Endoscopic Drainage of Pancreatic Pseudocysts, Abscesses, and Walled-Off (Organized) Necrosis

Chapter 53 Endoscopic Drainage of Pancreatic Pseudocysts, Abscesses, and Walled-Off (Organized) Necrosis



Pancreatic pseudocysts, abscesses, and pancreatic necrosis are types of pancreatic fluid collections (PFCs) that arise as a consequence of pancreatic injury. At the basis of this pancreatic injury is disruption of the main pancreatic duct and/or side branches. Ductal disruption can be due to acute pancreatic injury (acute pancreatitis, trauma, surgical resection, or injury to the pancreas during abdominal surgery) or chronic injury (chronic pancreatitis, autoimmune pancreatitis). The sequela to ductal injury is formation of a collection of fluid with or without solid debris.


The basis of endoscopic therapy is directed at either drainage of fluid and solid components using a transmural approach or treatment of pancreatic duct (PD) disruption or stricture using a transpapillary approach, when possible. Treatment of PD disruption is believed to decrease the long-term recurrence rate and improve the outcome following successful resolution of a collection and can be assessed and treated endoscopically. This chapter discusses endoscopic approaches to PFCs.


Video for this chapter can be found online at www.expertconsult.com.



Specific Types of Fluid Collections


Classification systems for defining types of PFCs are useful for understanding mechanisms of formation and allowing comparisons of therapies between and among disciplines. Since the previous edition of this text the classification and nomenclature for PFCs has been revised1 and continues to evolve.


However, the approach can be simplified by addressing three questions: (1) Is the collection a result of pancreatitis or does it represent a cystic neoplasm (see Chapter 48)? (2) Is the collection composed primarily of liquid or does it contain significant solid debris? (3) What is the PD anatomy? Using these three basic questions, the short- and long-term approaches to the patient with a PFC can be formulated. The approach to collections that are composed primarily of fluid is different than the approach to those containing significant solid debris, since liquified collections can be managed with placement of small diameter stents via a transpapillary or transmural approach alone, whereas those with solid debris usually require aggressive transmural dilation to allow egress of solid material and placement of large bore stents and/or irrigation catheters and are associated with worse outcomes.



Collections Composed Entirely or Predominantly of Liquid




1. Acute fluid collections. Acute fluid collections arise early in the course of acute pancreatitis, are usually peripancreatic in location, and usually resolve without sequelae but may evolve into pancreatic pseudocysts.1


2. Pancreatic pseudocysts.


a. Acute pancreatic pseudocysts. Acute pseudocysts arise as a sequela of acute pancreatitis, require at least 4 weeks to form, and are devoid of significant solid debris. Acute pancreatic pseudocysts usually form as a result of limited pancreatic necrosis and PD leak (Fig. 53.1). Alternatively, areas of pancreatic and peripancreatic fat necrosis may completely liquify over time and become a pseudocyst. Despite the requirement of at least 4 weeks for a pseudocyst to form, it is important to note that this time period does not define the collection as a pancreatic pseudocyst. Patients with significant pancreatic necrosis (≥30%) may evolve the early acute pancreatic necrosis and peripancreatic necrosis into a collection that resembles a pseudocyst radiographically but has been present for more than 4 weeks (see Walled-Off Necrosis below). By definition, collections that contain significant solid debris are not pseudocysts and endoscopic treatment of these collections by pseudocyst drainage methods results in infection because of inadequate removal of solid debris.


3. Pancreatic abscesses. True pancreatic abscesses are rare and not synonymous with infected pancreatic pseudocysts.1 However, for the purposes of this chapter and based on pending revisions of the existing nomenclature, an abscess will be considered as an infected PFC that contains little to no solid debris (as opposed to infected pancreatic necrosis, which is described later). I believe that when this definition is used, abscesses can be drained through modest-sized catheters without absolute need for irrigation or debridement.




Predrainage Evaluation


Prior to undertaking drainage of a liquified pancreatic collection, a predrainage evaluation should be performed. The goals of the predrainage evaluation include the following:



1. Establish whether the collection represents a PFC or a “masquerader” of a PFC such as a cystic neoplasm or other entity (Box 53.1; Fig. 53.3). If the patient does not have a well-documented history of acute or chronic pancreatitis, the endoscopist should be concerned that the collection does not represent a pseudocyst or other inflammatory collection. With the development of endoscopic ultrasound (EUS), cystic neoplasms have been better recognized and defined. However, clinical judgment and magnetic resonance cholangiopancreatography (MRCP) can also be useful in making this differentiation. Cystic neoplasms are discussed in more detail in Chapter 48.


2. Establish whether the collection is predominantly liquid or contains a significant amount of solid debris.


3. Establish the relationship of the collection to surrounding luminal and vascular structures.


4. Consider underlying etiologies of true pancreatic pseudocyst that have implications for alternative or adjuvant therapies, such as pancreatic cancer, autoimmune pancreatitis, and intraductal pancreatic mucinous neoplasms (IPMNs).




In addition to a complete history and physical examination, the following evaluation should be undertaken:




Consideration should be given to the following additional studies:




Drainage Techniques


Liquified PFCs may be drained using a transpapillary approach, transmural approach, or a combination of these.2,3 The decision to use one approach over the other depends on the size of the collection, its proximity to the stomach or duodenum, and the ability to enter the pancreatic duct and/or reach the area of disruption.4 For example, although the intended approach to draining a pseudocyst that formed from an obstructing PD stone may be transpapillary (Fig. 53.5, A and B), failure to negotiate a guidewire beyond the obstructing ductal stone may require transmural drainage. Assessment and treatment of the ductal stone at a later date by other techniques such as extracorporeal shock wave lithotripsy (ESWL) can then be performed (Fig. 53.5, C to E).




Transpapillary Drainage


If the collection communicates with the main pancreatic duct, placement of a pancreatic endoprosthesis with or without pancreatic sphincterotomy is an approach that is useful, especially for collections measuring ≤6 cm that are not otherwise approachable transmurally.5,6 The upstream end of the stent (toward the pancreatic tail) may enter the collection directly or bridge the area of leak into the pancreatic duct upstream from the leak (Fig. 53.6). The latter is the preferred approach (Fig. 53.7) since it restores ductal continuity. In patients with chronic pseudocysts it is important that the stent bridge any obstructive process (stricture or stone) between the duodenum and the leak site. The diameter of pancreatic stent used is dependent on the pancreatic ductal diameter (see Chapters 21 and 52), although 7 Fr stents are most frequently used. In patients with chronic pancreatitis, endoscopic therapy of underlying PD strictures and pancreatic stones may reduce the recurrence rate of pancreatic pseudocysts.7




The advantage of a transpapillary approach compared to a transmural approach is avoidance of bleeding and perforation. The disadvantage of transpapillary drainage is the potential for pancreatic stent-induced ductal injury in patients whose PD is otherwise normal. Examples include patients with acute pseudocysts and small side branch disruption and patients with ductal tail leaks after distal (tail) pancreatectomy (see Chapter 42).




EUS-Guided Transmural Drainage


EUS imaging may reduce adverse events related to transmural entry of PFCs, although this has not been proven.8 EUS localization of the collection can be followed by a second non-EUS-guided endoscopic puncture,9 although this can be inaccurate. EUS-guided puncture is similar to EUS-guided FNA (Fig. 53.9; see Chapter 30). Using a linear echoendoscope with or without Doppler capabilities, successful entry and one-step drainage has been reported in approximately 94% of patients with low adverse event rates, including those without an endoscopically visible extrinsic compression.9,10 Lack of EUS availability, however, does not preclude transmural drainage except in the following instances: small “window” of entry based on CT, especially in the absence of an endoscopically defined area of extrinsic compression or unusual location; coagulopathy or thrombocytopenia; documented intervening varices9; and failed transmural entry using non-EUS-guided techniques. Indeed, a randomized trial of EUS and non-EUS drainage found non-EUS-guided drainage to be an acceptable first-line therapy in patients with bulging collections.11


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Mar 11, 2017 | Posted by in GASTROENTEROLOGY | Comments Off on Endoscopic Drainage of Pancreatic Pseudocysts, Abscesses, and Walled-Off (Organized) Necrosis

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