Acute pancreatitis has no obvious cause after clinical, laboratory and radiologic investigation in 10%–30% of patients, and the diagnosis of idiopathic pancreatitis is given. This study investigated the role of linear EUS for identification of possible causes for acute pancreatitis when other investigative methods failed.

Between June 2012 and March 2017, 35 patients [25 women; mean age: 51.9 + 17.8 years] with idiopathic acute pancreatitis underwent linear EUS for investigation. All of these cases were contacted for a follow-up telephone interview to compare the EUS findings with the final diagnosis and outcome.

Pancreaticobiliary abnormalities were identified in 19 of 35 (54.3%) patients. Ten (28.6%) patients had microlithiasis or biliary sludge. Microlithiasis and choledocholithiasis were identified in 8 (22.8%) and a single (2.8%) patient, respectively. Two patients presented gallbladder biliary sludge, one of them with microlithiasis. Chronic pancreatitis was found on EUS in 6 (17.1%) patients, and pseudotumoral masses confirmed by EUS-FNA as autoimmune pancreatitis were detected in other 3 (8.6%) cases. Linear EUS was normal in 13 (37.1%) patients, and demonstrated findings of recent acute pancreatitis but no other etiological factor in 3 (8.6%) cases. After a mean follow-up of 33.3 months, no case with a normal EUS evaluation presented a new episode of pancreatitis, 1 of 9 cases with microlithiasis presented an episode of recurrent pancreatitis due to choledocolithiasis after cholecystectomy, and 3 of 9 cases with chronic pancreatitis presented recurrent episodes, including the 2 cases of autoimmune pancreatitis.

Linear EUS provides diagnostic information in approximately a half of patients with idiopathic acute pancreatitis. Exclusion of pancreaticobiliary abnormalities on EUS has an important prognostic value for absence of new episodes of acute pancreatitis.