Contrast Enhanced Ultrasound in Detecting Biliary Complications After ABO-Incompatible Liver Transplantation

Despite the improvements in surgical techniques, perioperative care and immunosuppressant therapies, ABO incompatible liver transplantation is still associated with a high risk of failure because of antibody-mediated rejection, vascular and biliary complications, therefore resulting a lower patient and graft survival. Thus, an early identification of such complications is crucial, and ultrasonography (USG) and magnetic resonance cholangiopancreatography (MRCP) represent the most important tools. Ultrasound is widely accessible and less expensive and is often a first-line screen tool for vascular and biliary complications, while MRCP provides more accurate imaging findings. ¹ According to imaging, different interventions might be arranged to treat biliary complications, which are one of the major concerns. They can present as anastomotic strictures causing dilatation of intra-hepatic ducts or, more rarely, as diffuse non-anastomotic strictures associated with refractory cholangitis. The literature reporting about different imaging techniques to diagnose biliary complications, focuses almost exclusively on USG and MRCP. We would like to emphasize the possible complementary role of the Contrast Enhanced Ultrasound (CEUS) and to highlight its potentialities, and possible usefulness in the posttransplant surveillance. ^2,3

In our over-20 years’ experience in transplantation, a routine USG follow up of patients who have undergone liver, kidney, or pancreas transplantation ³ has been carried out, and the evaluation of high-risk cases was performed with CEUS since it became available. Thus, higher level imaging examinations, such as CT scan and MRCP, are reserved for selected patients only. This policy was in accordance with the evidence in literature that CEUS improves the diagnostic assessment of hepatic artery complications and focal liver diseases, and also supporting that CEUS might be a potential alternative in evaluating arterial steal syndrome, hepatic vein obstruction and biliary complications. ²

In particular, CEUS can produce cholangiographic-like images of the biliary tree, overcoming the limited depiction of the biliary tree morphology on conventional USG. Moreover, intravenous CEUS has been reported to be promising in detecting ischemic-type biliary lesions by demonstrating low enhancement patterns of the bile duct walls. ² Therefore, we think that for the high risk patients such as those who had undergone ABO-incompatible transplantation, the use of CEUS as intermediate assessment between USG and MRCP, may also be useful in terms of cost-effectiveness and safety, as it could limit the use of more costly and more demanding examinations.

Although MRCP is undoubtedly the gold standard for the ischemic-type biliary lesions, and further studies are needed to confirm the diagnostic role of CEUS in post-transplant surveillance, we would like to emphasize it as a safe, easy, bedside and cost-effective tool to study biliary complications following liver transplantation, and particularly for ABO incompatible liver transplantation, allowing to avoid an excessive use of second level imaging, whenever is possible.