Acute Pancreatitis

Anatomy of the pancreas and surrounding vascular structures - Rosen's Emergency Medicine

Definition

1. Abdominal pain strongly suggestive of AP (epigastric, radiating to back)
2. Serum amylase and/or lipase ≥3× upper limit of normal
3. Characteristic imaging findings

• Grainger & Allison's Diagnostic Radiology, p. 677; Current Surgical Therapy 14e, p. 603

Etiology

• Rosen's Emergency Medicine, Box 77.1, p. 1266

Pathophysiology

• Local pancreatic inflammation and tissue destruction
• Release of pro-inflammatory cytokines (IL-1, IL-6, TNF-α)
• Systemic inflammatory response syndrome (SIRS)
• Increased microvascular permeability → third-spacing of fluids
• In severe cases: multiorgan dysfunction (lungs, kidneys, cardiovascular)

Classification (Revised 2012 Atlanta)

• Interstitial edematous pancreatitis - diffuse enlargement without necrosis; most common; usually resolves within first week
• Necrotizing pancreatitis - affects ~5-10% of patients; may involve pancreatic parenchyma and peripancreatic tissue; necrosis may be sterile, liquefy, or become infected

• Current Surgical Therapy 14e, p. 603-604

• Cardiovascular: systolic BP <90 mmHg or HR >130 bpm
• Pulmonary: PaO₂ <60 mmHg
• Renal: creatinine >2.0 mg/dL

Clinical Features

• Persistent epigastric or LUQ pain, typically moderate-to-severe, radiating to the back, chest, or flanks
• Pain relieved by sitting forward or leaning forward
• Nausea, vomiting, anorexia
• Note: pain intensity does NOT correlate with severity

• Vital signs: fever, tachycardia, and sometimes hypotension in severe disease
• Jaundice suggests obstruction (gallstone or tumor)
• Epigastric tenderness ± guarding; rebound less common
• Absent bowel sounds if ileus present
• Shallow respirations (pain splinting); basilar crackles or decreased breath sounds
• Cullen sign - bluish periumbilical discoloration (hemoperitoneum) - rare, poor prognosis
• Grey Turner sign - reddish-brown flank discoloration (retroperitoneal hemorrhage) - rare, poor prognosis
• Murphy sign if gallstone etiology

• ARDS, pleural effusions (up to 50% of patients, predominantly left-sided)
• Cardiovascular collapse and shock (from fluid shifts)
• Acute kidney injury (hypoperfusion + inflammatory mediators)
• DIC/coagulopathy
• Rosen's Emergency Medicine, p. 1265-1266

Investigations

• Lipase - preferred over amylase; more sensitive and specific; elevated for 1-2 weeks (amylase 3-5 days)
• Both begin rising within hours of onset; degree of elevation does NOT correlate with severity
• Amylase falsely negative in alcohol and hypertriglyceridemia-induced AP
• LFTs (ALT, AST, bilirubin) - evaluate for biliary etiology; ALT >3× ULN has PPV of 95% for gallstone pancreatitis
• FBC, BMP - assess for SIRS, organ failure
• Calcium, triglycerides - if no obvious etiology
• CRP >100 mg/L - useful marker of severity during hospitalization
• BUN - rising BUN associated with inadequate hydration and higher mortality

1. Diagnostic uncertainty or normal enzymes with high clinical suspicion
2. Ruling out other intra-abdominal pathology
3. Assessing complications when patient fails to improve after 48-72 hours

Severity Scoring Systems

BISAP Score (Bedside Index of Severity in Acute Pancreatitis)

Ranson Criteria

• Age >55 years
• WBC >16,000/mm³
• Glucose >200 mg/dL
• AST >250 IU/L
• LDH >350 IU/L

• Hematocrit drop >10%
• BUN rise >5 mg/dL
• Calcium <8 mg/dL
• PaO₂ <60 mmHg
• Base deficit >4 mEq/L
• Fluid needs >6 L

Other Systems

• APACHE II - can be calculated at any time; PPV 43%, NPV 89% for critically ill
• CT Severity Index (CTSI/Modified CTSI) - based on degree of necrosis, inflammation, and fluid collections on CT
• PASS (Pancreatitis Activity Scoring System) - dynamic, continuous monitoring throughout illness course

