Acute Pancreatitis — Written Clinical Reasoning

Part A — Diagnosis, aetiology and severity

Diagnosis

The patient meets two of the three Revised Atlanta diagnostic criteria for acute pancreatitis: characteristic epigastric pain radiating to the back, and serum lipase more than three times the upper limit of normal (1850 U per litre). The third criterion (characteristic imaging) is not required when the first two are met. A CT at this stage would be unnecessary and potentially misleading, because necrosis takes 72 hours to fully develop, and early contrast may theoretically worsen pancreatic perfusion [2].

Aetiological workup

The two dominant causes — gallstones (40 to 50 per cent) and alcohol (25 to 35 per cent) — must be evaluated first. The ALT is only mildly elevated (75 IU per litre), and the ultrasound shows no gallstones and a normal biliary tree, which makes gallstone aetiology less likely but does not exclude microlithiasis or biliary sludge. The patient drinks 60 grams of alcohol daily, which is a significant risk factor; alcohol is the most probable cause. The triglycerides (1.5 mmol per litre) and calcium (2.1 mmol per litre) are normal, excluding hypertriglyceridaemia (above 11 mmol per litre) and hypercalcaemia. [1]

A drug history is essential: azathioprine, mesalazine, didanosine, sulphonamides, thiazides, valproate, and oestrogens are the most commonly tested drug causes. The I GET SMASHED mnemonic organises the full list: Idiopathic, Gallstones, Ethanol, Trauma, Steroids, Mumps or Mycoplasma, Autoimmune, Scorpion sting, Hypertriglyceridaemia or Hypercalcaemia, ERCP, and Drugs. [1]

If no cause is identified after the standard workup (ultrasound, lipids, calcium, drug history, alcohol history), consider autoimmune pancreatitis (check IgG4, especially if there is painless jaundice or diffuse pancreatic enlargement), and arrange repeat biliary imaging after recovery (EUS or MRCP for occult microlithiasis). [1]

Severity assessment

The Revised Atlanta Classification defines three tiers [1]:

• Mild: no organ failure and no local or systemic complications. This patient does not yet qualify, because he is tachycardic and tachypnoeic, suggesting early SIRS.
• Moderately severe: transient organ failure (resolving within 48 hours) and/or local complications (necrosis, fluid collections) without persistent organ failure.
• Severe: persistent organ failure (more than 48 hours) involving respiratory, cardiovascular, or renal systems. [1]

At this stage, on the day of admission, he has not yet developed organ failure, but the tachycardia and tachypnoea signal SIRS and the risk of progression. The BISAP score (available within 24 hours) provides early risk stratification [6]. His BISAP: Blood urea nitrogen (if above 8.9 mmol per litre — needs to be checked), Impaired mental status (absent — 0 points), SIRS (present — tachycardia and tachypnoea meet two criteria), Age (unknown — if above 60, one point), Pleural effusion (needs chest X-ray). A BISAP of 3 or above identifies high-risk disease with a mortality of 5 to 20 per cent.

The CRP at 48 hours is the single most useful individual laboratory marker for necrosis: a CRP above 150 mg per litre at 48 hours suggests pancreatic necrosis. It is not useful on day 1 because it rises over 48 to 72 hours. [1]

Part B — Evidence-based management bundle

Fluid resuscitation — the WATERFALL paradigm

The 2024 ACG guideline recommends moderately aggressive, goal-directed fluid resuscitation with Ringer lactate, guided by frequent reassessment (every 6 hours) aiming to reduce the blood urea [2] [3]. This is a paradigm shift from the old teaching of aggressive 250 to 500 mL per hour fluids.

The WATERFALL trial (de-Madaria, NEJM 2022) randomised patients to aggressive resuscitation (20 mL per kg bolus over 2 hours, then 3 mL per kg per hour) versus moderate resuscitation (10 mL per kg bolus only if hypovolaemic, then 1.5 mL per kg per hour). The trial was stopped early by the Data Safety Monitoring Board because the aggressive arm caused significantly more fluid overload (including pulmonary oedema) without reducing moderately severe or severe pancreatitis [3].

