Practice Guidelines in Acute Pancreatitis

INTRODUCTION Guidelines for the diagnosis and treatment of acute pancreatitis were published by the American College of Gastroenterology in 1997 (1). These and subsequent guidelines (2–7) have undergone periodic review (6, 8–13) in accordance with advances that have been made in the diagnosis and treatment of acute pancreatitis. Guidelines for clinical practice are intended to apply to all health-care providers who take care of patients with acute pancreatitis and are intended to be flexible, and to suggest preferable (but not the only) approaches. Because there is a wide range of choices in any health-care situation, the physician should select the course best suited to the individual patient and the clinical situation. These guidelines have been developed under the auspices of the American College of Gastroenterology and its Practice Parameters Committee, and approved by the Board of Trustees. The world literature in English was reviewed using a MEDLINE search and also using the Cochrane Library. The ratings of levels of evidence for these guidelines are indicated in Table 1. The final recommendations are based on the data available at the time of the publication of this document and may be updated with appropriate scientific development at a later time. The following guidelines are intended for adult and not pediatric patients. The main diagnostic guidelines include an assessment of risk factors of severity at admission and determination of severity. The major treatment guidelines include supportive care, fluid resuscitation, transfer to intensive care unit, enteral feeding, use of antibiotics, treatment of infected pancreatic necrosis, treatment of sterile pancreatic necrosis, treatment of associated pancreatic duct disruptions, and role of magnetic resonance cholangiopancreatography (MRCP), endoscopic ultrasound (EUS), and endoscopic retrograde cholangiopancreatography (ERCP) with biliary sphincterotomy for detection and treatment of choledocholithiasis in biliary pancreatitis.Table 1: Ratings of Evidence Used for This GuidelinePATHOPHYSIOLOGY The pathophysiology of acute pancreatitis is generally considered in three phases. In the first phase, there is premature activation of trypsin within pancreatic acinar cells. A variety of mechanisms have been proposed including disruption of calcium signaling in acinar cells (14–18), cleavage of trypsinogen to trypsin by the lysosomal hydrolase cathepsin-B, and decreased activity of the intracellular pancreatic trypsin inhibitor (17, 18). Once trypsin is activated, it activates a variety of injurious pancreatic digestive enzymes. In the second phase, there is intrapancreatic inflammation through a variety of mechanisms and pathways (16, 18–28). In the third phase, there is extrapancreatic inflammation including acute respiratory syndrome (ARDS) (16, 19–21, 29). In both phases, there are four important steps mediated by cytokines and other inflammatory mediators: 1) activation of inflammatory cells, 2) chemoattraction of activated inflammatory cells to the microcirculation, 3) activation of adhesion molecules allowing the binding of inflammatory cells to the endothelium, and 4) migration of activated inflammatory cells into areas of inflammation. In the majority of patients, acute pancreatitis is mild. In 10–20%, the various pathways that contribute to increased intrapancreatic and extrapancreatic inflammation result in what is generally termed systemic inflammatory response syndrome (SIRS) (Table 2). In some instances, SIRS predisposes to multiple organ dysfunction and/or pancreatic necrosis. The factors that determine severity are not clearly understood, but appear to involve a balance between proinflammatory and anti-inflammatory factors. Recent evidence suggests that the balance may be tipped in favor of proinflammatory factors by genetic polymorphisms of inflammatory mediators that increase severity of acute pancreatitis (27, 30, 31).Table 2: Systemic Inflammatory Response Syndrome (SIRS)CLINICAL CONSIDERATIONS Clinical Diagnosis It has been estimated that in the United States there are 210,000 admissions for acute pancreatitis each year (13). Most patients with acute pancreatitis experience abdominal pain that is located generally in the epigastrium and radiates to the back in approximately half of cases. The onset may be swift with pain reaching maximum intensity within 30 min, is frequently unbearable, and characteristically persists for more than 24 h without relief. The pain is often associated with nausea and vomiting. Physical examination usually reveals severe upper abdominal tenderness at times associated with guarding (32). There is general acceptance that a diagnosis of acute pancreatitis requires two of the following three features: 1) abdominal pain characteristic of acute pancreatitis, 2) serum amylase and/or lipase ≥3 times the upper limit of normal, and 3) characteristic findings of acute pancreatitis on CT