Gastrointestinal & Hepatic · Topic 11 of 26
Acute Pancreatitis
Gastrointestinal · pancreatobiliary
Acute Pancreatitis
Diagnose with 2 of 3 criteria, then give moderate goal-directed lactated Ringer's, feed early, and skip prophylactic antibiotics.
Key numbers
Two of three: pain, lipase, imaginglipase > 3× ULN
Moderate lactated Ringer's, 1.5 mL/kg/hLR 1.5 mL/kg/h
Oral low-fat diet within 24–48 hoursfeed ≤ 24–48 h
Severe = organ failure beyond 48 hoursorgan failure > 48 h
ERCP within 24 hours only with cholangitisERCP ≤ 24 h if cholangitis
01 · Defined byTwo of three: pain, lipase, imaging
Acute pancreatitis = at least 2 of 3: typical pain (epigastric, often radiating to the back), serum lipase or amylase more than 3 times the upper limit of normal, or characteristic findings on imaging.
02 · DoModerate lactated Ringer's, 1.5 mL/kg/h
Give moderate goal-directed lactated Ringer's: 1.5 mL/kg/h, plus a 10 mL/kg bolus only if hypovolemic; reassess at 6 hours and over 24–48 hours (BUN, hematocrit, urine output) and stop pushing fluid after 48 hours.
03 · DoOral low-fat diet within 24–48 hours
In mild pancreatitis, start oral feeding within 24–48 hours as tolerated, beginning with a low-fat solid diet rather than clear liquids; early feeding protects the gut barrier and shortens the stay.
01
Causes & risk factors
Why it happensRight upper quadrant ultrasound in every patientGallstones (40–70%) and alcohol (25–35%) cause most cases: get an abdominal ultrasound in every patient, and when neither cause is present check triglycerides (above 1000 mg/dL is causative) and calcium.
Early predictors of a severe coursePredictors of a severe course: SIRS, BUN above 20 mg/dL or rising, hematocrit above 44%, altered mental status, older age, BMI over 30, pleural effusion or infiltrates — monitor these patients closely.
02
Diagnosis & monitoring
Work-upSevere = organ failure beyond 48 hours must knowRevised Atlanta severity: mild = no organ failure or complications; moderately severe = local or systemic complications, or organ failure that resolves within 48 hours; severe = persistent organ failure lasting more than 48 hours.
03
Do right now
In this orderFirst moves
1
→Moderate lactated Ringer's, 1.5 mL/kg/hLR 1.5 mL/kg/h
2
→Treat pain with parenteral opioids
3
→Right upper quadrant ultrasound in every patient
4
Oral low-fat diet within 24–48 hoursfeed ≤ 24–48 h
Why each step
Moderate lactated Ringer's, 1.5 mL/kg/hGive moderate goal-directed lactated Ringer's: 1.5 mL/kg/h, plus a 10 mL/kg bolus only if hypovolemic; reassess at 6 hours and over 24–48 hours (BUN, hematocrit, urine output) and stop pushing fluid after 48 hours.
Treat pain with parenteral opioidsPain usually needs adequate parenteral opioids — hydromorphone is usually preferred to morphine (theoretical sphincter of Oddi spasm) — plus antiemetics.
Right upper quadrant ultrasound in every patientGallstones (40–70%) and alcohol (25–35%) cause most cases: get an abdominal ultrasound in every patient, and when neither cause is present check triglycerides (above 1000 mg/dL is causative) and calcium.
Oral low-fat diet within 24–48 hoursIn mild pancreatitis, start oral feeding within 24–48 hours as tolerated, beginning with a low-fat solid diet rather than clear liquids; early feeding protects the gut barrier and shortens the stay.
04
Management
OrdersNo routine CT on admissionDo not order CT on admission routinely; reserve contrast-enhanced CT for an uncertain diagnosis or a patient not improving after 48–72 hours, when it shows necrosis (non-enhancing pancreas) and collections.
ERCP within 24 hours only with cholangitisGallstone pancreatitis with cholangitis needs ERCP within 24 hours; without cholangitis, medical therapy is preferred over early ERCP, and MRCP or endoscopic ultrasound confirms a retained duct stone first.
