Comparing and validation of definitions of postoperative acute pancreatitis after pancreatoduodenectomy and proposal for Atlanta-Helsinki grading system

BACKGROUND: Postoperative acute pancreatitis has been recognized as an important complication following pancreatic surgery, yet multiple, partly overlapping definitions exist. This study aimed to compare the most used definitions of postoperative acute pancreatitis and to evaluate the clinical relevance of their individual components. METHODS: All patients undergoing pancreatoduodenectomy between January 2013 and December 2021 at the Helsinki University Hospital were retrospectively analyzed. Postoperative biochemical and radiological data were collected, and established definitions of postoperative acute pancreatitis were identified from the literature and assessed in relation to short-term postoperative outcomes. RESULTS: Among 704 patients, the incidence of postoperative acute pancreatitis was 11.9%, 41.2%, and 17.6% according to the International Study Group for Pancreatic Surgery definition of postpancreatectomy acute pancreatitis, the Atlanta-adapted framework, and Connor's definition, respectively. These definitions utilize biochemical and/or radiological criteria. Up to 61.9% of patients with radiological signs of pancreatitis had no concomitant hyperamylasemia. Regardless of definition, both postoperative acute pancreatitis and postoperative hyperamylasemia were associated with increased postoperative morbidity. The Atlanta-adapted framework demonstrated the highest discriminative ability for severe postoperative complications (Clavien-Dindo IIIa or worse) (area under the curve, 0.68 [0.64-0.73]) compared with International Study Group for Pancreatic Surgery postpancreatectomy acute pancreatitis (area under the curve, 0.60 [0.55-0.65]) and Connor's definition (area under the curve, 0.62 [0.57-0.67]). A graded Atlanta-based classification (Atlanta-Helsinki classification-0: none, A: hyperamylasemia only; B: radiological findings only; and C: both) showed a stepwise increase in severe postoperative complication rates, occurring in 12.3%, 15.0%, 44.6%, and 56.3% of patients, respectively. CONCLUSION: Postoperative acute pancreatitis, irrespective of definition, is associated with increased postoperative morbidity after pancreatoduodenectomy. The proposed Atlanta-Helsinki graded classification offers a practical basis for both clinical use and future research.