Early postoperative pain and its association with complications after minimally invasive colorectal cancer surgery: a retrospective cohort study of a multicenter database

Background: Postoperative pain may impair recovery; however, its association with postoperative complications remains unclear. We investigated this association in patients undergoing minimally invasive colorectal cancer surgery. Methods: This retrospective multicenter study analyzed data from the Korean Enhanced Recovery After Surgery (ERAS) registry collected between October 2023 and December 2025. Adult patients who underwent colorectal cancer resection at six tertiary institutions were included. Pain intensity on postoperative day one was assessed using the pain/discomfort dimension of the EuroQol 5-Dimension 5-Level questionnaire and categorized as mild, moderate, or severe. The primary outcome was overall postoperative complications, defined as a Comprehensive Complication Index (CCI) score ≥ 8.7. The secondary outcomes were major complications (CCI ≥ 26.2) and length of postoperative hospital stay (LOS). Associations between pain severity and outcomes were evaluated using multivariable binary logistic regression for overall complications, Firth's penalized likelihood logistic regression for major complications, and multivariable linear regression for LOS. Results: A total of 985 patients were included. Compared with mild pain, severe pain was associated with higher odds of overall complications (odds ratio, 1.76; 95% CI, 1.11-2.81), whereas neither moderate nor severe pain was associated with major complications. Moderate and severe pain were both associated with longer LOS (LOS ratios, 1.07 [95% CI, 1.01-1.13] and 1.08 [95% CI, 1.02-1.15], respectively). Conclusions: Severe early postoperative pain was independently associated with a higher complication burden and longer LOS. As causality remains unproven, prospective studies are needed to determine whether optimized pain control can directly reduce complications.