investigations and diagnosis

Last edited 08/2018

According to the revised Atlanta classification diagnosis of acute pancreatitis requires two of the following three features:

• abdominal pain - acute onset of a persistent, severe, epigastric pain often radiating to the back)
• serum lipase activity (or amylase activity) at least three times greater than the upper limit of normal
• estimation of lipase is more sensitive and specific than measuring amylase levels
• enzyme levels maybe normal in around 5% of the patients at the time of admission to the hospital
• characteristic findings of acute pancreatitis on contrast-enhanced computed tomography (CECT) (1,2).

Patients with positive diagnosis of acute pancreatitis (established by abdominal pain and by increases in the serum pancreatic enzyme activities) do not usually require CECT. 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 (1).

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

• 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 – should be done in every patient within 24 hours of admission 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

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.

Notes:

• point-of-care urine trypsinogen test for the diagnosis of pancreatitis in the emergency department (1)
• sensitivity and specificity of urine trypsinogen for acute pancreatitis was examined in a small study and was, respectively, 100% (95% confidence interval [CI] = 77% to 100%) and 96% (95% CI = 92% to 98%)
• authors concluded that urine trypsinogen screening test for pancreatitis compared favourably with plasma lipase and amylase levels
• clearance of the pancreatic enzymes varies, hence the timing of the blood sampling from the onset of acute pancreatitis affects the test’s sensitivity
• lipase has a higher diagnostic accuracy compared to amylase (lipase levels are elevated for a longer period) (4)

Reference:

• (1) Banks PA et al. Classification of acute pancreatitis--2012: revision of the Atlanta classification and definitions by international consensus. Gut. 2013;62(1):102-11
• (2) Johnson CD, Besselink MG, Carter R. Acute pancreatitis. BMJ. 2014;349:g4859
• (3) Jang T et al. Point-of-care urine trypsinogen testing for the diagnosis of pancreatitis.Acad Emerg Med. 2007 Jan;14(1):29-34.
• (4) Shah AP, Mourad MM, Bramhall SR. Acute pancreatitis: current perspectives on diagnosis and management. J Inflamm Res. 2018;11:77-85.