Possible contribution of cytomegalovirus infection to the high risk of (recurrent) venous thrombosis after renal transplantation.

Renal transplant recipients are at an increased risk of venous thrombosis, which has been regarded as a postoperative complication, although it may persist afterwards. As numerous case reports have shown that active cytomegalovirus (CMV) infection can be found at time of onset of venous thrombosis, and is frequently found in renal transplant recipients, we hypothesized that one might be the result of the other. To calculate the risk of (recurrent) venous thrombosis in renal transplant recipients, and to see whether CMV infection influenced this risk, we retrospectively analysed 606 living consecutive renal transplant recipients. CMV status at time of transplantation and at time of enrolment was determined. Absolute risks of first venous thrombosis and recurrence were compared with CMV status, and were corrected for surgery related venous thrombosis, age, and anticoagulant treatment. Annual incidence of venous thrombosis was 0.88% (95% CI, 0.65-1.15) in all recipients and 0.59% (95% CI, 0.41-0.83) corrected for surgery related venous thrombosis. CMV positive and seroconverted recipients tended to have an increased risk of venous thrombosis compared to CMV negative recipients; corrected relative risks were 2.0 (95% CI, 0.9-5.2) and 1.7 (95% CI, 0.6-4.7), respectively. The cumulative 10-year recurrence rate of venous thrombosis in CMV seronegative, seroconverted, and seropositive recipients was 10%, 51% and 59%, respectively. We conclude that CMV infection tended to be associated with an increased risk of (recurrent) venous thrombosis. Prospective studies are warranted to establish this observation, which suggests that CMV infection influences the high risk of (recurrent) venous thrombosis in renal transplant recipients.