scan. This definition allows for the possibility that an amylase and/or lipase might be <3 times the upper limit of normal in acute pancreatitis. In a patient with abdominal pain characteristic of acute pancreatitis and serum enzyme levels that are lower than 3 times the upper limit of normal, a CT scan must be performed to confirm a diagnosis of acute pancreatitis. In addition, this definition allows for the possibility that presence of abdominal pain cannot be assessed in some patients with severely altered mental status due to acute or chronic illness. In general, both amylase and lipase are elevated during the course of acute pancreatitis. The serum lipase may remain elevated slightly longer than amylase. The height of the serum amylase and/or lipase does not correlate with the severity of acute pancreatitis. It is usually not necessary to measure both serum amylase and lipase. Serum lipase may be preferable because it remains normal in some nonpancreatic conditions that increase serum amylase including macroamylasemia, parotitis, and some carcinomas. In general, serum lipase is thought to be more sensitive and specific than serum amylase in the diagnosis of acute pancreatitis. Daily measurement of serum amylase or lipase after the diagnosis of acute pancreatitis has limited value in assessing the clinical progress of the illness or ultimate prognosis (32). If serum amylase and/or lipase remain elevated for several weeks, possibilities include persisting pancreatic/peripancreatic inflammation, blockage of the pancreatic duct, or development of a pseudocyst. The differential diagnosis of acute pancreatitis is broad and includes mesenteric ischemia or infarction, perforated gastric or duodenal ulcer, biliary colic, dissecting aortic aneurysm, intestinal obstruction, and possibly inferior wall myocardial infarction. In severe pancreatitis, the patients appear toxic and quite ill. In mild pancreatitis, the patients generally appear uncomfortable but not as ill (32). A detailed discussion of the approach to determining the etiology of acute pancreatitis is beyond the scope of this paper. During the initial hospitalization for acute pancreatitis, reasonable attempts to determine etiology are appropriate, and in particular those causes that may affect acute management. Relevant historical clues include any previous diagnosis of biliary tract disease or gallstones, cholecystectomy, other biliary or pancreatic surgery, acute or chronic pancreatitis or their complications, use of ethanol, medications and the timing of their initiation, recent abdominal trauma, weight loss or other symptoms suggesting a malignancy, or a family history of pancreatitis. Blood tests within the first 24 h should include liver chemistries, calcium, and triglycerides. Abdominal ultrasound is usually performed at the time of admission to assess for gallstones as the etiology rather than to establish the diagnosis of acute pancreatitis. Detection of common bile duct stones by ultrasound is limited by poor sensitivity, although specificity is quite high if they are identified. Dilation of the common bile duct alone is neither sensitive nor specific for the detection of common bile duct stones. Occasionally, the pancreas is well enough seen by abdominal ultrasound to reveal features that are consistent with the diagnosis of acute pancreatitis including diffuse glandular enlargement, hypoechoic texture of the pancreas reflective of edema, and ascites. Contrast-enhanced CT scan (and in particular a contrast-enhanced thin-section multidetector-row CT scan) is the best imaging technique to exclude conditions that masquerade as acute pancreatitis, to diagnose the severity of acute pancreatitis, and to identify complications of pancreatitis (33–35). Findings on CT scan that confirm the diagnosis of acute pancreatitis include enlargement of the pancreas with diffuse edema, heterogeneity of pancreatic parenchyma, peripancreatic stranding, and peripancreatic fluid collections. With the use of IV contrast, a diagnosis of pancreatic necrosis can be established. In addition, contrast-enhanced CT scan may give clues as to the etiology of acute pancreatitis: for example, a common bile duct stone may occasionally be directly visualized, pancreatic calcifications may indicate underlying chronic pancreatitis due to alcohol or other causes, a pancreatic mass may suggest malignancy, and diffuse dilation of the pancreatic duct or a cystic lesion may suggest intraductal papillary mucinous neoplasia or cystic neoplasm. The role of magnetic resonance imaging (MRI) and MRCP in the diagnosis of acute pancreatitis and establishment of severity is undergoing evaluation. These techniques are superior to CT scan in delineating pancreatic ductal anatomy (36–38) and detecting choledocholithiasis (39). Definitions The International Symposium, held in Atlanta, GA, in 1992, established a clinically based classification system for acute pancreatitis (40, 41). The goal was to