Dr. Elizabeth Squirell

Acute pancreatitis

Diagnosis, Atlanta severity, WATERFALL fluids, early feeding, and when ERCP or cholecystectomy

Reviewed October 2026 · For healthcare professionals. Follow your local protocols.

Is it this?

Two of three (ACG 2024):

  1. Abdominal pain consistent with pancreatitis (constant epigastric pain, often to the back).
  2. Lipase (preferred over amylase) or amylase >3× the upper limit of normal.
  3. Characteristic findings on imaging.

Find the cause

  • Transabdominal ultrasound in everyone for gallstones; repeat if inconclusive (ACG Rec 1).
  • Liver tests (biliary pattern), calcium, alcohol history, medications.
  • No gallstones and no significant alcohol use: check triglycerides; likely the cause if >11.3 mmol/L (1000 mg/dL) (ACG 2024).
  • Age >40 with no cause found: consider a pancreatic tumour (ACG 2024).

Severity (revised Atlanta)

Grade Definition
Mild No organ failure; no local or systemic complications
Moderately severe Organ failure that resolves within 48 h, and/or local complications, and/or exacerbation of a comorbidity
Severe Persistent organ failure >48 h

Severity can’t be fully assigned on day 1. Watch closely for organ failure in the first 48 h (ACG 2024). SIRS or organ failure: monitored bed (ACG 2024). Organ failure of grade 2 or more on the modified Marshall score: ICU (IAP 2025).

Fluids (adult)

Patient Regimen (lactated Ringer’s)
Normovolemic 1.5 mL/kg/h, no bolus
Hypovolemic 10 mL/kg bolus, then 1.5 mL/kg/h
  • WATERFALL moderate arm; ACG 2024 Rec 3 (moderately aggressive) and Rec 4 (lactated Ringer’s over normal saline).
  • Shock or organ failure at presentation is outside this regimen. WATERFALL excluded shock, respiratory failure, heart failure (NYHA II or worse, or EF <50%), eGFR <60, decompensated cirrhosis and signs of volume overload. Resuscitate to effect, and give further boluses while hypovolemia persists (ACG Rec 3).
  • Reassess within 6 h, then often over 24–48 h (WATERFALL protocol: 3, 12, 24, 48 and 72 h). Reasonable targets (IAP 2025): MAP 65–85 mm Hg, urine output 0.5 mL/kg/h, falling urea, hematocrit <44%. IAP 2025 also recommends lactated Ringer’s at 1.5 mL/kg/h, with a bolus only for hypovolemia or hypotension.
  • Most patients need about 3–4 L in the first 24 h (ACG 2024).
  • Caution with heart or kidney disease, and watch for overload (ACG 2024).

Orders

  • Feed early: mild AP, oral diet within 24–48 h as tolerated, starting with a low-fat solid diet (no need for clear fluids first) (ACG Rec 10–11). Can’t eat in moderately severe or severe AP: enteral feeding, nasogastric preferred over nasojejunal (similar safety and efficacy), not TPN (ACG 2024 key concepts 19–20).
  • No prophylactic antibiotics, even in severe or necrotizing AP (ACG Rec 8; IAP 2025 Rec 19). Treat a documented infection, or strongly suspected infected necrosis (e.g. gas in the collection on CT). A raised CRP, WBC or procalcitonin alone is not a reason to start antibiotics (IAP 2025 Rec 18).
  • Analgesia: opioids or NSAIDs are both acceptable first choices (IAP 2025, strong); opioids give better relief when pain is severe. NSAIDs relieve pain as well as opioids in the first 24 h and spare opioids (Thavanesan 2022). Avoid NSAIDs in AKI per local practice. Reassess pain with a numeric scale.
  • VTE prophylaxis per local protocol.

Imaging: when

  • No routine CT at admission. CT only if the diagnosis is unclear, or if the patient is not improving after 48–72 h (ACG 2024).
  • Suspected CBD stone without cholangitis: MRCP or EUS, not diagnostic ERCP (ACG 2024).

ERCP: who and when

Situation ERCP?
Gallstone AP with cholangitis Yes, within 24 h (ACG 2024)
Persistent biliary obstruction or a stone on MRCP/EUS Yes, not urgent
Gallstone AP without cholangitis, even if predicted severe No. Medical therapy (ACG Rec 5). APEC: urgent ERCP did not reduce complications or death

Disposition

  • Mild gallstone AP: cholecystectomy in the same admission, before discharge (ACG 2024). PONCHO: recurrent gallstone complications 5% vs 17% with interval surgery.
  • Necrotizing AP: delay cholecystectomy until collections have nearly resolved (IAP 2025 Rec 85) and delay drainage. For stable necrosis, wait about 4 weeks for collections to wall off (ACG key concept 23; IAP 2025: about 3–4 weeks). If infected necrosis is not improving on antibiotics and is at least partly encapsulated, earlier drainage may be appropriate (IAP 2025 Rec 38): discuss with the pancreatic team.
  • Hypertriglyceridemia-associated AP: insulin infusion lowers triglycerides (IAP 2025 Rec 64: recommended in diabetes, may be considered without); plasmapheresis only for persistent organ failure (IAP Rec 65).
  • Alcohol: brief intervention and follow-up. Hypertriglyceridemia: treat and follow up.

