In the present study, we examined POI in 213 cases of CRC surgery. The incidence of POI was 21 (9.9%). This frequency was almost the same as previously reported. Cases with POI showed a significant extension of hospital stay: 21.7 days compared to 14.7 days for non-POI cases. Previous reports have also reported that POI leads to extended hospital stays. Furthermore, in this study, a low SMI was an independent predictor of POI. To our knowledge, this is the first report on the relationship between POI and a low SMI. We report that SMI is a useful predictive marker for the occurrence of POI.
To date, several risk factors of POI have been reported, including hypoalbuminemia, lung disorders, male sex, a large amount of bleeding, and a long operation time [7, 9–12, 23]. The implementation of standardized accelerated postoperative care pathways, namely oral antibiotic bowel preparation, early NG tube removal, early ambulation, early oral feeding, patient education, opioid-sparing epidural analgesia, perioperative fluid management, and minimally invasive surgical techniques has been reported to reduce the risk of POI [7, 24]. However, despite the widespread implementation of these measures, the incidence of POI for CRC is still reported to be 10%-30% after abdominal surgery [7, 9] and 15%-30% after colon and rectal surgery [10–12]. Therefore, predicting POI is very important in CRC surgery.
In the present study, univariate and multivariate analyses demonstrated that bleeding was associated with POI. However, the relationship between the POI and the previously reported non-bleeding data (hypoalbuminemia, lung disorders, male sex, and a long operation time) has not been elucidated in this study. Regarding the influence of bleeding on POI, it has been reported that an increase in hemoglobin drop due to the addition of colloidal fluid for intraoperative bleeding causes electrolyte imbalance, inducing intestinal edema . Our results also demonstrated an association between bleeding and POI.
PSM was performed to further reduce the selection bias. As a result, a low SMI was found to be the only independent POI predictor in our examination of 74 matched cases.
The importance of sarcopenia in perioperative management has been shown in recent years, and there are a number of reports on the relationship between sarcopenia and postoperative complications. Lieffers et al. reported that 39% of 234 CRC surgery patients had sarcopenia, and the sarcopenia group showed a longer postoperative stay and more frequent infectious complications than the non-sarcopenia group . Furthermore, the association between sarcopenia and postoperative complications has also been reported in patients with other cancer types such as esophageal cancer, gastric cancer and pancreatic cancer [25–28].
However, to our knowledge, no report on the relationship between SMI and POI has yet been published. There have been recent reports of decreased intestinal peristalsis in patients with sarcopenia. According to the report by Vaes et al., the generation of contractile forces by the gastrointestinal musculature is further regulated by the smooth muscle contractile activity, and the enteric nervous system, consisting of the myenteric plexuses and the interstitial cells of Cajal. In cancer patients with sarcopenia, a decreased expression of a contractile smooth muscle marker called smoothelin and the accumulation of collagen around the intestinal plexus are both known to occur, thus resulting in an impairment of both the intestinal smooth muscle contractile function and its regulation . An in vivo study showed that the loss of smoothelin resulted in irregular slow wave patterns, impaired intestinal contraction, and hampered intestinal transit . It was also reported that structural alterations in the myenteric plexus in tumor-bearing rats resulted in decreased upper gastrointestinal transit .
These previous findings therefore suggest that patients with sarcopenia already have factors that predispose them to intestinal motility disorders, so they may be prone to developing POI induced by surgical intervention.
Our present findings suggested that sarcopenia in cancer patients was associated with the development of POI. It is important to predict the occurrence of POI, and by promoting intestinal peristalsis and inserting an NG tube for postoperative nausea, aspiration due to ileus can be prevented. Preoperative sarcopenia patients are at high risk of developing POI, so it is important to take appropriate measures, such as promoting intestinal peristalsis early after surgery and inserting a NG tube early when symptoms appear, to prevent POI.
However, several limitations associated with the present study warrant mention. First, this study was retrospective and conducted in a single institution with a relatively small sample size. Second, the definition of a low SMI was determined by a BIA, and we did not investigate muscle power or function. Currently, there are no clear criteria for sarcopenia in Japanese patients, so it is also necessary to consider whether or not the SMI is appropriate for defining sarcopenia. Finally, although we determined cut-off values for the SMI based on the results of ROC curve analyses as an objective statistical method, an optimal standardized method for determining optimal cut-off values should be established. Further prospective studies with larger numbers of patients are needed to validate the utility of the preoperative SMI for predicting POI.