Acute pancreatitis (AP) is an acute inflammatory process of the pancreas in which pancreatic enzymes are released and autodigest the gland with effects ranging from edema to necrosis. AP has a wide spectrum of disease from a mild, transitory illness to a severe, rapidly fatal disease. Approximately 80% of patients with the disease have a mild acute interstitial edematous pancreatitis with a low morbidity and mortality rate (≤1%). Mild pancreatitis is usually self-limiting, subsiding in most cases uneventfully within 3 to 4 days and rarely needing intensive care treatment or pancreatic surgery. Severe or necrotizing pancreatitis develops in about 20% of patients. Early death within 1 week of admission is related to systemic inflammatory response syndrome (SIRS), with infection of pancreatic and peripancreatic necrosis representing the single most important risk factor for a fatal outcome. Overall, AP is complicated by infection in approximately 10% of patients, with 70% to 80% mortality. With increasing amount of necrotic reaction, there is greater risk of subsequent infection of the gland. In patients with AP, organ failure and infected pancreatic necrosis indicate severe disease as they comparably influence mortality, with a doubled relative risk of mortality when both are present, indicating extremely severe disease. The prognosis and initial severity of a pancreatitis attack may be assessed by monitoring clinical signs and symptoms. The clinical findings in severe disease may include the presence of hypotension, hypoxemia, renal failure, altered mental status, hemoconcentration reflective of intravascular volume loss, and the presence of SIRS. Other findings may include abdominal pain and nausea, fever (>38.6°C [101.5°F]), ascites, and ecchymoses. Several classification systems have been developed in an attempt to provide reliable prognostic classification for patients with AP. The APACHE II scale (acute physiological assessment and chronic health evaluation), multiple organ system failure (MOSF) scale, and the BISAP criteria (bedside index of severity in acute pancreatitis) (Table 47.1) have all been used. These newer criteria may supplant the utility of Ranson’s criteria, and can usually be performed within a few hours after admission. The APACHE II scores are generated from multiple parameters, are considered highly accurate, allow prediction of severity from the day of admission, and may be recalculated on a daily basis. Unfortunately, because of the time-consuming and cumbersome nature of the APACHE II evaluation, it is rarely used in clinical practice. The MOSF system has better clinical utility for evaluating patients at admission and at 48 hours than the APACHE II score. The BISAP score is a scale assessment for prognostication during the initial 24 hours after admission.
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