What are the causes of acute pancreatitis?

Causes of Acute Pancreatitis

Gallstones and alcohol abuse account for the vast majority of acute pancreatitis cases, with gallstones being the leading cause at 45-60% and alcohol responsible for 20-25% of cases. 1, 2

Primary Etiologies

Gallstone Disease (Most Common)

• Gallstones cause 45-60% of all acute pancreatitis cases, making this the single most important etiology to identify 1
• Gallstone migration obstructs the pancreatic duct at the ampulla of Vater, leading to increased pancreatic duct pressure and enzyme activation 1, 3
• The mechanism involves both pancreatic hyperstimulation and bile-pancreatic duct obstruction with active trypsin reflux 3

Alcohol Abuse (Second Most Common)

• Alcohol accounts for 20-25% of acute pancreatitis cases overall, though this varies significantly by geographic region 1, 2
• In chronic pancreatitis populations, alcohol is the etiological factor in 60-70% of cases 1
• The incidence is increasing among younger populations due to rising alcohol consumption 4

Secondary and Less Common Causes

Metabolic Causes

• Hypertriglyceridemia with severe elevations (>11.3 mmol/L) can precipitate acute pancreatitis and represents both a cause and consequence of pancreatic inflammation 1, 2
• Hypercalcemia activates pancreatic enzymes prematurely, leading to autodigestion and must be checked in all patients, especially when gallstones and alcohol are excluded 2

Drug-Induced Pancreatitis

• Medications including azathioprine/6-mercaptopurine and valproic acid can trigger pancreatitis 1
• Onset may occur shortly after initial drug use or develop after years of chronic exposure 1

Anatomical and Structural Abnormalities

• Pancreas divisum and other pancreatic duct abnormalities obstruct normal pancreatic drainage 1
• Pancreatic tumors can occasionally present as acute pancreatitis, particularly in elderly patients with otherwise idiopathic disease 1

Autoimmune and Infectious Causes

• Autoimmune pancreatitis is an immune-mediated form that may be associated with IgG4-related disease 1
• Viral infections can occasionally trigger pancreatitis 1

Trauma and Iatrogenic Causes

• Direct pancreatic injury from abdominal trauma or surgical procedures, particularly after cardiac or abdominal operations 1
• Post-operative acute pancreatitis represents a high-risk subset with worse outcomes 4

Idiopathic Pancreatitis

• Approximately 10-25% of cases remain classified as "idiopathic," but no more than 20-25% should be labeled as such 1, 2
• This diagnosis should only be accepted after vigorous investigation, including at least two high-quality ultrasound examinations, as gallstones are frequently missed on initial imaging 1, 2
• In recurrent idiopathic cases, endoscopic ultrasound may detect microlithiasis in the gallbladder or common bile duct 2

Critical Clinical Pitfalls

Common diagnostic errors to avoid:

• Accepting idiopathic diagnosis prematurely: Repeat biliary ultrasound is essential, as gallstones are the most commonly missed etiology 1, 2
• Inadequate lipid and calcium screening: Fasting triglycerides and calcium must be checked when gallstones and alcohol are excluded 2
• Missing occult malignancy: Consider pancreatic tumors in elderly patients presenting with first episode of "idiopathic" pancreatitis 1
• Overlooking medication history: Comprehensive drug history is essential, as drug-induced pancreatitis can occur after prolonged use 1, 2