Liver transplantation is the treatment of choice for patients with acute or advanced chronic liver failure. Advances in organ preservation, surgical techniques and immunosuppressive therapy have improved outcomes, with graft survival reaching 93.2% at one year, 87.3% at three years and 84.1% at five years. Despite these improvements, postoperative complications remain a significant risk and may lead to graft failure or patient mortality. Vascular abnormalities, biliary complications, infection, rejection and recurrent malignancy can occur after transplantation. Imaging plays a central role in detecting these complications and guiding postoperative management, with many centres initiating imaging within the first postoperative day.
Immediate Postoperative Imaging Strategies
Early imaging after transplantation focuses on identifying biliary, vascular and parenchymal complications. Clinical and laboratory findings often overlap between patients with and without complications, which increases the importance of imaging in early assessment. Many centres combine laboratory monitoring with imaging on postoperative day 0 or day 1.
Duplex Doppler ultrasound of the abdomen plays a central role during this phase because it allows evaluation of hepatic vasculature, the biliary tree and the hepatic parenchyma. The technique can be performed at the bedside, which is particularly valuable because transplant recipients may be critically ill in the early postoperative period. Doppler analysis also enables measurement of arterial flow characteristics. In normal liver arterial waveforms, arterial acceleration time remains below 0.08 seconds and the resistive index ranges from 0.5 to 0.8. Deviations from these values may indicate vascular complications.
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Low early hepatic artery resistive indices below 0.6 demonstrate complete sensitivity and 80% specificity for vascular complications in transplant recipients. Absence of arterial flow strongly suggests hepatic artery thrombosis. Doppler ultrasound identifies more than 90% of cases of hepatic artery thrombosis. Abnormal portal venous flow may appear as increased pulsatility, slow flow, hepatofugal flow or absent flow.
Computed tomography also supports early postoperative evaluation. Contrast-enhanced CT identifies complications with sensitivity of 93.6%, specificity of 90.2% and diagnostic accuracy of 92%. Multiphase CT provides additional value because arterial, venous and parenchymal structures can be assessed within a single examination. This approach improves the ability to detect active bleeding or portal vein thrombosis and stenosis.
Imaging of Vascular and Biliary Complications
Vascular complications represent a major concern following transplantation because multiple vascular anastomoses are created during the surgical procedure. These complications occur in up to 7% of deceased donor transplants and 13% of living donor transplants. Arterial complications include thrombosis, stenosis, pseudoaneurysm and splenic artery steal syndrome. Venous complications include stenosis, thrombosis and occlusion affecting the portal vein, hepatic veins and inferior vena cava.
Doppler ultrasound remains an important initial examination in this context. Low resistive index values, prolonged systolic acceleration time and focal peak velocities above 200 cm/s suggest hepatic arterial stenosis. Studies combining Doppler criteria report diagnostic sensitivity of 97% and specificity of 64% for detecting arterial thrombosis or stenosis.
Computed tomography plays an additional role when ultrasound findings remain uncertain or when detailed anatomical information is required for planning intervention. Contrast-enhanced CT detects vascular complications with sensitivity and specificity reaching 100% and 97%. Multiphase CT allows evaluation of arterial and venous structures within a single study and can clarify false-positive or false-negative ultrasound findings.
Biliary complications affect approximately 25% of transplant recipients and commonly develop within the first three months. Complications include bile leaks, biliary obstruction, stones or casts, strictures and recurrent biliary disease. Biliary strictures occur in 15% to 18% of recipients and represent the most frequent cause of biliary obstruction. Ultrasound serves as the first-line imaging modality for suspected biliary complications because it can identify biliary dilation, calculi and peritransplant fluid collections.
Cross-Sectional Imaging and Posttransplant Surveillance
Magnetic resonance imaging and magnetic resonance cholangiopancreatography provide detailed evaluation when ultrasound findings raise concern for biliary abnormalities. MRI with MRCP demonstrates sensitivity of 99%, specificity of 96%, positive predictive value of 95%, negative predictive value of 99% and diagnostic accuracy of 97% for detecting biliary complications. MRCP also demonstrates sensitivity, specificity and accuracy exceeding 95% for identifying anastomotic strictures.
Gadoxetate disodium–enhanced MRI further improves the detection of biliary abnormalities. Approximately half of the administered contrast agent is taken up by hepatocytes and excreted into the biliary system, which allows hepatobiliary imaging approximately twenty minutes after contrast administration. Contrast within the bile ducts appears hyperintense on T1-weighted images. Leakage of contrast into a perihepatic fluid collection allows identification of active bile leaks. Delayed imaging up to 60–180 minutes may improve detection when bile ducts are dilated or hepatic function is impaired.
Long-term imaging surveillance is also necessary after transplantation because the rate of hepatic malignancy exceeds that of the general population. Recurrence of hepatocellular carcinoma occurs in 11% to 20% of recipients, usually within the first two years after transplantation. Surveillance commonly uses contrast-enhanced cross-sectional imaging such as multiphasic CT or MRI. Many institutions perform imaging every three to six months during the first years after transplantation before extending the interval to six to twelve months.
Imaging forms an essential component of clinical management after liver transplantation. Early postoperative imaging aims to identify vascular, biliary and parenchymal complications that threaten graft viability or patient survival. Duplex Doppler ultrasound provides rapid bedside evaluation of hepatic vascular flow, while contrast-enhanced CT offers detailed anatomical assessment when further investigation is required. MRI and MRCP support comprehensive evaluation of biliary abnormalities and improve diagnostic accuracy for strictures and bile leaks. Long-term surveillance with cross-sectional imaging also addresses the risk of malignancy recurrence. Together, these imaging approaches provide complementary diagnostic information and support timely clinical decision-making throughout the postoperative course.
Source: Journal of the American College of Radiology
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