背胰与主胰管并发变异的影像学特征

Imaging features in anatomical variations of the dorsal pancreas and main pancreatic duct

目的：总结背胰与主胰管并发变异的影像学检查特征，探讨其诊断及鉴别诊断要点。 方法：采用回顾性描述性研究方法。收集2013年11月宁波大学医学院附属医院收治的1例背胰与主胰管并发变异患者的临床资料。患者行CT、MRI平扫及增强扫描、MRCP检查。观察指标：（1）CT、MRI检查表现。（2）胰腺相关径线值：①主胰管：最大宽径和扩张长度。②胰腺实质：背胰宽度和腹胰宽度。③其他径线：腹胰中线， 背胰中线和背胰脾门。（3）随访情况：患者相关实验室及影像学复查结果。采用门诊和电话方式进行随访，随访期间，复查相关实验室及影像学检查。随访时间截至2016年1月。 结果：（1）CT、MRI检查表现：①CT检查：胰腺长度未见异常，胰体、尾部实质萎缩，胰头部体积稍增大，胰腺实质密度均匀，胰体、尾部主胰管扩张。②MRI检查：胰头部：T1加权成像（T1WI）、T2加权成像（T2WI）示胰头部体积稍增大，实质信号均匀，同、反相位无信号衰减，扩散加权成像（DWI）无弥散受限，增强扫描均匀明显强化。胰体、尾部：T1WI、T2WI示胰体、尾部变细，实质萎缩、变薄，DWI无弥散受限，增强扫描未见异常强化灶。胰管与胆管：①胰体、尾部主胰管明显扩张，内壁光整，以体部较宽，颈部主胰管变窄，头部主胰管无扩张，增强扫描见扩张的胰管内无异常强化灶；分支胰管均未见扩张。②MRCP检查示肝内、外胆管、胆囊未见扩张，腔内未见异常信号。胰腺边缘：光滑、规则，胰周脂肪间隙清晰。其他表现：脾脏下缘见一圆形软组织信号影，平扫及增强扫描信号强度均与脾脏一致。（2）胰腺相关径线值：①主胰管：最大宽径为12.6 mm，扩张长度为91.6 mm。②胰腺实质：背胰宽度为19.6 mm，腹胰宽度为26.7 mm。③其他径线：腹胰中线为54.6 mm，背胰中线为77.3 mm，背胰脾门为18.5 mm。（3）随访情况：2014年11月，患者复查相关实验室检查结果均正常；超声检查：胰头部体积稍增大，内部回声分布均匀，胰体、尾部缩小，主胰管扩张，最大宽径约为12.3 mm。2015年11月患者复查实验室和超声检查结果无进展。 结论：背胰与主胰管并发变异影像学检查主要表现为胰腺长度正常，胰体、尾部实质萎缩，主胰管扩张、内壁光整，胰头部轻度增大，增强扫描检查无异常强化灶。

Objective：To summarize the imaging features in anatomical variations of the dorsal pancreas and main pancreatic duct, and investigate the essentials of diagnosis and differential diagnosis. Methods：The retrospective descriptive study was adopted. The clinical data of 1 patient with the anatomical variations of the dorsal pancreas and main pancreatic duct who was admitted to the Affiliated Hospital of Ningbo University at November 2013 were collected. The patient received plain and enhanced scans of computed tomography （CT） and magnetic resonance image （MRI）, and magnetic resonance cholangiopancreatography （MRCP） examination. Observation indexes included： （1） manifestations of CT and MRI examinations. （2） Pancreas associated dimensions： ①the main pancreatic duct： the maximum width and the expansion length. ②The pancreatic parenchyma： the width of the dorsal pancreas and the ventral pancreas. ③Other dimensions： the distance from the ventral pancreas to the midline, the distance from the dorsal pancreas to the midline, the distance from the dorsal pancreas to the splenic hilum. （3）Followup situation： results of laboratory and imaging reexaminations. The followup of outpatient examination and telephone interview was performed on the patient up to January 2016. Results：（1） Manifestations of CT and MRI examinations： CT examination demostrated a normal pancreatic length with parenchyma of the pancreatic body and tail atrophy and a slightly enlarged pancreatic head. The pancreatic parenchyma showed homogeneous density and main pancreatic duct of the pancreatic body and tail showed dilatation. On MRI, T1 weight imaging （T1WI） and T2 weight imaging （T2WI） demonstrated a slightly enlarged pancreatic head with homogeneous signal. The inphase and outphase imagings showed no signal loss on and diffusion weighted imaging （DWI） showed no restricted diffusion. Enhanced scanning demonstrated a marked homogenous enhancement of pancreatic head. Pancreatic body and tail showed thin and parenchyma atrophy on T1WI and T2WI without restricted diffusion on DWI and abnormal enhancement on enhanced scan. Of pancreatic duct and bile duct, MRI examination showed main pancreatic duct dilatation of the pancreatic body and tail with smooth inner wall and narrowed main pancreatic duct of pancreatic neck and no dilatation of the pancreatic head. Enhanced scanning demonstrated no abnormal enhancement of the enlarged duct. The branch pancreatic duct showed no dilatation. MRCP examination demonstrated no dilatation of intra and extra bile duct and gallbladder and no abnormal signal of intracavity. Pancreatic margin showed smooth, regular and clear surrounding fat space. Other findings included a circular nodule under the spleen with a similar signal with the spleen on plain and enhanced scan. （2） Pancreas associated dimensions： ① the main pancreatic duct： the maximum width and the expansion length were 12.6 mm and 91.6 mm, respectively. ② the pancreatic parenchyma： the width of the dorsal pancreas and the ventral pancreas were 19.6 mm and 26.7 mm, respectively. ③ other dimensions： the distance from the ventral pancreas to the midline, the distance from the dorsal pancreas to the midline and the distance from the dorsal pancreas to the splenic hilum were 54.6 mm, 77.3 mm and 18.5 mm, respectively. （3） Followup status： results of laboratory reexaminations showed normal indexes at November 2014, and ultrasonography examination demonstrated slightly enlarged pancreatic head with homogenous internal echo, thin of the pancreatic body and tail, and an enlarged main pancreatic duct with the maximum width of 12.3 mm. The patient was followed up at November 2015, and laboratory reexaminations and ultrasonography examination demonstrated similar findings. Conclusion：Imaging features of anatomical variations of the dorsal pancreas and main pancreatic duct include normal length of the pancreas, atrophy of the pancreatic body and tail, main pancreatic duct dilatation with smooth inner wall, slightly enlarged pancreatic head without any abnormal signal on dynamic enhancement imaging.