Red flags

  • SIRS, rising urea or hematocrit despite fluids, hypoxemia, oliguria: early ICU review.
  • Jaundice with fever: think cholangitis, call for ERCP.
  • New fever or deterioration in a patient with necrosis: consider infected necrosis (antibiotics that penetrate necrosis; drainage delayed if possible, ACG 2024).

Pitfalls

  • Over-hydration (pulmonary edema, abdominal compartment syndrome).
  • Ordering CT on day 1 for “severity.”
  • Keeping the patient NPO “to rest the pancreas.”
  • Prophylactic carbapenems.
  • Discharging mild gallstone AP without a cholecystectomy.

Follow your local protocols for dosing and renal adjustment.

Sources

  1. Tenner S, et al. American College of Gastroenterology Guidelines: Management of Acute Pancreatitis. Am J Gastroenterol 2024;119:419–437. PMID 38857482 Rec 1 (ultrasound), 3–4 (moderately aggressive fluids, lactated Ringer's), 5 (medical therapy over early ERCP without cholangitis), 8 (no prophylactic antibiotics), 10–11 (early oral low-fat solid diet). Key concepts: 20 (nasogastric preferred to nasojejunal feeding), 23 (delay necrosis intervention, preferably 4 weeks), diagnosis 2 of 3; no routine early CT; TG >1000 mg/dL; monitored bed for SIRS or organ failure; ERCP within 24 h for cholangitis; MRCP or EUS before ERCP; cholecystectomy before discharge in mild biliary AP; 1.5 mL/kg/h if normovolemic, 10 mL/kg bolus if hypovolemic.
  2. IAP/APA/EPC/IPC/JPS Working Group. International Association of Pancreatology revised guidelines on acute pancreatitis 2025. Pancreatology 2025;25:770–814. PMID 40651900 Table 1: Rec 10–11 (lactated Ringer's, 1.5 mL/kg/h, bolus only if hypovolemic or hypotensive); GPS 12 (targets MAP 65–85, urine 0.5 mL/kg/h, urea and hematocrit <44%); Rec 14 (opioids or NSAIDs; opioids better for severe pain); GPS 15 (ICU for modified Marshall organ failure grade ≥2); Rec 17–19 (antibiotics only for proven infection or strongly suspected infected necrosis; not for CRP, WBC or procalcitonin alone; no prophylaxis); Rec 22–26 (early low-fat solid diet; enteral feeding within 72 h if not eating, NG or NJ); Rec 28–29 (early ERCP only with cholangitis); Rec 37–38 (delay necrosis intervention to about 3–4 weeks; earlier drainage may be appropriate if infected necrosis fails antibiotics and is partly encapsulated); Rec 64 (insulin for hypertriglyceridemia-associated AP); Rec 84–86 (same-admission cholecystectomy in mild biliary AP; delay in necrotizing AP).
  3. de-Madaria E, et al. Aggressive or Moderate Fluid Resuscitation in Acute Pancreatitis (WATERFALL). N Engl J Med 2022;387:989–1000. PMID 36103415 Moderate: 10 mL/kg bolus only if hypovolemic, then 1.5 mL/kg/h LR; assessments at 3, 12, 24, 48 and 72 h (NCT04381169). Excluded shock or respiratory failure at recruitment, NYHA ≥II heart failure or EF <50%, eGFR <60, decompensated cirrhosis, volume overload. Aggressive (20 mL/kg + 3 mL/kg/h) caused more fluid overload (20.5% vs 6.3%) with no benefit (moderately severe/severe 22.1% vs 17.3%).
  4. Banks PA, et al. Classification of acute pancreatitis—2012: revision of the Atlanta classification and definitions by international consensus. Gut 2013;62:102–111. PMID 23100216 Mild, moderately severe (transient organ failure, local complications or comorbidity exacerbation) and severe (organ failure >48 h).
  5. da Costa DW, et al. Same-admission versus interval cholecystectomy for mild gallstone pancreatitis (PONCHO). Lancet 2015;386:1261–1268. PMID 26460661 Recurrent gallstone complications or death: 5% same-admission vs 17% interval (RR 0.28).
  6. Schepers NJ, et al. Urgent ERCP with sphincterotomy versus conservative treatment in predicted severe acute gallstone pancreatitis (APEC). Lancet 2020;396:167–176. PMID 32682482 No reduction in major complications or death (38% vs 44%) without cholangitis; ERCP only for cholangitis or persistent cholestasis.
  7. Thavanesan N, et al. Analgesia in the initial management of acute pancreatitis: a systematic review and meta-analysis of randomised controlled trials. World J Surg 2022;46:878–890. PMID 34994837 Little level-1 evidence; NSAIDs similar to opioids in the first 24 h and opioid-sparing.
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