局限性自身免疫性胰腺炎的CT影像学特征分析

目的探讨局限性自身免疫性胰腺炎(focal autoimmune pancreatitis,f-AIP)的CT影像学表现特点,以期提高其影像学鉴别诊断水平。方法回顾性分析13例经组织学、IgG4检验或类固醇激素治疗证实的局限性自身免疫性胰腺炎患者的CT影像学资料,从胰腺形态表现、病变区密度及强化方式、胆胰管改变和假包膜结构显示等情况进行分析。结果本研究13例局限性自身免疫性胰腺炎患者中,13例均有局部胰腺肿大(胰头部3例,胰体尾部5例,胰尾部5例),与正常胰腺比较,CT平扫提示病变区密度降低(4例)或降低不明显(9例),增强扫描动脉期均见病变区强化程度较正常胰腺减低,门脉期及延迟期均提示病变区逐渐均匀强化,与正常胰腺强化程度相仿。7例显示病变区有假包膜结构,4例胆管扩张,胰管不规则硬化狭窄显示7例。结论局限性自身免疫性胰腺炎CT影像学表现具有一定的特征性,正确掌握这些特征有助于提高诊断准确率,从而避免不必要的手术治疗。

CT features of focal autoimmune pancreatitis

Objective To improve the diagnositic accuracy by investigating the CT features of focal autoimmune pancreatitis(f-AIP) and to avoid unnecessary surgery because of improper diagnosis.Methods Dynamic contrast-enhanced CT scans of 13 f-AIP patients were retrospectively analyzed.Data were reviewed by two radiologists in consenus.Images were analyzed regarding pancreatic enlargement,density or signal abnormalities,enhanced pattern,capsule-like rim,abnormalities of the main pancreatic duct(MPD) and the common bile duct(CMD),and other associatied findings such as calcification,peripancreatic nodes,vascular invasion,pseudocyst.Results Segment of pancreas involved enlargement were observed in 13 patients,wherein sausage-shaped enlargement were observed in 8 patients.Unenhanced CT showed f-AIP area(hypoattenuating) in 3(23.1%) of 13 patients.The enhanced degree of lesions was lower than that of normal pancreatic parenchyma on artery phase.The lesions were all homogeneously enhanced in delayed phases.The irregular narrowing of MPD were observed in 7(7 of 13,53.8%).Bile duct dilatation was observed in 4 cases(range,9~14 mm),which included 3 patients who had lesion at the pancreatic head and 1 at the tail,and distal common bile duct(CBD) showed no abrupt interruption signs.Peripancreatic lymphadenopathy was observed in 4 case.Patchy and fibrilliform soft tissue density shadows in peripancreatic fat space were observed in 5 patients,wherein 4 patients showed prerenal fascial thickening.No calcification and vascular invasion were found in all 13 cases.Conclusion Radiological features such as focal pancreatic enlargment with dilatation of upstream MPD less than 5mm or no dilatation,capsule-like rim,localized irregular narrowing rather than obstruction of the MPD,stricture of CBD(in patients with cholangiectasis),delayed enhancement pattern,no calcification and vascular invasion,can help physicans to make a correct diagnosis of f-AIP and avoid unnecessary sugery.