Endoscopy is a widely used modality for the diagnosis and classification of Gastroesophageal reflux disease (GERD), and the extent of esophageal mucosal breaks on endoscopy can be assessed. However, there were some limitation in diagnosis of GERD using endoscopy

1. More than half of patients with GERD reveal no visible abnormality on conventional endoscopy, it is possible that minute mucosal changes are underestimated by conventional endoscopy due to the limitation of visual ability
2. In addition of uncertainty in detecting mucosal breaks, uncertainty in describing severity of mucosal injury can lead to inconsistency among interpreters. Interobserver agreement regarding diagnosis and classification of GERD using endoscopy is unsatisfactory to apply daily practice.

Thus, the development of a new method to define the intra-esophageal injury for use in daily practice is a worthwhile endeavor and developed, such as narrow-band imaging (NBI), Fuji Intelligent Chromoen-doscopy (FICE) and i-scan.

Among them, i-scan technology is the most recently developed image enhancing technology, which consists of three modes of image enhancement, i.e. surface enhancement (SE), contrast enhancement (CE), and tone enhancement (TE).

Thus, the investigators examined the hypothesis that i-scan can improve the detection rate of reflux esophagitis and inter-observer agreement between endoscopists compared with conventional white light (WL) endoscopic examination.

Gastroesophageal reflux disease (GERD) is a condition that develops when reflux of stomach contents causes troublesome symptoms and/or complications. It is the most frequent problem in upper gastrointestinal tract in outpatient clinic and contributes substantially to morbidity and to costs. Endoscopy is a widely used modality for the diagnosis and classification of GERD, and the extent of esophageal mucosal breaks on endoscopy can be assessed. However, because more than half of patients with GERD reveal no visible abnormality on conventional endoscopy, it is possible that minute mucosal changes are underestimated by conventional endoscopy due to the limitation of visual ability.

In addition of uncertainty in detecting mucosal breaks, uncertainty in describing severity of mucosal injury can lead to inconsistency among interpreters. Asian gastroenterologists tend to diagnose endoscopically before they treat patients with symptoms suggestive of GERD and use the modified Los Angeles (LA) classification system that includes minimal changes as constituting a distinct grade of reflux esophagitis. In modified LA system, minimal change esophagitis is characterized by the mucosa such as erythema and/or whitish turbidity. However, because substantial overlap is noted between normal and minimal change, minimal change and LA class A, and LA class A and B, interobserver agreement regarding diagnosis and classification of reflux esophagitis is unsatisfactory to apply daily practice. Thus, the development of a new method to define the intra-esophageal injury for use in daily practice is a worthwhile endeavor.

Currently, new imaging technologies have applied in endoscopy to improve detecting and differentiating the subtle mucosal changes using digital contrast method such as narrow-band imaging (NBI), Fuji Intelligent Chromoen-doscopy (FICE) and i-scan. Among them, i-scan technology is the most recently developed image enhancing technology, which consists of three modes of image enhancement, i.e. surface enhancement (SE), contrast enhancement (CE), and tone enhancement (TE). SE enhances light-dark contrast and CE adds blue color in relatively dark areas digitally, by obtaining luminance intensity data for each pixel. Applying SE and CE might allow detailed observation of subtle irregularities around the surface and TE analyzes the individual RGB components of a normal image and recombines the color frequencies of each component to enhance minute mucosal structures with subtle color changes.

Thus, the investigators examined the hypothesis that i-scan can improve the detection rate of reflux esophagitis and inter-observer agreement between endoscopists compared with conventional white light (WL) endoscopic examination

Inclusion Criteria:

• aged 18 to 80 years
• completed standard questionnaire including upper gastrointestinal symptoms
• underwent screening endoscopy

Exclusion Criteria:

• a patients with history of gastrointestinal surgery such as gastrectomy, fundoplication, or distal esophagectomy
• a patients were not able to record video clips during the period of examination of the gastro-esophageal junction