclusions

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Further technological advances may lead to metal detectors being able to localise the exact position of the foreign body. This will require their subsequent investigation in similar methods to referenced studies.

References

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1) www.aditus.nhs.uk
2) www.liv.ac.uk
3) www.nice.org.uk
4) Gabbay M. The evidence-based primary care handbook. (Royal Society of Medicine Press Limited, London 1999).
5) Greenhalgh T. How to read a paper: the basics of evidence based medicine. (BMJ Publishing group, London 1999)
6) Dixon R A, Munro J E, Silcocks P B. The evidence based medicine workbook: critical appraisal for clinical problem solving. Oxford: Butterworth-Heinmann, 1997
7) Sackett D L, Straus S E, Richardson W S, Rosenberg W, Haynes B R. Evidence based medicine: how to practice and teach EBM. (Churchill Livingstone, London 2000)
8) Ros S P, Cetta F. Successful use of a metal detector in locating coins ingested by children. J Paediatr 1992; 120: 752-3
9) Biehler J. Tuggle D. Stacey T. Use of the transmitter-receiver metal detector in the evaluation of pediatric coin ingestions. Pediatric Emergency Care 1993; 9(4): 208-210.
10) Tidey B. Price G. Perez Avilla C. Kenney I. The use of a metal detector to locate ingested metallic foreign bodies in children. J Accid Emerg Med 1996; 13: 341-342
11) Ros S. Cetta F. Metal detectors: An alternative approach to the evaluation of coin ingestions in children? Pediatr Emerg Care 1992; 8(3): 134-136
12) Doraiswamy N, Baig H, Hallam L. Metal detector and swallowed metal bodies in children. Accid Emerg Med 1999; 16: 123-125.
13) Sacchetti A. Carraccio C. Lichenstein R. Hand held metal detector identification of ingested foreign bodies. Pediatr Emerg Care 1994; 10(4): 204-207
14) Nathman B J, Mueller C. Asymptomatic esophageal perforation by a coin in a child. Ann Emerg Med 1984; 13: 627-629
15) Pasguariello PS, Kean H. Cyanosis from a foreign body in the esophagus. Clin Pediatr 1975; 14: 223-225
16) Vella EE, Booth PJ. Foreign body in the esophagus. Br Med J 1965; 2:1042.
17) Obiako MN. Tracheoesophageal fistula: a complication of foreign body. Ann Otol Rhinol Laryngol 1982; 91: 325-327.
18) Hodge D, Tecklenbyrg F, Fleisher G. Coin Ingestion: does every child need a radiograph? Ann.

Source(s) of Funding

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none

Competing Interests

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none

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