Pancreatitis

• Definition: Acute pancreatitis is an acute inflammatory injury of the exocrine pancreas caused by inappropriate intracellular activation of digestive zymogens, producing glandular autodigestion, peripancreatic inflammation, and — when severe — a systemic inflammatory response with organ failure.
• Chronic pancreatitis: irreversible fibroinflammatory destruction of the gland after repeated or sustained injury, defined clinically by pain plus exocrine insufficiency (steatorrhea) and endocrine insufficiency (diabetes).
• Why it matters: acute pancreatitis is one of the leading gastrointestinal causes of inpatient hospitalization in the United States. Most attacks are mild and self-limited, but a substantial minority develop necrosis, persistent organ failure, or infected necrosis, where mortality rises sharply. Early risk stratification and fluid resuscitation change outcomes; enzyme levels do not predict them.

Epidemiology worth recalling

• Sex and etiology split: biliary pancreatitis predominates in women (gallstone prevalence); alcohol-related disease predominates in men and clusters in the fourth to fifth decades.
• Age: incidence rises with age, paralleling gallstone prevalence; pediatric cases suggest trauma, drugs, structural anomalies (pancreas divisum), or hereditary mutations.
• Rising causes: obesity, hypertriglyceridemia, and increasing ERCP volume have pushed metabolic and iatrogenic etiologies up in frequency.
• Trajectory: the revised Atlanta classification (2012) frames the disease as mild, moderately severe (transient organ failure <48 h or local complications), or severe (persistent organ failure >48 h) — the framework the ACG and AGA both use for management decisions.
• Course: a biphasic illness — an early SIRS-driven phase in the first week, then a later phase dominated by local complications and infection of necrotic tissue.

Obstructive (mechanical) mechanisms

• Gallstones: a stone impacted at the ampulla obstructs the pancreatic duct, raising intraductal pressure and driving zymogen activation. Microlithiasis/biliary sludge causes the same picture with a normal ultrasound.
• Structural/neoplastic obstruction: periampullary or pancreatic head tumor, duct stricture, pancreas divisum, ascariasis. A first attack in an older patient without stones or alcohol should raise concern for malignancy.
• Post-ERCP: instrumentation and contrast injection cause ductal hypertension and edema — the classic iatrogenic cause.

Toxic and metabolic mechanisms

• Alcohol: direct acinar toxicity from ethanol metabolites plus protein plug precipitation in small ducts; typically after years of heavy use, not a single binge.
• Hypertriglyceridemia: risk climbs above roughly 500 mg/dL and is highest above 1000 mg/dL; pancreatic lipase liberates free fatty acids that are directly cytotoxic to acinar cells and endothelium.
• Hypercalcemia: hyperparathyroidism or malignancy — calcium promotes intracellular trypsinogen activation.
• Drugs: azathioprine/6-MP, valproate, thiazides, corticosteroids, didanosine, GLP-1 receptor agonists (labeled warning), and estrogens (via triglycerides).

Other

• Trauma: blunt epigastric injury compressing the gland against the vertebral column (handlebar injury).
• Infection: mumps, coxsackievirus, CMV, HIV-associated opportunistic infection.
• Autoimmune (IgG4-related): painless obstructive jaundice, sausage-shaped pancreas, steroid-responsive.
• Genetic: PRSS1 gain-of-function (hereditary pancreatitis, autosomal dominant), SPINK1, CFTR — suspect in recurrent attacks in a young patient.

Modifiable versus non-modifiable

• Modifiable: alcohol use, tobacco (independently accelerates progression to chronic pancreatitis), obesity, hypertriglyceridemia, offending drugs.
• Non-modifiable: age, female sex for biliary disease, genetic mutations, anatomic variants, prior ERCP need.
• Idiopathic: after negative ultrasound, lipids, and calcium, the ACG supports EUS or MRCP to unmask microlithiasis or occult obstruction before labeling a case idiopathic.

• Normal protection: acinar cells package digestive enzymes as inactive zymogens in granules, keep them physically separate from lysosomal hydrolases, and express SPINK1 (pancreatic secretory trypsin inhibitor) to quench any trypsin that activates prematurely. Activation is normally deferred until enterokinase acts in the duodenum.
• Initiating insult: ductal obstruction (stone), toxic injury (ethanol metabolites, free fatty acids), or a sustained rise in cytosolic calcium causes colocalization of zymogen granules with lysosomes. Lysosomal cathepsin B cleaves trypsinogen to trypsin inside the acinar cell.
• Amplification: trypsin activates the remaining zymogen cascade — chymotrypsinogen, proelastase, prophospholipase A2 — overwhelming SPINK1. In hereditary pancreatitis, mutant PRSS1 trypsin resists autolysis, so the cascade is self-sustaining.

