• • Define acute pancreatitis in its early phase and later phase, and the persistent organ failure that can accompany its occurance. Serial Communicator Mecanique Automobile. • • List the various fluid collections encountered in acute pancreatitis as defined by the revised Atlanta classification. • • Identify the two phases of acute pancreatitis, the parameters that determine care, and the treatment for an infected walled-off necrosis. Accreditation and Designation Statement The RSNA is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

Mannelli L, Kim S, Hajdu CH, Babb JS, Taouli B. Serial diffusion-weighted MRI in patients with hepatocellular carcinoma: prediction and assessment of response to transarterial chemoembolization—preliminary experience. Eur J Radiol 2012 Dec 12 [Epub ahead of print] [Medline]. Schraml C, Schwenzer NF, Clasen S,.

The RSNA designates this journal-based activity for a maximum of 1.0 AMA PRA Category 1 Credit ™. Physicans should claim only the credit commensurate with the extent of their participation in the activity. Disclosure Statement The ACCME requires that the RSNA, as an accredited provider of CME, obtain signed disclosure statements from the authors, editors, and reviewers for this activity.

For this journal-based CME activity, author disclosures are listed at the end of this article. In 1992, the Atlanta classification for acute pancreatitis was introduced as a universally applicable classification system for the various manifestations of acute pancreatitis (). This system was designed to facilitate understanding and correlation of findings seen by gastroenterologists, pathologists, radiologists, and surgeons. This approach was to be particularly useful for assessment and treatment of the various fluid collections identified during the course of acute pancreatitis. It defined acute pancreatitis as an acute inflammatory process of the pancreas with variable involvement of other local tissues and remote organ systems. It is associated with elevated pancreatic enzyme levels in blood and/or urine. Mild pancreatitis was described as associated with minimal organ dysfunction and an uneventful recovery.

Severe pancreatitis was defined as associated with organ failure and/or local complications such as “acute” pseudocyst, pancreatic necrosis, or pancreatic abscess (). Both categories were described as having acute fluid collections early in the course of the disease. A Ranson score of 3 or higher or an APACHE II (Acute Physiology and Chronic Health Evaluation II) score of 8 or higher was suggested as clinically predictive of severity. Organ failure and systemic complications were diagnosed on the basis of signs of shock, pulmonary insufficiency, renal failure, gastrointestinal bleeding, disseminated intravascular coagulation, and severe metabolic disturbances. This initial Atlanta classification system represented major progress, but advancing knowledge of the disease process, improved imaging, and ever-changing treatment options such as minimally invasive radiologic, endoscopic, and laparoscopic procedures soon rendered some of the definitions inadequate or ambiguous (,), presenting a need to revise and update the Atlanta classification (). It was found that the definitions of severity and local complications of acute pancreatitis were not used consistently and that characterization of severity based on presence of organ failure had limitations (,). The definition of necrotizing pancreatitis was determined to be inadequate because it included sterile and infected necrosis and did not distinguish between pancreatic and peripancreatic necrosis ().

The initial Atlanta classification system also did not include exact radiologic criteria for local complications, and controversy developed over the natural course of pancreatic and peripancreatic fluid collections. In 2008, a global consensus statement was developed that included broad and international participation of many experts in the field of pancreatitis and was led by the Acute Pancreatitis Classification Working Group (). This working group gathered input and revised the Atlanta classification system to improve clinical assessment and management of acute pancreatitis and to clarify appropriate terms for peripancreatic fluid collections, pancreatic and/or peripancreatic necrosis, and their changes over time (–). It also recognized that morphologic characteristics and clinical severity might not directly correlate ().

Such a revised classification system facilitates standardized reporting of clinical and imaging data, as well as objective assessment of treatment, which can be used as an effective means of communication among physicians. It also enables comparison of results among different institutions. Precise description of pancreatic collections is particularly important, because treatment varies with collection type.

In short, the goal of this revised classification system is to facilitate more objective communication between physicians and institutions through a precise standardized classification system that allows better treatment planning. This revised classification is directly applicable only to adults (>18 years of age). Radiologic imaging has become increasingly important in staging and treating acute pancreatitis (,).

The revision of the Atlanta classification focuses heavily on morphologic criteria for defining the various manifestations of acute pancreatitis as outlined principally by means of computed tomography (CT). This revision places major emphasis on revised or new criteria for pancreatic fluid collections and revises some of the clinical criteria and terminology (). This review article will principally address the new definitions for the various manifestations of fluid collections and/or liquefaction and their CT criteria as they occur during the course of acute pancreatitis; it also briefly outlines the revised terminology for description of the clinical course of acute pancreatitis. The goal is to familiarize radiologists with the revisions so that they may adopt these criteria and the terminology in their clinical practice and research. The author has been a consultant to the working group for the description of the radiologic manifestations of the various forms and complications of acute pancreatitis and for the revision of the manuscript.

Some of his suggestions may have been included in the final report. This review will also briefly discuss treatment options for various complications of acute pancreatitis on the basis of CT and clinical findings. Course and Severity of Disease The revised Atlanta classification introduces two distinct phases of acute pancreatitis: a first, or early, phase that occurs within the 1st week of onset of disease; and a second, or late, phase that takes place after the 1st week of onset (,–).

