CT findings of walled-off pancreatic necrosis (WOPN): differentiation from pseudocyst and prediction of outcome after endoscopic therapy

Computed tomography (CT) findings that may differentiate walled-off pancreatic necrosis (WOPN) from pancreatic pseudocyst were investigated. CT examinations performed before endoscopic therapy of pancreatic fluid collection (PFC) in 73 patients (45 WOPN, 28 pseudocysts) were evaluated retrospectively by two radiologists. PFC was evaluated for size, extension to paracolic space, characteristics of wall and internal structure. The pancreas was evaluated for deformity or discontinuity, and pancreatic duct dilation. CT findings that were associated with WOPN or pseudocyst were identified. CT score (number of CT findings associated with WOPN minus number of findings associated with pseudocyst) was calculated for each PFC. PFC was categorized as WOPN or pseudocyst using a CT score threshold. Larger size, extension to paracolic space, irregular wall definition, presence of fat attenuation debris in PFC, pancreatic deformity or discontinuity (P < 0.05–0.0001) were findings associated with WOPN. Presence of pancreatic duct dilation was associated with pseudocyst. Using a CT score of 2 or higher as a threshold, CT differentiated WOPN from pseudocyst with an accuracy of 79.5–83.6%. Thus, CT can differentiate WOPN from pseudocysts.