9%20ECOGRAFIA%20ABDOMINAL%20COMO%20CUANDO%20DONDE

104
ABDOMINAL ULTRASOUND
redirecting the blood from the portal system
and so these patients have a lower incidence
of gastric varices and therefore a better
prognosis.)
● Periumbilical A substantial vessel can often be
seen in the liver lying in the ligamentum teres
(Fig. 4.22D, E), and running down the
anterior abdominal wall to a knot of vessels at
the umbilicus, the so-called ‘caput medusae’.
(A patent para-umbilical channel may
occasionally be seen in normal patients, but
with a diameter of 1 or 2 mm.)
● Porta hepatis Varices around the main portal
vein itself, especially if the latter is thrombosed
(see below).
● Gallbladder wall Rarely, varices form around
the gallbladder wall to bypass the main portal
vein and feed into the intrahepatic portal
branches (Fig. 4.22F).
● Coronary vein A vessel may be seen arising
from the portal vein near the superior mesenteric
vein, directing blood in a cephalic direction.
(This can sometimes be seen in normal patients.)
It is fair to say that the extent of portosystemic collaterals
is usually underestimated on ultrasound.
However, a systematic approach which investigates
all the possible sites can demonstrate up to 90% of
collaterals. 20, 24 (Fig. 4.22G).
The hepatic artery This may also be another
ultrasound clue to compromised portal venous
flow. The main hepatic artery may demonstrate
increased flow velocity, especially if the PV is
thrombosed. This is a compensatory mechanism to
maintain the blood flow into the liver. The main
hepatic artery may appear enlarged and more obvious
than usual on ultrasound, and in some cases,
peripheral intrahepatic arterial flow is also easily
demonstrated (Fig. 4.23).
+24.8MM
NORMAL 3372
HZ
NORMAL 2098
A
B
Figure 4.23 (A) Vigorous, high-velocity middle hepatic artery (MHA) flow in the presence of portal vein thrombosis.
(B) Arterial flow is also readily demonstrated in the peripheral intrahepatic arteries.