Materials and Methods
Using adult abdominal CT data of 1 mm width,
each scan section similar to the ultrasonic examination and the movement of the probe on the body surface were recorded as animation on a 3D workstation ( Fig. 1 ).
The data used were abdominal contrast cases and drip infusion cholangiography (DIC) CT cases.
DIC CT was used to identify the running direction of the extrahepatic bile duct.
Hepatic segmentation was color-coded,
in accordance with the portal vein branch.
The 3D workstations used are Virtual Place (AZE,
Japan) and Synapse VINCENT (Fujifilm,
Japan).
Findings and procedure details
In abdominal ultrasound examination,
it is important to perform systematic scanning and observe the entire abdomen.
Here we explain the point of identification by ultrasound of the pancreas and the extrahepatic bile duct,
which is often difficult to visualize,
the anatomy at each scan section,
and the anatomy of the liver segment.
Identification of the pancreas
The pancreas is identified using the splenic vein traveling on the back of the pancreas,
the superior mesenteric artery,
the superior mesenteric vein and so on ( Fig. 2 ).
The pancreatic head is observed with the superior mesenteric vein and the inferior vena cava.
In the head of the pancreas,
the dorsal pancreas is located on the ventral side and the ventral pancreas is on the dorsal side so as to sandwich the superior mesenteric vein ( Fig. 3 ).
The head of the pancreas is long in the craniocaudal direction,
and it is important to observe firmly to the lower end of the pancreas head.
The inferior vena cava is located on the dorsal side of the pancreatic head.
Often the stomach is covered widely at the front of the pancreas,
and to relieve artifacts due to gastrointestinal tract gas,
we will use pressure by the probe,
breathing method,
posture change and so on.
The tail of the pancreas is continuous until the splenic hilum part ( Fig. 4 ).
It is difficult to observe the end of the pancreatic tail with the upper abdominal midline scan and/or the left subcostal scan.
In the observation of the pancreas tail,
it is desirable to observe the spleen as an acoustic window by the left intercostal scan ( Fig. 5 ).
The splenic vein is traveling in the head-side direction of the pancreas.
The pancreatic tail is identified using the splenic vein as the index.
The splenic vein is easy to identify using Doppler.
Many artifacts due to small intestinal gas are present in this area,
and it is often difficult to observe the pancreas tail.
Identification of extrahepatic bile duct
The extrahepatic bile duct travels to the right side of the portal vein at the hepatic portal.
The extrahepatic bile duct is separated from the portal vein on the caudal side from the hepatic portal part and travels toward the dorsal side of the pancreatic head part ( Fig. 6 ).
The extrahepatic bile duct is easy to observe when conscious of the caudal end of the extrahepatic bile duct in the lower left lateral decubitus and tracing while slightly rotating the probe slowly in the clockwise direction ( Fig. 7 ).
The identification of the extrahepatic bile duct is a useful technique for retrieving the cause during obstructive jaundice.
Identification of hepatic segment
By coloring each segment of the liver,
it is easy to understand each hepatic segment in an arbitrary cross section ( Fig. 8 ).