Which ultrasound findings are characteristic of hepatic artery thrombosis (HAT) following whole-liver orthotopic liver transplantation (OLTX)?

Updated: Mar 01, 2019
  • Author: Paul D Russ, MD; Chief Editor: John Karani, MBBS, FRCR  more...
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Answer

Answer

HAT is one of the most common and potentially most disastrous arterial complications (see images below). HAT is estimated to occur in 4-12% of adult OLTX patients and in 9-42% of pediatric transplantation patients. [25] Causes include allograft rejection, hepatic artery kinking due to vascular redundancy, underlying HAS, and technical problems at the anastomosis. Doppler ultrasonography (US) has a sensitivity of approximately 90% in detecting HAT. [26]

Spectral Doppler ultrasonographic waveform of the Spectral Doppler ultrasonographic waveform of the right hepatic artery in a 60-year-old man, 8 years after orthotopic liver transplantation. The image demonstrates the typical rounded tardus parvus waveform morphology, which is indicative of upstream arterial thrombosis or severe stenosis. Subsequent angiography confirmed occlusion at the hepatic arterial anastomosis.
Magnetic resonance angiogram in a transplantation Magnetic resonance angiogram in a transplantation patient with hepatic artery thrombosis. Magnetic resonance angiogram of the recipient celiac axis depicts complete occlusion of the hepatic artery.
Magnetic resonance angiogram demonstrates intrahep Magnetic resonance angiogram demonstrates intrahepatic arterial segments reconstituted from mesenteric collaterals. Collateralization explains how, in some patients, intrahepatic flow can be present in the setting of complete extrahepatic arterial occlusion.
Digital subtraction angiogram shows complete hepat Digital subtraction angiogram shows complete hepatic artery thrombosis in a liver transplant recipient.

A finding on Doppler ultrasound evaluation that would merit close follow-up is the presence of significantly elevated peak systolic velocities in the main hepatic artery, which may be suggestive of hepatic artery stenosis (HAS), an independent risk factor for HAT. [27] Doppler ultrasonographic findings consistent with HAT include absent flow at the porta hepatis (ie, no flow in the donor proper hepatic artery) with absent intrahepatic arterial flow, and absent flow in the donor hepatic artery with abnormal intrahepatic flow. Persistent intrahepatic flow in the setting of complete proper HAT can result from collateralization via nearby superior mesenteric artery branches. Collateralized intrahepatic flow can be differentiated from normal flow by its tardus parvus Doppler waveform morphology. Tardus parvus can be diagnosed objectively when the intrahepatic arterial resistive index (RI) is less than 0.5 and the systolic acceleration time (SAT) is 0.08 second or longer.

Without aggressive diagnosis and treatment, HAT is associated with a mortality rate of greater than 80%. Unfortunately, percutaneous thrombolytic therapy of HAT is problematic, because it often occurs soon after OLTX. Thrombolysis and angioplasty of underlying HAS have been successful in a few patients; however, HAT usually requires urgent retransplantation for patient survival.


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