Anastomotic Leakage After Colorectal Surgery: Exploratory Analysis of Perioperative Risk Factors in a 672-Patient Cohort

Background Anastomotic leakage (AL) is a serious complication of colorectal surgery, associated with re-intervention, prolonged hospitalization, and impaired long-term outcomes. Although patient- and procedure-related risk factors are well established, the impact of perioperative conditions, thermal management, fluid balance, intraoperative blood loss, and vasopressor-supported hemodynamics remains incompletely defined, with heterogeneous and confounded evidence. Methods In this retrospective single-center cohort study, 672 colorectal procedures with primary anastomosis at the University Hospital Erlangen (2013-2018) were analyzed. The primary endpoint was anastomotic leakage within 30 days, defined by clinical and/or radiologic evidence requiring intervention. Examined variables included age, sex, body mass index (BMI), ASA class, surgical urgency, operative duration, minimum intraoperative core temperature, estimated blood loss (>500 mL), total crystalloid volume (>3500 mL), and intraoperative norepinephrine administration. Associations with anastomotic leakage were evaluated using univariable and exploratory multivariable logistic regression. Results Anastomotic leakage (AL) occurred in 20/672 procedures (3.0%) and was associated with a markedly longer hospital stay (41.5 [IQR 31.3-60.3] vs. 11 [IQR 9.0-17.0] days; p < 0.001). In an exploratory multivariable logistic regression, ASA class III/IV (OR 3.8, 95% CI 1.3-11.3; p = 0.016) and operative duration ≥300 min (OR 3.6, 95% CI 1.2-13.6; p = 0.025) were independently associated with leakage. In contrast, intraoperative hypothermia (<35.5°C), estimated blood loss (>500 mL), and any norepinephrine use showed unadjusted associations with AL but were not independently associated after adjustment. Conclusion High ASA class (III/IV) and prolonged operative duration were the only independent risk factors for anastomotic leakage in this study. Intraoperative exposure variables such as hypothermia, estimated blood loss, and any norepinephrine use were not independently associated after adjustment.