Hepatic artery stenosis
Hepatic artery stenosis occurs in approximately 11% of cases and most frequently at the anastomotic site (18). Causes include clamp injury, intimal trauma from perfusion catheters and disrupted vasa vasorum leading to ischemia of the arterial ends. Stenosis can lead to biliary ischemia and hepatic dysfunction. Severe anastomosis can reduce blood flow, which in turn can lead to thrombosis.
Focally elevated velocities are seen at the site of the stenosis upto 2 to 3 m/s (image 6a, 6b). Turbulence is present in the artery distal to the area of stenosis. If the area of stenosis is not directly visualized, a tardus parvus waveform is seen in the intrahepatic arteries (30) similar to that seen in the hepatic artery thrombosis. The acceleration time is usually more than 100 msec and the resistive index is less than 0.5. Mild stenosis may not give any changes on Doppler ultrasound (30).
Celiac artery stenosis may be seen due to atherosclerotic changes or medial arcuate ligament syndrome. The latter can be corrected at the time of surgery; however narrowing due to atherosclerotic changes may require an aorto-hepatic graft interposition.
Interventional treatment by fibrinolysis and PTA represents a valid alternative to surgery in the management of arterial steno-obstructive lesions after liver transplantation. Stents have also been used for treatment of these lesions as well (31, 32). Evaluation of the hepatic artery waveform in the region of the stent maybe challenging due to the change in the flow dynamics caused by the stent placement. Assessment of the intrahepatic arterial waveforms and the post stent portion of the hepatic artery are important in these patients with a return to normal sharp upstroke, normal velocity and normal resistive index.