Introduction Flexible sigmoidoscopy (FS) is a validated screening test to reduce the incidence of colorectal cancer. Bowel Scope screening is due to be implemented in the UK by 2016. There is variability in FS performance between operators; internal colonoscopic markings are unreliable for colonoscope position. Three dimensional magnetic imaging systems eg Scopeguide™ (Olympus) (SG) represent real time instrument position but are not widely available. Hand-held metal detectors (HHMD) can easily localise metal objects within the body. We assessed use of HHMD to confirm flexible endoscopic tip placement at the splenic flexure (SF).
Methods Adult subjects undergoing outpatient FS/colonoscopy were eligible. When examination was judged complete to the SF, an independent observer placed the HHMD at the left 10th intercostal space, anterior-axillary line (corresponding to the internal fixation of the colon at the SF). A positive result was recorded if the HHMD beeped. Position was then assessed by SG. If SF could not be reached, the patient was excluded. We evaluated 3 HHMD from different manufacturers. Patient experience was also studied. Ethical review NREC no. 13/LO/1065.
Results 44 subjects were recruited consecutively: mean age 64 years (range 17–74), 50% male (n = 22), mean BMI 27 kg/m2 (range 20–41). Endoscopic confirmation of position at SF showed concordance with Scopeguide™ in 95% (42/44). Subjects 1–6 were examined using BDS200 (Black and Decker) HHMD. Despite promising results on training models, this proved insensitive in humans and was abandoned. For subjects 7–30 (n = 24) studied with GMS120 (Bosch), positive reading at the correct anatomical marking was recorded in 88% of examinations with SG validation. Of the 3 failures, 2 had a BMI of >30 kg/m2. Use of an X-Ray screening trolley improved specificity. For subjects 31–44 (n = 14), a detector with increased sensitivity and directional capabilities, GPP (Garrett Metal Detectors, USA), was used on standard endoscopy trolleys. This showed concordance with SG in 100% of cases (n = 14) including 4 patients with BMI >30 kg/m2. There was one true HHMD negative versus endoscopic assessment confirmed by 3D imaging. The technique was further validated by loss of signal on scope withdrawal. Patient questionnaires showed high acceptability.
Conclusion Use of HHMD in FS has shown excellent concordance with Scopeguide™ for colonoscope localisation at SF. Specificity and sensitivity are improved by adapting the specifications of the HHMD. A HHMD is an accurate and very cheap (£100 per unit) means of assuring quality during FS and further studies may confirm its role as a useful training tool especially during future service expansion.
References 1 Atkin W et al. BMJ 2010
2 Leicester R et al. Lancet 1981
Disclosure of Interest None Declared.
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