Acute pancreatitis: diagnosis, severity and management after the revised Atlanta classification

Making the diagnosis

The revised Atlanta classification of 2012 asks for two of three features: abdominal pain consistent with pancreatitis (acute, persistent, severe, epigastric and often radiating to the back); serum lipase or amylase at least three times the upper limit of normal; and characteristic findings on contrast-enhanced CT, MRI or ultrasound. If the first two are present, imaging is not needed for the diagnosis. The level of the enzyme does not predict severity.

Early CT is not a test for severity. Necrosis may not be visible for 72 hours, so a contrast-enhanced CT in the first days is reserved for diagnostic doubt or a patient who is failing to improve. Every patient should have an abdominal ultrasound to look for gallstones.

Finding the cause

Gallstones and alcohol are the common causes in the UK. Others to look for are hypertriglyceridaemia, hypercalcaemia, drugs, ERCP, trauma and, in the older patient without another cause, a pancreatic or periampullary tumour. If no cause is found after ultrasound, lipids and calcium, endoscopic ultrasound or MRCP may find microlithiasis that the first scan missed — the label ‘idiopathic’ should be earned.

Grading severity

The grade can only be assigned in retrospect, because it depends on whether organ failure persists. Scoring systems are used to predict it. The Glasgow (Imrie) score counts eight criteria over the first 48 hours; three or more predict a severe attack. An APACHE II score of 8 or more and a C-reactive protein above 150 mg/L at 48 hours are also used. Persistent systemic inflammatory response syndrome is a simple warning sign.

PaO₂

Below 8 kPa

Age

Over 55 years

Neutrophils

White cell count above 15 × 10⁹/L

Calcium

Below 2 mmol/L

Renal

Urea above 16 mmol/L

Enzymes

LDH above 600 IU/L or AST above 200 IU/L

Albumin

Below 32 g/L

Sugar

Glucose above 10 mmol/L

Collections: named by time and content

Most early fluid collections resolve and need no treatment. Sterile necrosis is managed conservatively. Infection is suspected when a patient deteriorates or fails to improve after the first week or so, and is supported by gas within the collection on CT; fine-needle aspiration is rarely needed.

Early management

• Fluids. Goal-directed intravenous crystalloid. More is not better: the WATERFALL trial (de-Madaria, NEJM 2022) was stopped because aggressive resuscitation caused more fluid overload without improving outcome.
• Analgesia and monitoring. Adequate analgesia, oxygen and a level of care matched to the predicted and actual severity; organ failure means critical care.
• Feeding. Oral diet as soon as tolerated. If enteral nutrition is needed, it is preferred to parenteral; a nasogastric tube is as good as nasojejunal for most. The PYTHON trial (Bakker, NEJM 2014) found no benefit from early tube feeding over an oral diet on demand.
• Antibiotics. Not given as prophylaxis (NICE NG104). They are for proven or strongly suspected infection, including infected necrosis and cholangitis.

Gallstones: ERCP and cholecystectomy

Urgent ERCP is indicated for gallstone pancreatitis with cholangitis, and for persisting biliary obstruction. Without cholangitis, early ERCP does not improve outcome: in the APEC trial (Schepens, Lancet 2020) urgent ERCP with sphincterotomy did not reduce complications or death in patients predicted to have severe gallstone pancreatitis.

After mild gallstone pancreatitis, cholecystectomy during the same admission prevents recurrent biliary events. The PONCHO trial (da Costa, Lancet 2015) showed fewer readmissions for gallstone-related complications than with interval cholecystectomy, with no increase in operative difficulty. UK guidance (the British Society of Gastroenterology, and the Academy of Medical Royal Colleges’ Evidence-Based Interventions programme) is cholecystectomy during the same admission or, failing that, within two weeks of discharge. After severe pancreatitis with collections, cholecystectomy waits until the collections have resolved or until about six weeks, and is sometimes combined with their treatment. A patient unfit for cholecystectomy can be protected from recurrence by endoscopic sphincterotomy.

Infected necrosis: the step-up approach

Open necrosectomy in the early phase carries a high risk of organ failure and death. The PANTER trial (van Santvoort, NEJM 2010) established the step-up approach: percutaneous or endoscopic drainage first, proceeding to minimally invasive necrosectomy only if the patient does not improve. Many patients never need the second step.

• Delay. Intervention is deferred, where the patient allows, until the necrosis is walled off, typically about four weeks. The POINTER trial (Boxhoorn, NEJM 2021) found no advantage in draining infected necrosis immediately rather than after a period of antibiotics.
• Route. The endoscopic transluminal step-up approach and the surgical step-up approach have similar mortality and major complications; the TENSION trial (van Brunschot, Lancet 2018) found fewer pancreatic fistulas and a shorter stay with the endoscopic route.
• Disconnected duct. Necrosis of the pancreatic neck can leave the tail disconnected from the main duct, a cause of recurrent collections that influences how a collection is drained.