Acute Pancreatitis

Detailed Overview

Acute pancreatitis most commonly results from gallstones obstructing the ampulla of Vater or chronic heavy alcohol use. The premature activation of trypsin triggers a cascade of enzymatic damage, causing microvascular leakage, edema, and fat necrosis. While 80% of cases are mild and self-limiting (interstitial edematous pancreatitis), 20% progress to severe necrotizing pancreatitis, characterized by tissue death, infection, and multiorgan failure. Early aggressive fluid resuscitation is the cornerstone of preventing necrosis.

Epidemiology & Demographics

Incidence: ~30-40 cases per 100,000 population annually. It is a leading cause of GI-related hospital admissions in the US. Gallstone pancreatitis is more common in women, while alcohol-induced pancreatitis is more common in men.

Etiological Mechanism

The 'I GET SMASHED' mnemonic: Idiopathic, Gallstones (40%), Ethanol (30%), Trauma, Steroids, Mumps, Autoimmune, Scorpion sting, Hypercalcemia/Hypertriglyceridemia (>1000 mg/dL), ERCP, Drugs.

Primary Causes

Cholelithiasis (Gallstones)

Heavy alcohol consumption

Hypertriglyceridemia

Post-ERCP complication

• Biliary disease: Presence of small gallstones or microlithiasis.
• Alcohol Use Disorder: Chronic consumption sensitizes acinar cells to premature enzyme activation.
• Obesity: Increases the risk of severe disease and complications.

The inciting event causes a block in the apical secretion of zymogens from the pancreatic acinar cells. Zymogen granules fuse with lysosomes, and lysosomal cathepsin B activates trypsinogen into trypsin intracellularly. Trypsin subsequently activates other proenzymes (elastase, phospholipase A2) within the pancreas. This leads to enzymatic autodigestion of the pancreatic parenchyma and surrounding peripancreatic fat (fat necrosis with calcium saponification). The localized tissue damage releases massive amounts of pro-inflammatory cytokines (IL-1, IL-6, TNF-alpha) into the systemic circulation, causing a third-spacing of fluids, distributive shock, and potentially ARDS.

Characteristic Clinical Presentation

• Abdominal pain: Severe, boring, constant epigastric pain that frequently radiates directly to the back.
• Nausea and Vomiting: Profound and intractable; vomiting does not relieve the pain.
• Anorexia: Inability to tolerate any oral intake.

Physical Examination Signs

• Epigastric tenderness to palpation, sometimes with involuntary guarding.
• Decreased or absent bowel sounds (secondary paralytic ileus).
• Cullen's sign (periumbilical ecchymosis) in severe hemorrhagic pancreatitis.
• Grey Turner's sign (flank ecchymosis) in severe hemorrhagic pancreatitis.

• Pancreatic Pseudocyst: A fluid collection rich in amylase enclosed by a wall of fibrous tissue, occurring >4 weeks after onset.
• Walled-Off Necrosis (WON): Maturation of necrotic tissue collection, highly prone to secondary bacterial infection.
• Acute Respiratory Distress Syndrome (ARDS): Systemic cytokine release damages pulmonary capillaries.

Diagnostic Criteria & Guidelines

Requires 2 of the following 3 criteria: 1) Characteristic severe epigastric pain. 2) Serum lipase or amylase >3 times the upper limit of normal. 3) Characteristic findings on cross-sectional imaging (CT or MRI).

Differential Diagnosis

• Perforated peptic ulcer
• Acute cholecystitis / Biliary colic
• Mesenteric ischemia
• Myocardial Infarction (inferior wall)

Laboratory Tests & Biomarkers

• Serum Lipase: Elevated > 3x normal (more sensitive and specific than amylase; remains elevated longer).
• BUN / Hematocrit: Often elevated on admission due to severe hemoconcentration/dehydration. A rising BUN predicts severe disease.
• Triglycerides: Check to rule out hypertriglyceridemia if gallstones/alcohol are absent.

Imaging Modalities & Findings

• Right Upper Quadrant Ultrasound: Initial test of choice to identify gallstones/biliary dilation as the cause.
• CT Abdomen/Pelvis with IV contrast: Not needed initially if clinical/labs confirm diagnosis. Used at 72 hrs to detect necrosis (areas of non-enhancement) if patient is failing to improve.

• Mild Acute Pancreatitis
  No organ failure, no local or systemic complications. Usually resolves in 3-5 days.
• Moderately Severe Acute Pancreatitis
  Transient organ failure (<48 hrs) or local complications (pseudocyst).
• Severe Acute Pancreatitis
  Persistent organ failure (>48 hrs); high mortality due to infected necrosis.

Second-Line & Adjunctive Therapy

If PO intake is not tolerated for >3-5 days, initiate enteral feeding via a nasojejunal or nasogastric tube. Total parenteral nutrition (TPN) is only used as a last resort. ERCP is indicated within 24 hours only if there is concurrent acute cholangitis.

Surgical & Procedural Management

Laparoscopic cholecystectomy is indicated prior to discharge for mild gallstone pancreatitis to prevent recurrence. Endoscopic or surgical necrosectomy (step-up approach) is used for infected pancreatic necrosis after walled-off (usually >4 weeks).

Recommended Lifestyle Changes

• Strict and permanent abstinence from alcohol.
• Smoking cessation (smoking increases risk of recurrent pancreatitis and pancreatic cancer).
• Weight loss and fat-restricted diet if hypertriglyceridemia is the cause.

Patient Counseling & Advice

Advise the patient that one attack of acute pancreatitis significantly increases the risk of future attacks if the underlying cause (like alcohol use or gallstones) is not eliminated. Repeated attacks can lead to chronic pancreatitis, causing permanent pain and diabetes.

Follow-Up & Monitoring Schedule

Outpatient clinical follow-up in 2-4 weeks to ensure resolution of pain and ability to eat. Repeat imaging (CT/MRI) in 4-6 weeks if a pseudocyst or necrosis was suspected and symptoms persist.

Preventive Strategies

Cholecystectomy for gallstone disease. Fibrates and strict diet for severe hypertriglyceridemia. Avoidance of offending drugs.

Mild acute pancreatitis has a mortality rate < 1%. Severe acute pancreatitis with persistent multiorgan failure and infected necrosis carries a mortality rate of 20-30%.