Ultrasound notes

1. Topic:
Bile Duct
Prepared By:
Safi. Khan

2. ANATOMY
The bile ducts are generally divided into the intrahepatic and
extrahepatic portions.
The intrahepatic ducts run in the portal triads with the portal veins
and hepatic arteries.
The right and left hepatic ducts are anterior to the adjacent Portal
veins.
The peripheral intrahepatic ducts run parallel and adjacent to the
hepatic arteries and portal veins, but
The relative anterior and posterior relationship of the three
structures is more variable than the extrahepatic ducts.

6. Extrahepatic portion of the bile ducts includes the
common hepatic duct, the common bile duct, and a portion
of the central right and left ducts. The common hepatic duct
is the segment located above the cystic duct insertion and
the common bile duct is the segment below.

7. Cystic duct insertion distinguish the common hepatic from the
common bile duct.
Therefore many people simply refer to the duct as the
common duct and divide it subjectively into the proximal,
mid, and distal segments.

8. Normal anatomy. The relationship of the bile duct and hepatic artery
is that the bile duct comes from the liver (a right-sided structure)
and the hepatic artery arises from the aorta (a leftsided Structure).
The right hepatic artery passes between the common duct and the
portal vein in 90% of patients.
A, Relative location and orientation of the bile ducts, hepatic artery,
and portal vein (PV).

9. B, Longitudinal view shows the relationship of the extrahepatic bile
ducts to the hepatic artery and the portal vein.
At the porta hepatis (the proximal common duct) Bile duct (D)
located anterior to the PV and the right hepatic artery (RHA)
located between these two structures.
The distal duct enters the head of the pancreas (P). The inferior
vena cava (V), the right renal artery (RRA), and the crus of the
right hemidiaphragm (arrowhead) are often seen on this view.

10. C, Longitudinal view shows the mid duct (cystic duct) runs posterior
to the duodenum. The cystic duct (CD) insertion (seen posterior) at
the junction of the common hepatic duct (CHD) and the common
bile duct (CBD). The pancreatic head (P) is also seen.
D, The (distal) common bile duct enters the head of the pancreas.
Longitudinal view of the head of the pancreas (P) shows the distal
CBD (D) running through the posterior pancreas. This is opposed
to the gastroduodenal artery (GDA), which runs along the anterior
pancreatic head. Also seen are the PV and the vena cava (V).

11. E, Transverse view of the inferior porta hepatis shows the celiac
axis (CA) arising from the aorta (A) and dividing into the splenic
artery (SA) and common hepatic artery (CHA). The hepatic artery
travels anterior to the PV and medial to the common duct (D).
Note the close relationship between the PV and the vena cava
(V).
F, Transverse view of the superior porta hepatis shows the classic
Mickey Mouse view with the common duct (D) located anterior to
the PV and to the right of the proper hepatic artery (PHA). The
gallbladder (GB) and the vena cava (V) are often seen on this
view.

14. Normal anatomic variants A, Longitudinal view shows the right
hepatic artery (RHA) located anterior to the common duct (D)
and the portal vein (PV).
B, Longitudinal view shows two hepatic arteries (HA) anterior and
posterior to the common duct (D). The PV is also seen.
C, Longitudinal view shows two hepatic arteries (HA) posterior to
the common duct (D) and anterior to the PV.

15. Hepatic artery is relatively curved, and so it is difficult to display
more than 2 to 3 cm of its long axis in any plane as compared
with the common duct.
Hepatic artery maintains a relatively similar diameter throughout its
course and it may cause an extrinsic impression on the bile duct
and/or the portal vein.
Common duct is relatively straight, has a diameter that varies
along its course, and does not produce an impression on
adjacent vessels.

18. Occasionally a tortuous gallbladder neck simulates the appearance
of the proximal common duct.
A, Longitudinal view of the porta hepatis shows a tubular structure
(white arrow) simulating the common duct.
B, A slightly different plane show that this structure communicates
with the GB and is the GB neck.
C, At another plane, the real common duct is identified
(arrowheads). The portal vein (PV) and the right hepatic artery
(black arrow) are also seen on these views.

19. TECHNIQUE
The proximal common duct is usually best seen by placing the
patient in a left lateral decubitus or left posterior oblique
position and by scanning from a right subcostal approach
during a deep inspiration.
The portal vein is a valuable landmark for the common duct.

21. 1. Most pathological processes affecting the bile duct occur
distally. The distal common duct is located in the posterior
and right lateral aspect of the head of the pancreas.
2. If overlying bowel gas is a problem,pressure can be applied with
the transducer to push the gas out of the way.
3. In some cases it is necessary to have the patient drink water to
displace the gas out of the stomach and the duodenum.
4. Changing the patient from a supine to an upright position is also
occasionally useful.
5. Place the patient in a right lateral decubitus position until
the gas moves out of these structures. The patient can then
be moved into a supine or left lateral decubitus position to
reimage the bile duct.

22. BILIARY OBSTRUCTION
Obstructed bile ducts are diagnosed sonographically by finding ductal
dilatation.
Both A and B, views of the liver show the parallel channel sign with
adjacent tubular structures of similar diameter. The color Doppler view
shows that the larger posterior structure is vascular and is intrahepatic
portal vein (PV).
The anterior structure is avascular it exceeds 40% of the diameter of the
adjacent PV, it is dilated and is a bile duct. The hepatic artery can be
seen between the duct and the PV.

23. Least restricted segment of the bile duct is the mid segment
(between the right hepatic artery and the pancreas). so, this
segment dilates first in the setting of obstruction.
It is considered dilated when it is 7 mm or greater in diameter, with the
measurement taken from the inner to the inner wall it may be
normal in elderly patients and in postcholecystectomy patients.

24. Common bile duct stones.
A, Dilated bile duct (D) with a shadowing stone impacted at the
ampulla (arrow). The gallbladder (GB) is also seen.
B, Nondilated (1.8 and 4.9 mm) bile duct (cursors) with a
nonimpacted shadowing stone (arrow) in the distal aspect.

25. Intrahepatic arterial calcification.
View of the liver shows a linear echogenic structure with some
shadowing.
Note the anterior and posterior wall of the artery producing two
bright parallel lines. In some cases this will distinguish arterial
calcification from pneumobilia and ductal stones.

26. Normal intrahepatic ducts is more than 40% of the diameter portal
vein, and peripheral ducts should not be more than 2 mm in
diameter.