The medical system when Dr. Takada (the first author) qualified as a doctor in the mid-1960s was based on experience. The Japanese Society of Abdominal Emergency Medicine was founded in 1983, and in 1990, preparation of Clinical Practice Guidelines (CPG) was explored. In 2003, using an evidence-based medicine approach, the first edition of CPG focused on acute pancreatitis was published. At that time, acute pancreatitis was considered an intractable disease because of high mortality. This was followed by revisions in 2007, 2010, and 2015. By 2014 acute pancreatitis had been removed from the registry of intractable diseases. However, the results of a national survey in 2016 revealed that some problems remained, and it was considered very important to step up efforts to raise awareness of the Guidelines. In the 2021 version, 2D Barcode were added to link easy-to-understand explanations and reference materials. A convenient format allowing this information to be downloaded free of charge via the 2D Barcode using a mobile application has also been added. It is hoped that physicians will use these documents when explaining to patients and their families in clinical practice.

The Japanese (JPN) guidelines for the management of acute pancreatitis were first released in 2003 in Japanese, followed by releases in 2007, 2010 and 2015. Since a nationwide epidemiological survey in 2016 in Japan reported that enteral nutrition for patients with severe acute pancreatitis was not started within 48 hours of admission and that unnecessary prophylactic antibiotics were used in almost all patients, the committee focused these issues and emphasized early enteral nutrition in small amounts even if gastric feedings are used and no administration of prophylactic antibiotics in patients with mild pancreatitis. The importance of Pancreatitis Bundles was emphasized, which were shown to be effective in improving prognosis, and CQ sections for local pancreatic complications had been expanded to ensure adoption of a step-up approach. Furthermore, a unique educational tool of "easy-to-understand explanations" was added so that not only physicians but other medical professionals, students, patients and their families can understand. All members of the committee hope that more people will have a common understanding and that better medical care will be disseminated and improve the survival of patients with acute pancreatitis.

The Japanese guidelines for the management of acute pancreatitis 2021 have been revised based on the results of a nationwide epidemiological survey conducted in 2016 in Japan. The prognosis of patients with acute pancreatitis has improved by optimization of clinical practice. However, lethal cases still develop, which demonstrates the necessity for recognition of high-risk groups and therapeutic principles. The new guidelines include revised Pancreatitis bundles 2021, which emphasize early enteral nutrition and not administering prophylactic antibiotics to patients with mild acute pancreatitis. The effects of modified statements regarding fluid resuscitation, recommended therapeutic drugs and a treatment strategy for late complications need to be clarified by a future nationwide epidemiological survey.

The diagnosis of acute pancreatitis requires two of the following three features, including upper abdominal pain, abnormal value of serum or urinary pancreatic enzymes, and characteristic findings of acute pancreatitis on imaging studies. The urinary trypsinogen-2 dipstick is a useful diagnostic tool to evaluate outpatients. The etiology of acute pancreatitis must be investigated immediately after the diagnosis is made because indications for emergent endoscopic treatment should be considered for some patients with biliary pancreatitis. Severity assessment of acute pancreatitis is mandatory during the early management phase. Japanese severity criteria for acute pancreatitis include a prognostic score and contrast-enhanced computed tomography scan severity grade. Prognostic scores can be repeatedly determined. It is recommended that the severity score for acute pancreatitis should be repeatedly assessed at the time of admission, within 24 hours, and between 24 and 48 hours using the Japanese prognostic score. Serum IL-6 is useful to predict the severity of acute pancreatitis on admission.

In Japan, as guidelines for the management of patients with acute pancreatitis have become more widely used, the outcomes of these patients have improved. However, some patients with severe forms of this illness do not survive. In clinical practice, there are still many patients where doctors are so caught up in following conventions that they do not follow the guideline recommendations, or, conversely, they carelessly do that which they should not do. A basic medical treatment policy for patients with acute pancreatitis was developed as a management flowchart. The Pancreatitis Bundles 2021 were created to provide a list of clinical studies and treatments that are recommended to be performed in clinical practice. There is evidence that greater compliance with items in Pancreatitis Bundles 2010 and 2015, results in improved outcomes. We hope that the Pancreatitis Bundles 2021 will be used as a clinical indicator for the treatment of patients with acute pancreatitis in the future.

The initial treatment of patients with acute pancreatitis has undergone a paradigm shift in the last 10-15 years. Regarding enteral nutrition, long periods of fasting were recommended, but in recent years, guidelines in the world and Japan recommend early initiation of enteral nutrition. Evidence has accumulated that early enteral nutrition contributes to an improved prognosis. In addition, prophylactic administration of antibiotics has long been recommended for patients with severe pancreatitis, but the latest editions of guidelines for acute pancreatitis have deprecated the use of such agents. Furthermore, the guidelines do not recommend regional arterial infusion of protease inhibitors and antibiotics in the pancreas. As described above, the trend is changing drastically in Japan and the rest of the world. Therefore, all professionals involved in the initial treatment of acute pancreatitis must comply with the recommendations of the Japanese guidelines. In addition, the guidelines and their sponsoring academic societies must educate the public about the recommendations and repeat cross-sectional epidemiological studies.

