Magnetic endoscope imaging: a new technique for localizing colonic lesions

The precise localization of advanced colorectal lesions preoperatively directs the appropriate surgical management. The use of internal landmarks at colonoscopy can be inaccurate, and other methods are therefore necessary to localize lesions precisely. Magnetic endoscope imaging (MEI), a real-time, nonradiographic technique for imaging of the colonoscope, may assist in determining the location of lesions found at colonoscopy.

A prospective study was carried out to determine the accuracy of MEI for localizing the colonoscope tip anatomically. The MEI system was used to identify one of four predetermined locations within the colon. Once identified, two endoscopic marking clips were attached to the colonic mucosa, and 400 - 500 ml of Urografin radiographic contrast medium was injected to produce an air-contrast "enema." The clips were subsequently localized using plain abdominal radiography, assessed by a single experienced radiologist who was blinded to the colonoscopic findings.

Twenty-nine consecutive patients were enrolled in the study. The overall accuracy of MEI in comparison with the air-contrast "enema" was 90 % (26 of 29 cases). There were three slight errors of localization - clips localized to the descending rather than the sigmoid-descending colon junction (n = 1), or to either side of the mid-transverse (n = 1) and hepatic flexure (n = 1) - but these were not considered to be of surgical or clinical importance.

MEI is a reliable and accurate method for determining the anatomical position of the endoscope tip during colonoscopy. When it becomes commercially available, we believe the use of MEI will avoid the need for unnecessary barium enemas for localization of lesions prior to definitive surgery.