Effectiveness of RL- vs LL-starting Position in Unsedated Water Immersion Colonoscopy

Inclusion Criteria: * Adult ≥18 years old with the indication for colonoscopy, such as chronic diarrhea, chronic constipation, hematochezia, chronic lower abdominal pain, positive fecal occult blood test, and other change of bowel habit symptoms indicative of the need for diagnostic colonoscopy examination. Exclusion Criteria: * Patients who refuse to participate, patients with obstructive lesions in the colon distal of the cecum. , patients with experienced colon resection, patients who are hemodynamically unstable, and patients with severe cardiac disorders (such as acute myocardial infarction, unstable angina, malignant arrhythmia, and moderate to severe congestive heart failure ).