How enzymes generate the clinical picture

• Elastase digests vascular elastin → vessel wall disruption, retroperitoneal hemorrhage → Cullen and Grey Turner signs.
• Phospholipase A2 destroys cell membranes and surfactant → contributes to ARDS and pleural effusions (left-sided classically).
• Lipase hydrolyzes peripancreatic and omental fat → fat necrosis; liberated fatty acids chelate calcium as insoluble soaps (saponification) → hypocalcemia with Chvostek/Trousseau signs.
• Retroperitoneal inflammation irritates the celiac plexus and splanchnic nerves → boring epigastric pain radiating to the back, relieved by leaning forward; adjacent bowel becomes atonic → ileus, distension, and vomiting.

Systemic phase

• Cytokine release (TNF-α, IL-1, IL-6) and complement activation produce SIRS with capillary leak. Massive third-spacing into the retroperitoneum causes intravascular depletion, hemoconcentration (rising hematocrit), prerenal azotemia (rising BUN), hypotension, and shock — the reason early fluid resuscitation is the central intervention.
• Hypoperfusion of the gland converts interstitial edematous pancreatitis into necrotizing pancreatitis; gut barrier failure allows bacterial translocation, seeding necrosis later in the course.
• Chronic disease: repeated injury activates pancreatic stellate cells → fibrosis, duct strictures, calcified protein plugs, and loss of acini (steatorrhea) then islets (diabetes).

Symptoms

• Epigastric pain: acute in onset, constant, severe, radiating straight through to the back, worse supine and eased by sitting forward or curling up — retroperitoneal location of the inflamed gland explains both the radiation and the positional relief.
• Nausea and persistent vomiting that does not relieve the pain: reflex plus ileus from adjacent inflammation.
• Anorexia and abdominal distension from paralytic ileus; obstipation may mimic bowel obstruction.
• Pain onset timing: biliary pancreatitis often begins abruptly after a fatty meal; alcoholic pancreatitis typically develops over hours to a day or two after a heavy drinking episode in someone with chronic use.

Examination findings

• Epigastric tenderness with guarding, often out of proportion to the modest findings on palpation; true rigidity suggests perforation instead.
• Fever and tachycardia early from cytokine-mediated SIRS, not necessarily infection.
• Hypotension, oliguria, tachypnea: capillary leak and third-spacing; hypoxemia may reflect ARDS or a left pleural effusion.
• Jaundice: points to a retained common bile duct stone or, in the painless-jaundice patient, autoimmune or malignant obstruction.
• Cullen sign (periumbilical ecchymosis) and Grey Turner sign (flank ecchymosis): retroperitoneal blood tracking to the skin — uncommon, late, and a marker of severe hemorrhagic disease.
• **Tetany, perioral paresthesias, positive *Chvostek*/*Trousseau***: hypocalcemia from fat saponification.
• Xanthomas, lipemic serum, eruptive skin lesions: hypertriglyceridemic etiology.
• Parotid swelling in a young unvaccinated patient: mumps.

The stem's usual demographic

• A middle-aged woman with prior biliary colic, obesity, or recent cholecystitis — think gallstones and order an ultrasound.
• A middle-aged man with chronic heavy alcohol use presenting after a binge, sometimes with prior identical episodes.
• A patient one day after ERCP, or one on azathioprine, valproate, or a thiazide.
• Chronic pancreatitis: years of recurrent pain, weight loss, greasy floating stools, and new diabetes; pain may paradoxically diminish as the gland burns out.

Diagnostic criteria — two of three (revised Atlanta)

• Characteristic pain: acute, persistent, severe epigastric pain often radiating to the back.
• Serum lipase or amylase ≥3× the upper limit of normal: lipase is preferred for sensitivity, specificity, and its longer window of elevation. Levels do not grade severity, and serial enzyme measurements have no role.
• Characteristic imaging on contrast-enhanced CT, MRI, or ultrasound. Imaging is not required when the first two criteria are met.

Initial workup in every patient

• Transabdominal right upper quadrant ultrasound: the ACG recommends this on admission for all patients to look for gallstones and biliary dilation — it is the test that most often changes management.
• Labs: CBC (hematocrit as a marker of hemoconcentration), BMP (BUN, creatinine, calcium), LFTs, triglycerides, and calcium. An ALT greater than roughly three times normal strongly favors a biliary cause. Hyperglycemia, hypocalcemia, and a rising BUN reflect severity.
• Contrast-enhanced CT abdomen: reserved for diagnostic uncertainty, failure to improve, or clinical deterioration. Necrosis is under-represented in the first 48–72 hours, so CT performed too early falsely reassures; delayed scanning shows non-enhancing parenchyma.
• MRCP or endoscopic ultrasound: for suspected choledocholithiasis with equivocal ultrasound, and for evaluating recurrent or idiopathic disease.

