Acute Pancreatitis

Definition and Epidemiology

• Current Surgical Therapy 14e, p. 604
• Harrison's Principles of Internal Medicine 22E, p. 2790

Etiology ("I GET SMASHED" mnemonic)

• Grainger & Allison's Diagnostic Radiology, p. 677
• Current Surgical Therapy 14e, p. 604

Pathophysiology

1. Autodigestion of pancreatic parenchyma and peripancreatic fat
2. Local inflammatory cascade - cytokine release (IL-1, IL-6, TNF-α) causes acinar cell necrosis
3. Systemic inflammatory response syndrome (SIRS) - in severe cases, systemic spillover of activated enzymes and cytokines causes distant organ injury (ARDS, AKI, cardiovascular collapse)

Diagnosis

1. Abdominal pain characteristic of AP (epigastric, radiating to the back, onset over hours, aggravated by eating)
2. Serum lipase or amylase ≥3× upper limit of normal
3. Characteristic imaging findings on CT, MRI, or ultrasound

Note: Lipase is preferred over amylase - it is more sensitive and specific, and remains elevated longer. Amylase can be normal in hypertriglyceridemia-induced AP.

• Grainger & Allison's Diagnostic Radiology, p. 677
• Harrison's 22E, p. 2789

CT Evolution of Necrotizing Pancreatitis

Severity Classification (2012 Revised Atlanta)

• Current Surgical Therapy 14e, Table 1

Severity Scoring Systems

Ranson's Criteria

BISAP Score (≥3 = high risk)

• (B) BUN >25 mg/dL
• (I) Impaired mental status (GCS <15)
• (S) SIRS (≥2 of 4 criteria present)
• (A) Age >60 years
• (P) Pleural effusion on imaging

APACHE II Score

• ≥8 at 24 h predicts severe disease; performs similarly to Ranson's criteria

CT Severity Index (CTSI / Balthazar Score)

• Combines degree of pancreatic inflammation (grades A-E) with extent of necrosis (0%, <33%, 33-50%, >50%)
• CTSI ≥7 associated with high morbidity and mortality

Additional Severity Markers

• Harrison's 22E, Table 359-2

Local Complications (2012 Revised Atlanta Definitions)

• Current Surgical Therapy 14e, Tables 1-2

Management

Management Algorithm (Maingot's Abdominal Operations)

1. Fluid Resuscitation

• Preferred fluid: Lactated Ringer's (LR) - shown to decrease systemic inflammation (lower CRP) vs. normal saline; avoids hyperchloremic acidosis
• Traditionally: bolus 15-20 mL/kg, then 2-3 mL/kg/h
• A 2022 RCT (WATERFALL trial) demonstrated that moderate resuscitation (10 mL/kg bolus, then 1.5 mL/kg/h) is preferred over aggressive, as aggressive hydration increases fluid overload risk without improving outcomes
• Monitor: urine output >0.5 mL/kg/h, hematocrit, BUN every 8-12 h; falling Hct and BUN at 12-24 h confirms adequate resuscitation
• Avoid overresuscitation - abdominal compartment syndrome is a recognized complication

2. Analgesia

• IV opioids are standard; no evidence favors one agent over another
• Earlier concerns about morphine causing sphincter of Oddi spasm are not clinically significant

3. Nutrition

• Mild AP: resume oral diet as soon as tolerated (often within 24-48 h), typically starting with low-fat soft diet
• Moderate-severe AP: early enteral nutrition (EN) is preferred over TPN - maintains gut mucosal integrity, reduces bacterial translocation, reduces infectious complications
• Route: nasojejunal (NJ) or nasogastric (NG) tube feeding is equally effective; NJ is traditional but NG is simpler
• TPN only if EN is not tolerated or contraindicated

4. Antibiotics

• Not routinely indicated in AP, even with necrosis
• Indications: confirmed infected necrosis (positive FNA cultures, gas in necrosis on CT), or concurrent cholangitis
• Prophylactic antibiotics in sterile necrotizing pancreatitis: NOT recommended (multiple RCTs show no benefit and risk of fungal superinfection)
• If infected necrosis: broad-spectrum agents penetrating pancreatic tissue (carbapenems, fluoroquinolones + metronidazole)

5. Etiology-Specific Management

• Gallstone pancreatitis with cholangitis - urgent ERCP within 24-48 h
• Gallstone pancreatitis without cholangitis - cholecystectomy during same admission (mild AP) or after recovery (severe AP) to prevent recurrence; biliary sphincterotomy for non-surgical candidates
• Hypertriglyceridemia-induced AP - IV insulin to lower triglycerides; NPO for 24-36 h; long-term fibrates/omega-3s
• Drug-induced AP - withdraw offending agent immediately

6. Management of Necrosis

• Sterile necrosis - conservative management; surgical debridement only for persistent symptoms after ≥4 weeks
• Infected necrosis (fever, leukocytosis, gas on CT, positive FNA):
  • Step-up approach is standard: percutaneous or endoscopic drainage first, escalating to minimally invasive or open necrosectomy only if needed
  • Timing: delay intervention until necrosis is "walled-off" (>3-4 weeks) to reduce morbidity
  • Endoscopic ultrasound-guided transmural drainage increasingly preferred for WON adjacent to the stomach/duodenum
• Harrison's 22E, pp. 2790-2792
• Current Surgical Therapy 14e, pp. 604-608

Systemic Complications

• Grey Turner's sign - flank ecchymosis (retroperitoneal hemorrhage)
• Cullen's sign - periumbilical ecchymosis Both indicate hemorrhagic pancreatitis and poor prognosis.

Summary: Key Clinical Points