Diagnostic ultrasound ( PDFDrive )

1754 PART V Pediatric Sonography
FIG. 51.23 Essential Splanchnic Vein Reference Points in Doppler
Sampling for Possible Portal Hypertension in Children With Liver
Disease. A, Main portal vein; B, intrahepatic portal vein; C, right portal
vein; D, left portal vein; E, splenic vein at hilum; F, splenic vein; G, left
coronary vein; H, superior mesenteric vein; I, hepatic veins. Evaluation
of the hepatic artery and inferior vena cava should be done as well.
(With permission from Patriquin H, Lafortune M, Burns PN, Dauzat M.
Duplex Doppler examination in portal hypertension: technique and
anatomy. Am J Roentgenol. 1987;149[1]:71-76. 64 )
real-time ultrasound. he arteries to the right lobe of the liver
(especially segments 5, 7, and 8) are usually easy to identify in
this manner. he hepatic arterial branch accompanying the
umbilical portion of the let portal vein (to segment 4) is especially
easy to examine with Doppler imaging because of the almost
ideal vessel beam angle, which can be obtained through an anterior
abdominal approach (Fig. 51.25). For this reason, I routinely
look for arterial Doppler signals at this site in children who have
undergone liver transplantation.
Abnormal Flow Patterns Within the
Portal System
Absent Doppler Signal
Proof of absence of a Doppler signal is much more diicult to
establish than is its presence. he examiner who fails to obtain
a Doppler signal from a given vessel usually questions the sensitivity
of the machine and tests other nearby vessels. Failure to obtain
a pulsed, color, or power Doppler signal from a splanchnic vein
examined at an angle of less than 60 degrees, full Doppler gain,
and low pulse repetition frequency, with 50-Hz wall ilter and
restricted Doppler window, means that blood is lowing at a
velocity of less than 4 cm/sec (extremely slow). hus absence of
a Doppler signal in this situation generally means absence of
low or a prethrombotic state.
Arterialized Portal Venous Flow
When the normal, gently undulating low within a portal vein
is replaced by systolic peaks and high diastolic Doppler shits,
this is termed an “arterialized low pattern” and may signal the
presence of an arterioportal istula. 69
FIG. 51.24 Diagram of Common Spontaneous Portosystemic
Collateral Routes. HV, Hemorrhoidal vein; IMV, inferior mesenteric
vein; IVC, inferior vena cava; LGV, left gonadal vein; SMV, superior
mesenteric vein; SVC, superior vena cava; 1, left gastric-azygos route
(esophageal varices); 2, paraumbilical-hypogastric/internal mammary route
(caput medusa); 3, splenorenal route; 4, IMV-hemorrhoidal route; 5,
spleno-retroperitoneal-gonadal route. (With permission from Patriquin
HB, LaFortune M. SPR Annual Meeting Syllabus. Pediatr Radiol. 1994. 67 )
Causes of Absent Doppler Signal
Doppler angle greater than 60 degrees
Low Doppler gain
Low pulse repetition frequency
High ilter (best is 50 Hz)
Small sample volume
Portal vein low decreases when fasting
Hepatic artery low decreases after a meal
Reversed or To-and-Fro Flow
Reversed low in a splanchnic or intrahepatic portal vein is the
most reliable Doppler sign of portal hypertension. However,
hepatofugal low in the portal vein occurs late and relatively
rarely in patients with liver disease. To-and-fro low in the portal
vein also suggests the presence of portal hypertension. Highly