Inclusion Criteria:  ≥ 18 years old Weight > 30 kg Confirmed diagnosis of acute gallstone cholecystitis Symptomatic or asymptomatic cholecystitis Under surgery for cholecystectomy: for the 5 first patients : cholecystectomy will take place within 72 hours of the first symptoms of cholecystitis after the 5 first patients : cholecystectomy will be allowed at any time after the first symptoms and at physician judgment Patient agrees to signed the informed consent  Exclusion Criteria:  < 18 years old ≤ 30 kg Known hypersensibility to mesna Patient taking anticoagulant at the screening visit Patient having a pancreatitis or angiocholitis Patients suffering from hepatic or renal disorders Unable to sign the informed consent Participation in any study involving an investigational drug or device within the past 3 Months. Patient is pregnant, breastfeeding or has wish of pregnancy during the study. Individuals under tutorship or trusteeship