Perioperative changes in systemic inflammatory markers predict major complications after distal pancreatectomy.

Postoperative complications after distal pancreatectomy (DP), notably clinically relevant postoperative pancreatic fistula (CR-POPF) and peripancreatic fluid collections, drive morbidity. Existing scores rely on intraoperative variables and do not capture individual inflammatory responses. We evaluated whether preoperative, postoperative, and perioperative changes in routine inflammatory indices predict complications. Single-center retrospective cohort of patients undergoing DP for pancreatic malignancy (2010-2024). Pre- and postoperative inflammatory indices were derived from complete blood counts: neutrophil-to-lymphocyte ratio (NLR), systemic immune-inflammation index (SII), and systemic inflammatory response index (SIRI). Associations with outcomes were assessed using Firth's penalized logistic regression and time-to-event analyses. Of 568 patients, 198 met inclusion criteria. Postoperative fluid collection occurred in 71 (35.9%) and CR-POPF in 20 (10.1%). On multivariable analysis, male sex independently predicted fluid collection (OR 1.91, CI 1.02-3.62; p = 0.044) and intensive care unit (ICU) admission predicted CR-POPF (OR 4.24, CI 1.22-14.91; p = 0.024). Postoperative NLR, SII, and SIRI were associated with adverse events on univariable analysis but were not independently predictive. Receiver-operating characteristic analysis gave modest discrimination for preoperative SIRI (AUC 0.602) and higher discrimination for perioperative change in SIRI (ΔSIRI) and SIRI ratio for major adverse events (MAE) (AUC 0.759). Kaplan-Meier analysis showed earlier fluid collections in patients with elevated preoperative SIRI, SII, and postoperative NLR. Perioperative changes in routine inflammatory markers outperformed static preoperative values for predicting MAE after DP. These inexpensive, widely available indices merit prospective validation as adjuncts for risk-adapted surveillance and management.