Inclusion Criteria:  All patients aged >= 18 years old Undergoing diagnostic OGD for evaluation of their symptoms in the Prince of Wales Hospital will be included in the study.  Exclusion Criteria:  Patients in which a full endoscopic examination is not required including patients with a specific diagnostic purpose without the need for a full evaluation, follow-up endoscopy within 8 weeks for a previously diagnosed disease or condition, Patients' condition requiring therapeutic endoscopy, Early termination of endoscopy due to patient intolerance, presence of large amount of food residue, presence of mechanical obstruction or for reasons of safety, Patients with altered anatomy such as history of esophagectomy, gastrectomy, gastric bypass surgery, or Whipple's operation, Patient who are not suitable for EGD examination (such as acute peritonitis with suspected perforated bowel) Pregnant females Patients who refuse to participate in the study Patients who are unfit for consent.