Severity scoring

• BISAP: BUN >25 mg/dL, impaired mental status, SIRS, age >60, pleural effusion — usable within 24 hours.
• Ranson criteria: five admission variables (including age >55, WBC >16,000, glucose >200 mg/dL, elevated AST and LDH) plus 48-hour variables (hematocrit fall, BUN rise, calcium <8 mg/dL, hypoxemia, base deficit, fluid sequestration); its 48-hour requirement limits real-time utility.
• APACHE II and persistent organ failure remain the strongest severity discriminators.

Chronic pancreatitis

• CT or MRCP showing **calcifications, ductal dilation, and a chain of lakes duct**; fecal elastase-1 is the practical test for exocrine insufficiency. Amylase and lipase are often normal in burnt-out disease.

Immediate resuscitation (first 24–48 hours)

• Goal-directed IV crystalloid: the ACG and AGA recommend early fluid resuscitation, with lactated Ringer's preferred over normal saline (less hyperchloremic acidosis, signal toward less SIRS). Titrate to heart rate, mean arterial pressure, urine output, BUN, and hematocrit rather than to a fixed volume, and reassess frequently — over-resuscitation causes pulmonary edema and abdominal compartment syndrome.
• Analgesia: opioids are first-line; there is no evidence that morphine's effect on the sphincter of Oddi worsens outcomes, so withholding it is a distractor.
• Antiemetics and correction of electrolytes, particularly calcium, magnesium, and potassium.

Nutrition

• Early oral feeding as tolerated in mild disease (AGA) — prolonged NPO offers no benefit. If oral intake fails, use enteral nasogastric or nasojejunal feeding; parenteral nutrition is reserved for enteral failure because it increases infectious and line complications.

Etiology-directed therapy

• Urgent ERCP with sphincterotomy within 24 hours for gallstone pancreatitis complicated by acute cholangitis or persistent biliary obstruction. ERCP is not indicated for gallstone pancreatitis without cholangitis or obstruction.
• Cholecystectomy during the index admission for mild biliary pancreatitis (ACG) — deferring it risks early recurrence; in necrotizing disease, delay until collections resolve or stabilize.
• Hypertriglyceridemia: insulin infusion (with glucose to prevent hypoglycemia), plus apheresis in severe or refractory cases; fibrates long term.
• Autoimmune (IgG4) disease: corticosteroids.

Escalation and complications

• Antibiotics are for suspected or confirmed infected necrosis, not for sterile inflammation — a carbapenem such as meropenem penetrates necrotic pancreas well. The ACG advises against routine prophylaxis in sterile necrosis and against antifungal prophylaxis.
• Step-up approach for infected walled-off necrosis: percutaneous or endoscopic transluminal drainage first, then minimally invasive necrosectomy if needed; open necrosectomy is last resort. Intervention is delayed beyond about four weeks to allow the collection to wall off.

Early / systemic (first week — SIRS-driven)

• Hypovolemic shock and acute kidney injury: capillary leak and retroperitoneal third-spacing; signaled by rising BUN, rising hematocrit, and oliguria. Rising BUN at 24 hours is among the strongest predictors of death.
• ARDS: phospholipase A2 degrades surfactant plus systemic cytokines → hypoxemia with bilateral infiltrates. Emergency.
• Hypocalcemia: calcium consumed by saponification of necrotic fat; look for perioral tingling, *Chvostek*/*Trousseau*, prolonged QT.
• Hyperglycemia from islet injury and counter-regulatory stress; DIC in fulminant cases.
• Abdominal compartment syndrome: often iatrogenic from over-resuscitation — rising bladder pressure, oliguria, difficulty ventilating. Emergency.

Local (weeks 1–4 and beyond)

• Acute peripancreatic fluid collection → evolves into a pseudocyst after about four weeks: an encapsulated collection lacking a true epithelial lining, presenting with persistent pain, early satiety, or a palpable mass; drain only if symptomatic, infected, or expanding.
• Pancreatic necrosis → walled-off necrosis → infected necrosis: suspect when fever, leukocytosis, and clinical deterioration reappear after day 7–10; CT showing gas within the collection is the tell. Emergency requiring antibiotics and step-up drainage.
• Splenic vein thrombosis: perivenous inflammation → isolated gastric varices with a normal liver and normal portal pressures; bleeding is treated with splenectomy.
• Pseudoaneurysm, classically of the splenic artery, from enzymatic vessel wall digestion → sudden hemorrhage into a pseudocyst or GI tract. Emergency — angiographic embolization.
• Pancreatic duct disruption: pancreatic ascites or pleural effusion with very high fluid amylase; pancreaticoduodenal fistula.
• Colonic necrosis or obstruction from contiguous inflammation of the transverse colon.

