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The initial imaging of a patient with suspected AP should include chest X‐ray and flat and upright abdominal radiographs. Their usefulness is to exclude other causes of abdominal pain, and occasionally to visualize findings suggestive of AP (i.e. sentinel loop, colon cutoff sign, and left pleural effusions) [47]. Abdominal surface ultrasound should follow radiological imaging. Its best role is for gallbladder visualization with determination of the presence of cholelithiasis. It can visualize the pancreas in approximately two‐thirds of patients, revealing peripancreatic changes of inflammation; however, this is markedly decreased when the individual is obese and or if an ileus is present.

CT is the gold standard for pancreatic imaging. However, when possible, it should not be performed until the patient has been rehydrated. This delay will prevent renal injury from contrast and allow the clinician to decide if CT is needed. The primary reason for early CT scan (<72 hours) is diagnostic uncertainty. Early CT does not improve clinical outcome or influence treatment nor does it improve prediction of severe disease over clinical scoring. Optimal timing for initial CT assessment is 72–96 hours after onset of symptoms [49], which also allows time for necrosis to occur. The advantages of CT over magnetic resonance imaging (MRI) is its increased availability and decreased cost. It has increased sensitivity for definition of small air bubbles and calcification within the pancreas [50].

MRI may be equivalent to CT for evaluating severity of disease. MRCP is especially useful for depicting 3–5 mm choledocholithiasis. If biliary stone disease remains a consideration after MRCP, EUS is the next procedure and it has up to an 80% success rate. In addition, MRCP can visualize disruption (partial or complete) of the main pancreatic duct [51].