Investigations and diagnosis

The diagnosis can be confirmed if at least two of these three criteria are met: (1)

• Upper abdominal pain (epigastric or left upper quadrant)
• Elevated serum lipase or amylase; >3 times upper limit of normal. (Remember that estimation of lipase is more sensitive and specific than measuring amylase levels and that enzyme levels maybe normal in around 5% of the patients at the time of admission to the hospital)
• Characteristic findings on abdominal imaging (CT, MRCP, ultrasound)

Patients with a positive diagnosis of acute pancreatitis (established by abdominal pain and by increases in the serum pancreatic enzyme activities) do not usually require CT. Patients who presents with serum amylase and/or lipase activity less than three times the upper limit of normal (seen in delayed presentation) but with abdominal pain strongly suggestive of acute pancreatitis will require imaging to confirm the disease. (2)

Other investigations carried to assist diagnosis, classify the severity of disease, and predict outcomes in pancreatitis include: (3)

• laboratory tests
  • FBC - may reveal a leucocytosis and/or a rise in haemoglobin concentration due to haemoconcentration
  • comprehensive metabolic panel including renal and hepatic function
    • elevated liver enzymes points towards gallstones as the cause of the acute pancreatitis
      • hepatic function test is recommended in all patients within 24 hours of admission
  • urinalysis
  • triglyceride levels
  • calcium levels
  • lactate dehydrogenase level
  • arterial blood gases
  • C-reactive protein level
• imaging
  • abdominal ultrasonography – to look for gallstones in the gallbladder
  • chest x-ray - may show elevation of the left hemidiaphragm with atelectasis and pleural effusion
  • plain abdominal x-ray - may show a ground glass appearance due to the presence of a peritoneal exudate. Bowel gas is generally absent apart from a central dilated section of duodenum or jejunum known as a "sentinel" loop; it indicates localised ileus.
  • non standard imaging tests
    • endoscopic ultrasonography
    • magnetic resonance cholangiopancreatography

Remember - abdominal imaging is not a pre-requisite to confirm the diagnosis but all patients with acute pancreatitis need a transabdominal ultrasound to confirm or exclude cholelithiasis. (4)

In UK practice, in line with recommendations from the International Association of Pancreatology/American Pancreatic Association and the World Society of Emergency Surgery, abdominal CT scanning for the purpose of assessing disease severity is not performed until 72 to 96 hours after the onset of symptoms, by which time the complete extent of necrosis should be visible (5)

Stool examination - may reveal unsuspected gallstones.

Peritoneal lavage - confirms the diagnosis if an odourless, yellow-brown, amylase-rich fluid is aspirated. May relieve pain and avoid unnecessary laparotomy.

Reference:

1. Working Group IAP/APA Acute Pancreatitis Guidelines. IAP/APA evidence-based guidelines for the management of acute pancreatitis. Pancreatology. 2013 Jul-Aug;13(4 suppl 2):e1-15.
2. Johnson CD, Besselink MG, Carter R. Acute pancreatitis. BMJ. 2014;349:g4859
3. Quinlan JD; Acute pancreatitis. Am Fam Physician. 2014 Nov 1;90(9):632-9.
4. Leppäniemi A, Tolonen M, Tarasconi A, et al. 2019 WSES guidelines for the management of severe acute pancreatitis. World J Emerg Surg. 2019 Jun 13;14:27.
5. Leppäniemi A, Tolonen M, Tarasconi A, et al. 2019 WSES guidelines for the management of severe acute pancreatitis. World J Emerg Surg. 2019 Jun 13;14:27.