Acute pancreatitis: A pictorial review of early pancreatic fluid collections

Table 1 Key points of clinical and imaging differential diagnosis between acute peripancreatic fluid collection and acute necrotic collection

Key points	Acute peripancreatic fluid collection	Acute necrotic collection
Clinical severity	Mostly mild acute pancreatitis	Moderately severe acute pancreatitis or severe acute pancreatitis
Management algorithm	Conservative treatment (usually resolves spontaneously without intervention)	Likely increased morbidity and intervention rates (drainage or surgical treatment)
Course and prognosis	The hospital stay is usually about one week after onset; a good prognosis	Hospitalization often lasts from weeks to months; increased infection and mortality rates
CT/MRI imaging pattern	Occurs only in the setting of interstitial oedematous pancreatitis	Occurs in the setting of acute necrotising pancreatitis (including peripancreatic necrosis only)
Location and number of collections on CT/MRI	Mostly confined to simple retroperitoneal space or interfascial plane	Mostly in transabdominal-pelvic cavities and multiple spaces or interfascial planes
Shape, size, edge	Linear/strip-shaped, a small amount of collections, clear edge	Large patchy-shaped, a large amount of collections, unclear or irregular edge
Density/intense, enhancement characteristics	Homogeneous low density/hypointense T1 hyperintense T2 signal; no enhancement	Mixed features, mainly low density/hypointense T1 /hyperintense T2 signal, containing low density fat/fat signal intensity and low density or hypointense pancreas fragments; fragments are not enhancing
Secondary or concomitant signs	Rare	Frequent secondary infection with “bubble sign” (caused by infection itself or intestinal fistula with adjacent intestine); when a large area of intrapancreatic collections is present, “pancreatic duct disruption syndrome” may occur (further invasive operation is often required)

CT: Computed tomography; MRI: Magnetic resonance imaging.