Cholecystectomy before discharge for gallstone pancreatitisAfter mild gallstone pancreatitis settles, arrange cholecystectomy during the same admission to prevent recurrent attacks.
Cannot eat: nasogastric enteral feeding, not TPNIf the patient cannot eat, feed enterally through a nasogastric tube (a nasojejunal tube is not required); use parenteral nutrition only if the enteral route is impossible, not tolerated or insufficient.
Delay necrosis drainage beyond 4 weeksIn a stable patient, delay drainage or necrosectomy of infected necrosis, preferably beyond 4 weeks, so it liquefies and walls off; use a minimally invasive approach (endoscopic or percutaneous) before open surgery.
05
Red flags & don'ts
Avoid harmInfected necrosis: gas on CT, deterioration complicationSuspect infected necrosis when the patient deteriorates or fails to improve after 7–10 days; gas in the necrosis on CT is enough to start necrosis-penetrating antibiotics (carbapenem, fluoroquinolone, metronidazole) — no fine-needle aspiration needed.
Pseudocyst versus walled-off necrosis after 4 weeks complicationCollections that persist about 4 weeks develop a wall: a pseudocyst holds fluid only, walled-off necrosis holds fluid plus solid necrosis. Drain a pseudocyst only if expanding, infected, bleeding or likely to rupture.
06
The rules
Know theseNo prophylactic antibiotics, even when severe must knowDo not give prophylactic antibiotics, whatever the severity and even with sterile necrosis; start antibiotics only for a documented infection — cholangitis, infected necrosis, pneumonia, bacteremia or urinary infection.
07
Pseudocyst or walled-off necrosis?
Commonly confused| Contents | Fluid only |
|---|---|
| When the wall forms | After about 4 weeks |
| Natural course | About one-third resolve on their own |
| Drain when | Expanding, infected, bleeding or about to rupture |
08
More detail
ReferenceShow 8 reference facts
Give rectal indomethacin 100 mg to patients at high risk of post-ERCP pancreatitis; add a prophylactic pancreatic duct stent for the highest-risk patients.
Organ failure is a modified Marshall score of 2 or more in any system: systolic BP below 90 not responding to fluid, creatinine 1.9 mg/dL or higher, or PaO2/FiO2 of 300 or less.
Lipase is preferred over amylase — more specific and elevated longer; enzymes rise on day 1, usually normalize in 3–5 days, and can also rise in renal failure, perforated ulcer or mesenteric ischemia.
Grey Turner sign (flank ecchymosis) and Cullen sign (periumbilical ecchymosis) reflect hemorrhagic exudate, occur in under 3% of cases and carry a poor prognosis.
Hypocalcemia and hyperglycemia are common; check magnesium in a hypocalcemic patient. Left-sided or bilateral pleural effusion on chest radiograph signals severe disease.
Drug causes include azathioprine, 6-mercaptopurine, valproate, sulfa drugs, furosemide, ACE inhibitors, asparaginase, pentamidine and GLP-1 receptor agonists; ERCP causes pancreatitis in about 5–8% of procedures.
Other local complications include splenic vein thrombosis, pseudoaneurysm and gastric outlet dysfunction. Early deaths (first week) come from multiorgan failure; later deaths add infected necrosis.
About one-third of pseudocysts resolve on their own; in about one-third of patients with pancreatic necrosis the necrosis becomes infected by gut bacteria, with very high morbidity and mortality.
Moderate fluids, food early, and antibiotics only for proven infection — the three ACG 2024 reversals of old teaching.
Sources · Merck Manual Professional — Acute Pancreatitis (Aug 2026; cites ACG 2024) · Tenner S et al. American College of Gastroenterology Guidelines: Management of Acute Pancreatitis. Am J Gastroenterol 2024;119:419–437 · The Hospitalist (SHM), June 2026 — Applying the 2024 ACG Guidelines on Acute Pancreatitis to Hospital Medicine · de-Madaria E et al. Aggressive or Moderate Fluid Resuscitation in Acute Pancreatitis (WATERFALL). N Engl J Med 2022;387:989–1000 · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).