Imaging acute pancreatitis

The incidence of acute pancreatitis is increasing in Europe, with significant medical, surgical and financial implications. The overall incidence of acute pancreatitis is 22.4 per 100,000 population in England with a hospital admission rate of 9.6 per year per 100,000 population in the United Kingdom (1;2). In more than 80% of patients, acute pancreatitis is secondary to gallstone disease or alcohol abuse. Recognising the importance of this condition, the UK Working Party on Acute Pancreatitis has issued guidelines for the management of acute pancreatitis that provide an overview of the clinical perspective and management. Acute pancreatitis is an acute inflammatory disease of the pancreas caused by inappropriate intracellular activation of proteolytic enzymes and subsequent autodigestion of the pancreatic parenchyma and surrounding tissues. The majority of patients have mild interstitial oedematous pancreatitis (IOP) which is self-limiting and responds rapidly to conservative management. However, 20% have severe acute pancreatitis (SAP) which can progress to a systemic inflammatory response syndrome (SIRS) and result in septic systemic complications with significant morbidity and mortality. This sub-group requires immediate medical care to prevent life-threatening complications. Imaging, most commonly with contrast-enhanced computed tomography (CE-CT), plays a significant role in the identification of local and systemic complications and in planning further management. Image-guided interventional procedures tend to be less invasive than surgery, often reducing the need for surgical intervention, and thereby improving outcome. Severity scoring There are several clinical and biochemical scoring systems that can be employed to assess the severity of acute pancreatitis. In 1985, Balthazar et al introduced a scoring system based on radiological findings by grading the severity of pancreatitis into five different groups on unenhanced CT (table 1, figures 1a-e). To improve the prognostic value of this system, CE-CT findings of the degree of necrosis were incorporated to give the CT severity index (CTSI) (table 1). The system was further modified by Mortelé et al in 2004, combining pancreatic inflammation, necrosis and extra-pancreatic complications in a 10-point scale to give the modified CTSI (table 2) which shows a stronger correlation between outcome and severity than the original. Contrast-enhanced computed tomography CE-CT is considered to be the gold standard imaging modality in the evaluation of patients with acute pancreatitis. MRI and ultrasound (US) are used in specific clinical situations and can be useful in determining aetiology. Ideally, CE-CT should be performed 48-72 hours after