establish international standards of definitions of acute pancreatitis and its complications to make possible valid comparisons of severity of illness and results of therapy and also to establish criteria for patient selection in randomized prospective trials. According to the Atlanta Symposium, acute pancreatitis was defined as an acute inflammatory process of the pancreas that may also involve peripancreatic tissues and/or remote organ systems. Criteria for severity included organ failure (particularly shock, pulmonary insufficiency, and renal failure) and/or local complications (especially pancreatic necrosis but also including abscess and pseudocyst). Early predictors of severity within 48 h of initial hospitalization included Ranson signs and APACHE-II points (Table 3).Table 3: Severe Acute Pancreatitis as Defined by Atlanta SymposiumInterstitial pancreatitis was defined as focal or diffuse enlargement of the pancreas with enhancement of the parenchyma that is either homogeneous or slightly heterogeneous in response to IV contrast. There may be inflammatory changes in peripancreatic fatty tissue characterized by a hazy appearance. Pancreatic necrosis was defined as diffuse or focal areas of nonviable pancreatic parenchyma that was typically associated with peripancreatic fat necrosis. The criteria for the CT diagnosis of necrosis included focal or diffuse well-marginated zones of nonenhanced pancreatic parenchyma greater than 3 cm in size or greater than 30% of the pancreas. It was recognized that pancreatic necrosis could be either sterile or infected and that infected necrosis was characterized by the presence of bacteria (and/or fungi) within the necrotic tissue. An extrapancreatic fluid collection was defined as pancreatic fluid that extravasates out of the pancreas during acute pancreatitis into the anterior pararenal spaces and other areas as well. Fluid collections may occur both with interstitial and necrotizing pancreatitis. Most fluid collections remain sterile and disappear during the recovery period. A pancreatic pseudocyst was defined as a collection of pancreatic juice enclosed by a nonepithelialized wall that occurs as a result of acute pancreatitis, pancreatic trauma, or chronic pancreatitis. It is generally believed that a period of at least 4 wk is required from the onset of acute pancreatitis to form a well-defined wall composed of granulation and fibrous tissue. Pancreatic pseudocysts contain considerable pancreatic enzymes and are usually sterile. According to the Atlanta Symposium, an infected pancreatic pseudocyst should be termed a pancreatic abscess. A pancreatic abscess may also occur when an area of pancreatic necrosis undergoes secondary liquefaction and then becomes infected. Mild acute pancreatitis was defined as pancreatitis associated with minimal organ dysfunction and an uneventful recovery. Severe pancreatitis was defined as pancreatitis associated with organ failure and/or local complications (necrosis, abscess, or pseudocyst). Organ failure was defined as shock, pulmonary insufficiency, renal failure, or gastrointestinal bleeding (Table 4). There were a number of additional systemic complications that were identified as characteristic of severe acute pancreatitis including disseminated intravascular coagulation (platelets ≤100,000/mm3, fibrinogen ≤100 mg/dL, fibrin split products >80 μg/mL), or a severe metabolic disturbance (serum calcium ≤7.5 mg/dL).Table 4: Organ Failure as Defined by Atlanta SymposiumThe Atlanta Symposium was an important initiative in establishing a clinically based classification system. However, it is now clear some of the information included in the classification was subject to different interpretations, and that criteria of severity as defined by the Atlanta Symposium have not been used in a uniform fashion in recent publications (3, 10, 13, 25, 27, 31, 42–165). In addition, there is new scientific information that should be included in a revised classification. Areas of major concern are as follows: In the Atlanta Symposium, a uniform threshold was not established for serum amylase and/or lipase for the diagnosis of acute pancreatitis. In recently published articles, the threshold varied from ≥2 times to ≥4 times the upper limit of normal. In the Atlanta Symposium, criteria for severe pancreatitis included organ failure and/or local complications (Table 3). This broad definition describes a heterogeneous group of patients with varying levels of severity. For example, the prognosis of pancreatic necrosis is more serious than a pseudocyst or pancreatic abscess. Also, almost all patients with necrotizing pancreatitis without organ failure survive, whereas those with multisystem organ failure have a median mortality of 47% (48, 66, 68, 83, 120, 163, 164). There was no distinction between transient and persistent organ failure. Patients with persistent organ failure have a more serious prognosis than those with transient organ failure (71, 72, 151). Criteria