In a large number of patients, with episodes of acute pancreatitis the etiology is not identified, even after initial clinical history, detailed physical examination, laboratory tests and biochemical exams and an transabdominal ultrasound. This patient are considered with a unexplained acute pancreatitis. In this cases the treatment is restricted to improvement of symptoms. These patients after treated tend to have new episodes with the risk of raising the rates of morbidity and mortality. Therefore, the identification of a cause and its prompt treatment prevent at recurrent episodes of pancreatitis. This review aims to draw attention to how best diagnostic approach when the light of evidence-based medicine, to search for causes of difficult identification with microlithiasis, occult stones, the anatomical variations of biliary and pancreatic duct and in addition to sphincter of Oddi dysfunction.