Chronic sequelae and treatment-related

• Exocrine insufficiency → steatorrhea and fat-soluble vitamin (A, D, E, K) and B12 deficiency; type 3c diabetes, which is brittle because glucagon-producing alpha cells are lost too.
• Pancreatic adenocarcinoma risk, highest in hereditary pancreatitis.
• Iatrogenic: post-ERCP pancreatitis, fluid overload/pulmonary edema, catheter-related infection from TPN, and opioid dependence in chronic pain.

• Diagnosis needs two of three: characteristic pain, lipase ≥3× upper limit of normal, or characteristic imaging (revised Atlanta). If pain and lipase are both there, CT is not the next step — this is the most commonly missed "best next step" item.
• The single best next step after diagnosing acute pancreatitis is a right upper quadrant ultrasound plus early goal-directed lactated Ringer's. The ultrasound identifies gallstones, which determines whether the patient needs cholecystectomy before discharge (ACG).
• ERCP is only for gallstone pancreatitis with cholangitis or persistent biliary obstruction. Reflexively choosing ERCP for every biliary attack is the classic distractor — and ERCP itself causes pancreatitis.
• Mild gallstone pancreatitis gets cholecystectomy on the same admission, not as an interval outpatient procedure; delay leads to recurrent attacks.
• Enzyme magnitude does not equal severity. Use BISAP, APACHE II, persistent organ failure, or the Ranson criteria; a lipase of 5,000 in a well-appearing patient can be mild disease.
• Fever and deterioration after day 7–10 with gas in a peripancreatic collection = infected necrosis. Treat with a carbapenem plus delayed step-up drainage; do not give prophylactic antibiotics for sterile necrosis.
• Isolated gastric varices with a normal liver = splenic vein thrombosis from pancreatitis. This is the association examiners test most reliably.
• Hypocalcemia with tetany after an alcoholic binge and epigastric pain = saponification of fat by liberated fatty acids — a severity marker, not a primary parathyroid problem.
• Do not withhold morphine out of concern for the sphincter of Oddi, and do not keep patients NPO once they tolerate oral intake — early feeding is recommended by the AGA.
• Recurrent pancreatitis in a young patient with no stones, alcohol, or drugs → think PRSS1, SPINK1, CFTR, or pancreas divisum; in an older patient with a first unexplained attack, think pancreatic head malignancy.

• Acute pancreatitis: sudden-onset epigastric pain radiating to back, elevated lipase (more specific than amylase), elevated liver enzymes/bilirubin if biliary etiology
• Chronic pancreatitis: recurrent/chronic pain, steatorrhea, diabetes, pancreatic calcifications on imaging
• Amylase peaks at 24-48 hours then falls; lipase remains elevated longer (3-14 days) → lipase preferred for late presentations
• Ranson criteria/APACHE II predict severity and mortality in acute pancreatitis
• Most common causes: gallstones (40%), alcohol (35%); other: hypertriglyceridemia, medications, autoimmune, trauma

1. 1.Using amylase alone: Amylase is less specific (elevated in salivary disorders, ectopic pregnancy) and normalizes quickly; lipase is more sensitive and specific and stays elevated longer → use lipase for diagnosis
2. 2.Confusing amylase/lipase elevation with severity: Enzyme levels do NOT correlate with severity; use Ranson criteria, APACHE II, or imaging (CT) to assess prognosis
3. 3.Missing chronic pancreatitis complications: Screen for diabetes, fat-soluble vitamin deficiencies (A, D, E, K), pancreatic cancer risk, and portal hypertension from splenic vein thrombosis

Acute Pancreatitis

• NPO (bowel rest), aggressive IV hydration with normal saline (0.5-1 L/hr)
• Analgesia (opioids if needed)
• Treat underlying cause (ERCP + sphincterotomy for gallstone obstruction)
• Monitor for complications (necrosis, infection); prophylactic antibiotics only if necrosis present
• Nutritional support: enteral feeding (nasogastric or nasojejunal) preferred over TPN

Chronic Pancreatitis

• Pancreatic enzyme replacement (lipase-amylase-protease tablets) for steatorrhea
• Fat-soluble vitamin supplementation (A, D, E, K)
• Insulin for diabetes
• Pain management; avoid alcohol
• Screen for pancreatic cancer