Pancreatic allograft thrombosis: Suggestion for a CT grading system and management algorithm

Abstract

Pancreatic allograft thrombosis (PAT) remains the leading cause of nonimmunologic graft failure. Here, we propose a new computed tomography (CT) grading system of PAT to identify risk factors for allograft loss and outline a management algorithm by retrospective review of consecutive pancreatic transplantations between 2009 and 2014. Triple-phase CT scans were graded independently by 2 radiologists as grade 0, no thrombosis; grade 1, peripheral thrombosis; grade 2, intermediate non-occlusive thrombosis; and grade 3, central occlusive thrombosis. Twenty-four (23.3%) of 103 recipients were diagnosed with PAT (including grade 1). Three (2.9%) grafts were lost due to portal vein thrombosis. On multivariate analysis, pancreas after simultaneous pancreas-kidney transplantation/solitary pancreatic transplantation, acute rejection, and CT findings of peripancreatic edema and/or inflammatory change were significant risk factors for PAT. Retrospective review of CT scans revealed more grade 1 and 2 thromboses than were initially reported. There was no significant difference in graft or patient survival, postoperative stay, or morbidity of recipients with grade 1 or 2 thrombosis who were or were not anticoagulated. Our data suggest that therapeutic anticoagulation is not necessary for grade 1 and 2 arterial and grade 1 venous thrombosis. The proposed grading system can assist clinicians in decision-making and provide standardized reporting for future studies.

Keywords: clinical research/practice; coagulation and hemostasis; complication; graft survival; health services and outcomes research; pancreas/simultaneous pancreas-kidney transplantation; thrombosis and thromboembolism.

Figure 1

Representative cross‐sectional images demonstrating grades 1‐3 of venous and arterial pancreas allograft thrombosis. IMAGE 1: Grade 1 venous thrombus: axial image of a portal phase study demonstrating non‐occlusive thrombus (arrow) within an SMV tributary within fat, at the transected margin of the graft. IMAGE 2: Grade 2 venous thrombus: coronal reformatted image of a portal phase study demonstrating non‐occlusive thrombus extending along the splenic vein within the body of graft pancreas (arrow). Adjacent patent splenic artery (short arrow). IMAGE 3: Grade 3 venous thrombus: unenhanced axial image demonstrating acute hyper‐dense thrombus in an expanded SMV. IMAGE 4: Grade 3 venous thrombus: portal phase axial image demonstrating thrombus in the SMV extending into the IVC (arrow). This component is seen as hypo‐dense within otherwise opacified cava. IMAGE 5: Grade 1 arterial thrombus: axial arterial phase image demonstrating minimal thrombus in the distal splenic artery (arrow). IMAGE 6: Grade 2 arterial thrombus: axial arterial phase image demonstrating thrombus extending into the mid SMA. IMAGE 7: Grade 3 arterial thrombus: (image not from current series; obtained from a library) arterial phase coronal reformatted image demonstrating acute occlusive thrombus expanding the Y graft and SMA (arrow). Enhancement of the residual patent proximal Y graft stump (short arrow)

Figure 2

Death‐censored graft survival. Graft survival was significantly inferior in the thrombosis group compared to controls. All graft losses in this group occurred within two weeks of transplantation

Figure 3

Patient survival. There was no difference in patient survival between thrombosis and no‐thrombosis groups

Figure 4

Flowchart depicting the 2 distinct stages of the retrospective study

Figure 5

Death‐censored graft survival. Graft survival was similar between thrombosis‐Anticoagulated (Grade 1 and 2) and Thrombosis‐Not anticoagulated groups

Figure 6

Patient survival. There was no statistical difference in patient survival between thrombosis‐Anticoagulated (Grade 1 and 2) and Thrombosis‐Not anticoagulated groups

Figure 7

Management algorithm for allograft thrombosis based on the Cambridge Pancreas Allograft Thrombosis (CPAT) grading system