The present study was to investigate if the incidence, patterns and surgical outcomes of mechanical ileus have changed in the era of minimally invasive surgery (MIS).

Mechanical ileus, generally caused by post-operative bowel adhesion, represented 12-16% of emergency surgical admissions and 20% of emergency surgical procedures. Opening the peritoneal cavity, in whatever type of surgery, leads to the formation of potentially obstructive structures (adhesions or bands) in almost 95% of patients. The adhesion resulted from the irritation of the peritoneum caused by surgical trauma or intra-abdominal infection. Bowel adhesions can lead to clinical manifestations within a few weeks or even several years after the surgery. It has been reported that traditional open surgery (TOS) for colorectal cancer were associated with a particularly higher risk of adhesion formation and related complications. Within two years after colorectal surgery, 14.3% of the patients will suffer from small bowel obstruction, and 2.6% will require a surgical intervention for the treatment of this obstruction, and this incidence is even higher after rectal surgery. Adhesive ileus has been a clinical conundrum. Overall, nearly one-fifth of patients needed re-admission for a recurrent disease, even they had been successfully treated by surgical, or non-surgical methods during the index admission.

During the last decade, minimally invasive surgery (MIS), either via laparoscopic or robotic approach, has become the standard procedures for the treatment of colorectal cancer. Theoretically, MIS is associated with a much lower rate of postoperative formation of adhesions than TOB, since adhesion formation represents a stepwise failure of peritoneal tissue repair mechanisms, which can be prevented by the clean dissection, minimal blood loss and/or less-environmental exposure of the bowel inherent in MIS. Some researchers supported this concept by showing MIS colorectal surgery is associated with fewer adhesion-related admissions than open surgery. However, most reported case series were retrospective uncontrolled studies and were liable to some uncertainty; even in some rare randomized controlled trials, the conclusions were contradictory. Moreover, adhesive ileus is just one variant of mechanical ileus; some researchers have pointed out the MIS can paradoxically create some specific types of mechanical ileus, such as internal or external herniation of small intestine, or bowel twisting over the anastomotic site, and so on. Therefore, it remains unclear whether MIS colorectal resection can reduce the incidence of the mechanical ileus and improve the long-term bowel function, as compared with the TOS.

Considering the aforementioned reasons, we conducted the present study to investigate if the incidence, patterns and the treatment outcomes of post-operative mechanical ileus changed in the era of MIS for colorectal cancer.

Inclusion Criteria:

• patients whose primary colorectal cancers were resected in the fashion of curative and elective surgery.

Exclusion Criteria:

• patients who underwent palliative or emergency surgery to treat their primary colorectal cancer;
• patients encountered anastomotic leakage, intra-abdominal abscess or the other surgical complications requiring an additional abdominopelvic surgical or non-surgical procedures to treat the complications;
• simultaneously underwent some other abdominal or pelvic surgical procedures before or after the primary colorectal surgery, e.g., reverse Hartmann's procedure or closure of the temporary colostoma.

The patients who diagnosed as colorectal cancer and underwent curative intent surgery