**1. Introduction**

Acute pancreatitis is mild in majority of the cases and categorized as interstitial edematous pancreatitis. About 15–20% of cases develop necrotizing pancreatitis involving necrosis of variable proportion of pancreatic parenchyma. Pancreatic fluid collections (PFCs) are a common local complication of acute pancreatitis. PFCs have been classified according to the revised Atlanta criteria based on duration (<4 or >4 weeks) and contents of fluid collection [1]. Acute collections include acute pancreatic or peri-pancreatic fluid collections (APFCs) and acute necrotic pancreatic fluid collections (ANPFCs) which develop after acute interstitial and acute necrotizing pancreatitis, respectively (**Figure 1**). APFCs and ANPFCs get walled off after about 4–6 weeks into pseudocysts and walled off necrosis (WON), respectively. By definition, pseudocysts have clear contents and WON consists of variable amount of necrotic debris (**Figures 2** and **3**).

#### **Figure 1.**

*Endosonographic image of acute necrotic pancreatic fluid collections. Note the ill-defined boundaries and the solid component within the fluid collection.*

#### **Figure 2.**

*Endosonographic image in a case with pancreatic pseudocyst. Not the well-defined boundaries without any echogenic debris in the cyst cavity.*

#### **Figure 3.**

*Endosonographic image in a case with walled off necrosis. Not the well-defined boundaries with echogenic necrotic debris in the cyst cavity.*

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**Figure 4.**

*Endoscopic Management of Pancreatic Fluid Collections: An Update*

APFCs develop in about 20–40% of patients after acute interstitial pancreatitis [2–4]. Majority (~90%) of APFCs resolve and do not transform into pseudocyst. Moreover, majority of the pseudocysts resolve or reduce in size with time and therefore, do not require an intervention [4]. On the other hand, majority (90–100%) of the patients with acute necrotizing pancreatitis develop ANPFCs. Nearly half of the patients with ANPFCs develop walled off necrosis (WON) [2, 3]. The natural history of WON is not well known and appears to be more unpredictable than pseudocysts. An intervention may be required in one quarter to more than half of

The options of drainage for PFCs include surgery, percutaneous catheter drainage, and endoscopic transmural drainage (ETD). Open necrosectomy is associated with substantial rates of new onset multiple organ failure as compared to minimally invasive surgical step up approach (see later) [5]. Subsequent studies comparing endoscopic necrosectomy to open as well as minimally invasive surgical debridement concluded the superiority of endoscopic approach [6, 7]. Reduced mortality, less frequent new onset multiple organ failure, and the development of pancreatic fistulas are distinct advantages of endoscopic necrosectomy [8, 9]. In the current era, a step up approach is preferred for its obvious benefits in reducing a proinflammatory response and prevention of new onset organ failure. In the ensuing sections, we would discuss endoscopic approach to PFCs and its advantages over

Characterization of PFCs into pseudocysts and WON is important prior to ETD. WON has variable amount of necrotic debris and therefore, has a protracted course and more frequent requirement of re-interventions as compared to pseudocysts (**Figures 2** and **3**). Computed tomography is frequently used to localize the site of collection. However, it may not accurately differentiate between the solid and liquid contents of the collection (**Figures 4** and **5**). Magnetic resonance imaging (MRI)

*CT image in a case of pancreatic pseudocyst. Note the well-defined boundary and clear contents of the cyst.*

**1.1 Natural history of pancreatic fluid collections**

**2. Management of pancreatic fluid collections**

*DOI: http://dx.doi.org/10.5772/intechopen.89764*

the patients with WON [2, 3].

surgical and percutaneous drainages.

**2.1 Endoscopic drainage of PFCs**
