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Background
Biliary complication is the most common type to occur following liver transplantation and carries an associated mortality rate of 10%. It is important for radiologists to not only recognize biliary complications but also understand the role and limitations of imaging modalities to better aid clinicians in making prompt diagnosis. The purpose of this exhibit is to review liver transplant anatomy, imaging features of biliary complications across several modalities, and the role of interventional radiology.

Educational Goals / Teaching Points
Liver transplantation surgical technique will be reviewed to provide a background knowledge on the expected postoperative anatomy. The most common types of biliary complications including strictures, biliary leaks, and stones will be described as well as their expected timeline and incidence. Imaging features of these complications across modalities including ultrasound, computed topography (CT), nuclear medicine, magnetic resonance imaging (MRI), and cholangiography will be reviewed with emphasis on the appropriateness and limitations of each modality. Given the limitations of certain modalities such as ultrasound, emphasis will be placed on when radiologists should recommend additional studies across different modalities. Finally the role of interventional radiology will be briefly explored.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Transplant surgical techniques including choledochocholedochostomy (duct to duct anastomosis) and choledochojejunostomy (bilio-enteric anastomosis) will be distinguished. The pathophysiology of biliary complications will be explained especially in relationship to vascular complications as the transplant biliary system is especially prone to ischemia. Complications including anastomotic and non-anastomotic biliary strictures, biliary leaks, and stones/sludge will be described with corresponding findings across different imaging modalities. Emphasis will be placed on the limited role of ultrasound to rule out biliary complications (i.e. strictures) due to its poor sensitivity, ranging from only 38-68%. For MRI, the importance of fluid sensitive sequences with maximum intensity projections will be stressed along with examples.

Conclusion
Biliary complications are a common consequence of liver transplantation associated with relatively high morbidity and mortality. Radiologists must be familiar with liver transplantation anatomy to distinguish expected post-transplant findings from abnormalities across several modalities. Prompt recognition of common biliary complications aids the radiologist to be the effective consultant to the transplant team.