*6.1.1 Acute peripancreatic fluid collection*

Acute peripancreatic fluid collection occurs early, and has no specific wall. It resorbs spontaneously [27, 48].

## *6.1.2 Necrotizing pancreatitis*

Necrotizing pancreatitis can involve both the pancreas and peripancreatic tissues. A variable amount of fluid and necrotic tissue may develop within the necrosis,and is known as Acute Necrotic Collection (ANC) when a clear wall cannot be defined, and as Wall-off Necrosis (WON) when there is a mature, encapsulated and well-defined wall. WON is a pancreatic pseudocyst that occurs around 4 weeks after an AP attack, and that has a noticeable wall, for which drainage may be required. In either case, the necrotic area may be sterile or infected, and the type of treatment is determined based on the presence or absence of infection [84, 86–88].
