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. ACG 2013: CECT and/or MRI of the pancreas should be reserved for patients in whom the diagnosis is unclear or who fail to improve clinically. Do not quote an unsourced "necrosis takes 72 hours to fully develop" clock as if it were in that abstract. ^[10].

Aetiological workup

The two dominant causes — gallstones and alcohol together about 80 per cent of episodes (Hasibeder); Moody 30 to 50 per cent gallstones; Davidson 56 per cent / 16 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 hypertriglyceridaemic disease at Hu's 11.3 mmol per L risk threshold 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). Wu: mortality ranged from more than 20 per cent in the highest-risk group to less than 1 per cent in the lowest-risk group (AUC 0.82 versus APACHE II 0.83) — not a sourced "BISAP 3 or above equals 5 to 20 per cent mortality" rule.

Vinish: CRP above 150 mg per litre at 48 hours predicted pancreatic fluid collections and necrosis on CT at 72 hours. It is not useful on day 1. ^[11]