A 56-year-old gentleman is admitted for severe epigastric pain, tarry stools and generalised malaise. He has a past history of ischaemic heart disease, gout and recent biliary pancreatitis which he underwent endoscopic retrograde cholangiopancreatography for stone removal. He is a non-drinker and takes a COX-2 inhibitor for his joint pain.
•Low-grade fever, pulse 100 bpm, BP 124/69mmHg, SaO2 97% on RA.
•Hydration is satisfactory.
•Examination of the hands reveals no clubbing and normal-appearing palmar creases.
•Head and neck examination is unremarkable.
•Cardiovascular: HS dual, no murmur.
•His chest is clear on auscultation.
•Abdominal examination reveals mild epigastric discomfort, with no definite mass.
•Per rectal examination: old melaena.
•No signs of oedema.
–WBC 12.2 x 109/L;
–haemoglobin 10.4g/dL dropped to 8.5g/dL;
–platelets 259 x 109/L.
•CXR: grossly clear, with no free gas under the diaphragm.
•Amylase 310 IU/L.
•Liver and renal function tests are normal.
What is your differential diagnosis?