Diagnostic ultrasound ( PDFDrive )

1752 PART V Pediatric Sonography
A
B
FIG. 51.21 Superb Microvascular Imaging (SMI). (A) Color Doppler images show lack of color low in the main extrahepatic portal vein in a
patient with chronic liver disease (B) SMI images show illing of the portal vein with blue color, relecting the very-low-velocity low in this still-patent
portal vein. See also Video 51.8 and Video 51.9.
minimize its movement. he frequency for the examination may
vary from 3.0 to 7.5 MHz, depending on the child’s size and
transducer availability. Because a small or upset child tends to
breathe rapidly, the examiner must be familiar with the Doppler
equipment to manipulate it quickly. All technical settings should
be preadjusted or preprogrammed to minimize examination
time. he vessel to be examined is identiied with real-time
sonography. Color Doppler ultrasound can be used to guide the
placement of the sample volume. A spectral display of the Doppler
shit is then usually readily obtained, even though it may disappear
during part of the respiratory cycle.
Child With Liver Disease: Doppler
Examination for Portal Hypertension
he aim of the Doppler examination is to assess the presence
and direction of low in splanchnic veins, the main portal vein
and its segmental intrahepatic branches, the hepatic veins, and
the IVC 63-66 (Fig. 51.23). In addition, the presence of low in the
main hepatic artery and its intrahepatic branches should be
determined. When the clinical or basic Doppler examination
raises suspicion for portal hypertension, a systematic search
for portosystemic collateral veins follows. Fig. 51.24 outlines the
usual sites for spontaneous portosystemic shunts. 65,67 he lesser
omentum 68 (from splenomesenteric junction to esophagus) and
the renal, splenic, and hepatic hila as well as the pelvis are screened
for the presence of dilated, tortuous veins. If hepatofugal (reversed)
low is found in a splanchnic vein, this vein is traced to the
recipient systemic vessel. In cases of portal hypertension, the
let gastric vein drains blood into the inferior esophageal vein;
the splenic vein drains into the renal (or pararenal) veins; the
superior and inferior mesenteric veins drain into gonadal,
retroperitoneal, or hemorrhoidal veins; and the paraumbilical
veins follow the round and falciform ligaments to drain into the
anterior abdominal and iliac veins to form the classic caput
medusae or into veins of the anterior chest wall and the internal
mammary vein.
Direction of low in one or several veins of the portal venous
system may change in portal hypertension, and it is essential to
record the low direction accurately. he Doppler sample volume
should be placed in the center of the vessel lumen. If the direction
of low within a vessel is diicult to ascertain, a nearby vessel
with known low direction can be used as a reference (e.g., splenic
or hepatic artery or adjacent vein).
he main portal vein and its right hepatic branches are best
studied through a right intercostal approach. Sometimes the
superior mesenteric vein is also clearly seen from this position.
he let portal vein and three of its four branches (portal branch
to caudate lobe is rarely seen) and the hepatic veins are best
seen through an oblique subcostal approach. he splenic vein
is explored through a transverse approach over the spleen. he
superior mesenteric vein and main portal vein are best visualized
through a sagittal right paramedian approach. he let gastric
vein usually ends near the splenoportal junction and, when
enlarged, is easily observed through a sagittal let paramedian
view. he inferior mesenteric vein, when normal, can rarely be
visualized sonographically. When enlarged, it may be traced
through a let lateral approach to its junction with the splenic
or superior mesenteric vein.
he various possible origins of the hepatic artery may be
diicult to recognize. We irst look for the artery at its usual
origin from the celiac axis and also as it passes between the
portal vein and the CBD. When the let hepatic artery arises
from the superior mesenteric artery, it passes through the ligamentum
venosum. he intrahepatic arterial branches accompany
branches of the portal vein and can be detected with a slightly
enlarged Doppler sample volume placed over a portal venous
branch, even when the arterial branch cannot be seen with