for organ failure that were established have not been used in a uniform fashion. Some reports have restricted organ failure to shock, hypotension, renal failure, and gastrointestinal bleeding (10, 13, 44, 46, 50–52, 57, 73, 74, 83, 84, 89, 140, 145, 148). Other reports have altered thresholds for organ failure, or have included additional criteria, or have used alternative or nonspecified scoring systems (3, 25, 31, 43, 45, 47, 48, 53, 54, 56, 58–61, 64, 66–69, 77–80, 82, 86–88, 90–95, 97–100, 102, 103, 105–112, 114, 119–123, 125–129, 134–136, 138, 139, 142, 143, 146, 147, 149–153, 155, 156, 159–161, 165). A revision of the Atlanta criteria will undoubtedly delete gastrointestinal bleeding (which is rarely encountered in acute pancreatitis) and will retain shock, hypotension, and renal failure as the important components of organ failure. In addition, a revision will likely include one of the formal scoring systems for organ failure that are currently available. In the Atlanta Symposium, pancreatic necrosis was considered as either greater than 30% of the pancreas or greater than 3 cm in size. These are, in effect, two different definitions. Because of the variability in the minimum criteria used for the presence of necrosis, it is difficult to compare studies from different institutions (10, 13, 25, 27, 31, 44–60, 62–64, 66–74, 77–92, 98, 100–102, 104–107, 113, 115, 116, 119–121, 126–129, 131, 133–135, 137, 138, 140, 142–148, 150, 153, 154, 156, 157, 159, 161). A revision of the Atlanta criteria will undoubtedly provide a uniform threshold for the diagnosis of pancreatic necrosis. Regarding the term pancreatic pseudocyst, a distinction was not made between two relatively distinctive entities. The first is a collection of pancreatic juice enclosed by a nonepithelialized wall that occurs mostly near the pancreas. While the contents may also include peripancreatic necrotic material, the contents are usually mostly fluid. The second type of pancreatic pseudocyst is that which takes place within the confines of the pancreas and involves pancreatic necrotic tissue with variable amounts of pancreatic fluid. This entity, frequently termed “organized necrosis” (166), is a distinct clinical entity that poses substantially greater management challenges (167). Additional terminology will be needed to separate these two conditions. Overview of Acute Pancreatitis Overall, 85% of patients have interstitial pancreatitis; 15% (range 4–47%) have necrotizing pancreatitis (25, 44, 46, 50, 68, 83, 86, 128, 140, 169). Among patients with necrotizing pancreatitis, 33% (range 16–47%) have infected necrosis (62, 66, 68, 83, 91, 111, 113, 117, 118, 120, 121, 147, 159, 169, 170). Approximately 10% of patients with interstitial pancreatitis experience organ failure, but in the majority it is transient with a very low mortality. Median prevalence of organ failure in necrotizing pancreatitis is 54% (range 29–78%) (31, 50, 54, 82, 83, 120, 147, 148). Prevalence of organ failure is the same or somewhat higher in infected necrosis (34–89%) than in sterile necrosis (45–73%) (66, 83, 138, 161). The overall mortality in acute pancreatitis is approximately 5%: 3% in interstitial pancreatitis, 17% in necrotizing pancreatitis (30% in infected necrosis, 12% in sterile necrosis) (Table 5).Table 5: Mortality in Acute PancreatitisThe mortality in the absence of organ failure is 0 (50, 66, 68, 83), with single organ failure is 3% (range 0–8%) (66, 83, 163), with multisystem organ failure 47% (range 28–69%) (48, 66, 68, 83, 120, 163, 164). Although older literature suggested that 80% of deaths occur after several weeks of illness as a result of infected necrosis, more recent surveys have shown considerable variation with several reports showing a reasonably even distribution of early deaths (within 1–2 wk) versus later deaths (46, 72, 76, 150, 151, 163), a few showing the majority of deaths within the first 2 wk (67, 75), and others showing the majority of deaths after the first 2 wk (59, 89, 135). These variations reflect a variety of influences including percentage of very ill patients referred to a reporting hospital compared to patients admitted directly. Deaths within the first 2 wk are generally attributed to organ failure; deaths after this interval are generally caused by infected necrosis or complications of sterile necrosis. DIAGNOSTIC GUIDELINE I: LOOK FOR RISK FACTORS OF SEVERITY AT ADMISSION Older age (>55), obesity (BMI >30), organ failure at admission, and pleural effusion and/or infiltrates are risk factors for severity that should be noted at admission. Patients with these characteristics may require treatment in a highly supervised area, such as a step-down unit or an intensive care unit. Level of evidence: III The importance of establishing risk factors of severity of acute pancreatitis at admission is several-fold: to transfer those patients who are most likely to have a severe episode to a step-down unit or an intensive care unit for