Practical approach for this patient: Ringer lactate at 5 to 10 mL per kg per hour for the first 24 to 48 hours, reassessing the blood urea, haematocrit, and urine output every 6 hours, and reducing the rate once the urea is normalising. Avoid boluses unless he is hypotensive or clearly hypovolaemic. Ringer lactate is preferred over normal saline because it reduces the systemic inflammatory response and avoids hyperchloraemic metabolic acidosis. [1]

Analgesia

Adequate analgesia is essential. Morphine 2.5 to 5 mg IV every 4 hours, or a patient-controlled analgesia pump for severe pain. The historical concern that morphine causes sphincter of Oddi spasm and worsens pancreatitis is not supported by clinical evidence — do not withhold adequate analgesia. [1]

Nutrition — early enteral feeding

The old dogma of NPO with total parenteral nutrition to rest the pancreas has been overturned. Multiple randomised trials show that early enteral feeding within 24 to 48 hours reduces infectious complications, reduces the need for surgery, and shortens hospital stay compared with NPO [2]. For this patient, if his pain and vomiting settle, introduce a low-fat oral diet within 24 to 48 hours. If he cannot tolerate oral feeding, start nasogastric enteral feeding (as effective as nasojejunal in most trials). Reserve parenteral nutrition for patients who cannot meet their nutritional needs enterally after 5 to 7 days.

Antibiotics — NOT prophylactic

Prophylactic antibiotics are NOT recommended in acute pancreatitis, including severe necrotising disease. Multiple randomised trials and meta-analyses confirm that prophylactic antibiotics (whether carbapenems, quinolones, or beta-lactams) do not reduce infected necrosis or mortality, and increase the risk of fungal infection and resistance [2]. Antibiotics are reserved for: proven or strongly suspected infected necrosis (gas in the necrotic collection on CT, or clinical deterioration with fever and rising inflammatory markers), concomitant cholangitis, or another extrapancreatic infection.

The probiotic lesson

Probiotics are contraindicated in predicted severe acute pancreatitis. The PROPATRIA trial (Besselink, Lancet 2008) showed that probiotic prophylaxis did not reduce infectious complications and significantly increased mortality (16 versus 6 per cent) and bowel ischaemia (9 patients with ischaemia, all in the probiotic arm) [5]. Never administer probiotics to a patient with acute pancreatitis.

Part C — Local complications and the step-up approach

Morphological framework

The Revised Atlanta Classification organises local complications by whether there is necrosis and whether the collection has been present for more or less than 4 weeks [1]:

For interstitial oedematous pancreatitis (about 90 per cent): acute peripancreatic fluid collection (APFC, less than 4 weeks, fluid only) and pseudocyst (more than 4 weeks, fluid with a defined capsule, no necrosis). [1]

For necrotising pancreatitis (about 10 per cent): acute necrotic collection (ANC, less than 4 weeks, fluid and necrosis) and walled-off necrosis (WON, more than 4 weeks, necrosis with a defined capsule). [1]

Infected necrosis — the step-up approach

The PANTER trial (van Santvoort, NEJM 2010) established the step-up approach as the standard for infected necrotising pancreatitis [4]. The trial randomised 88 patients with infected necrosis to primary open necrosectomy versus a step-up approach (percutaneous or endoscopic drainage first, with minimally invasive retroperitoneal necrosectomy only if drainage failed). The step-up approach reduced the primary composite endpoint (major complications or death) from 69 to 40 per cent, and about 35 per cent of patients were managed with drainage alone.

The modern step-up algorithm: antibiotics and supportive care first (many patients improve with antibiotics alone); percutaneous or endoscopic catheter drainage as the first intervention when a walled-off collection is symptomatic or infected; endoscopic or minimally invasive necrosectomy (VARD) if drainage fails; and open necrosectomy as the last resort. Timing is critical: intervene late, not early, allowing the collection to become walled-off (usually after 4 weeks) before drainage is attempted. [1]

For this patient, if he develops infected necrosis (gas in the collection on CT, clinical deterioration), the correct sequence is: commence meropenem 1 g IV every 8 hours covering enteric gram-negatives and anaerobes; proceed to percutaneous or endoscopic drainage; and reserve necrosectomy for non-responders. Open necrosectomy is the last resort. [1]