Handheld Metal Detector Screening for Metallic Foreign Body Ingestion in Children

Summary

Here, we present a protocol to use the handheld metal detector, to screen for the presence of ingested metallic foreign bodies in children who present to the pediatric emergency medicine department with a history of foreign body ingestion.

Abstract

Coins are the most common ingested metallic foreign bodies among children. The goal of this protocol is to assess the accuracy and feasibility of using a handheld metal detector to detect ingested metallic foreign bodies in children. We propose that by introducing handheld metal detector screening early in the triage process of children with high suspicion of metallic foreign body ingestion, the number of radiographs being ordered to localize the metallic foreign body can be reduced in this radio-sensitive population. The study protocol requires the screening of the participants for history of foreign body ingestion and exclusion of patients with respiratory distress or metallic implants. The patient changes to hospital gown and items that could contain metal like eyeglasses, earrings, pendants, and ornaments are removed. The patient is positioned in the center of the room away from other metallic interferences. The working status of the handheld metal detector is first confirmed by eliciting a positive audio-visual signal. Then the screening is done in an erect position with head in extension to expose the neck, from the level of the chin to the level of the hip joint, to cover the anatomical areas from neck to pelvis in a zig-zag manner both anteriorly and posteriorly. A positive audio-visual signal is carefully noted during the scanning for the presence of metallic foreign body. Relevant radiographs are ordered as per the area detected on the metal detector screening. The handheld metal detector was able to precisely identify all the coins among the ingested metallic foreign bodies in our study. The handheld metal detector could not consistently detect non-coin metallic foreign bodies. This protocol demonstrates the accuracy of handheld metal detector in the identification and localization of coins and coin like metallic foreign bodies.

Introduction

Foreign body ingestion is a widespread problem among children presenting to the pediatric emergency department because of the natural inquisitive nature of infants and children to explore objects by tasting and swallowing them^1,2. Previous studies have reported that metallic objects constituted 85% of all foreign body ingestions in their cohort of patients^3,4. The goal of this protocol is to assess the accuracy and feasibility of using a handheld metal detector to detect ingested metallic foreign bodies in children. We propose that by introducing the handheld metal detector screening protocol early in the triage process of children with high suspicion of metallic foreign body ingestion, the number of radiographs being ordered to localize the metallic foreign body can be reduced in this radio-sensitive population.

Handheld metal detector (HHMD) is an inexpensive, easily accessible adjunct that can help expedite the management of ingested metallic foreign bodies. Metal detector is a very low frequency device, which has a receiver and a transmitter that detects the change in its electromagnetic field caused by the presence of a metallic object in its vicinity³. If a metallic object is within the field, the electromagnetic field is disrupted and the sensor will set off an audio-visual alarm on the device⁴. The metal detector examination can be thoroughly performed in less than 2 minutes⁵. Hence, the HHMD screening can be introduced early in the triage process of children with high suspicion of metallic foreign body ingestion for topographical localization.

Coins are the most common swallowed metallic foreign bodies^1,4,6,7. Due to the lack of sharp edges and general non-toxic nature, the majority of coin ingestions are managed conservatively. Other types of materials commonly ingested include magnets, button batteries, small toys, peanuts, jewelry, buttons, bones, seeds, and popcorn^8,9. Impaction of foreign bodies most commonly occurs in the esophagus at three sites, namely upper esophageal sphincter, mid-esophagus at the level of aortic arch, and lower esophageal sphincter¹⁰. Metallic foreign bodies (MFBs) located in the esophagus may be asymptomatic in 40% of patients^11,12 and its prolonged impaction can lead to various complications like esophageal perforation, mediastinitis, tracheoesophageal fistula, tracheal stenosis, and aorto-esophageal fistulas^1,13,14,15. Other locations of foreign body impaction include pylorus, duodenum, and ileo-caecal junction¹⁰.

Performing radiographs of neck, chest, and abdomen to diagnose suspected foreign body ingestion is a widespread practice in the emergency departments⁵. Among all types of the ingested foreign bodies, only 10% are radio-opaque¹⁰. The radiological tests are time-consuming and have a risk of radiation exposure in children. Precise topographical localization of ingested metal objects is very crucial to guide therapy. The introduction of HHMD screening early in the triage process can help mitigate extraneous ordering of radiographs by topographically localizing the ingested metallic foreign body.

