Gimeno-García et al. (2019)19 A structured LRD the day before the examination for breakfast, lunch, and snacks and a CLD for dinner designed by an endocrinologist specialized in nutrition. A structured LRD for 3 days before the examinations for all meals and a CLD for the last dinner before the examination designed by an endocrinologist specialized in nutrition. 2-L split-dose polyethylene glycol plus ascorbic acid. Positive FOBT: 49 (25.0) Positive FOBT: 51 (26.3) Postpolypectomy surveillance :34 (17.3) Postpolypectomy surveillance: 38 (19.6) Change of bowel habit: 25 (12.8) Change of bowel habit: 18 (9.3) Anemia: 19 (9.7) Anemia: 22 (11.3) Rectal bleeding: 24 (12.2) Rectal bleeding: 19 (9.8) Inflammatory bowel disease: 14 (7.1) Inflammatory bowel disease :16 (8.2) Abdominal pain: 14 (7.1) Abdominal pain: 13 (6.7) Screening in first-degree relative: 12 (6.1) Screening in first-degree relative: 15 (7.7) Jiao et al. (2019)20 LRD one day before colonoscopy, and then fasted for about 11 hours (10 PM to 9 AM on the day of the procedure). LRD three day before colonoscopy, and then fasted for about 11 hours (10 PM to 9 AM on the day of the procedure). 3-L PEG electrolyte solution between 9 to 11 AM on the day of colonoscopy, followed by oral administration of 30 mL simethicone. Constipation history: 20 (18.02) Constipation history: 24 (21.82) Digestive tract symptoms: 81 (72.97) Digestive tract symptoms: 91 (82.73) Jiao et al. (2020)24 Low-residue foods refer to foods that have a low fiber content, including rice porridge, noodles, taro, bread, tofu, Chinese steamed eggs, chicken, some peeled and cored fruits, and cooked vegetables (such as apples and carrots). Patients were told to avoid eating vegetables, fruits, and whole grains. Patients began the LRD 1 day before the colonoscopy and started fasting (food and water) at 10:00 PM the day before the examination. Low-residue foods refer to foods that have a low fiber content, including rice porridge, noodles, taro, bread, tofu, Chinese steamed eggs, chicken, some peeled and cored fruits, and cooked vegetables (such as apples and carrots). Patients were told to avoid eating vegetables, fruits, and whole grains. Patients began the LRD 2 day before the colonoscopy and started fasting (food and water) at 10:00 PM the day before the examination. 3 L of PEG-ES from 9:00 AM to 11:00 AM on the day of the examination, followed by 30 mL of simethicone. Gastrointestinal symptoms (abdominal pain, bloating, altered bowel habit, bloody stool, etc.)=112 (69.57) Gastrointestinal symptoms (abdominal pain, bloating, altered bowel habit, bloody stool, etc.)=101 (63.13) Taveira et al. (2019)21 A 1-day LRD for all meals until dinner of the day before colonoscopy suggested by the Nutrition department. A 3-day LRD for all meals until dinner of the day before colonoscopy suggested by the Nutrition department. 3-L PEG preparation on the late afternoon of the day prior to the examination and a 1-L PEG preparation in the morning of the day of the examination, ending 4 hours before the scheduled examination time. Screening: 39 (18.9) Screening: 40 (19.4) Symptoms/diagnostic: 23 (11.2) Symptoms/diagnostic: 14 (6.8) Polypectomy: 40 (19.4) Polypectomy: 41 (19.9) Postpolypectomy surveillance: 97 (47.1) Postpolypectomy surveillance: 102 (49.5) Family history of colorectal cancer: 7 (3.4) Family history of colorectal cancer: 9 (4.4) Machlab et al. (2021)22 An endocrinologist specialized in nutrition devised dietary instructions for one day. Subjects were provided with a logbook and instructed to record their diet one day before colonoscopy. An endocrinologist specialized in nutrition devised dietary instructions for three days. Subjects were provided with a logbook and instructed to record their diet one day before colonoscopy. Low volume PEG plus ascorbic acid in split-dose regimens was prescribed. The first dose was administered in the evening before colonoscopy at 20:00 hours. The second dose was scheduled to finish 2 to 4 hours before the colonoscopy CRC screening: 420 (100) CRC screening: 416 (100) Scaglione et al. (2023)23 Daily intake of less than 10 g of fiber for one day, contained in specific foods were formulated under the guidance of a nutritionist. Daily intake of less than 10 g of fiber for three days, contained in specific foods were formulated under the guidance of a nutritionist. PEG (4 L) Positive FOBT: 63 (44.7) Positive FOBT: 66 (46.2) PEG+bisacodyl (2 L) Abdominal pain: 31 (22) Abdominal pain: 27 (18.9) PEG+ascorbate (2 L), Bowel habit modification: 21 (14.9) Bowel habit modification: 18 (12.6) Sodium picosulfate+magnesium citrate Bleeding: 18 (12.8) Bleeding: 19 (13.3) Post-polipectomy surveillance: 9 (6.4) Post-polipectomy surveillance: 11 (7.7) Anemia: 11 (7.8) Anemia: 6 (4.2) Family history: 9 (6.4) Family history: 8 (5.6) Inflammatory bowel diseases: 5 (3.5) Inflammatory bowel diseases: 8 (5.6) Weight loss: 5 (3.5) Weight loss: 4 (2.8)