Acute Pancreatitis

Acute inflammation of the pancreas with activation of digestive enzymes in the gland, local injury, and in severe cases a systemic inflammatory response with organ failure.

• Diagnosis needs two of three: typical epigastric pain radiating to the back, serum lipase or amylase of more than 3 times the upper limit of normal, and characteristic changes on imaging.
• Severity: mild (no organ failure or local complications; about 80% of cases), moderately severe (transient organ failure for less than 48 hours or local complications), severe (persistent organ failure for more than 48 hours; mortality about 20 to 40%). Overall mortality is about 2 to 5%.
• Incidence is about 30 to 40 per 100,000 per year.
• Causes: gallstones and biliary sludge (40%), alcohol (30%), hypertriglyceridaemia (triglycerides more than 11.3 mmol/L or 1000 mg/dL), drugs, endoscopic retrograde cholangiopancreatography (3 to 5% of procedures), hypercalcaemia, trauma, autoimmune disease, infection (mumps, Ascaris, hepatitis), scorpion sting, pancreas divisum and tumours, and idiopathic (10 to 20%).
• Mechanism: premature activation of trypsinogen in acinar cells causes autodigestion, inflammation, microvascular injury and cytokine release, leading to third space fluid loss and necrosis.

Sudden, severe, constant epigastric pain radiating to the back, relieved by sitting forward; nausea, vomiting, fever, tachycardia, abdominal distension, reduced bowel sounds.

• Signs of severity: hypotension, tachypnoea, hypoxaemia, oliguria, confusion; Cullen sign (periumbilical bruising) and Grey Turner sign (flank bruising) in haemorrhagic disease.
• History: gallstone symptoms, alcohol intake, drugs, family history, recent endoscopic procedures, hypertriglyceridaemia, and trauma.
• Differential diagnosis: perforated peptic ulcer, acute cholecystitis, cholangitis, intestinal obstruction, mesenteric ischaemia, aortic dissection, myocardial infarction (inferior), ruptured aortic aneurysm, diabetic ketoacidosis, basal pneumonia, renal colic.
• Complications: systemic inflammatory response and organ failure (respiratory, renal, cardiovascular), acute peripancreatic fluid collection, pancreatic pseudocyst (after 4 weeks), acute necrotic collection and walled-off necrosis, infected necrosis (about 30% of necrotising disease), haemorrhage and pseudoaneurysm, splenic and portal vein thrombosis, abdominal compartment syndrome, diabetes, exocrine insufficiency, and chronic pancreatitis.

Serum lipase (more sensitive and more specific than amylase; more than 3 times the upper limit of normal), amylase, full blood count, urea, creatinine, electrolytes, calcium, glucose, liver tests, lactate dehydrogenase, triglycerides, C-reactive protein, and arterial blood gas.

• Aetiology: alanine aminotransferase of more than 150 U/L predicts gallstones (about 95% positive predictive value); ultrasound of the biliary tract for stones, sludge and common bile duct dilatation; triglycerides and calcium; alcohol history; drug review; and IgG4 when autoimmune disease is suspected.
• Severity markers: haematocrit of more than 44%, urea of more than 7.1 mmol/L (20 mg/dL) and rising at 24 hours, C-reactive protein of more than 150 mg/L at 48 hours, persistent systemic inflammatory response, organ failure scoring.
• Contrast-enhanced CT is not needed in the first 72 hours except when the diagnosis is uncertain; use it at 72 hours or more for suspected necrosis or complications, and MRI with MRCP for common bile duct stones and ductal disruption.
• Chest X-ray (effusion, acute respiratory distress syndrome), ECG, and troponin to exclude myocardial infarction.
• After a first idiopathic episode: endoscopic ultrasound, MRCP, and genetic tests for recurrent disease; computed tomography of the abdomen after age 40 to exclude tumour.

Admit to high-dependency care if there is organ failure, a persistent systemic inflammatory response, or a risk of severe disease; intensive care for organ failure.

