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Tebala et al. Mini-invasive Surg 2018;2:32 I http://dx.doi.org/10.20517/2574-1225.2018.37 Page 11 of 18

Prevention of postoperative ileus
Postoperative ileus still remains a major problem after colorectal surgery, and in particular after extensive
[89]
rectal operations, with a prevalence rate as high as 28% . Its global impact on LOS overlaps the impact
[90]
of anastomotic leak . Its etiology is multifactorial and usually is not related to a substandard surgical
technique. Smoking, major laparotomy, ASA classification and duration of surgery were considered inde-
pendent causative factors [91,92] . Molecular level evidence has recently demonstrated the role of intestinal mi-
[93]
crobioma in the regulation of bowel motility , possibly through its action on bowel macrophages, whose
[94]
activation leads to generalized intestinal nervous plexa dysfunction and paralytic ileus . This can be taken
as a confirmation of the positive role of oral non-absorbable antibiotics in the preparation of the bowel for
[49]
colorectal surgery , even if the exact mechanism of action and the bacteria species involved in the process
[50]
are not yet fully understood .
[95]
Compliance with ERAS principles is a protective factor against postoperative ileus . According to ERAS
principles, early recovery of bowel peristalsis is based on four cornerstones: (1) mini-invasive technique; (2)
restrictive fluid infusion; (3) avoidance of opiates; and (4) early re-feeding.

Multiple RCTs and meta-analyses have demonstrated that early feeding stimulates recovery of bowel func-
tion [23,96] ; this is particularly true in younger patients operated on by subspecialist colorectal surgeons using
laparoscopic techniques [97,98] .

It is well known that opioids may impair the gastrointestinal motility through a direct action on the mu-
receptors of the bowel, causing ileus and constipation. Therefore, the use of peripheral opioid antagonists
[97]
may reduce the risk of postoperative ileus . Although this has been incorporated into the American ERAS
[23]
[98]
guidelines , some Authors suggest prudence as definitive evidence is not yet available . A recent phase
2 study from Scotland confirmed that oxycodone and naloxone reduces time to first bowel motion when
compared to oxycodone only within an ERAS protocol in laparoscopic colorectal surgery, but the authors
[99]
admit that a proper RCT is still needed .

It has been proposed that chewing gum may stimulate bowel motility - via vagal stimulation or gastro-
[100]
intestinal hormones secretion - with an earlier return of intestinal function and reduced LOS , but un-
fortunately the vast majority of colorectal studies are small sized and of poor quality [101,102] . A large RCT
on 402 patients clearly demonstrated that, although there is no detriment, there is no beneficial effect
[103]
[18]
either . Although chewing gum has been added to the ERAS Society guidelines , this matter remains
unclear.
The use of oral laxatives such as magnesium oxide and disodium phosphate can reduce the time to first
[104]
[18]
bowel motion , but it has not been fully evaluated yet and it is considered a weak recommendation .
Postoperative nutrition
Early studies confirmed that early oral feeding after a colorectal operation does not increase the risk of
complications and, on the contrary, can be beneficial in reducing the post-surgical catabolism, improving
the immune function, reducing the systemic inflammatory response and reducing bacterial translocation.
The ERAS protocols suggest early re-feeding with liberal fluid intake by mouth immediately after surgery,
[18]
provided that PONV is well controlled, and early return to a normal diet . In cases where oral feeding is
not deemed to be sufficient to get a correct caloric intake, it may be necessary to add oral proteic supple-
[18]
ments .

Even if the application of simple rules can yield great results, the implementation of a specific gastrointesti-