closer supervision, to allow physicians to compare results of optimal therapy, and to facilitate the identification of seriously ill patients for inclusion in randomized prospective trials. A variety of potential risk factors have been investigated as follows. It is intuitive that older individuals would have more severe pancreatitis because of comorbid disease. In many (50, 55, 60, 67, 70, 75, 83, 86–88, 91, 128) but not all (31, 46, 53, 61, 165, 168) reports, older age (generally ≥55 yr of age) has correlated with a more severe prognosis. There have been a variety of studies that have sought to determine whether obesity is a risk factor for severity in acute pancreatitis (56–60, 75, 87, 88). A recent meta-analysis concluded that obese patients (defined as those with a BMI >30) had more systemic and local complications but not greater mortality (57). In one recent report, the combination of APACHE-II and obesity (a classification termed APACHE-O) measured within the first 24 h of admission improved the prediction of severity in patients with acute pancreatitis (58). Several reports have pointed out that patients with organ failure at admission have a higher mortality than those who do not experience organ failure at admission (50, 61, 69, 71, 72, 83, 163). The progression of single organ failure to multisystem organ failure is a major determinant in the high mortality associated with organ failure at admission (83). Survival among patients with organ failure at admission has also been shown to correlate with the duration of organ failure (71, 72, 151). When organ failure is corrected within 48 h, mortality was close to 0. When organ failure persisted for more than 48 h, mortality was 36% (72). Several reports have pointed out that a pleural effusion obtained on chest X-ray within the first 24 h of admission correlates with greater severity in terms of necrosis or organ failure (84) or greater mortality (75, 86). Additionally, the presence of infiltrates on chest X-ray within 24 h has been associated with greater mortality (75, 85, 86). Several reports have indicated that gender has no prognostic significance (31, 46, 73, 83, 87, 91, 165). Furthermore, etiology has also been shown to have no prognostic significance (46, 53, 60, 61, 75, 83, 87, 91, 168) other than one report that indicated that patients with alcoholic pancreatitis in their first episode of pancreatitis have a greater need for intubation and greater prevalence of pancreatic necrosis (74). In three reports (82, 83, 171), almost all deaths in acute pancreatitis occurred during the first two episodes, fewer in the third episode. Studies in the future should stratify patients on the basis of number of prior episodes to confirm this observation. In one report (172), but not in another (83), a short interval between onset of symptoms and hospitalization correlated with more severe disease, presumably because abdominal pain was particularly intense among patients with early spread of inflammatory changes in the retroperitoneum and elsewhere that would cause early third space losses. DIAGNOSTIC GUIDELINE II: DETERMINATION OF SEVERITY BY LABORATORY TESTS AT ADMISSION OR ≤48 H The two tests that are most helpful at admission in distinguishing mild from severe acute pancreatitis are APACHE-II score and serum hematocrit. It is recommended that APACHE-II scores be generated during the first 3 days of hospitalization and thereafter as needed to help in this distinction. It is also recommended that serum hematocrit be obtained at admission, 12 h after admission, and 24 h after admission to help gauge adequacy of fluid resuscitation. Level of evidence: III The APACHE-II severity of disease classification system includes a variety of physiologic variables, age points, and chronic health points, which can be measured at admission and daily as needed to help identify patients with severe pancreatitis (1, 7, Table 6). A variety of reports have correlated a higher APACHE-II at admission and during the first 72 h with a higher mortality (<4% with an APACHE-II <8 and 11–18% with an APACHE-II >8) (31, 46, 52, 72, 83, 128, 147). There are some limitations in the ability of the APACHE-II score to stratify patients for disease severity. For example, in one report, there was no sharp cutoff between interstitial and necrotizing pancreatitis (52). In three reports, APACHE-II scores were not statistically different among patients with sterile and infected necrosis (66, 83, 134). In one recent report, APACHE-II generated within the first 24 h had a positive predictive value of only 43% and negative predictive value of 86% for severe acute pancreatitis as compared to the 48-h Ranson score of 48% and 93%, respectively (53). The advantage of the APACHE-II score was the availability of this information within the first 24 h and daily (53). In general, an APACHE-II score that increases during the first 48 h is strongly suggestive of the development of severe pancreatitis, whereas an