CT and MRI Manifestations of Autoimmune Pancreatitis

Objective: To explore the CT and MRI manifestation features of Autoimmune pancreatitis(AIP), deepen the understanding to this rare disease, and improve the diagnosis level of AIP. Methods: The CT and MRI imaging data of 11 cases confirmed as AIP by operation and clinic were retrospectively analyzed, summarize the imaging features. All the 11 cases took CT examination, including 7 cases of MRI examination at the same time. Results: 7 cases of AIP were characterized by diffuse enlargement in pancreas, and the other 4 cases localized enlargement. Diseased pancreas appeared isodensity and low density on CT scanning. The signal intensity of pancreas on T1 WI was lower, and slight elevated on T2 WI. The enhancement decreased during enhanced scanning in arterial phase, and the enhancement became progressive and evenly in portal venous phase and delayed phase. Capsular ring can be seen in six cases on MRI, and 4 cases of capsular ring showed on CT, CT cannot display stenosis of the pancreatic duct. 4 cases of stenosis showed on MRCP. The manifestations of related organs and tissues outside the pancreas are mainly presented as follows: bile duct wall thickening and luminal stenosis in 5 cases, splenic vessels embedding became thinner in 4 cases, renal involvement in 3 cases, and retroperitoneal lymph node enlargement in 6 cases. The fibrosis around mesenteric blood vessels in 1 case and retroperitoneal fibrosis in 1 case after treatment with steroids, imaging review showed that internal and external pancreatic lesions both have different degree of improvement. Conclusion: The internal and external CT and MRI manifestation of AIP presents some specific characteristics. With its imaging manifestation in combination with effective steroid hormone therapy, correct diagnosis can be made, and unnecessary surgical treatment for patients can be avoided.