During the 1st week of acute pancreatitis, the pathologic conditions in and around the pancreas progress from early inflammation with variable degrees of peripancreatic edema and ischemia to resolution or to permanent necrosis and liquefaction. In this early phase, severity is entirely based on clinical parameters, because the need for treatment in the first phase is determined primarily by the presence or absence of organ failure caused by systemic inflammatory response syndrome and much less by morphologic findings involving the pancreas and peripancreatic areas. For organ failure, the Marshall scoring system () is most commonly used, and the respiratory, cardiovascular, and renal systems need to be assessed (,). Over the course of the 1st week, organ failure either resolves or becomes more severe. Patients with organ failure that resolves in 48 hours are considered to have mild pancreatitis without complications and have a mortality rate of 0% (,). Severe acute pancreatitis in the first phase is defined as organ failure that lasts more than 48 hours or death (,). Expansion of systemic inflammatory response syndrome and ensuing multiorgan failure is responsible for many deaths during this phase ().

In this initial time period, there is not always a direct correlation between clinical severity with or without organ failure and extent of morphologic characteristics in and around the pancreas (, ) (,). Figure 2: Axial CT image of IEP in a 51-year-old man with persistent organ failure (lipase, 1027 U/L [17.15 microkatals per liter]; Marshall score of 3 with persistently low systolic pressure of. It is standard clinical practice within the first 3 days of admission of a patient with acute pancreatitis to record markers of severity (eg, hematocrit; score from APACHE II, Ranson, or other system; pulmonary complications on chest radiograph, including pleural effusion; and serum levels of C-reactive protein) (,). Other severity markers may also be used (CT severity index or modified CT severity index; serial blood, urea, nitrogen measurements; levels of creatinine, serum lactate dehydrogenase, serum and/or urinary trypsinogen, and cytokines; and other parameters of acute pancreatic injury). Potential risk factors to assess are age, comorbidities, and body mass index (). Serum amylase and lipase are important for diagnosing acute pancreatitis but are not clinical markers of severity. These latter parameters should be evaluated but are not part of the revised Atlanta classification system, and their discussing is beyond the scope of this review.

Think Psychology Baird 2011 Ebook Login on this page. Moreover, these markers for forecasting severity within the first 24–72 hours are of limited value for predicting the development of pancreatic necrosis, persistent organ failure, or death. The late phase begins after the 1st week, may extend for weeks to months, and is characterized by increasing necrosis, infection, and persistent multiorgan failure (). Local complications may manifest systemically with bacteremia and sepsis when necrotic tissue becomes infected. The need for treatment in this phase is determined by the presence of symptoms and/or complications of acute pancreatitis, and the type of treatment is based on the imaging findings in the area of the pancreas and peripancreatic region as seen on contrast-enhanced CT or MR images and by the presence of local complications.

Morphologic data help guide therapy and must be added to the clinical criteria in this phase. Development of increasing necrosis, persistent systemic inflammatory response syndrome, and multiorgan failure cause a significant increase in mortality (). The mortality rates for sterile necrosis remain relatively low (5%–10%), but superinfection of the necrosis increases the mortality rate substantially (20%–30%) ().

There is an ongoing discussion about introducing a third category called “moderate acute pancreatitis.” This category would include disease in patients who have sterile pancreatic or peripancreatic complications or transient organ failure but no persistent systemic complications. This leads to a morbidity rate that is higher than that expected for mild pancreatitis but has very low mortality rate. Therefore it is quite different from severe pancreatitis. Imaging According to the revised Atlanta classification, contrast-enhanced CT is the primary tool for assessing the imaging-based criteria because it is widely available for these acutely ill patients and has a high degree of accuracy (,). Contrast-enhanced CT is especially suited for staging in patients with acute pancreatitis, helping assess complications, and monitoring of treatment response through follow-up studies. Not all patients with acute pancreatitis need to undergo contrast-enhanced CT.

Contrast-enhanced CT is not indicated initially in patients with acute pancreatitis who have no clinical signs of severe pancreatitis and who show rapid clinical improvement. However, contrast-enhanced CT should be performed in patients who develop or are likely to develop severe acute pancreatitis or complications related to acute pancreatitis. The ideal time for assessing these complications with CT is after 72 hours from onset of symptoms. CT should be repeated when the clinical picture drastically changes, such as with sudden onset of fever, decrease in hematocrit, or sepsis. CT also is useful to guide catheter placement for drainage and to assess success of treatment in patients who underwent percutaneous drainage or other interventions.

