This study investigated the influence of mechanical bowel preparation (MBP) on faecal microflora, using rRNA-targeted reverse transcription–quantitative polymerase chain reaction in patients undergoing colonic cancer resection.


Forty-two patients undergoing elective colonic surgery were randomized into MBP or no-MBP groups (21 in each group). The main outcome was the bacterial microflora and faecal organic acid content of faecal material obtained at operation.


Clinical characteristics were similar in the two groups. Bowel content in the resected specimens did not differ significantly. The count of bacterial microflora, such as Bifidobacterium and total Lactobacillus, in both intraoperative faecal material and first material after surgery was significantly lower in the MBP group than the no-MBP group (P < 0·050). Levels of faecal organic acids, such as acetic acid, propionic acid and butyric acid, in intraoperative faecal material were significantly lower, and levels of lactic acid were significantly higher, in the MBP group than in the no-MBP group (P < 0·050). The succinic acid level was significantly higher after surgery than before operation in the MBP group (P = 0·008).


Preoperative MBP caused an imbalance in the bowel microflora, suggesting that it offers no advantages in terms of enterobacterial microflora for patients undergoing colonic cancer resection. Registration number: UMIN000003153 ( Copyright © 2010 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd.