Recognition of different types of pancreatic fluid collections is crucial for appropriate management.
Endoscopic-ultrasonography (EUS)-guided drainage is the treatment of choice in the management of pancreatic pseudocysts, with clinical outcomes comparable to surgical cystogastrostomy.
The endoscopic management of walled-off necrosis (WON) is more complex and is tailored to the size and location of the fluid collection. An algorithmic step-up approach, consisting of the creation of multiple transmural tracts, percutaneous drain insertion, and endoscopic necrosectomy, may be required to achieve successful clinical outcomes.
Identification of disconnected pancreatic duct syndrome (DPDS) is crucial in patients with WON, as they require plastic transmural stents to remain in situ indefinitely to minimize the risk of recurrence.
Pancreatic fluid collections (PFCs) can be broadly divided into four main types: (1) acute peripancreatic fluid collection, (2) pancreatic pseudocyst, (3) acute necrotic collection, and (4) WON, with the classification depending on the presence of a mature wall and the degree of solid, necrotic debris.
Acute peri-PFC and pancreatic pseudocysts both result from acute interstitial edematous pancreatitis and therefore contain no necrotic material. Acute PFCs usually develop less than 4 weeks from the onset of acute pancreatitis and can be differentiated from pancreatic pseudocysts by the absence of a mature outer wall. In contrast, pancreatic pseudocysts are characterized by the presence of a mature wall, which usually requires 3 to 4 weeks to develop from the inciting event ( Fig. 23.1A and B ).
Acute necrotic fluid collections and WON occur as a result of acute necrotizing pancreatitis and therefore are characterized by the presence of solid, necrotic debris of varying quantity. Similar to the difference between acute peri-PFC and pancreatic pseudocysts, acute necrotic fluid collections are present early on in the course of acute necrotizing pancreatitis ( Fig. 23.2A and B ), whereas WON develops after sufficient time has passed for a mature wall to form around the necrotic collection (usually >4 weeks after the onset of acute pancreatitis) ( Fig. 23.3A and B and Table 23.1 ).
|Pancreatic Fluid Collection Types||Etiology||Time for Development (Weeks)||Presence of a Mature Wall||Necrotic Debris|
|Acute peripancreatic fluid collection||Interstitial pancreatitis||<4||No||No|
|Acute necrotic collection||Necrotizing pancreatitis||<4||No||Yes|
|Walled-off necrosis||Necrotizing pancreatitis||≥4||Yes||Yes|
Computed tomography (CT) with contrast enhancement is the most commonly performed imaging modality to diagnose PFCs; however, studies have shown superiority of magnetic resonance imaging (MRI) over CT for quantification of necrotic debris. The differentiation between necrotic and nonnecrotic PFCs is, in turn, critical owing to the difference in clinical outcomes, with significantly higher treatment success rates, lower adverse events rates, fewer reinterventions, and shorter duration of hospitalization observed following endoscopic drainage of pseudocysts compared to WON. Therefore pseudocysts and WON must be recognized as separate disease entities warranting different management strategies. Furthermore, PFCs can arise in peripancreatic regions with extension into the retroperitoneal space, such as the paracolic gutters, which can pose additional management challenges. In this chapter, we outline the various EUS-guided treatment strategies that can be adopted to maximize treatment success.
Indications for Intervention
The general consensus is that interventions should be avoided in acute peripancreatic or necrotic collections and should ideally be delayed until a mature wall has developed around the fluid collection. Also, patients with asymptomatic PFCs do not require drainage, regardless of the PFC size. However, intervention is required in patients with either symptomatic or infected PFCs, which can result in abdominal pain, failure to thrive, persistent organ failure despite maximum supportive therapy, sepsis, gastric/intestinal outlet obstruction, and biliary obstruction.
Types of Interventions
Surgical interventions in pancreatic pseudocysts primarily consist of either open or laparoscopic cystogastrostomy or cystoenterostomy. However, as pseudocysts are primarily fluid-filled and lack necrotic debris (unlike WON), the larger transmural conduit that can be created via surgical cystogastrostomy is not required. In a randomized trial comparing surgical cystogastrostomy with EUS-guided cystogastrostomy for the drainage of pancreatic pseudocysts, high treatment success was achieved with both modalities (95% in endoscopy vs. 100% in surgery group); however, endoscopic drainage was associated with a significantly shorter hospital stay, better physical and mental health, and lower costs. Therefore EUS-guided drainage is the modality of choice in the management of uncomplicated pseudocysts.
There has been a paradigm shift in the surgical management of WON in recent times, from invasive to minimally invasive surgical techniques. Open surgical necrosectomy is now no longer recommended due to the high morbidity (40% to 55%) and mortality (15% to 20%) associated with this technique. Minimally invasive surgical drainage options currently include cystogastrostomy with laparoscopic transabdominal necrosectomy and videoscopic-assisted retroperitoneal debridement (VARD). In a randomized trial (PAncreatitis, Necrosectomy versus sTEp up appRoach [PANTER] trial: Minimally invasive step-up approach versus maximal necrosectomy in patients with acute necrotizing pancreatitis) comparing the step-up minimally invasive surgical approach (consisting of percutaneous drain placement followed by minimally invasive surgical drainage) to open necrosectomy, the latter technique was associated with a significantly higher rate of major adverse events. Additionally, according to the results from a recent randomized trial (TESION trial: Transluminal endoscopic step-up approach vs. minimally invasive surgical step-up approach in patients with infected necrotizing pancreatitis), when compared to the step-up endoscopic approach (transmural drainage followed by endoscopic necrosectomy), the step-up minimally invasive surgical technique (percutaneous drain insertion followed by minimally invasive surgical necrosectomy) resulted in similar rates of major adverse events. However, endoscopic therapy was associated with shorter duration of hospitalization, lower costs, and lower rates of pancreatic fistula formation. Therefore when the requisite expertise is available, endoscopic drainage (with or without necrosectomy) should be undertaken as the first-line therapy in the management of WON.
Percutaneous drain insertion under radiologic guidance is increasingly performed as the initial treatment modality in the step-up surgical approach to the management of WON, and as adjunctive therapy in patients with collections not amenable to endoscopic drainage. One of the main advantages of this modality is that no further necrosectomy may be required in a significant proportion (up to 55%) of WON patients following percutaneous drainage ; in those requiring further interventions, the percutaneous tract can be dilated to provide a conduit for sinus tract necrosectomy or VARD. However, as yet, no clear guidelines exist regarding the timing of drainage, the size of drain required, or the optimal duration of insertion, and there have been no studies comparing percutaneous drainage alone with endoscopic drainage. Also, adverse event rates associated with percutaneous drainage can range from 22% to 50%, and consist of bleeding, colonic perforation, and pancreaticocutaneous or pancreaticoenteric fistula formation. In our practice, we request insertion of a large bore percutaneous drain (16 Fr) for large WON >12 cm in size with extension into the paracolic gutters, so it can be used in conjunction with EUS-guided transmural drainage as a part of the “dual-modality” technique (see section on dual-modality).
Since the first description of the single-step technique in 1998, EUS-guided drainage is now the standard of care technique for endoscopic drainage of PFCs. The treatment success following EUS-guided drainage of pancreatic pseudocysts is high at 73% to 100%, in contrast to the suboptimal treatment success rates of 60% to 70% observed with WON. In the following section, various EUS-guided drainage techniques will be described, with the aim of optimizing clinical outcomes and minimizing adverse events.
Prior to EUS-guided drainage of PFCs, the following steps should be undertaken:
History and physical examination, with a review of vital signs and laboratory values to determine the indication for drainage, the presence of systemic inflammatory response syndrome (SIRS), sepsis, and organ failure.
Review of the most recent cross-sectional imaging to assess for the presence of solid debris and confirmation of the presence of a mature wall.
Optimization of coagulation parameters (international normalized ratio [INR] ≤ 1.5, platelet count > 50,000/mm 3 ).
Optimization of nutritional status with enteral feeding via nasojejunal or percutaneous gastrojejunal tube if unable to tolerate adequate oral diet.
Administration of broad-spectrum intravenous antibiotics prior to instrumentation. Intravenous ciprofloxacin or piperacillin/tazobactam are the preferred antibiotics of choice and should be continued for 5 days postdrainage.
Multidisciplinary care in consultation with pancreatic surgeons and interventional radiologists.
Cautions Prior to Endoscopic Ultrasonography-Guided Pancreatic Fluid Collection Drainage
Prior to drainage of any PFC, a careful EUS examination should be performed as EUS has been shown to alter the management in up to 37.5% of patients referred for endoscopic drainage, due to several reasons. First, the suitability for endoscopic drainage as determined by the presence of a mature wall around the PFC that is adherent to the gastric or duodenal wall can be confirmed on EUS, especially if less than 3 to 4 weeks have passed since the inciting event. If the wall is still immature without adequate adherence, endoscopic drainage should be postponed ( Video 23.1 ). Second, the presence of malignancy can be excluded as the etiology of the PFC on EUS, which has been shown to occur in 1.25% of patients referred for endoscopic drainage ( Video 23.2 ). Finally, other types of cysts can mimic PFCs, such as duplication cysts and mucinous cysts (mucinous cystic neoplasms and intraductal papillary mucinous neoplasm). In one study, 5% of patients originally diagnosed with pancreatic pseudocysts on CT were found to have mucinous cystic neoplasms on EUS ( Video 23.3 ).
Video Showing Features of Acute Necrotic Collection on Endoscopic UltrasonographyVideo 23.2
Video Showing Pancreatic Cancer Resulting in a Pseudo-PseudocystVideo 23.3
Video Showing a Duplication Cyst, Which May Mimic a Pancreatic Fluid Collection
EUS-guided drainage of PFCs should be performed in a thoughtful and systematic manner, adopting variations in endoscopic techniques according to the type, size, and location of the PFC, and the subsequent response to treatment. This approach, in conjunction with collaborative management with pancreatic surgeons and interventional radiologists, is especially important in the management of WON, where treatment success can be suboptimal at only 60% to 70%.
The single-gate technique consists of the creation of a single transmural tract through which plastic or metal stents are placed for PFC drainage. This is a multistep process when plastic stents are being deployed ( Video 23.4 ), but can be a single-step process when using lumen-apposing metal stents (LAMS) with an electrocautery-enhanced delivery system (Hot AXIOS, Boston Scientific Corporation, Marlborough, Massachusetts) ( Video 23.5 ).
Video Showing the Single-Gate Technique of Pancreatic Fluid Collections Drainage Using Plastic StentsVideo 23.5
Video Showing the Single-Gate Technique of Pancreatic Fluid Collections Drainage Using Lumen-Apposing Metal Stents With an Electrocautery-Enhanced Delivery System
Plastic Stent Insertion
Therapeutic linear array echoendoscope with a 3.7-mm working channel
19-Gauge fine-needle aspiration (FNA) needle
Syringe for aspiration of PFC contents for Gram stain and culture
0.025- or 0.035-inch guidewire
Two types of dilators: (1) a 4.5-Fr tapered tip endoscopic retrograde cholangiopancreatography (ERCP) cannula, or needle-knife catheter, or cystotome catheter; AND (2) a graded balloon dilator
Two or more 7 Fr diameter 4 cm length double pigtail plastic stents
PFC puncture and guidewire insertion
After excluding the presence of vasculature in the path of the needle by using color Doppler ultrasound, a 19-gauge FNA needle is used to puncture the PFC under EUS guidance ( Fig. 23.4 ). A sample of the PFC fluid is aspirated at this time and sent for Gram stain and culture if there is a clinical suspicion of infection. In patients with WON, where endoscopic necrosectomy may be required in the future, the creation of transmural tracts should be avoided in the cardia and fundus, if possible, as these sites make future access to the necrotic cavity difficult or impossible ( Fig. 23.5 ; Video 23.6 ).