• Rosen's Emergency Medicine, Table 77.1, p. 1267; Harrison's 22e, p. 2791; Current Surgical Therapy 14e, p. 604

Management

1. Fluid Resuscitation (cornerstone of treatment)

• Aggressive IV fluid replacement - Lactated Ringer's preferred over normal saline (lower incidence of SIRS)
• Typical rate: 250-500 mL/hr initially
• Target: urine output >0.5 mL/kg/hr, decreasing BUN and hematocrit
• A decrease in hematocrit and BUN within 12-24h confirms adequate resuscitation
• Less aggressive strategy may be sufficient for milder disease; adjust for cardiac/pulmonary/renal comorbidities

2. Pain Management

• IV opioids are safe and recommended
• Hydromorphone or morphine; meperidine no longer preferred
• NSAIDs and patient-controlled analgesia can supplement

3. Nutrition

• Mild AP: low-fat solid diet once patient can tolerate oral intake
• Severe AP: enteral nutrition preferred over TPN - initiated within 2-3 days of admission
  • Enteral feeding maintains gut barrier integrity, limits bacterial translocation, lower cost, fewer complications than TPN
  • Gastric feeding (nasogastric) is safe; jejunal (nasojejunal) has possible physiologic advantages but not proven superior
• Nil-by-mouth has no benefit and worsens outcomes in most cases

4. Antibiotics

• No role for prophylactic antibiotics in necrotizing pancreatitis - does not improve survival and may promote opportunistic fungal infections
• Empiric antibiotics indicated for: clinical decompensation, suspected infected necrosis, confirmed infection
• Drug-induced pancreatitis: discontinue offending agent

5. Addressing Etiology

• Gallstone pancreatitis: cholecystectomy (same admission for mild AP; after resolution for severe)
• Post-ERCP: rectal indomethacin and/or pancreatic duct stenting for prophylaxis
• Hypertriglyceridemia: insulin infusion, fibrates; adjuncts include heparin or plasmapheresis (limited evidence); outpatient lipid-lowering therapy
• Hypercalcemia: treat underlying hyperparathyroidism or malignancy

6. ICU Triage

• Lower BISAP, normal hematocrit, low BUN → regular ward
• Persistent SIRS at 24h or significant comorbidities → step-down unit
• Higher BISAP, elevated hematocrit and BUN, respiratory failure, organ failure → ICU
• Harrison's 22e, p. 2791-2792; Rosen's Emergency Medicine, p. 1268-1270

Local Complications

Management of Necrosis

• Sterile necrosis: managed conservatively unless complications arise
• Infected necrosis (suspected): empiric broad-spectrum antibiotics (carbapenems penetrate necrosis well)
• Fine-needle aspiration (FNA) of necrosis for Gram stain/culture is no longer universally recommended - risk of contaminating sterile collections
• Drainage/debridement ("step-up approach"):
  1. Percutaneous/endoscopic drainage first
  2. Video-assisted retroperitoneal debridement (VARD) or endoscopic necrosectomy if drainage fails
  3. Open surgical necrosectomy (last resort - high morbidity/mortality)
• Interventions delayed until necrosis is walled off (typically >4 weeks) for better outcomes

• Harrison's 22e, p. 2792; Current Surgical Therapy 14e, p. 604-605

Prognosis

• Overall mortality ~5% (declining over time despite rising incidence)
• Severe AP: 36-50% mortality
• Infected pancreatic necrosis: extremely high mortality
• Rising BUN during hospitalization = inadequate hydration + higher in-hospital mortality
• Persistent SIRS at 24h = predictor of organ failure and necrosis
• CRP >100 mg/L during hospitalization = marker of severity

Key Pearls

• Lipase is preferred over amylase (more sensitive, specific, and remains elevated longer)
• Degree of enzyme elevation does NOT predict severity
• CT should NOT be routine - wait 48-72h (ideally 3-7 days) to assess complications
• No role for prophylactic antibiotics in necrotizing pancreatitis
• Enteral nutrition over TPN in severe AP
• Lactated Ringer's over normal saline for fluid resuscitation
• Delay intervention on necrosis until it is walled off (>4 weeks)
• ALT >3× ULN has 95% PPV for biliary pancreatitis