Objective  To evaluate the clinical features and explore the prognostic factors of acute necrotic collection (ANC) and walled-off pancreatic necrosis (WOPN) following acute pancreatitis.

  Methods  A retrospective study was conducted to analyze the clinical data of 164 patients with moderate to severe acute pancreatitis treated in Peking Union Medical College Hospital from October 2013 to October 2015. Clinical and laboratory indexes were compared between ANC and non-ANC, WOPN and non-WOPN patients.

  Results  The proportions of systemic complications and infection were significantly higher in patients with ANC following acute pancreatitis (respiratory failure 47.1% vs. 30.2%, cardiovascular failure 14.7% vs. 5.2%, renal failure 38.2% vs. 15.6%, infection 19.1% vs. 6.3%, all P < 0.05). Within 48 hours of admission, higher levels of heart rate, high-sensitive C-reactive protein, glucose, serum creatinine, urea, and lower level of PaO₂ were observed in patients with ANC compared with patients without ANC (all P < 0.05). Among ANC patients, higher proportions of infection, intervention therapy and surgery were found in patients with WOPN (infection 40.7% vs. 4.9%, P < 0.001; intervention 29.6% vs. 7.3%, P=0.020; surgery 22.2% vs. 0, P=0.003); these patients also had longer hospital stay29.0(15.0, 56.0)d vs. 13.0(4.5, 26.3)d, P=0.005 and higher total costs72 818.3(27 805.1, 168 932.9)RMB vs. 28 155.2(6057.6, 51 259.1)RMB, P=0.015. Within the first 1-2 weeks after onset, a higher temperature, heart rate, breathe rate, counts of white blood cells, counts of neutrophils, and a lower level of blood calcium were shown in patients with WOPN compared with patients whose necrotic materials were absorbed.

  Conclusions  ANC and WOPN are associated with more severe clinical manifestations, higher risk of infection, higher proportion of intervention therapy and surgery, longer hospital stay and increased cost. Laboratory tests are useful in the prediction and monitoring of local complications in acute pancreatitis.