The goal of this clinical trial is to clarify whether aggressive intravenous hydration with lactated Ringer's solution could reduce the incidence of post-ESWL pancreatitis in patients with chronic pancreatitis.

Chronic pancreatitis (CP) is a disease caused by genetic and environmental factors that lead to progressive fibrosis of the pancreatic tissue, resulting in irreversible damage to the structure and function of the pancreas. The incidence of pancreatic duct stones in CP is as high as 90%. Stones can lead to pancreatic duct obstruction, pancreatic parenchymal hypertension and ischemia, inducing frequent abdominal pain and accelerating the decline of pancreatic function, therefore, removal of pancreatic duct stones is important for relieving CP symptoms. For large stones and complex stones, pancreatic extracorporeal shock wave lithotripsy (P-ESWL) was recommended. Acute pancreatitis is the most common complication after P-ESWL with an incidence of 6.3-12.5%, which result in prolonged hospitalization, increased medical costs, and can be life-threatening.

There are few studies on the prevention of postoperative pancreatitis after P- ESWL. Only one prospective randomized controlled study found the role of NSAIDs in the prevention of acute pancreatitis after ESWL, and preoperative use of rectal indomethacin reduced post-ESWL pancreatitis from 12% to 9%. ERCP placement of pancreatic duct stent is one of the effective methods to prevent post-ERCP pancreatitis. However, studies have shown that pancreatic duct stenting before ESWL is not effective in preventing acute pancreatitis after P-ESWL. More research is needed in the prevention and treatment of pancreatitis after P-ESWL.

There have been more high-quality studies on the prevention of post-ERCP pancreatitis. In addition to NSAIDs, several prospective randomized controls have found that perioperative high-dose lactated Ringerolysis (LRS) hydration is effective in preventing acute pancreatitis after ERCP. In a meta-analysis, active hydration of LRS was found to reduce post-ERCP pancreatitis from 13% to 6%. Based on above findings, international guidelines recommend aggressive perioperative LRS hydration to reduce the risk of post-ERCP pancreatitis.

Previous studies have suggested various mechanisms leading to post-ERCP pancreatitis, including mechanical injury, chemical injury, hydrostatic injury, and infection. Given the potentially similar pathogenesis of postoperative pancreatitis, we propose to conduct a randomized controlled trial to investigate the efficacy of active hydration of lactated Ringer's solution for the prevention of post-ESWL pancreatitis.

Inclusion Criteria:

All patients with chronic pancreatitis aged between18 and 85 years who were eligible for treatment with ESWL for pancreatic stones were eligible for enrolment.

Exclusion Criteria:

1. Patients readmitted to the hospital for ESWL during the study period.
2. Acute pancreatitis in the last 3 days.
3. Signs of congestive heart failure, such as pitting edema or a New York Heart Association classification greater than class I heart failure. For patients ≥ 70 years old, brain natriuretic peptide (BNP) and cardiac ultrasound would be performed before ESWL. Patients with BNP>100pg/ml or Ejection Fraction value<50% should be excluded.
4. Respiratory insufficiency (pO2 < 60 mmHg or saturation < 90% despite FiO2 of 30% or requiring mechanical ventilation). For patients ≥ 70 years old, pulmonary function tests would be performed before ESWL. Patients with Forced Expiratory Volume in the first second (FEV1) <70% are excluded.
5. Severe liver disease (cirrhosis, liver abscess).
6. Patients receiving more than 1.5 mL/kg/h or 3 L/24 h of intravenous fluids in the 24 h before ESWL.
7. Hypotension (systolic blood pressure <90 mmHg or mean arterial pressure <70 mmHg).
8. Hypo- or hypernatremia (serum Na+ levels < 130 or > 150 mmol/L).
9. Pregnancy.
10. Unwilling or unable to provide consent.