Usual Site of Complicated Pancreatitis
Complicated pancreatitis primarily involves the pancreas itself and the peripancreatic tissues in the retroperitoneum, with necrosis extending to peripancreatic fat and potentially spreading to the retroperitoneal spaces, and less commonly to the peritoneal cavity. 1, 2
Anatomic Distribution of Complications
Primary Sites
Pancreatic parenchyma and peripancreatic fat are the primary sites where necrosis develops in complicated pancreatitis, representing diffuse or focal areas of non-viable tissue 1
The retroperitoneum is the predominant space where complications manifest, as infection tends to spread from the pancreas to peripancreatic tissues and throughout the retroperitoneal compartment 2
Acute fluid collections occur in or near the pancreas in 30-50% of severe cases, located within the pancreatic bed and adjacent retroperitoneal spaces 1
Secondary Extension Sites
The peritoneal cavity may be involved more rarely when infection or fluid spreads beyond the retroperitoneum 2
Retroperitoneal gas can be visualized on imaging as a late sign when gas-forming organisms (such as Clostridium perfringens) infect necrotic tissue 1, 3
Pleural spaces may develop effusions as part of the systemic inflammatory response 1
Clinical Implications by Location
Epigastric Region
An epigastric mass with vomiting suggests an acute fluid collection in the pancreatic region that may persist to form a pseudocyst 1, 4
This represents fluid accumulation in the lesser sac or peripancreatic spaces causing mechanical obstruction 4
Extent and Prognosis
Patients with three or more fluid collections (indicating widespread retroperitoneal involvement) have greater risk of complications and death 1
The volume of necrosis in the pancreatic and peripancreatic tissues is the main determinant of infection risk and mortality 5
Diagnostic Localization
Dynamic CT scanning should be performed between 3-10 days to delineate the extent of pancreatic and peripancreatic necrosis 1
CT is essential for planning drainage procedures and identifying the anatomic distribution of complications including pseudo-aneurysms 1
Free gas in the retroperitoneum on plain abdominal radiographs is a late sign indicating infection with gas-forming organisms in the retroperitoneal necrotic tissue 1