Department of Radiology and Research Institution of Radiological Science, Yonsei University College of Medicine, Gangnam Severance Hospital, 612 Eonjuro, Gangnam-gu, Seoul 135-720, Republic of Korea.
Eur Radiol. 2010 Feb;20(2):385-94. doi: 10.1007/s00330-009-1542-z. Epub 2009 Aug 6.
The intrahepatic non-tumorous arterioportal shunt (APS) is one of the important causes of transient hepatic enhancement differences (THED) on dynamic CT or MRI. Most small APSs are located in the peripheral portion of the liver. Because of the parenchymal distortion in the advanced cirrhotic liver, many small APSs tend to show an amorphous or nodular appearance, making them difficult to distinguish from hypervascular tumors. In addition to the use of dynamic CT or MRI, iso-attenuation densities or iso-intensities on pre-contrast and equilibrium phases, MRI using a liver-specific contrast agent can be useful to characterize the hypervascular pseudolesions. Because there is no difference in water diffusion in the hepatic parenchyma in the region of the APS, diffusion-weighted MRI also has great potential to distinguish non-tumorous shunts from true focal lesions. Larger (>2 cm) APSs of direct arterio-portal venous fistulas from extrinsic insults show typical subcapsular wedge-like THEDs that are only temporarily depicted several months after the traumatic event; most of these THEDs gradually decrease in size or vanish completely. By understanding the nature of non-tumorous APSs, radiologists will be able to provide a more accurate assessment of many THEDs during daily interpretations of CT or MR images of the liver.
肝内非肿瘤性动静脉分流（APS）是动态 CT 或 MRI 上瞬时肝增强差异（THED）的重要原因之一。大多数小的 APS 位于肝脏的周边部分。由于肝硬化肝脏的实质变形，许多小的 APS 往往呈无定形或结节状外观，使其难以与富血管肿瘤区分。除了使用动态 CT 或 MRI 外，平扫和平衡期等密度或等信号，使用肝脏特异性对比剂的 MRI 也有助于对富血管性假性病变进行特征描述。由于 APS 区域肝实质内的水扩散没有差异，扩散加权 MRI 也具有很大的潜力来区分非肿瘤性分流与真正的局灶性病变。由外在损伤引起的较大（>2cm）直接动静脉瘘 APS 显示典型的包膜下楔形 THED，仅在创伤事件后几个月暂时显示；这些 THED 中的大多数会逐渐缩小或完全消失。通过了解非肿瘤性 APS 的性质，放射科医生将能够在日常解读肝脏 CT 或 MRI 图像时，对许多 THED 做出更准确的评估。
