Over the past few decades, there have been rapid developments in surgical techniques that have played an important role in treatment of colorectal cancer. The type of surgical approach is important for both treatment and evaluating the postoperative recovery of patients with colorectal cancer. This interest in postoperative recovery has led to developments in strategies such as minimally invasive approaches, optimal pain control, and aggressive postoperative rehabilitation including early oral feeding and early ambulation. On the basis of these strategies, the concept of enhanced recovery after surgery (ERAS) was introduced [1]. Several studies have shown that ERAS reduces the length of hospitalization and complications after elective colorectal surgery [2, 3]. However, there is a concern that early discharge might affect other proposed quality measures, including readmission rates. Readmission worsens the physical and psychological burden on patients, wastes social health resources, and increases costs [4]. The readmission rate in patients who underwent elective colorectal surgery ranged between 6% and 20% [4-6]. A recent study suggested that readmission rates in patients who underwent elective colorectal surgery over the past 20 years have increased [7]. In addition, length of stay (LOS), comorbidities, and postoperative complications were reported to be closely associated with readmission. Other studies suggested that the C-reactive protein (CRP)/albumin ratio is a prognostic factor associated with readmission or short-term survival [8, 9].

This study aimed to evaluate the readmission rate in 30 days after elective colorectal surgery and the risk factors that affect the 30-day readmission rate. We specifically focused on the impact of comorbidities to determine factors associated with a higher risk of readmission after elective colorectal surgery. In addition, we aimed to identify causes for readmission, disease-free survival (DFS), and overall survival (OS) in a single institution.

Technologic advances in colorectal surgery have increased interest in evaluating the postoperative recovery rate of patients with colon cancer. Unplanned readmission and LOS are widely used as quality indicators of colorectal surgery [10]. In addition, the ERAS program has played an important role in preoperative management of patients undergoing colorectal surgery. The implementation of this program has led to reduced LOS and postoperative complications, early recovery of organ function after surgery, and early return to daily life [11].

This study aimed to assess the readmission rate 30 days after elective colorectal surgery and predictive factors related to 30-day readmission. This study showed a 30-day readmission rate of 10.5%, similar to the 9%–11% readmission rates reported in previous studies [7, 12, 13].

The present study identified 4 statistically significant risk factors for readmission: hepatic disease, pulmonary disease, TNM stage, and operation time. According to our study, patients with preoperative hepatic disease were approximately 9 times more likely to be readmitted (OR, 8.98; 95% CI, 7.35–10.61). In addition, preoperative pulmonary disease was significantly associated with readmission (OR, 4.90; 95% CI, 3.65–6.14). Yang et al. [14] reported that patients with preoperative complications were 2.91 times more likely to be readmitted than those without preoperative complications (OR, 2.91; 95% CI, 1.32–6.99).

However, the factors associated with readmission rate in this study were inconsistent with those reported in previous studies. In our univariate analysis, LOS was not a significant predictor of readmission (P=0.335). In a few recent studies, LOS was significantly associated with readmission [7, 12].

CRP(D/C)/albumin ratio was not a statistically significant risk factor for readmission (P=0.273). Oh et al. [15] reported that CRP/albumin ratio was an independent risk factor for mortality in postoperative patients admitted to the intensive care unit. Xu et al. [16] reported that CRP/albumin ratio was useful for predicting the survival of patients with esophageal cancer.

Our study showed causes of unplanned readmission. The most common causes of readmission were wound bleeding or surgical site infections (n=10, 41.7%) and ileus or intestinal obstructions (n=5, 20.8%). Kariv et al. [13] reported that surgical site infection and ileus were associated with higher readmission rate. A meta-analysis by Li et al. [17] showed that the most common reason for readmission was bowel obstruction or ileus, followed by surgical site infection. Wick et al. [4] reported that one-third of the total number of readmissions in patients who underwent colorectal surgery were considered preventable.

The OS and DFS rates of the nonreadmitted group were significantly higher than those of the readmitted group (OS, P=0.00; DFS, P=0.04). Also, the 5-year survival rate of the readmitted group was relatively low (OS, 70.0%; DFS, 70.0%). These results are concordant with previous reports by Schneider et al. [7] and Greenblatt et al. [18].

The present study has several potential limitations. First, our study was a retrospective analysis conducted in a single center; thus, selection bias may exist. Second, the sample size was relatively small (n=229), which limits statistical power. Third, many data for statistical analysis were missing and several patients no longer visited the outpatient clinic, possibly because most patients were aged 60 years or older (66.4%).

Despite these limitations, this study has important implications. This is the first study to investigate the unplanned readmission rate and risk factors that affect 30-day unplanned readmission rate after elective colorectal surgery in our medical center.

Our study showed that the readmission rate can be reduced by focusing on treatment of wound infection, which is the primary cause of readmission in these patients.

This study provides an impetus for performing multicenter prospective cohort studies in the future to overcome these limitations.

In conclusion, preoperative comorbidities including hepatic and pulmonary diseases were risk factors associated with higher readmission rates after elective colorectal surgery. Moreover, the most common cause for readmission in patients who underwent elective colorectal surgery was wound bleeding or surgical site infection.