Acute Pancreatitis

Etiology & Pathophysiology - Ignition & Inferno

• Common Causes (Ignition):
  • Gallstones (most common, ~40%): Ampullary obstruction.
  • Alcohol (~30%): Acinar cell sensitization, premature enzyme activation.
  • Hypertriglyceridemia (TG > 1000 mg/dL).
  • Post-ERCP.
  • Drugs (e.g., thiazides, azathioprine, valproate).
  • 📌 Other causes: I GET SMASHED (mnemonic for less common etiologies like Idiopathic, Trauma, Steroids, Mumps, Autoimmune, Scorpion sting, Hypercalcemia, etc.).
• Pathophysiology (Inferno):
  • Core Defect: Intra-acinar premature activation of trypsinogen to trypsin.
  • Autodigestion: Activated enzymes (trypsin, chymotrypsin, elastase, phospholipase A2) digest pancreas & peripancreatic tissues.
  • Inflammatory Cascade: Release of cytokines (TNF-α, IL-1, IL-6) → local inflammation, edema, necrosis, hemorrhage.
  • Systemic Impact: Can lead to Systemic Inflammatory Response Syndrome (SIRS), ARDS, renal failure, multi-organ failure (MOF).

⭐ Trypsinogen activation within acinar cells, not primarily in the ductal system, is the critical initiating event in most cases of acute pancreatitis leading to autodigestion and inflammation.

Clinical Features & Diagnosis - Spotting the Sizzle

• Symptoms:
  • Abdominal Pain: Severe, constant epigastric, radiates to back; sudden onset.
  • Nausea & Vomiting.
  • Fever, tachycardia.
• Signs:
  • Epigastric tenderness.
  • Cullen's sign (periumbilical ecchymosis).
  • Grey Turner's sign (flank ecchymosis) - indicates severe disease.
• Diagnostic Criteria (Need ≥2 of 3):
  • Characteristic abdominal pain.
  • Serum amylase and/or lipase >3x upper limit of normal (ULN).
  • Characteristic findings on imaging (US, CT, MRI).
• Key Investigations:
  • Labs: ↑Amylase, ↑Lipase (more specific), ↑WBC, ↑CRP, ↓Ca.
  • Imaging: US (initial, for gallstones); CECT Abdomen (gold standard for severity/necrosis, after 48-72h if severe).

⭐ Serum lipase is more specific and remains elevated longer than amylase in acute pancreatitis.

Severity Assessment & Prognosis - Measuring the Mayhem

• Objective: Stratify risk for severity, organ failure (OF), mortality.
• Scoring Systems:
  • Ranson's Criteria: Admission & 48h. 📌 "GA LAW", "C HOBBS". Score ≥3 = severe AP.
  • BISAP: <24h. (BUN >25 mg/dL, Imp. mental status, SIRS, Age >60 yrs, Pleural Effusion). Score ≥3 = ↑ mortality.
  • APACHE II: ICU standard, complex.
  • Mod. Marshall: Defines OF (Resp, Renal, CV); score ≥2/system = OF.
  • CTSI (CT Severity Index): Balthazar grade + Necrosis. Max 10 (score ≥7 severe).
• Atlanta Classification (Revised):
  • Mild: No OF, no local/systemic complications.
  • Mod. Severe: Transient OF (<48h) OR local/systemic complications without persistent OF.
  • Severe: Persistent OF (>48h).

⭐ Persistent organ failure (>48h) is key determinant of severe AP.

Management & Complications - Dousing & Dealing

• Initial Management (First 24-72h):
  • Fluid Resuscitation: Aggressive IV crystalloids (Lactated Ringer's, 5-10 mL/kg/hr bolus, then 250-500 mL/hr). Target: UOP >0.5 mL/kg/hr, ↓HR, ↓Hct.
  • Pain Control: IV opioids (fentanyl, hydromorphone).
  • Nutrition: Mild AP: early oral low-fat diet. Severe AP: early enteral nutrition (nasojejunal) if NPO >3-5 days.
• Specific Interventions:
  • Antibiotics: NOT prophylactic. For infected necrosis (carbapenems). Diagnose by CT-FNA or gas on CT.

    ⭐ Prophylactic antibiotics do not prevent infection and may increase fungal superinfections.

  • ERCP: Within 24h for severe gallstone pancreatitis + cholangitis; within 72h if biliary obstruction.
• Complications & Management:
  • Local: Pseudocyst (>4 wks): Drain if symptomatic, >6 cm, or complicated. Walled-Off Necrosis (WON) (>4 wks): Step-up approach (drainage then necrosectomy) if infected/symptomatic.
  • Systemic: ARDS, AKI, SIRS, MODS, hypocalcemia.

High‑Yield Points - ⚡ Biggest Takeaways

• Gallstones and alcohol are the most common etiological factors for acute pancreatitis.
• Serum lipase is a more specific and sensitive diagnostic marker than serum amylase, remaining elevated longer.
• Severity assessment is critical using scores like Ranson's criteria or APACHE II.
• Contrast-Enhanced CT (CECT) is the imaging modality of choice for detecting necrosis and complications.
• Initial management focuses on aggressive intravenous fluid resuscitation, analgesia, and bowel rest (NPO).
• Infected pancreatic necrosis is a life-threatening complication requiring antibiotics and often surgical debridement.
• Pancreatic pseudocyst is a common late complication, typically managed if symptomatic or large.