Acute pancreatitis after posterior spinal fusion in children is associated with high intraoperative blood loss. Inflammation, oxidative stress, and pancreatitis markers were assessed during this period. Five of the 17 patients studied developed acute pancreatitis 3–7 days after surgery. Intraoperative blood loss (4850±2315 vs 1322±617 ml) and peak tumor necrosis factor α levels (15.29±5.3 vs 8.27±4.6 pg/ml) in the immediate postoperative period were significantly higher in these five patients than in controls, respectively. No differences were noted in serum interleukin 8, interleukin 6, pancreatis-associated protein, or urine malondialdehyde levels. Urine trypsin-associated peptide, elevated initially in all patients, was significantly higher in the acute pancreatitis group at diagnosis. Length of stay was significantly longer in the acute pancreatitis group. Greater blood loss and peak tumor necrosis factor α are associated with subsequent risk of acute pancreatitis, suggesting a role of ischemia–reperfusion injury.