After its surgical manipulation, each part of the gastrointestinal tract recovers its normal motility at different times, on average: the small bowel in the first 12 h, the stomach in the first 24 to 48 h, and the colon in 3 to 5 days. In the postoperative period, some patients present with an inhibition of the coordinated activity of the gastrointestinal tract which contributes to the accumulation of fluids and gas that in turn causes nausea, vomiting, abdominal distension, and constipation. This is traditionally defined as postoperative ileus and is the most common cause of delayed hospital release in the United States.1,2

Gastrointestinal tract motility is controlled by 3 different nervous systems: the parasympathetic, sympathetic, and intrinsic. The parasympathetic system increases motility, whereas the activation of the sympathetic system decreases it. Unlike the most proximal segments, the cellular configuration of the colon conditions less coordination of its motility, making it practically independent from the rest of the gastrointestinal tract; its motility depends mainly on the presence of content and on its extrinsic innervation. Surgical stress conditions a sustainedly increased sympathetic tone.1

The release of inflammatory mediators also contributes to the development of postoperative ileus. Intestinal manipulation conditions an increase in vascular permeability, inflammatory cell migration to the muscle layer, and augmented production of nitric oxide, prostaglandins, vasoactive intestinal peptide, calcitonin, and substance P. Other theoretical mechanisms are: the release of endogenous substances by the intestinal bacteria,1 postoperative pain, overhydration, the administration of general anesthesia, and the use of opioid analgesics.2,3

The diagnosis of prolonged postoperative ileus is eminently clinical, given that there is no laboratory or imaging study that confirms or excludes it. The usefulness of radiologic studies is evident when mechanical obstruction or some other specific cause is suspected.3 The endpoints that are traditionally used in studies that investigate the resolution of postoperative ileus are subjective: the return of peristalsis, first bowel movement, and tolerance of oral diet.2,3 Currently, there is no internationally accepted definition, and thus its incidence is estimated at between 3 and 32% of the cases of major abdominal surgery.4,5

Vather et al. (2013) recently published a meta-analysis of 52 publications and proposed the definitions of “normal postoperative ileus” and “prolonged postoperative ileus”:4

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  Normal postoperative ileus: absence of passage of flatus/stool or inability to tolerate oral diet before the fourth postoperative day.

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  Prolonged postoperative ileus: 2 or more of the following criteria after the fourth postoperative day:

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    Nausea or vomiting.

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    Inability to tolerate oral diet.

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    Absence of passage of flatus or stool.

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    Abdominal distension.

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    Radiologic confirmation.

The aim of our study was to investigate the preoperative, intraoperative, and postoperative risk factors for the development of prolonged postoperative ileus in patients that underwent elective colon resection due to any cause, and to identify the most useful factors in its prevention.

A retrospective, observational, cross-sectional, and analytic study was conducted on all the patients above 16 years of age that underwent elective colon resection due to any cause within the time frame of March 2011 and September 2014 at the Hospital Christus Muguerza Alta Especialidad, a private tertiary care hospital in the northeast of Mexico. All the surgeries were performed by general or colorectal surgeons affiliated with the medical staff of the hospital.

The variables included were: sex, age, body mass index, previous abdominal surgeries, and the classification of surgical risk according to the American Society of Anesthesiologists (ASA); also included were the comorbidities of heart disease, smoking, diabetes mellitus, high blood pressure, chronic obstructive pulmonary disease, and prior treatment with chemotherapy or radiotherapy.

With respect to the surgical procedure, the following elements were documented: days of hospital stay, preoperative hemoglobin values, procedure indication (malignancy vs benign disease), type of procedure, conventional vs laparoscopic approach, estimated surgery duration, estimated anesthesia duration, estimated blood loss, intraoperative transfusions, and the use of intraoperative opioids (expressed in milliequivalents of morphine).

The documented postoperative variables were the time of the first passage of flatus, time of the first passage of stool, time of appearance of peristalsis, and time of toleration of oral diet. The documented postoperative management variables were the use of parenteral nutrition, prokinetics, opioid analgesics or nonsteroidal anti-inflammatory drugs (NSAIDs), anti-thrombotic prophylaxis, and the need for intensive care management.

