Acute Pancreatitis

Anatomy

Diagrammatic representation of the pancreas, anterior view - Rosen's Emergency Medicine

Etiology

• Gallstones (40-70% of cases)
• Chronic alcohol use (25-35% of cases)

Pathophysiology

• Increased microvascular permeability and third-spacing of fluid
• Pulmonary involvement (ARDS, pleural effusions - left-sided more common, atelectasis)
• Cardiovascular collapse (fluid shifts, shock)
• Renal failure (hypoperfusion + inflammatory mediators)
• Coagulopathy / DIC
• Hyperglycemia (reduced insulin secretion), hypocalcemia (low albumin/magnesium)

Classification (2012 Revised Atlanta Classification)

Morphological Types

Severity Grades

Local Complications (Revised Atlanta Terminology)

• Acute Peripancreatic Fluid Collection (APFC) - homogeneous, non-encapsulated fluid collection adjacent to pancreas; <4 weeks from onset
• Pancreatic Pseudocyst - encapsulated fluid collection with well-defined wall, no necrosis; >4 weeks from onset

• Acute Necrotic Collection (ANC) - heterogeneous fluid + necrosis, intrapancreatic and/or extrapancreatic
• Walled-Off Necrosis (WON) - heterogeneous fluid + necrosis with well-defined wall; >4 weeks from onset

Clinical Features

• Persistent, moderate-to-severe epigastric or left upper quadrant pain radiating to the back, chest, or flanks
• Pain often worse in supine position; relieved by leaning forward
• Nausea, vomiting, anorexia

• Fever, tachycardia, elevated respiratory rate
• Jaundice (suggests biliary obstruction)
• Shallow respirations from pain splinting; basilar crackles or reduced breath sounds (pleural effusion)
• Cullen sign - bluish periumbilical discoloration (hemoperitoneum)
• Grey Turner sign - reddish-brown flank discoloration (retroperitoneal bleeding)
• Both are late findings (sign of hemorrhagic pancreatitis)
• In severe cases: hypotension, signs of shock

Diagnosis

Diagnostic Criteria

1. Abdominal pain strongly suggestive of acute pancreatitis
2. Serum amylase and/or lipase ≥3× upper limit of normal
3. Characteristic imaging findings

Laboratory Tests

Testing both amylase and lipase together does not improve sensitivity or specificity. Use lipase alone.

Imaging

• First-line to evaluate for biliary/gallstone etiology
• Limited for direct pancreatic visualization (obscured by bowel gas)
• Can identify cholelithiasis, bile duct dilation; guides need for MRCP/EUS

• NOT routine upfront; reserve for:
  1. Diagnostic uncertainty or atypical presentation
  2. Rule out other serious intra-abdominal pathology
  3. Assess complications in patients not improving after 48-72 hours
• Best performed 3-7 days after onset (necrosis evolves; early CT can miss it)

• 90% sensitivity and specificity

• Shows: parenchymal enlargement, loss of texture/borders, peripancreatic fat stranding, areas of non-enhancement (necrosis)

CT appearance of acute interstitial pancreatitis (arrows = peripancreatic fluid and fat stranding):

Rosen's Emergency Medicine, Fig. 77.2 - Axial view: swollen pancreas with peripancreatic fluid and fat stranding

• Similar diagnostic utility to CT; superior for gallbladder and biliary tract
• Preferred when contrast is contraindicated
• MRI is more costly and less available

Chest X-ray if pulmonary complications are suspected. Plain abdominal films show only non-specific findings.

Severity Scoring Systems

These scoring systems show similar predictive accuracy. Procalcitonin and CRP (at 24-48h) are useful additional severity markers.

