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Critical appraisal of the patient’s history, physical examination findings, laboratory profile, and imaging abnormalities is a fundamental prerequisite for appropriate management of pancreatic pseudocysts and exclusion of their mimics. A multidisciplinary approach, enlisting the expertise of interventional endoscopists, interventional radiologists, and pancreatico‐biliary surgeons in the evaluation of this complex patient population is highly desirable. Because an interventional approach to management is not risk‐free and a significant proportion of pseudocysts can regress or even resolve spontaneously, only patients with sizeable (>6 cm diameter) pseudocysts causing significant symptoms or complications, such as intractable abdominal pain, nausea, vomiting, malnutrition, other evidence of gastric outlet obstruction, sepsis, gastrointestinal bleeding, biliary obstruction, compression of major peripancreatic vasculature and/or features of abdominal compartment syndrome, require drainage therapy [2–7] (Figure 17.1). In contrast, it is reasonable to withhold or delay intervention in the setting of asymptomatic or minimally symptomatic pancreatic pseudocysts, following them up with serial cross‐sectional imaging instead as there is no immediate clinical benefit to be gained by the patient and the risk of intervention may outweigh the risk of developing a complication due to the pseudocyst. Patient comorbidity is particularly relevant in this context. In cases of diagnostic uncertainty as to whether a small pseudocyst is symptomatic, it is possible to simply needle‐aspirate the pseudocyst to dryness under endoscopic ultrasound (EUS) guidance and evaluate the subsequent clinical course. In general, the larger the pseudocyst, the greater the incidence of compressive symptoms, and the lower the probability of not only spontaneous resolution but, in our experience, also that of intervention‐related complications. Conversely, transluminal stent‐assisted drainage of collections smaller than 6 cm in diameter potentially increases the procedural risk of perforation and pseudocyst wall dehiscence and is therefore discouraged. Spontaneous resolution is more common in pseudocysts secondary to acute pancreatitis. Factors associated with a reduced likelihood of spontaneous resolution include communication with the main pancreatic duct, presence of multiple cysts, increase in size during follow‐up, and presence of a pancreatic duct stricture. Additionally, pseudocysts occurring in the setting of chronic pancreatitis with imaging evidence of calcification are unlikely to spontaneously resolve.

Table 17.1 Revised definitions of morphological features of acute pancreatitis.

Interstitial edematous pancreatitis Acute inflammation of the pancreatic parenchyma and peripancreatic tissues, but without recognizable tissue necrosis:Pancreatic parenchyma enhancement by intravenous contrast agentNo findings of peripancreatic necrosis Necrotizing pancreatitis Inflammation associated with pancreatic parenchymal necrosis and/or peripancreatic necrosis:Lack of pancreatic parenchymal enhancement by intravenous contrast agent and/orPresence of findings of peripancreatic necrosis Acute peripancreatic fluid collection Peripancreatic fluid associated with interstitial edematous pancreatitis with no associated peripancreatic necrosis. This term applies only to areas of peripancreatic fluid seen within the first four weeks after onset of interstitial edematous pancreatitis and without the features of a pseudocyst:Occurs in the setting of interstitial edematous pancreatitisHomogeneous collection with fluid densityConfined by normal peripancreatic fascial planesNo definable wall encapsulating the collectionAdjacent to pancreas (no intrapancreatic extension) Pancreatic pseudocyst An encapsulated collection of fluid with a well‐defined inflammatory wall usually outside the pancreas with minimal or no necrosis. This entity usually occurs more than four weeks after onset of interstitial edematous pancreatitis to mature:Well circumscribed, usually round or ovalHomogeneous fluid densityNo nonliquid componentWell‐defined wall, i.e. completely encapsulatedMaturation usually requires more than four weeks after onset of acute pancreatitis; occurs after interstitial edematous pancreatitis Acute necrotic collection A collection containing variable amounts of both fluid and necrosis associated with necrotizing pancreatitis; the necrosis can involve the pancreatic parenchyma and/or the peripancreatic tissues:Occurs only in the setting of acute necrotizing pancreatitisHeterogeneous and nonliquid density of varying degrees in different locations (some appear homogeneous early in their course)No definable wall encapsulating the collectionLocation: intrapancreatic and/or extrapancreatic Walled‐off necrosis A mature encapsulated collection of pancreatic and/or peripancreatic necrosis that has developed a well‐defined inflammatory wall. This usually occurs more than four weeks after onset of necrotizing pancreatitis:Heterogeneous with liquid and nonliquid density with varying degrees of loculations (some may appear homogeneous)Well‐defined wall, i.e. completely encapsulatedLocation: intrapancreatic and/or extrapancreaticMaturation usually requires four weeks after onset of acute necrotizing pancreatitis

Figure 17.1 CT scan of 12‐cm collection causing a degree of gastric outflow obstruction, associated portal vein occlusion, and varices in stomach wall.

Source: courtesy of Muhammad F. Dawwas and Kofi W. Oppong.

Diagnostic imaging, in the form of contrast‐enhanced computed tomography (CT), magnetic resonance imaging (MRI), or EUS, serves several important goals in the evaluation of pancreatic pseudocysts [2–7]. First, it provides anatomical information on the pseudocyst’s size, wall maturity, solid content, location, and proximity to the wall of the stomach and duodenum. This information is fundamental to decision‐making with regard to the appropriateness and timing of drainage therapy, choice of drainage route, and selection of drainage device. Second, it helps confirm the diagnosis and rule out other cystic lesions with similar radiological appearance such as pancreatic cystic neoplasms and duplication cysts, for which drainage therapy is not only unnecessary but may also potentially render an otherwise resectable tumor unresectable. Third, it can detect pseudoaneurysms arising from the splenic artery or other peripancreatic vessels that would otherwise increase the risk of potentially fatal bleeding in the setting of drainage therapy. Last, it may help evaluate the structural integrity of the pancreatic duct and existence of communication with the pseudocyst, yielding information with important implications for subsequent management.

MRI and endosonography have superior diagnostic accuracy compared with CT for detection of necrotic content and septation, thereby helping to distinguish pseudocysts from both walled‐off necrotic collections and pancreatic cystic neoplasms, respectively. In experienced hands, secretin‐stimulated magnetic resonance cholangiopancreatography (MRCP) and, to a lesser extent, EUS and endoscopic retrograde cholangiopancreatography (ERCP) can be used to evaluate the integrity of the main pancreatic duct and guide endoscopic therapy, such that patients with no evidence of ductal disruption would be candidates for transluminal drainage alone without anticipated benefit from transpapillary stent placement; those with incomplete disruption could potentially benefit from either transluminal or transpapillary drainage (or both); and those with complete rupture (otherwise known as disconnected duct syndrome; see later section) would require long‐term transluminal placement of one or more plastic stents [3,4]. In the setting of suspected peripancreatic pseudoaneurysms, CT and magnetic resonance angiography offer superior diagnostic utility, facilitating preemptive angiographic embolization prior to undertaking an otherwise risky drainage intervention. EUS or image‐guided percutaneous fine‐needle aspiration can potentially determine if a pseudocyst is infected and also exclude a mucinous tumor masquerading as a pseudocyst; however, the procedure is not generally recommended given the high false‐negative and false‐positive rates, and the risk of contaminating an otherwise sterile pseudocyst [2–7].