APACHE-II that decreases within the first 48 h strongly suggests mild pancreatitis.Table 6: APACHE II Score APACHE II score = (acute physiology score) + (age points) + (chronic health points) Acute Physiology ScoreRanson signs have been used for many years to assess severity of acute pancreatitis but have the disadvantage of requiring a full 48 h for a complete evaluation. In general, when Ranson signs are <3, mortality is 0–3% (46, 86, 145); when ≥3, 11–15% (46, 86, 145); when ≥6, 40% (46). However, a more recent comprehensive evaluation of 110 studies concluded that Ranson signs provided very poor predictive power of severity of acute pancreatitis (173). In two studies, the Ranson score was the same in sterile and infected necrosis (66, 134). There have been studies that have attempted to correlate severity of pancreatitis with one or more serum measurements that are available at admission. In one study, creatinine at admission >2.0 mg/dL and a blood glucose >250 mg/dL were associated with a greater mortality (39% and 16%, respectively) (46). In two additional studies, serum creatinine >2.0 mg/dL within 24 h of admission was also associated with a greater mortality (75, 86). In another study, serum glucose >125 mg/dL at admission correlated with a variety of parameters including longer hospital stay but not organ failure, length of intensive care, or mortality (140). The addition of an obesity score to the standard APACHE-II (so-called APACHE-O score) appears to increase accuracy of APACHE-II for severity. In this scoring system, a point is added to the APACHE-II score when the BMI is 26–30 and 2 points are added when the BMI is greater than 30 (58). In severe acute pancreatitis, there is considerable extravasation of intravascular fluid into third spaces as a result of inflammatory mediators as well as local inflammation caused by widespread enzyme-rich pancreatic exudate. The reduction in intravascular volume, which can be detected by an increased serum hematocrit, can lead to decrease in the perfusion of the microcirculation of the pancreas and result in pancreatic necrosis. As such, hemoconcentration has been proposed as a reliable predictor of necrotizing pancreatitis (82). In this report, hematocrit ≥44 at admission and failure of admission hematocrit to decrease at 24 h were the best predictors of necrotizing pancreatitis. In another study, patients who presented with hemoconcentration and then had a further increase in hematocrit at 24 h were at particularly high risk of pancreatic necrosis, whereas 41% of patients whose hematocrit decreased by 24 h did not develop pancreatic necrosis (172). Other reports have not confirmed that hemoconcentration at admission or at 24 h is a risk factor for severe acute pancreatitis (44, 75). However, there is agreement that the likelihood of necrotizing pancreatitis is very low in the absence of hemoconcentration at admission (44, 82). Hence, the absence of hemoconcentration at admission or during the first 24 h is strongly suggestive of a benign clinical course. C-reactive protein (CRP) is an acute phase reactant. Plasma levels greater than 150 mg/L within the first 72 h of disease correlate with the presence of necrosis with a sensitivity and specificity that are both >80%. Because the peak is generally 36–72 h after admission, this test is not helpful at admission in assessing severity (16, 77, 79). A variety of additional tests, including urinary trypsinogen activation peptide, serum trypsinogen-2, serum amyloid A, and calcitonin precursors, have shown promise at admission in distinguishing mild from severe pancreatitis in many (77–80, 159) but not all (165) reports. None of these tests is available commercially. DIAGNOSTIC GUIDELINE III: DETERMINATION OF SEVERITY DURING HOSPITALIZATION Pancreatic necrosis and organ failure are the two most important markers of severity in acute pancreatitis. The distinction between interstitial and necrotizing pancreatitis can be reliably made after 2–3 days of hospitalization by contrast-enhanced CT scan. Level of evidence: III A. Imaging Studies CONTRAST-ENHANCED CT SCAN. Many patients with acute pancreatitis do not require a CT scan at admission or at any time during the hospitalization. For example, a CT scan is usually not essential in patients with recurrent mild pancreatitis caused by alcohol. A reasonable indication for a CT scan at admission (but not necessarily a CT with IV contrast) is to distinguish acute pancreatitis from another serious intra-abdominal condition, such as a perforated ulcer. A reasonable indication for a contrast-enhanced CT scan a few days after admission is to distinguish interstitial from necrotizing pancreatitis when there is clinical evidence of increased severity. The distinction between interstitial and necrotizing pancreatitis can be made much more readily when a contrast-enhanced CT scan is obtained on the second or third day after admission rather than at the time of admission (34). Additiona