 Development of pancreatic exocrine insufficiency after first attack of moderately severe or severe AP confirmed by fecal elastase-1 test is the primary endpoint of this study. Also, the persistence pancreatic exocrine insufficiency and probable new developments of it during the follow-up will be assessed secondary endpoints. 30-day and hospital mortality and 5-year survival after first attack of moderately severe or severe AP will be determined as well secondary endpoints. 