Postoperative bowel obstruction was a quite common complication after colorectal surgery[8]. Previous studies showed that risk factors of prolonged or early postoperative bowel obstruction for patients after colorectal surgery[9–11]. But few studies analyzed multiple risk factors for early postoperative bowel obstruction and no one previous study was found focusing on the prediction model of early postoperative bowel obstruction[12]. As far as we knew, our study was the very first to establish a nomogram to predict patient-specific factors for early postoperative bowel obstruction with high discriminative ability and excellent calibration. In this study, we identified COPD, hypothyroidism, probiotic indications, duration of antibiotics and time of first postoperative feeding as potential risk factors and created a statistical predictive model for early postoperative bowel obstruction.
Recent findings highlighted that gut microbiota might play an important role in shaping lung inflammation[13]. Both imbalance of gut microflora, which led to the release of intestinal endotoxin and translocation of intestinal flora, which led to the release of inflammatory mediators could directly or indirectly promote the beginning and development of COPD[14]. Several studies found that COPD was the only preoperative morbidity predictive of complications after colorectal cancer resection[15, 16]. A history of COPD was an independent risk factor of postoperative 30-day morbidity, mortality, and hospital duration of stay in patients underwent colectomy, small bowel resection and appendectomy[17]. In that study, COPD was also found as an independent predictor for early postoperative bowel obstruction in patients underwent colorectal surgery[18].
Patients with chronic constipation and abdominal distension should be considered with the diagnosis of hypothyroidism in 1969[19]. S. Goto et al[20] compared daily stool volume of rat between hypothyroidism group and sham operated group. They found[20] that hypothyroidism impaired colonic motility and function as frequently seen in rats. Another case report[21] reported that a patient got intestinal symptoms from hypothyroidism in which previous conventional examinations were negative. In our study, the incidence of early postoperative bowel obstruction was higher in patients with hypothyroidism. Hypothyroidism might impaired gut motility[22].
During recent years the impact of antibiotic agents on the intestinal microflora has been investigated in patients undergoing colorectal surgery[23]. Prophylactic antibiotics are effective in preventing surgical-wound infections[24]. Antibiotics impact the intestinal microflora depends on the agents’ spectrum and concentration[25]. Antibiotics usually had significant additional effects on many tissues. The study comparing the contractile responses of ileum smooth muscle to different agonists in adult guinea pigs indicated that antibiotics may impaired small bowel smooth muscle contractility, which was the implication for the long-term use of parenteral antibiotics in the postoperative period[26]. In our study, duration of antibiotics (11.92 ± 9.10 day) was longer in early postoperative bowel obstruction group (OR 1.10, 95%CI 1.05–1.15). According to the guideline of probiotics use[27], three most common clinical indications were prevention of antibiotic-related side effects, treatment of antibiotic-related side effects and irritable bowel syndrome. Our study indicated that patients with antibiotic-related side effects such as diarrhea and abdominal distension (also as probiotic indications), were potential victims of early postoperative bowel obstruction. But there was no difference between patients with and without using probiotics.
A meta-analysis[28] evaluating the effect on the early time of oral feeding after upper gastrointestinal surgery found that early postoperative oral feeding reduced the length of hospital stay and decreased relevant complications as anastomotic leak and incidence of nasogastric tube reinsertion. Sabrina Toledano et al[29] showed that early oral feeding reduced the time to first flatus and first ostomy output compared with traditional diet in the patients who had an ostomy creation, which may promote the recovery of bowel function. In our study, time to first postoperative feeding was an independent risk factor of early postoperative bowel obstruction.
Previous studies mechanical bowel preparation was routinely used to improve postoperative recovery of colon surgery[30]. But bowel cleaning with oral antibiotics can reduce the incidence of surgical site infection, anastomotic leakage and other morbidity compared with mechanical bowel preparation[31–35] for patients undergoing colorectal surgery. Recently, Koskenvuo et al recruited a multicenter, parallel, single blind trial to fund that oral antibiotics bowel preparation cannot reduce the occurrence of surgical site infection or overall morbidity after colonic surgery[36]. There was no significant difference in mechanical bowel preparation with or without oral antibiotics for early postoperative bowel obstruction.
Plasma albumin is involved in the transport of human of metabolites, maintenance of colloid osmotic pressure and other physiological function[37]. Plasma albumin value is performed to evaluate the postoperative nutritional status[38]. Another study showed no significant difference in postoperative day of flatus or postoperative day of intake between patients with albumin levels dropped below 3.5g/dl and patients with albumin greater or equal to 3.5g/dL[39]. Our study showed that hypoproteinemia may not be an independent risk factor of early postoperative bowel obstruction for patients after colorectal surgery.
Analgesia is becoming more acceptable by surgical patients. Opioids are the most commonly used for analgesia. Almost 93.6% patients choose opioids for analgesia in our study. But opioids have numerous side-effects such as breath inhibition, nausea, vomiting, ileus and urinary retention[40]. One study showed that intravenous acetaminophen helps to reduce opioids consumption, which reduced time to return of bowel function for patients undergoing colorectal surgery[41]. In our study, both analgesic protocol and duration of analgesia were not the risk factors of early postoperative bowel obstruction for patients underwent colorectal surgery.
It is that the incidence of postoperative morbidity mortality increased in elderly patients[42], which elderly patients were more likely to present with later stage disease. ASA classification is associated with postoperative morbidity in the patients undergoing major abdominal cancer surgery[43]. ASA score predicts postoperative length of stay and complication risk[44]. Age and ASA classification may increase the incidence of early postoperative bowel obstruction after unifactor analysis but was not an independent factor for early postoperative bowel function after logistic regression analysis in this study.
We investigated multiple factors that may be associated with early postoperative bowel obstruction. But there were also some limitations, because the data was collected retrospectively. It was still unclear whether the predict model could be applied in all patients, because our data were collected from China. Nevertheless, we think our nomogram could help the postoperative management of patients undergoing colorectal surgery.