Pancreatitis: A High-Yield USMLE Review

Pancreatitis is inflammation of the pancreas caused by premature intrapancreatic activation of digestive enzymes leading to autodigestion. Gallstones and alcohol account for roughly 80% of acute cases. It is a board favorite for its classic pain pattern, the 2-of-3 diagnostic criteria, fluid-based management, and its severe complications like necrosis. Chronic pancreatitis leads to exocrine then endocrine failure and increases pancreatic cancer risk.

Presentation

• Severe, constant, 'boring' epigastric pain radiating to the back (retroperitoneal location)
• Pain relieved by leaning forward (moves pancreas away from spine) and worsened by eating (CCK stimulates the pancreas)
• Nausea and vomiting
• Signs of SIRS: fever, tachycardia, and hypotension in severe cases
• Epigastric tenderness with guarding and decreased bowel sounds (ileus)
• Rarely, Cullen's sign (periumbilical ecchymosis) or Grey Turner's sign (flank ecchymosis) indicating hemorrhagic pancreatitis

Diagnosis

• Diagnosis requires 2 of 3: characteristic pain + lipase >3x upper limit of normal + characteristic imaging
• LFTs: ALT >3x ULN suggests a gallstone etiology; RUQ ultrasound to evaluate for gallstones even in presumed alcoholic pancreatitis
• CBC and BMP for severity markers; calculate BISAP score (BUN >25, Impaired mental status, SIRS, Age >60, Pleural effusion) with score ≥3 indicating high mortality risk
• CT at 72–96 hours if not improving to assess for necrosis; gas within a necrotic collection is pathognomonic for infection
• For occult or idiopathic cases: MRCP or EUS to detect microlithiasis, ductal anomalies, and early parenchymal changes; check IgG4 for autoimmune pancreatitis and consider genetic testing (PRSS1, SPINK1, CFTR) if young or recurrent

Management

• Aggressive IV fluid resuscitation with lactated Ringer's (goal-directed, adjusted by urine output, heart rate, hematocrit; avoid both under- and over-resuscitation)
• Pain control with opioids — do not withhold for theoretical sphincter of Oddi spasm
• NPO initially, then early enteral feeding preferred over TPN; resume oral diet when pain improves and hunger returns
• Treat the underlying cause: urgent ERCP for cholangitis/persistent biliary obstruction, cholecystectomy during same admission for gallstone pancreatitis, alcohol cessation, insulin infusion or plasmapheresis for hypertriglyceridemia
• Prophylactic antibiotics are NOT recommended routinely; use antibiotics only for documented or strongly suspected infection
• Infected necrosis: step-up approach — antibiotics (carbapenems have best tissue penetration) → minimally invasive drainage (endoscopic or percutaneous) → necrosectomy, delaying intervention to let necrosis wall off (~4 weeks)

High-yield

• Diagnose acute pancreatitis with 2 of 3: characteristic pain, lipase >3x ULN, and imaging findings
• Gallstones and alcohol cause ~80% of cases; ALT >3x ULN points to gallstones
• Position of relief: leaning forward eases pain because the pancreas is retroperitoneal; lying flat presses it against the spine
• Cullen's sign (periumbilical) and Grey Turner's sign (flank) ecchymoses indicate hemorrhagic pancreatitis
• Gas in a necrotic collection is pathognomonic for infected necrosis; treat with step-up approach
• In chronic pancreatitis, calcifications on CT are diagnostic; exocrine failure (malabsorption) precedes endocrine failure (diabetes), and cancer risk is increased
• Autoimmune (IgG4-related) pancreatitis: 'sausage-shaped' diffusely enlarged pancreas with rim-like halo, elevated IgG4, dramatic response to corticosteroids

Pitfalls

• Do not give prophylactic antibiotics routinely — they do not prevent infected necrosis and are reserved for documented or strongly suspected infection
• Do not intervene early on necrosis; delay drainage to allow it to wall off (step-up approach) — early aggressive surgery historically carried high mortality
• Do not assume alcoholic etiology without ruling out gallstones — obtain RUQ ultrasound even in presumed alcoholic cases
• Painless jaundice and weight loss in a chronic pancreatitis patient should raise concern for pancreatic adenocarcinoma, not just a flare
• Autoimmune pancreatitis can mimic pancreatic cancer (mass, jaundice, weight loss); recognizing it prevents unnecessary surgery
• Do not withhold opioids over fear of sphincter of Oddi spasm — this concern is largely theoretical