Background and Aims: Acute kidney injury (AKI) is a common early complication in patients with severe acute pancreatitis (SAP), and it is also an important cause for early death in patients with SAP. Effective prevention and treatment of early AKI in SAP patients are critical for the prognosis of patients. The abdominal cavity of patients with SAP at the early stage often accumulates pancreatitis-related ascitic fluid (PAAF), which can not only form intra-abdominal hypertension and cause kidney ischemic injury, but also can cause kidney injury through the reabsorption of a large number of inflammatory mediators, enzymes and other toxic substances into the blood. Therefore, removing PAAF may have a protective effect against SAP-related AKI. Abdominal paracentesis drainage (APD) can drain PAAF timely and effectively without increasing the risk of abdominal infection. However, whether APD can improve SAP-related AKI is unclear. To this end, this study was conducted to investigate whether early APD has a protective effect on SAP-related AKI, and try to provide clinical evidence for the early prevention and treatment of SAP-related AKI. 
Methods: The clinical data of 186 SAP patients who met the inclusion criteria admitted to the Western Theater General Hospital from January 2011 to January 2020 were retrospectively analyzed. According to whether acute kidney injury (AKI) had occurred at the time of admission, they were divided into AKI group (57 cases) and non-AKI group (129 cases). In AKI, 30 patients underwent APD and 27 patients did not receive APD; in non-AKI group, 65 patients underwent APD and 64 patients did not receive APD. The differences in treatment efficacy between patients with and without APD were compared in either group, respectively. The studied variables included acute kidney injury stage (AKIN stage), renal function indexes, inflammation indexes, and APACHE II score. 
Results: In AKI group, the downgrading rates of the AKIN stage in patients with and without APD were 80% (24/30) and 51.9% (14/27), respectively (χ2=5.067, P=0.024), while the upgrading rates were 0.0% (0/30), 18.5% (5/27), respectively (P=0.019); after 7 days of treatment, the renal function indexes, inflammation indexes, and APACHE II scores of the patients were significantly reduced, but the decreasing amplitudes of all indexes in patients undergoing APD were significantly greater than those in patients without APD treatment (all P<0.05). In non-AKI group, the upgrading rates of the AKIN stage (the incidence of AKI) in patients with and without APD were 4.6% (3/65) and 17.2% (11/64) (χ2=5.268, P=0.022); after 7 days of treatment, the renal function indexes, inflammation indexes, and APACHE II scores of the patients were significantly reduced, but the decreasing amplitudes of all indexes in patients undergoing APD were significantly greater than those in patients without APD treatment (all P<0.05). 
Conclusion: For SAP patients with a large amount of PAAF, regardless of whether they are combined with AKI at the time of admission, early APD treatment can not only effectively reduce the stage of renal injury in patients with AKI, reduce the incidence of renal injury in patients without AKI, but also effectively decrease renal function index and improve the systemic inflammation. So, it has preventive and therapeutic effects against kidney injury, with a demonstrable efficacy.