Background:Early administration of enteral nutrition can improve intestinal mucosal barrier in patients with severe acute pancreatitis (SAP),reduce infection and complications;but when should the enteral nutrition be started is still controversial. Aims:To study the effect of different initiation time of enteral nutrition on elderly obese patients with SAP. Methods:The clinical efficacy,hospitalization time,hospitalization cost and the risk of complication were analyzed retrospectively in the two groups of patients with either ultra-early enteral nutrition (group A)or early enteral nutrition (group B),as well as the serum levels of inflammatory cytokines before and after treatment. Results:No significant difference in total effective rate was found between group A and group B (90. 9% vs. 79. 2%,χ2 = 1. 227,P > 0. 05). Compared with group B,the recovery time of blood and urine amylase,and hospitalization time in group A were significantly shortened and the cost of hospitalization was significantly decreased (P < 0. 05). The time of abdominal pain, bloating,vomiting and fever in group A was significantly shorter than that in group B (P < 0. 05). After 14 days of treatment,levels of IL-6,TNF-α and CRP in group A were significantly lower than those in group B (P < 0. 05). The incidence of infection was significantly lower in group A than in group B (P < 0. 05). Conclusions:Compared with early enteral nutrition group,ultra-early enteral nutrition for elderly obese patients with SAP has better efficacy,and has a shorter hospital stay and lower hospitalization cost.