• Fluid resuscitation (the most important early treatment): lactated Ringer solution (or balanced crystalloid) 5 to 10 mL/kg/hour for the first 12 to 24 hours (a bolus of 10 mL/kg if hypovolaemic), reassess every 6 hours and adjust to urine output of more than 0.5 mL/kg/hour, heart rate less than 120 beats per minute, mean arterial pressure of 65 to 85 mmHg, and falling urea and haematocrit; avoid excess fluid (more than 4 L in the first 24 hours is linked with harm) and watch for pulmonary oedema and abdominal compartment syndrome.
• Oxygen to SpO2 94 to 98%, with high-flow nasal oxygen or ventilation for respiratory failure.
• Analgesia:
  • Paracetamol 1 g IV or oral every 6 hours (maximum 4 g daily; 3 g in alcohol misuse or weight less than 50 kg).
  • Morphine 2 to 5 mg IV every 2 to 4 hours as needed, or fentanyl 25 to 50 micrograms IV, or hydromorphone 0.5 to 1 mg IV; patient controlled analgesia for severe pain; thoracic epidural for refractory pain in intensive care.
  • Avoid NSAIDs when there is renal impairment or bleeding risk.
• Nutrition: oral feeding as soon as pain allows, with a low fat diet within 24 hours; enteral nutrition by nasogastric or nasojejunal tube (30 kcal/kg/day) when oral intake fails after 48 to 72 hours; parenteral nutrition only when enteral feeding is not possible.
• No prophylactic antibiotics; give antibiotics for proven or suspected infection: cholangitis, infected necrosis (fever, gas in collection, positive culture), or other infections, with meropenem 1 g IV every 8 hours (or imipenem-cilastatin 500 mg IV every 6 hours, or piperacillin-tazobactam 4.5 g IV every 6 hours) for 2 to 4 weeks guided by cultures.
• Biliary disease: urgent endoscopic retrograde cholangiopancreatography within 24 hours for cholangitis, and within 72 hours for persisting common bile duct obstruction (bilirubin rising or stone visible); cholecystectomy during the same admission for mild gallstone disease, and after resolution of collections (about 6 weeks) in necrotising disease.
• Hypertriglyceridaemia: insulin infusion 0.1 to 0.3 units/kg/hour with 5% dextrose, targeting triglycerides of less than 5.65 mmol/L (500 mg/dL); plasma exchange in selected severe cases (evidence limited).
• Metabolic: correct hypocalcaemia only if symptomatic (calcium gluconate 10% 10 to 20 mL IV over 10 minutes), correct hypokalaemia, hypomagnesaemia and glucose (insulin infusion for glucose of more than 10 mmol/L); enoxaparin 40 mg SC daily for thromboprophylaxis; omeprazole 40 mg daily only if there is a separate indication.
• Necrotising disease and collections: delay intervention for 4 weeks until walled off; intervene for infection, obstruction (gastric outlet, biliary) or persistent symptoms with the step-up approach: endoscopic transluminal drainage with lumen-apposing metal stent, or percutaneous drainage, then endoscopic necrosectomy or minimally invasive retroperitoneal debridement if no improvement. Pseudocysts that are symptomatic need endoscopic cystgastrostomy.
• Special groups: children (fluid at 1.5 to 2 times maintenance, early feeding, search for biliary, drug, genetic and metabolic causes); pregnancy (gallstones and hypertriglyceridaemia are common, fluids, analgesia with paracetamol or morphine, endoscopic retrograde cholangiopancreatography with shielding if needed, cholecystectomy in the second trimester, insulin and plasmapheresis for hypertriglyceridaemia); elderly (higher mortality, careful fluid titration); renal impairment (adjust antibiotics and avoid NSAIDs and contrast where possible); immunosuppression (low threshold for infection investigation); alcohol misuse (withdrawal prevention).
• Red flags: persistent organ failure beyond 48 hours, shock, oxygen requirement, oliguria, abdominal compartment syndrome (bladder pressure of more than 20 mmHg), fever with a collection, bleeding, jaundice with fever.
• Follow-up: review at 2 to 4 weeks, with repeat imaging at 6 weeks if collections were present; assess glucose, nutrition and pancreatic enzymes; stop alcohol and smoking; follow for diabetes and exocrine insufficiency; pancreatic enzyme replacement with pancrelipase 25,000 to 50,000 units with meals and 10,000 to 25,000 units with snacks when steatorrhoea develops.