Diagnosis of autoimmune pancreatitis with computed tomography / 中华消化杂志

ABSTRACT

Objective To investigate the computed tomography (CT) features of autoimmune pancreatitis (AIP).Methods The CT imaging data of 33 patients with AIP confirmed by pathology and/or steroid therapy were retrospectively analyzed.Image analysis including the shape of pancreas, density of lesion, contrast enhancement, the changes of pancreatic duct and biliary duct, peripancreatic appearances and adjacent organ involvement.T test was performed for statistical analysis.Results Among 33 patients with AIP, 23 cases (70%) with pancreatic parenchyma diffuse enlargement, eight cases (24%) with partial enlargement and two cases (6%) with normal pancreas.The lesions appeared hypoattenuating or isoattenuating on plain CT scan.After contrast-enhanced scan, the average CT values of lesions were (75.7±17.0) Hu at arterial phase, which was lower than that of venous phase (90.7±12.0) Hu, and the difference was statistically significant (t=3.378,P=0.002).The lesions demonstrated as progressive enhancement at venous phase.Among 33 patients, the main pancreatic duct was visible in six patients (18%).Sixteen patients (48%) presented with intrahepatic and extrahepatic biliary tract dilatation caused by intrapancreatic common bile duct stenosis.Thickened envelope-like structure around the lesions, presenting as capsule sign was seen in 14 patients (42%).Extra-pancreatic organ involvement was found in seven patients including three cases of kidney involvement.After treated with steroid, seven patients repeated CT which showed different degrees of improvement.Conclusion The main CT findings of AIP are diffuse and partial enlargement of pancreas with progressive enhancement at venous phase, envelope-like structure around pancreas, and stenosis of intrapancreatic common bile duct, which are important in the diagnosis and differential diagnosis of AIP.