糸井 隆夫, 祖父尼 淳, 糸川 文英, 栗原 俊夫, 森安 史典

Takao ITOI, Atsushi SOFUNI, Fumihide ITOKAWA, Toshio KURIHARA, Fuminori MORIYASU

東京医科大学消化器内科

Gastroenteology and Hepatology, Tokyo Medical University

キーワード : extratransabdominal ultrasonography, pancreaticobiliary diseases, fundamental imaging, tissue harmonic imaging

体外式超音波検査法による胆膵疾患の基本的な描出法と注目すべき所見について解説した．肝内胆管の描出には肝内胆管がグリソン鞘内で門脈と並走していることを念頭に置く．カラードプラ法を用いることで門脈と胆管の鑑別は容易となる．肝内胆管病変では肝内胆管拡張と肝内腫瘤に着目する．肝外胆管描出は右肋弓下縦‐斜走査で肝門部の門脈を指標にしてその腹側に描出される管腔を見つける．この際にもドプラは有用である．胆管を描出後長軸に胆管が描出出来るようにプローブを微調整して下部胆管へとスキャンする．左側臥位からの描出や膵内胆管の短軸像を描出した後に胆管を長軸にして下部胆管を描出する方法も時に有用である．肝外胆管では胆管拡張，内腔の病変，および胆管壁に注目して所見を読み取る．胆嚢の描出は肝十二指腸間膜に連続した胆嚢床をメルクマールとする．胆嚢頸部と底部は見落としやすいので特に注意する必要がある．肝外胆管同様左側臥位での観察が有効である．観察時には胆嚢の大きさ，内腔，および胆嚢壁に注目する．膵臓描出の基本となる横走査では脾静脈を指標としてその腹側の膵頭体尾部を長軸に観察する．吸気時には肝臓をウインドウにして描出するが，呼気時の方がよく描出されることが多い．横走査では膵尾部の脾門部付近では不十分なことが多く，左肋間からの描出が有用である．描出にあたっては膵臓の大きさ，膵管拡張，腫瘤に注目する．

We explain basic imaging methods and important points concerning transabdominal ultrasonography in patients with pancreaticobiliary diseases. When imaging the intrahepatic bile duct, it is important to recognize that it is adjacent to the portal vein in Glisson′s capsule. Distinguishing between the portal vein and the bile duct is simplified with the use of Doppler ultrasound. It is essential to note dilatation and mass in the intrahepatic bile duct. To detect the lumen of the extrahepatic bile duct next to the portal vein, we repeatedly moved the probe diagonally toward the midline of the abdomen, descending along the axis from the middle of the right costal arch and moving it toward the pelvis. Doppler mode ultrasound is also useful in this procedure. Once the portal vein is located, the extrahepatic duct along it is traced. An alternative method involves imaging from a left lateral decubitus approach to detect the intrapancreatic bile duct, then fixing on it and rotating the probe about 90° to allow detection and following the image of the duct laterally. Pathologic conditions include bile duct dilatation, intraluminal lesions, and changes in the wall of the bile duct. To visualize the gallbladder, first locate the gallbladder bed as a landmark and then follow it to the hepatoduodenal ligament. Particular care is necessary in imaging the neck and fundal portion of the gallbladder, which are easily overlooked. Note the size of the gallbladder and the condition of the lumen and gallbladder wall. The entire pancreas is observed along its long axis using the splenic vein as a landmark. The bifurcation of the splenic vein is seen near the pancreatic tail, but because imaging is often insufficient using wide scanning, depiction from the left intercostals space may be better. The size of the pancreas, condition of the main pancreatic duct, and presence of any dilatation or mass must be carefully noted.