Differential Diagnosis

Management

General Principles

1. Fluid Resuscitation

• Most critical in the first 24 hours
• Inadequate resuscitation → increased SIRS, organ failure, pancreatic necrosis, ICU admission
• Overly aggressive resuscitation → increased mechanical ventilation, abdominal compartment syndrome, earlier sepsis
• IAP/APA: Goal-directed 5-10 mL/kg/h targeting HR <120/min, MAP 65-85 mmHg, urine output >0.5-1 mL/kg/h
• ACG: 250-500 mL/h
• Preferred fluid: Lactated Ringer's (LR) over normal saline - LR may provide anti-inflammatory benefits; large volumes of NS cause hyperchloremic metabolic acidosis which activates trypsinogen and worsens inflammation
• Colloids not generally recommended; consider if Hct <24% or albumin <2 g/dL
• Monitor with Hct, BUN, creatinine

2. Pain Management

• IV opioids (e.g., morphine, hydromorphone) are acceptable
• Goal: adequate analgesia to allow normal respiratory effort

3. Nothing by Mouth (NPO) / Nutrition

• NPO initially; reinstate oral feeding as soon as tolerated (once pain subsides, nausea/vomiting resolves)
• Mild AP: Early oral feeding (within 24h) is safe and reduces hospital stay
• Severe/prolonged AP: Early enteral nutrition (via nasojejunal or nasogastric tube) is preferred over parenteral nutrition - reduces infectious complications, maintains gut barrier, decreases bacterial translocation
• Total parenteral nutrition (TPN) reserved for those who cannot tolerate enteral feeding

4. Antibiotics

• Not indicated for prophylaxis in sterile pancreatitis (even necrotizing)
• Indicated for documented infected pancreatic necrosis or other concurrent infection (e.g., cholangitis)
• Organisms: gram-negative predominate; increasing gram-positive organisms also seen
• Use broad-spectrum IV antimicrobials with good pancreatic tissue penetration (e.g., carbapenems, fluoroquinolones + metronidazole)

5. Biliary Pancreatitis / ERCP

• Abdominal ultrasound early for all patients to identify gallstones
• Urgent ERCP (within 24-72h) indicated if there is concurrent acute cholangitis or persistent biliary obstruction
• Not indicated for mild gallstone pancreatitis without cholangitis
• Cholecystectomy should be performed during the same admission or shortly after for gallstone pancreatitis (prevents recurrence)

6. Management of Local Complications

• Most resolve spontaneously; intervention only if symptomatic (pain, obstruction, infection)
• Drainage options: endoscopic (EUS-guided cystgastrostomy), percutaneous, or surgical

• Step 1: Broad-spectrum IV antibiotics
• Step 2: Percutaneous catheter drainage or endoscopic (transgastric/transduodenal) drainage
• Step 3: If no improvement → minimally invasive necrosectomy: VARD (video-assisted retroperitoneal debridement), MIRP, or endoscopic direct necrosectomy (DEN)
• Open necrosectomy reserved for failure of minimally invasive approaches; associated with substantial morbidity
• The PANTER trial demonstrated the step-up approach reduced major complications vs. open necrosectomy (12% vs. 50%) with similar mortality

7. ICU Care

• Continuous monitoring of organ function in severe AP
• Ventilatory support for ARDS
• Vasopressors for refractory shock
• Renal replacement therapy for acute kidney injury

Systemic Complications

Prognosis & Disposition

• Mild AP: Most resolve within 3-7 days; low mortality (<5%); can often manage with supportive care
• Severe AP: Mortality 30-50%; extremely high with infected necrosis
• Persistent organ failure >48h is the strongest predictor of death
• Most patients require hospital admission; ICU for severe/complicated disease
• Reassess severity at 24h, 48h, 7 days, and weekly

Recurrence Prevention

• Gallstones: Cholecystectomy (same admission or early outpatient)
• Alcohol: Abstinence counseling and addiction support
• Hypertriglyceridemia: Lipid-lowering therapy (fibrates), dietary changes
• Medications: Identify and discontinue offending drug
• Idiopathic/Recurrent: Consider EUS, MRCP, genetic testing (SPINK1, CFTR, PRSS1 mutations)