Diagnostic ultrasound ( PDFDrive )

132 PART II Abdominal and Pelvic Sonography
A
B
FIG. 4.66 Transjugular Intrahepatic Portosystemic Shunt (TIPS). (A) Color Doppler image of TIPS shows low throughout the shunt appropriately
directed toward the heart, with a turbulent pattern. (B) Angle-corrected midshunt velocity is normal at 150 cm/sec.
with monitoring of the portal pressure gradient and illing
of varices on portal venography. A bridging stent is let in
place. 224
In addition to acute problems directly attributed to the
procedure itself, TIPS may be complicated by stenosis or occlusion
of the stent caused by hyperplasia of the pseudointimal lining.
At 1 year, primary patency rates vary from 25% to 66%, with a
primary assisted patency of about 83%. 225,226 Doppler sonography
provides a noninvasive method for monitoring of TIPS patients
because malfunction of the grat may be silent in its early phase.
Scans should be performed immediately ater the procedure, at
3-month intervals, and as indicated clinically.
Normal postprocedural Doppler indings include highvelocity,
turbulent blood low (mean peak systolic velocity,
135-200 cm/sec) 227 throughout the stent and hepatofugal low
in the intrahepatic portal venous branches, as the liver parenchyma
drains through the shunt into the systemic circulation. Increased
hepatic artery peak systolic velocity is also a normal observation,
as is increased velocity in the main portal vein, because the stent
serves as a low-resistance conduit, bypassing the high-resistance
hepatic circulation. he reported mean main portal vein velocity
in patients with patent shunts ranges from 37 to 47 cm/sec. 228-230
Hepatic artery velocities increase from 79 cm/sec preshunt to
131 cm/sec ater the procedure. 227
Sonographic evaluation should include measurement of
angle-corrected stent velocities at three points along the stent
and in the main portal vein, as well as evaluation of the direction
of low in the intrahepatic portal vein and in the involved hepatic
vein (Figs. 4.66 and 4.67).
Sonographically detected complications include the
following:
• Stent occlusion
• Stent stenosis
• Hepatic venous stenosis
Malfunction of Transjugular Intrahepatic
Portosystemic Shunts: Sonographic Signs
DIRECT SIGNS
No low, consistent with shunt thrombosis or occlusion
Peak shunt velocity: <90 or >190 cm/sec
Change in peak shunt velocity: decrease of >40 cm/sec or
increase of >60 cm/sec
Main portal vein velocity <30 cm/sec
Reversal of low in hepatic vein away from inferior vena
cava, suggesting hepatic vein stenosis
Hepatopetal intrahepatic portal venous low
SECONDARY SIGNS
Reaccumulation of ascites
Reappearance of varices
Reappearance of recanalized paraumbilical vein
Detection of these complications is related to identiication
of both direct abnormalities and secondary signs. 231-234 Direct
signs include no low, abnormal peak shunt velocity, a change
in the peak shunt velocity, a low velocity in the main portal vein,
reversal of hepatic vein low, and hepatopetal intrahepatic portal
venous low. Secondary signs include reaccumulation of ascites
and reappearance of varices and of recanalized paraumbilical
vein.
PERCUTANEOUS LIVER BIOPSY
Percutaneous biopsy of malignant disease involving the liver
has a sensitivity greater than 90% in most study series. 235,236