Definition And Classification

Inflammatory disorder of pancreatic parenchyma.
Diagnosis requires minimum two of three criteria:
- Compatible abdominal pain.
- Serum amylase and/or lipase $\ge$ 3 times upper limit of normal.
- Suggestive cross-sectional imaging findings.

Category	Clinical Criteria
Mild	Absence of organ failure or local/systemic complications; resolves within 1 week.
Moderately Severe	Transient organ failure (<48 hours), local complications, or exacerbation of comorbid disease.
Severe	Persistent organ failure (>48 hours), single or multiple organs; high mortality risk.

Pathophysiology

Initial insult triggers pathological intracellular trypsinogen activation.
Cathepsin B activates trypsinogen to trypsin within acinar cells.
Trypsin activates additional proenzymes, precipitating autodigestion.
Abnormal sustained calcium release impairs mitochondrial permeability, depletes ATP, and induces acinar necrosis.
Proinflammatory cytokines released, triggering systemic inflammatory response syndrome (SIRS).

Category	Specific Causes
Trauma	Blunt abdominal injury (bicycle handlebars, motor vehicle accidents), child abuse, surgical injury.
Biliary Tract	Choledochal cyst, cholelithiasis, microlithiasis (sludge), pancreas divisum, anomalous junction.
Drugs/Toxins	Valproic acid, L-asparaginase, 6-mercaptopurine, azathioprine, steroids, tetracycline.
Systemic/Immune	Hemolytic uremic syndrome, Henoch-Schönlein purpura, systemic lupus erythematosus, inflammatory bowel disease, shock.
Infections	Mumps, Epstein-Barr virus, hepatitis A, coxsackievirus, rubella.
Metabolic	Diabetic ketoacidosis, hypercalcemia, hypertriglyceridemia, organic acidemias.
Genetic	Mutations in PRSS1 (cationic trypsinogen), SPINK1, CFTR, CTRC.

Severe, steady epigastric or upper quadrant abdominal pain.
Pain frequently radiates to back.
Nausea and persistent vomiting.
Antalgic positioning: hips/knees flexed, sitting upright, lying on side.
Abdominal distension, tenderness, palpable mass.
Hemorrhagic pancreatitis signs: Cullen sign (periumbilical ecchymosis), Grey Turner sign (flank ecchymosis).

Serum Lipase: Test of choice; high specificity/sensitivity. Rises 4-8 hours, peaks 24-48 hours, remains elevated 8-14 days.
Serum Amylase: Rises rapidly, normalizes within 3-5 days. Normal in up to 20% of patients initially.
Associated Laboratories: Leukocytosis, hyperglycemia, hypocalcemia, hemoconcentration (elevated BUN/hemoglobin), coagulopathy.
Abdominal Ultrasonography: First-line imaging. Evaluates for gallstones, biliary sludge, pancreatic edema, peripancreatic fluid.
Computed Tomography (CT): Indicated if diagnosis unclear or patient fails to improve after 72 hours/1 week. Identifies necrosis, abscess, pseudocysts. Avoid routine early CT due to radiation and delayed appearance of necrosis.

Fluid Resuscitation: Critical first-line intervention. Isotonic crystalloids (Lactated Ringer's preferred) at 1.5 to 2 times maintenance rate during initial 24-48 hours. Titrate to urine output and vital signs.
Analgesia: Adequate pain control mandatory. Intravenous opioids recommended for moderate-severe pain; nonsteroidal anti-inflammatory drugs/acetaminophen for mild pain.
Nutritional Support: Early enteral nutrition (within 2-3 days) via oral, nasogastric, or nasojejunal routes decreases complications, systemic inflammation, and hospital stay. Withhold oral intake only during active vomiting.
Antimicrobial Therapy: Prophylactic antibiotics contraindicated. Broad-spectrum antibiotics (carbapenems, quinolones) reserved exclusively for documented infected necrosis or extrapancreatic infections.
Interventional Therapy: ERCP indicated for biliary obstruction/impacted stones. Cholecystectomy indicated for gallstone pancreatitis prior to discharge.

Classification	Specific Complications
Local (<4 weeks)	Acute peripancreatic fluid collection, acute necrotic collection.
Local (>4 weeks)	Pancreatic pseudocyst (encapsulated fluid without necrosis), walled-off necrosis.
Systemic	Systemic inflammatory response syndrome (SIRS), acute respiratory distress syndrome, renal failure, shock, disseminated intravascular coagulation, gastrointestinal hemorrhage.