To examine the effect of the "four-steps" treatment on infectious pancreatic necrosis(IPN).

The data of 207 patients who were diagnosed with IPN from January 2013 to December 2017 at Department of Pancreaticobiliary Surgery, the First Affiliated Hospital of Harbin Medical University were analyzed retrospectively. Among 207 patients, 132(63.8%) were males and 75(36.2%) were females. The median age was 45 years old (range: 19 to 80 years old). One hundred and fifty-eight patients(76.3%) suffered severe acute pancreatitis and 49 patients(23.7%) suffered moderately severe acute pancreatitis. Percutaneous catheter drainage(PCD) was performed on all the patients(Step 1). Patients received "four-steps" minimally invasive treatment strategy in step-up group(173 patients). The following steps after PCD were mini-incision access pancreatic necrosectomy(MIAPN) (Step 2), sinus tract endoscopic debridement and(or) PCD for residual infections(Step 3) and finally conventional open pancreatic necrosectomy(OPN) (Step 4). Patients(34 cases) received conventional open pancreatic necrosectomy after invalided PCD in OPN group. The perioperative parameters and prognosis were compared between Step-up group and OPN group. Normally distributed quantitative variables were analyzed by t-test, non-normally distributed quantitative variables were analyzed by Wilcoxon chi-square test and categorical variables were analyzed by χ ² test or Fisher exact test, respectively.

The basic characteristics of the two groups of patients were similar, but the referral rate of patients and the rate of preoperative 3 days organ failure in the OPN group were significantly higher than those of step-up group patients(47.1% vs. 28.9%, χ ²=4.313, P=0.038; 26.5% vs. 9.2%, χ ²=2.819, P=0.011). The frequency of PCD and the number of PCD tube (root) were less than those in the step-up group(1(1) vs. 2(1), Z=-3.373, P=0.018; 2(1) vs. 3(2), Z=-2.208, P=0.027). Compared with the OPN group, the interval time from onset to surgery and the MIAPN operation time were significantly shorter in the step-up group(29(15) days vs. 36(17)days, Z=-0.567, P=0.008; 58(27)minutes vs. 90(56)minutes, Z=-3.908, P<0.01); postoperative mortality was lower(5.8% vs.17.6%, χ ²=4.070, P=0.044); the overall incidence of postoperative complications was reduced(23.1% vs. 55.9%, χ ²=14.960, P<0.01) and the incidence of new-onset organ failure was decreased after operation in the step-up group(37.5% vs.47.4%, χ ²=7.133, P=0.007). The incidence of local abdominal complications (pancreatic fistula, intra-abdominal hemorrhage, gastrointestinal fistula) showed no significant difference between the two groups (P>0.05). Fewer patients required ICU treatment after operation in the step-up group compared with OPN group(22.0% vs. 44.1%, χ ²=6.204, P=0.013). Patients in the Step-up group has shorter hospital stay than patients in OPN group (46(13) days vs. 52(13)days, Z=-1.993, P=0.046).

The clinical effects of "four-steps" exhibited the superiority of minimally invasive treatment of IPN.And MIAPN is a simple, safe and effective procedure to remove pancreatic necrotic tissue and decrease complications.

Pancreatitis, acute necrotizing; Infected pancreatic necrosis; Percutaneous catheter drainage; Mini-incision access pancreatic necrosectomy; Step-up approach.