Bowel Preparation Before Surgery

General Principles for Colorectal Surgery

The American Society of Colon and Rectal Surgeons recommends that mechanical bowel preparation (MBP) should not be used routinely for most elective colorectal surgeries, but combined MBP with oral antibiotics is strongly recommended when bowel preparation is indicated, particularly for rectal surgery with anastomosis 1, 2, 3
Routine mechanical bowel preparation should be avoided for elective colonic resections, as it causes dehydration, electrolyte imbalances, patient discomfort, and provides no clinical benefit in reducing anastomotic leaks, wound infections, or mortality 1, 2, 4
MBP alone actually increases spillage of bowel contents and may worsen outcomes 2, 4
For low anterior resection with planned diverting ileostomy, MBP may be necessary, though evidence is limited 1, 5
For total mesorectal excision (TME) with diverting stoma, consider MBP (weak recommendation due to low evidence) 1, 5
For laparoscopic low rectal surgery, one trial showed higher infectious morbidity without MBP when >80% had diverting stomas 1, 5

The American College of Surgeons recommends that routine MBP should not be used for elective gynecologic procedures 6, 7
No evidence supports the benefit of MBP in gynecologic surgery 6, 7
MBP is not indicated before hepatic resection 8
No studies or evidence support the use of MBP in liver surgery 8

The American Society of Anesthesiologists recommends that clear liquids be permitted until 2 hours before anesthesia induction 2, 6, 3, 4, 7
A light meal is permitted until 6 hours before induction 6, 7, 9
A full meal requires 8+ hours of fasting 6, 7
Carbohydrate loading with 400 mL of complex carbohydrate drink (50g CHO) 2 hours before surgery reduces insulin resistance and improves outcomes 3, 8, 9

The American Gastroenterological Association recommends that for diagnostic colonoscopy, split-dose preparation is superior 10
The second portion of the preparation should begin 4-6 hours before colonoscopy 10
The preparation must be completed at least 2 hours before the procedure start 10
Every additional hour between the last purgative and colonoscopy decreases preparation quality by 10% 10