Outcomes of allograft from donor kidney microthrombi and secondary recipient thrombotic microangiopathy: should we consider loosening the belt?

There is currently a huge worldwide demand for donor kidneys for organ transplantation. Consequently, numerous marginal donor kidneys, such as kidneys with microthrombi, are used to save patients' lives. While some studies have shown an association between the presence of microthrombi in donor kidneys and an increased risk for delayed graft function (DGF) (McCall et al., 2003; Gao et al., 2019), other studies have demonstrated that microthrombi negatively impact the rate of DGF (Batra et al., 2016; Hansen et al., 2018), but not graft survival rate (McCall et al., 2003; Batra et al., 2016; Gao et al., 2019). In contrast, Hansen et al. (2018) concluded that fibrin thrombi were not only associated with reduced graft function six months post-transplantation but also with increased graft loss within the first year of transplantation. On the other hand, Batra et al. (2016) found no significant differences in the DGF rate or one-year graft function between recipients in diffuse and focal microthrombi groups. To date, however, the overall influence of donor kidney microthrombi and the degree of influence on prognosis remain controversial, necessitating further research.