Acute pancreatitis is a common disease (3rd cause of hospital admission for digestive causes), which is associated with significant patient suffering, a 2-4% probability of death and considerable healthcare costs. Sixty percent of acute pancreatitis are due to the presence of stones in the gallbladder. The risk of suffering another acute biliary pancreatitis (ABP, that is to say, pancreatitis due to gallstones) or of other biliary complications in the following weeks or months is high (20% or greater) if measures are not taken to avoid it, being surgical removal of the gallbladder the most effective. Unfortunately, most Spanish centers have a surgical waiting list that makes gallbladder surgery unfeasible in a period of less than weeks or months, which is why readmission for biliary problems derived from the stones is a common problem. This, of course, causes danger and great stress and anger for patients affected by these complications on the waiting list, damaging their relationship with the health system and it is linked to increased cost. In addition, there is a very vulnerable group, those patients who due to age or serious diseases cannot undergo gallbladder surgery but have a high probability of suffering biliary problems due to the stones they have. Ursodeoxycholic acid (UDCA) is very safe drug which is used to dissolve gallstones, but its role in preventing biliary complications after ABP has not been studied adequately so it is not frequently used. Our objective is to investigate if UDCA is useful in this scenario, which would avoid suffering and adverse consequences for the patient and reduce the consumption of resources.