A total of 95 patients were found during the study period and they were distributed as follows: 2011, 20 (21%); 2012, 16 (18%); 2013, 32 (33%); and 2014, 24 (26%). The decision was made to calculate a significant sample with a 5% percentage of error and a 95% confidence interval, which resulted in 76 cases. Complete information was obtained for 89 patients (93%) and 4 patients were excluded due to early complication or death. The final analysis included 85 patients, conferring a significance level on the sample that was close to 99%.

The register of values, formula calculations, graphs, conversions, and result interpretations were performed using the Microsoft Excel 2013 program. The inferential statistical analysis was carried out with MedCalc Statistical Software version 14.8.1.

The definition we used for prolonged postoperative ileus followed the recommendations published by Vather et al. (2013): the absence of passage of flatus/stool or inability to tolerate oral diet ≥ 4 postoperative days. The sample was divided into 2 groups (ileus/non-ileus) and odds ratio (OR) tests were performed to validate each variable as a risk factor for prolonged postoperative ileus. The values were expressed as crossed products and 95% confidence intervals. Chi-square tests were also carried out for statistical significance and the Fisher's exact test was used for the variables that had values below 5.

Some of the continuous variables were converted to discrete dichotomies to facilitate their analysis:

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  BMI: presence or absence of obesity (BMI ≥ 30).

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  Surgery duration: duration longer or not longer than 180 min.

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  Anesthesia duration: duration longer or not longer than 180 min.

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  Intraoperative bleeding: blood loss approximately greater or less than 500 ml.

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  Preoperative hemoglobin level: presence or absence of anemia (M < 13, W < 12 g/dl).

The present study identified the administration of only 2 narcotic medications: fentanyl and sufentanil. They are both morphine derivatives and the values were converted to morphine equivalents to facilitate their analysis. The following conversion parameters were used:

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  Fentanyl: conversion factor of 0.1.

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  Sufentanil: conversion factor of 1.

All statistically significant cases had a p ≤ 0.05.

The present study analyzed 25 potential predictors of prolonged postoperative ileus in patients that underwent elective colon resection. However, the greatest limitation of our study was the small number of patients that met the inclusion criteria. In addition, we only presented the experience at a single center in which there was no standardized colon surgery service. But unlike other published studies, ours has the advantage of analyzing the incidence of postoperative ileus in different pathologies.

The analysis of the 85 study patients demonstrated a 22.3% frequency, which is slightly above that published by Chapuis et al.5 (14%), Millan et al.6 (15.3%), or Kronberg et al.7 (10.2%). As mentioned above, there is no standardized definition of prolonged postoperative ileus among the studies evaluated, and it tended to be defined as the absence of the passage of flatus or stool between postoperative days 3 and 6.

One of the main goals of this protocol was to investigate the correlation of variables published as risk factors in other studies. Those variables include male sex, age, the need for intraoperative transfusion, the presence of pulmonary disease as a comorbidity, previous intra-abdominal surgery, the use of intraoperative opioids, blood loss, and a surgery duration longer than 3 h. In our case series of patients, only obesity (BMI ≥ 30) was found to be an independent discrete risk factor for prolonged ileus; OR 1.119 (0.015-1.230) and p = 0.048.

Several studies have demonstrated the benefits of laparoscopic surgery in relation to a reduced incidence of postoperative ileus in abdominal surgery.8 No statistically significant relation between the results of our study and those published by Kuruba et al.9 was found in the comparison of the 2 approaches. Nevertheless, only taking frequency into account, prolonged postoperative ileus presented more commonly in open procedures.

Analyzing the “prophylactic” measures utilized in our patient sample, the use of intraoperative peridural analgesia in colon surgery was shown to be a protective factor against the appearance of ileus with an OR of 0.363 (0.127-1.033) and a p = 0.057. Other commonly employed measures, such as nasogastric tubes, early parenteral nutrition, and prokinetics, did not demonstrate any benefit in relation to a reduced risk for ileus. None of the patients analyzed received chewing gum as a protective measure. Patient admission into the intensive care unit resulted in an increased risk of 3.5 with a p = 0.05, which should be interpreted with caution, because that population usually presents with various simultaneous adverse conditions.

The multifactorial etiology of prolonged ileus makes each patient different; the studies on risk factors only calculate theoretical probabilities. It was concluded in the present study that obesity represented a risk factor for the appearance of prolonged postoperative ileus and the administration of peridural analgesia as a protective factor.

No financial support was received in relation to this study.

The authors declare that there is no conflict of interest.