Differentiating autoimmune pancreatitis from pancreatic adenocarcinoma using dual-phase computed tomography.

OBJECTIVE: This article aimed to study features on dual-phase computed tomography (CT) that help differentiate autoimmune pancreatitis (AIP) from pancreatic adenocarcinoma (PA).

METHODS: The CTs of 32 patients with AIP were matched with equal number of PA and were independently evaluated by 3 radiologists who assigned a diagnosis of AIP, PA, or unsure. Interobserver agreement between radiologists was evaluated using κ statistics.

RESULTS: The mean accuracies for diagnosing AIP and PA were 68% and 83%, respectively. There was moderate agreement between radiologists (κ, 0.58; P < 0.0001). The most common findings for AIP were common bile duct (CBD) stricture (63%), bile duct wall hyperenhancement (47%), and diffuse parenchymal enlargement (41%). The most common findings for PA were focal mass (78%; κ, 0.58; P < 0.0001) and pancreatic ductal dilatation (69%; κ, 0.7; P < 0.0001). Findings helpful for diagnosing AIP were diffuse enlargement, parenchymal atrophy as well as absence of pancreatic duct dilatation and focal mass. Findings helpful for diagnosing PA were focal mass and pancreatic ductal dilatation. Misdiagnosis of PA in patients with AIP was due to focal mass, pancreatic duct dilatation, and pancreatic atrophy, whereas misdiagnosis of AIP in patients with PA was due to absence of atrophy, presence of diffuse enlargement, and peripancreatic halo.

CONCLUSIONS: Diffuse enlargement, hypoenhancement, and characteristic peripancreatic halo are strong indicators for a diagnosis of AIP. Radiologists demonstrated moderate agreement in distinguishing AIP from PA on the basis of CT imaging.