This study evaluated the accuracy of HHMD to localize MFBs in a systematic topographic fashion and determined the effectiveness and feasibility of HHMD in the local Pediatric population. We also examined how well this radiation free screening tool was accepted by the patients and parents. Between May and July 2016, all the consecutive patients who presented to the pediatric emergency department with a history of foreign body ingestion were included in the study. Informed consent was obtained from the parent or legal guardian. Patients with alleged foreign body ingestion were systematically scanned using HHMD. The gold standard of care for identification and localization of ingested metallic foreign bodies is performing plain radiographs of the cervical area, thorax, and abdomen. To facilitate the conduct of the study, a standardized workflow was created (Figure 1). A log book specifically created based on the workflow was used to collect the initial data, which were subsequently transcribed to a spreadsheet (Figure 2). The data in the result section are depicted as the number of cases followed by percentages.

Protocol

The protocol follows the guidelines of Institutional Human Research Ethics committee. The central institutional review board provided the ethics approval for the study.

1. Participant Screening

1. Recruit patients who present to the pediatric emergency department with history of foreign body ingestion.
2. Exclude the patients who are in respiratory distress and has implanted devices like pace makers.

2. Prepare the Patient

1. Dress the patient in a hospital gown.
2. Remove all items that may contain metallic objects such as clothes, eye glasses, earrings, pendants, and ornaments prior to the examination to avoid interference with the HHMD screening.
3. Place the patient in the center of the room away from other potential metallic interferences.

3. Prepare the Examiner and Caregivers

1. Remove all metallic accessories such as jewelry and watch.
2. Request the caregiver to remove all metallic accessories such as jewelry and watch.

4. Metal Detector Screening

1. Use the HHMD (Figure 1) to conduct the screening.
2. Confirm the working status of the HHMD by eliciting a positive audio-visual signal by waving over a piece of metal.
3. Perform the HHMD scanning in a standing position for bigger children.
4. Perform the HHMD scanning in an erect position for infants by having the caregiver hold the patient appropriately.
5. Hold the hands of the patient up and away from the body.
6. Position the head of the patient in extension to expose the neck.
7. Scan from the level of the chin to the level of hip joint to cover the anatomical areas from neck to pelvis.
8. Perform the scan in a zig-zag manner across the body to ensure that every area has been scanned.
9. Scan both anteriorly and posteriorly as the thickness of patient must be taken into consideration.
10. Carefully note the positive audio-visual signal during the scanning for the presence of MFBs.

5. Perform the Relevant Radiograph

1. Order the relevant radiograph of the neck, chest, or abdomen, as per the area detected by the HHMD screening for the MFBs.
2. Proceed with all the X-ray views (neck, chest, and abdomen) if the MFB was not detected during HHMD screening and the clinical index of suspicion for foreign body ingestion is high.

6. Record the Test Results

1. Record the test results in the logbook (Figure 2) specifically created based on the workflow (Figure 1).
2. Correlate the positive audio-visual HHMD signal with the underlying bony landmark on the body, by palpating the following prominent bony landmarks - sternal notch, xiphisternum, pubic symphysis, and bilateral Iliac crest.
3. Record the landmark on the logbook's anatomical reference outline before proceeding with the X-ray examination.

Results

The researchers recruited 36 patients for this observational study. These patients had presented to the pediatric emergency department with a history of foreign body ingestion. Among these, 28 patients had metallic foreign body ingestions (Figure 3). The remaining 8 patients had ingested non-metallic foreign bodies such as fish bones, satay stick, and plastic button. Coins were the most common type of foreign body ingested (Table 1), which co...

Discussion

Metallic foreign body ingestion in children is a common problem and in the majority of patients, this is managed conservatively^7,16. Single or repeated radiographs can expose the radio-sensitive pediatric population to unwanted radiation risk while attempting to localize the ingested metallic foreign body. Several studies have described the use of metal detectors in MFB ingestion in children, with sensitivity more than 96% and specificity greater than 80%

Materials

Name	Company	Catalog Number	Comments
Hand held metal detector	Garrett Super Scanner V	NA	NA