Furthermore, in patients with their first episode of pancreatitis who are over 40 years of age and have no identifiable cause for pancreatitis, contrast-enhanced CT should be used to exclude a possible neoplasm (). The radiologist should address whether pancreatic necrosis is present, characterize pancreatic parenchymal and extrapancreatic fluid collections, and describe the presence of ascites and extrapancreatic findings such as gallstones, biliary dilatation, venous thrombosis, aneurysms, and contiguous inflammatory involvement of the gastrointestinal tract. According to the revised Atlanta classification, MR imaging or transabdominal or endoscopic US may be used for special indications (–). MR imaging is reserved for detection of choledocholithiasis not visualized on contrast-enhanced CT images and to further characterize collections for the presence of nonliquefied material (–). Nonliquefied material refers to solid and semisolid components, usually pancreatic and extrapancreatic debris and necrotic fatty tissue and may appear on contrast-enhanced CT images as a homogeneous or heterogeneous fluid collection. MR imaging has an important role in patients in whom contrast-enhanced CT is contraindicated (eg, due to allergy to iodinated intravenous contrast agents or pregnancy) (–).

Transabdominal US can be helpful for determining the presence of stones in the gallbladder, but it is less accurate than contrast-enhanced CT or MR imaging for visualizing distal common bile duct stones and has the disadvantage of being operator dependent (). In patients with renal insufficiency who cannot undergo administration of iodinated contrast material or gadolinium, unenhanced CT or MR imaging may be used (,,). Endoscopic retrograde cholangiopancreatography has no role in this morphologic imaging–based classification of acute pancreatitis.

The morphologic classification system based on contrast-enhanced CT findings requires close collaboration between the diagnostic radiologist, the “interventionalists” (endoscopist, surgeon, interventional radiologist), and the clinician. The findings identified on CT or MR images allow appropriate staging of acute pancreatitis and help predict complications (,). The clinician in turn integrates the reported morphologic findings into the clinical picture to optimize treatment, which should lead to improved outcomes. Morphologic Stages of Acute Pancreatitis In the 1992 Atlanta classification, a distinction was made between interstitial pancreatitis and sterile or infected necrosis. In the revised Atlanta classification, these two types are defined similarly as IEP and acute necrotizing pancreatitis, but necrotizing pancreatitis is further subdivided into parenchymal necrosis alone, peripancreatic necrosis alone, and a combined type (peripancreatic and parenchymal necrosis) with or without infection ( ).

The imaging-based revised classification involves careful assessment of CT images of collections of fluid and/or nonliquefied material in and around the pancreas (ie, areas of pancreatic parenchymal and peripancreatic necrosis). The terminology for fluid collections is completely revised.

It is important for the radiologist to adopt this new nomenclature so that imaging descriptions are standardized and communication with clinical and surgical colleagues is precise. The revised Atlanta classification also outlines other important findings to be evaluated with imaging such as causes of pancreatitis, including cholecystolithiasis and choledocholithiasis, or complications related to acute pancreatitis, including extrahepatic biliary dilatation; splenic, portal, and mesenteric venous thrombosis; varices; arterial pseudoaneurysm; pleural effusion; and ascites. In addition, other intraabdominal findings caused by pancreatic secretions need to be reported.

These are inflammatory changes due to pancreatic secretions in the stomach, duodenum, small bowel, colon, spleen, kidney, ureters and liver. Interstitial Edematous Pancreatitis In patients with IEP, contrast-enhanced CT demonstrates acute pancreatitis as localized or diffuse enlargement of the pancreas, with normal homogeneous enhancement or slightly heterogeneous enhancement of the pancreatic parenchyma related to edema ( ). The peripancreatic and retroperitoneal tissue may appear normal, usually in early mild disease, or may show mild inflammatory changes in the peripancreatic soft tissue that appear as “mistiness” or mild fat stranding with varying amounts of peripancreatic fluid (see Pancreatic and Peripancreatic Collections).

On a contrast-enhanced CT study obtained within the first several days of acute onset of pancreatitis, the pancreas occasionally demonstrates increased heterogeneous enhancement of the parenchyma ( ) that cannot be characterized definitively as either IEP or ill-defined necrosis. With these findings, the presence or absence of pancreatic necrosis needs to be described initially as indeterminate. Contrast-enhanced CT performed 5–7 days later permits definitive characterization. Necrotizing Pancreatitis The revised Atlanta classification system distinguishes three forms of acute necrotizing pancreatitis, depending on location.

This represents a distinct change from the initial classification. All three types can be sterile or infected.

Pancreatic parenchymal necrosis alone.—Pancreatic parenchymal necrosis alone can be seen in fewer than 5% of patients and appears on contrast-enhanced CT images as lack of parenchymal enhancement (). In the 1st week of necrotizing pancreatitis, contrast-enhanced CT demonstrates necrosis as a more homogeneous nonenhancing area of variable attenuation ( ) and, later in the course of the disease, as a more heterogeneous area. The radiologic changes are the result of a process in which the nonviable and necrotic tissues (primarily pancreatic parenchyma and peripancreatic fat) slowly begin to liquefy. Often the extent of parenchymal necrosis is divided on contrast-enhanced CT studies into three categories: less than 30%, 30%–50%, greater than 50% of the gland involved (). In a newer modified CT grading system only two categories are distinguished: less than 30% and greater than 30% (). At times, areas of no or poor enhancement that are estimated to be less than 30% in the early phase may actually be findings of edema rather than necrosis (,).

A definitive diagnosis in these patients requires a follow-up study.