Hepatic artery thrombosis (HAT) is a serious medical event that occurs when a blood clot forms within the hepatic artery, the main vessel delivering oxygenated blood to the liver. Although the hepatic artery provides only 25 to 30% of the liver’s total blood supply, it supplies almost all the oxygen required by the organ’s bile duct system. The sudden blockage creates an immediate and severe oxygen deficit in the affected liver tissue. This condition demands prompt recognition and intervention due to the high risk of rapid liver damage and failure.
What Hepatic Artery Thrombosis Is
The formation of a clot, or thrombus, within the hepatic artery immediately obstructs the flow of oxygen and nutrients to the liver cells, a condition known as ischemia. While the liver receives the majority of its blood flow from the portal vein, that blood is rich in nutrients but relatively low in oxygen compared to the arterial supply. Although the liver’s dual blood supply usually provides some resistance to damage, a complete blockage of the hepatic artery can overwhelm this protective mechanism.
The bile ducts are the most sensitive structures to this oxygen deprivation, relying almost exclusively on the hepatic artery for survival. When the artery is thrombosed, the resulting ischemia can lead to necrosis, or death, of the bile duct tissue, known as ischemic cholangiopathy. This tissue death can cause bile leaks, abscess formation, and severe inflammation, leading to rapid deterioration of liver function. The severity of the resulting liver damage and the clinical presentation depend heavily on whether the blockage is total and how quickly collateral blood vessels can develop to reroute blood flow.
Key Factors That Increase Risk
Hepatic artery thrombosis is most frequently encountered as a complication following liver transplantation, where it represents the most common vascular complication of the procedure. The incidence ranges from 4% to 8% in adults and is higher in pediatric recipients, usually occurring within the first month after surgery. Technical surgical factors, particularly issues with the arterial anastomosis (the connection of the donor and recipient arteries), are a primary cause.
Risk Factors in Transplant Recipients
Other factors increase the risk of HAT in transplant recipients:
- A prolonged warm ischemia time, which is the period the organ is without blood flow before being placed in the recipient.
- Recipient characteristics such as older age, higher Model for End-Stage Liver Disease (MELD) scores, or a history of a previous liver transplant.
- Non-surgical issues, such as episodes of acute cellular rejection or infection with viruses like cytomegalovirus.
Risk Factors in Native Liver
Outside of transplantation, HAT can occur in a native liver due to underlying medical conditions. Individuals with hypercoagulable states, which cause the blood to clot too easily, are at increased risk. Other causes include severe atherosclerosis leading to plaque buildup, vasculitis (inflammation of the blood vessels), or injury from blunt abdominal trauma.
How Doctors Identify the Problem
The symptoms of HAT can be vague, often mimicking other post-operative complications like infection or rejection, making timely diagnosis challenging. Clinical signs prompting investigation include the sudden onset of fever, severe abdominal pain, and rapid deterioration of liver function tests. Lab work commonly shows a significant, often dramatic, elevation of liver enzymes, such as alanine transaminase (ALT) and aspartate transaminase (AST).
The primary method for confirming the diagnosis is Doppler ultrasound, a non-invasive imaging study. This test uses sound waves to visualize blood flow through the hepatic artery and detects the absence of flow characteristic of thrombosis. If the Doppler ultrasound is inconclusive or more detail is needed, doctors may use computed tomography (CT) angiography. This involves injecting contrast dye into the bloodstream to produce detailed images that confirm the clot and show any resulting areas of liver tissue death.
Options for Treatment and Recovery
Management of hepatic artery thrombosis requires prompt intervention focused on re-establishing blood flow to the liver, typically through medical or surgical means. One common approach is catheter-directed thrombolysis, where clot-busting drugs, such as urokinase, are delivered directly to the clot site via a catheter. Alternatively, an emergency surgical thrombectomy may be performed, involving the physical removal of the clot and a revision of the arterial connection.
While these revascularization procedures can be successful, they carry risks, including bleeding complications from the clot-busting drugs. If initial interventions fail to restore adequate blood flow, or if the liver has sustained irreversible damage, the ultimate treatment option is urgent re-transplantation with a new organ.
The recovery process, even with successful revascularization, is often complicated by biliary issues due to the initial ischemic injury to the bile ducts. Patients may require long-term supportive care, including management of subsequent bile duct strictures and infections. The outcome depends largely on the speed of diagnosis, the success of the revascularization effort, and the extent of damage sustained before treatment began.