Acute Pancreatitis

Acute pancreatitis is a sudden inflammation of the pancreas, most commonly triggered by gallstones or alcohol, that ranges from a mild, self-limiting illness to severe disease with pancreatic necrosis and organ failure. It is diagnosed by characteristic abdominal pain together with raised pancreatic enzymes or imaging findings, and it is a major reason for emergency surgical and gastroenterological care.

Definition

Acute pancreatitis is an acute inflammatory process of the pancreas, diagnosed when at least two of the following are present: characteristic upper-abdominal pain, serum lipase or amylase elevated to at least three times the upper limit of normal, and characteristic findings on cross-sectional imaging.

Scope

This topic covers the causes and mechanism of pancreatic injury, the diagnostic definition, the revised Atlanta classification of severity and of local complications, and the principles of supportive and step-up management of necrotizing disease. It is a reference account and is not individualized clinical advice.

Key concepts

• Gallstone and alcohol aetiology
• Premature intra-acinar enzyme activation
• Interstitial oedematous versus necrotizing pancreatitis
• Revised Atlanta classification (mild, moderately severe, severe)
• Local complications and pancreatic fluid collections
• Step-up approach to infected necrosis

Mechanisms

Acute pancreatitis is initiated by premature activation of digestive enzymes within pancreatic acinar cells, leading to autodigestion, local inflammation, and release of inflammatory mediators. The response may remain confined as interstitial oedematous pancreatitis or progress to necrotizing pancreatitis with devitalised pancreatic and peripancreatic tissue. Systemic inflammation can produce organ failure, which - especially when persistent - defines severe disease. Local complications evolve over time into fluid collections and, in necrotizing disease, walled-off necrosis that may become infected.

Clinical relevance

Severity in acute pancreatitis is stratified largely by the presence and persistence of organ failure and by local complications, as codified in the revised Atlanta classification; most cases are mild and self-limiting, whereas necrotizing disease, particularly when infected, carries substantial risk and may require intervention. This entry describes how the condition is defined and classified for reference and educational purposes and is not a basis for individual treatment decisions.

Epidemiology

Acute pancreatitis is one of the most common gastrointestinal causes of hospital admission; gallstones and alcohol account for the large majority of cases, and gallstone (biliary) pancreatitis links the condition closely to the biliary disease covered elsewhere in this area.

Evidence & guidelines

The revised Atlanta classification (2012) standardised the definitions of severity and of local complications, and the IAP/APA evidence-based guidelines address management; for infected necrotizing pancreatitis, the PANTER trial supported a minimally invasive step-up approach over primary open necrosectomy.

Debates

Management of infected necrotizing pancreatitis

The PANTER randomized trial found that a step-up approach (percutaneous or endoscopic drainage followed, if needed, by minimally invasive necrosectomy) reduced major complications compared with primary open necrosectomy, shifting practice toward less invasive, staged intervention.

Seminal works

• banks-2013
• van-santvoort-2010
• forsmark-2016

Frequently asked questions

What are the most common causes of acute pancreatitis?

Gallstones and alcohol together account for most cases; gallstone pancreatitis occurs when a stone transiently obstructs the pancreatic outflow at the level of the bile and pancreatic ducts.

What does the revised Atlanta classification do?

It provides internationally agreed definitions for the severity of acute pancreatitis (mild, moderately severe, severe) and for its local complications, allowing consistent description and comparison of cases.