Idiopathic acute pancreatitis (IAP) presents a diagnostic challenge and refers to cases where the cause of acute pancreatitis remains uncertain despite a comprehensive diagnostic evaluation. Endoscopic ultrasound (EUS) has emerged as a valuable tool in the diagnostic workup of IAP. This review explores the pivotal role of EUS in detecting the actual cause of IAP and assessing its accuracy, timing, safety, and future technological improvement. In this review, we investigate the role of EUS in identifying the actual cause of IAP by examining the available literature. We aim to assess possible existing evidence regarding EUS accuracy, timing, and safety and explore potential trends of future technological improvements in EUS for diagnostic purposes. Following PRISMA guidelines, 60 pertinent studies were selected and analysed. EUS emerges as a crucial diagnostic tool, particularly when conventional imaging fails. It can offer intricate visualization of the pancreas, biliary system, and adjacent structures. Microlithiasis, biliary sludge, chronic pancreatitis, and small pancreatic tumors seem to be much more accurately identified with EUS in the setting of IAP. The optimal timing for EUS is post-resolution of the acute phase of the disease. With a low rate of complications, EUS poses minimal safety concerns. EUS-guided interventions, including fine-needle aspiration, collection drainage, and biopsies, aid in the cytological analysis. With high diagnostic accuracy, safety, and therapeutic potential, EUS is able to improve patient outcomes when managing IAP. Further refinement of EUS techniques and cost-effectiveness assessment of EUS-guided approaches need to be explored in multicentre prospective studies. This review underscores EUS as a transformative tool in unraveling IAP's enigma and advancing diagnostic and therapeutic strategies.

Endoscopic ultrasound (EUS) is useful in the diagnostic workup of idiopathic acute pancreatitis but its role as a predictor of recurrence has not been thoroughly assessed. Our aim was to study the performance of EUS in idiopathic acute pancreatitis, its impact on the natural history of the disease, and the factors related to recurrence.

Patients with idiopathic acute pancreatitis referred to our endoscopy unit were enrolled and followed, with assessment of the performance of endoscopic retrograde cholangiopancreatography (ERCP), cholecystectomy, and the incidence of recurrence. EUS findings and recurrence rates were compared between patients with a first episode or recurrent attacks and in patients with previous cholecystectomy versus those with gallbladder in situ.

One hundred six patients were included (mean follow up: 53.59±27.79 months). Biliary disease related to stones was the most common finding on EUS (49.1%), and patients referred for recurrent attacks showed the highest recurrence rate during follow up (57.1%). ERCP or cholecystectomy reduced recurrences to 14.3% in patients with biliary disease. Age under 65 (odds ratio [OR] 3.56, 95% confidence interval [CI] 1.21-10.44; P=0.02), previous cholecystectomy (OR 3.19, 95%CI 1.11-9.17; P=0.03), and no lithiasis on EUS (OR 2.87, 95%CI 1.04-7.87; P=0.04) were independent risks factors for recurrence.

EUS-directed ERCP/cholecystectomy was associated with lower relapse rates in idiopathic acute pancreatitis. Along with age and gallbladder status, it provides predictive information about recurrence likelihood.

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.

The role of sphincter of Oddi manometry (SOM) in the management of patients with idiopathic recurrent acute pancreatitis requires clarification. We evaluated the therapeutic effects of endoscopic sphincterotomy in patients with recurrent acute pancreatitis and the prognostic significance of pancreatic sphincter dysfunction (SOD).

We performed a randomized trial of endoscopic retrograde cholangiopancreatography with SOM for patients with idiopathic recurrent acute pancreatitis. Patients with pancreatic SOD (n = 69) were assigned randomly to groups that received only biliary sphincterotomy (BES) or a combination of biliary and pancreatic sphincterotomy (DES); patients who underwent normal SOM (n = 20) were assigned randomly to groups that received BES or a sham surgery. The primary outcome was incidence of recurrent acute pancreatitis during the follow-up period (minimum, 1 year; maximum, 10 years). We also determined the incidence of chronic pancreatitis and analyzed factors associated with recurrence of acute pancreatitis.

Among the 69 patients with SOD, 48.5% who received BES and 47.2% who received DES had recurrent acute pancreatitis (95% confidence interval, -22.3 to 24.9; P = 1.0). In patients with normal SOM (n = 20), 27.3% of those who received BES and 11.1% of those who received the sham surgery had recurrent acute pancreatitis (95% confidence interval, -49.5 to 17.2; P = .59). Overall, 16.9% of subjects developed chronic pancreatitis during a median follow-up period of 78 months (interquartile range, 35-108 mo). The odds of recurrent acute pancreatitis during follow-up evaluation were significantly greater among patients with SOD than those with normal SOM (unadjusted hazard ratio, 3.5; 95% confidence interval, 1.07-11.4; P < .04), and remained so after adjusting for potential confounders (hazard ratio, 4.3; 95% confidence interval, 1.3-14.5; P < .02).

Among patients with pancreatic SOD, DES and BES have similar effects in preventing recurrence of acute pancreatitis. Pancreatic SOD is an independent prognostic factor, identifying patients at higher risk for recurrent acute pancreatitis.

Clinicaltrials.gov (NCT01583517).