necrosis becomes conuent and demarcated. The distinction between these two is important since APFC is usually self-limited, resolving spontaneously over time (Fig.4.1), and therefore supportive measures alone usually sufcient [8, 9]. Since both pseudocyst and WOPN represent mature forms of acute pancreatitis complica­tions, the distinction is usually easier than APFC and ANC.In contrast to a pseudo­cyst, WOPN contains necrotic pancreatic parenchyma or necrotic fat which appears as solid heterogeneous density within the walled-off cavity on imaging. The ability to differentiate between these pathologies is extremely important since it guides decision-making about their management. The majority of pancreatic uid collec­tions (acute and chronic) remains asymptomatic and resolve spontaneously over time, and therefore do not require any intervention. About 25% become symptom­atic or infected, which necessitates intervention. Any of the above pancreatitis­related collections and complications can be sterile or secondarily infected (Fig. 4.5a–d). Collections that contain solid material are more likely to become infected (i.e., ANC and WOPN) [10]. Infection can be suggested by clinical criteria with signs and symptoms of sepsis as well as on contrast-enhanced CT images by the presence of gas bubbles, which are produced by gas-forming organisms, or from