Although the overall mortality rate of patients with acute pancreatitis is decreasing, the mortality rate of patients with infected pancreatic necrosis, a late local complication, is still high and remains an important clinical problem. Invasive treatment is indicated for infectious cases and symptomatic cases. The endoscopic step-up approach, which usually involves EUS-guided transluminal drainage and endoscopic necrosectomy, has been developed, with good clinical results. Therefore, it is recommended as the first-choice treatment in cases that can be approached transluminally in the Japanese clinical guidelines for acute pancreatitis. However, endoscopic necrosectomy is associated with serious adverse events and requires careful attention, including the indication for necrosectomy. Recently, a dedicated large bore metal stent, the lumen-apposing metal stent, has been covered by insurance in Japan, and is expected to improve outcomes because it is highly effective in achieving drainage, allowing efficient conduct of the necrosectomy. However, in cases that extend into the pelvic cavity, endoscopic treatment alone is difficult, and additional percutaneous or surgical treatment should be considered.

According to a nationwide epidemiological survey of acute pancreatitis in 2016, the fatality rate for patients with severe acute pancreatitis 2 weeks after onset showed no improvement compared to 2011, suggesting that there is room for improvement in the treatment of local complications such as walled-off necrosis, which is problematic in the late onset phase. Against this background, the description of interventional therapy for local pancreatic complications was substantially revised in the 2021 guidelines. As key points for revision, it was suggested that when performing interventional treatment of patients with infected pancreatic necrosis, an endoscopic step-up approach is used 4 weeks after onset, a surgical step-up approach is chosen when the endoscopic approach is difficult, and retroperitoneal necrosectomy is performed when a surgical necrosectomy is performed. In the treatment of disconnected pancreatic duct syndrome, surgical treatment such as pancreatectomy, pancreatico-jejunostomy, and cyst-jejunostomy are performed when endoscopic treatment such as ultrasound endoscopic drainage is not effective.

Background: The efficacy of pembrolizumab for solid tumors with a high frequency of microsatellite instability (MSI-H) has been reported. For the treatment of pancreatic cancer, it is important to collect appropriate specimens for MSI evaluation; however, the factors that affect the ability to evaluate MSI have not been clarified. Methods: We prospectively collected MSI evaluation results for patients diagnosed with pancreatic cancer by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). Results: From September 2019 to April 2021, MSI was found in 73 patients, and could be evaluated in 72 (98.6%). MSI could not be evaluated for one patient as it took 584 days from EUS-FNA to MSI evaluation, and there was DNA degradation in the specimen. MSI-H was found in one patient. Conclusion: The success rate for MSI evaluation using EUS-FNA specimens was high, and no factors significantly affecting the ability to evaluate MSI could be identified. However, long-term storage of specimens could result in the inability to evaluate MSI because of DNA degradation.

A 78-year-old male presented after a cystic lesion in the pancreatic body was found on plain CT scan. MRCP revealed a dilated branch appearing like a "bunch of grapes" 20mm in size and a localized stenosis of the main pancreatic duct (MPD) in the surrounding area with mild proximal dilation. The delayed phase on contrast-enhanced (CE) CT scan exposed a faint hyper-attenuated area around the MPD stricture and dilated branch. ERP revealed a dilated branch connected to the MPD containing mucin. Pancreatic juice cytology showed atypical cells suggesting adenocarcinoma. The patient underwent distal pancreatectomy because of suspicion for invasive intraductal papillary-mucinous carcinoma (IPMC) or concomitant ductal carcinoma of the pancreas. The pathological diagnosis was mixed-type IPMC, non-invasive. Enhanced images on the CE-CT scan were presumed to have shown a fibrotic area around the tumor. There are reports that a hypoechoic area on EUS suggests non-invasive carcinoma, related to fibrosis around affected ducts. They have attracted attention as being important indirect observations of the tumor. However, there are few reports of fibrosis detected on CT scan so far. This is a clinically significant case where fibrosis around pre-invasive IPMC was detected as focal faint enhancement by CE-CT scan.

A 79-year-old woman presented with sudden onset of upper-abdominal pain and nausea. Contrast-enhanced computed tomography scan revealed splenic infarction and a thrombus in the descending aorta. Anticoagulation and antiplatelet therapy were begun. One day after admission, the abdominal pain acutely worsened, and the amylase level and white blood cell count were elevated. Computed tomography scan revealed occlusion of the gastroduodenal artery due to a thrombus and parenchyma in the pancreatic body was not enhanced, while the thrombus in the descending aorta disappeared. The patient was diagnosed with acute pancreatitis caused by pancreatic ischemia due to thromboembolism. Although necrotizing pancreatitis with acute necrotic collection and walled-off necrosis developed, the patient recovered with non-operative treatment including antibiotics. The thrombus in the gastroduodenal artery resolved without further intervention. The patient was discharged in good condition 25 days after admission.

The thromboembolism led to pancreatic ischemia and acute pancreatitis which is often followed by a more serious course than other causes with a high mortality rate. Ischemic pancreatitis resolved after treatment with antithrombotic therapy and treatment for acute pancreatitis. We report a patient with ischemic pancreatitis due to the occlusion of gastroduodenal artery.