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

100
ABDOMINAL ULTRASOUND
The vein may appear dilated and tortuous, but
not invariably. (The normal portal vein diameter
does not usually exceed 16 mm in a resting state;
see Chapter 2).
Portal venous flow may be:
● normal in direction (hepatopetal) and
velocity. 20
● reduced in velocity 21 (Fig. 4.21A), < 10 cm/sec,
although there is overlap with the normal range.
● damped, in which there is a lack of normal
respiratory variation of both the calibre and the
waveform of the splenic and portal veins. The
normal spectrum has a ‘wavy’ characteristic,
which may be lost.
● reversed (hepatofugal) (Fig. 4.21B). This
indicates serious liver disease. Interestingly,
patients with hepatofugal PV flow are much
less likely to suffer from bleeding varices,
suggesting a type of ‘protective’ mechanism
here.
● balanced, in which both forward and reverse
low velocity flow is present, a condition
which may precede imminent thrombosis
(Fig. 4.21C).
● thrombosed (Fig. 4.21D). Low-level echoes
from the thrombus may be evident but with
fresh thrombus the vein may appear anechoic,
as in the normal vein. Although PV thrombosis
most commonly results from portal
hypertension in cirrhosis, there are many
A
Box 4.1
Causes of portal vein thrombosis
Chronic liver disease
—especially cirrhosis
Inflammatory
—pancreatitis
—acute cholecystitis
—necrotizing enterocolitis
Malignancy
—pancreatic tumour
—gastric tumour
Coagulation disorders
—may be associated with Budd–Chiari
syndrome
B
Figure 4.21 The MPV in portal hypertension. (A) Portal
vein (PV) velocity is greatly reduced. (B) Reversed PV flow in
portal hypertension. Note the increased velocity of hepatic
arterial flow indicated by the light colour of red just
anterior to the portal vein. The patient has macronodular
cirrhosis with ascites.
(Continued)