Outcomes of Persistent Microvascular Inflammation in Repeated Kidney Allograft Biopsies

Microvascular inflammation (MVI) with sum glomerulitis and peritubular capillaritis (g+ptc) ≥ 2 is an integral component of kidney allograft antibody-mediated rejection (AMR). It is unclear what the outcomes are among those with persistent MVI, despite treatment.

We included all kidney transplant recipients (KTRs) with persistent MVI ≥ 2 on first and second allograft biopsies who had third biopsies within 2 years of the first biopsy. KTRs were categorized into two groups, MVI (+) and MVI (-) on third biopsy. Risk factors for persistent MVI ≥ 2 on third biopsy, and graft survival based on MVI (+) and MVI (-) at last follow-up were outcomes of interest.

A total of 108 KTRs transplanted between 2013 and 2022 fulfilled our selection criteria, 75 (69%) were MVI (+) and 33 (31%) MVI (-). Most baseline characteristics were similar between the groups. In Cox regression analysis, none of the commonly assessed baseline characteristics, Banff scores, or DSA status at first or second biopsy were associated with persistent MVI on the third biopsy. Also, in Cox regression analysis, after adjusting for various characteristics, persistent MVI on third biopsy was not associated with increased or decreased risk for uncensored graft failure (aHR: 0.55, 95% CI: 0.23-1.29; p = 0.17).

The lack of difference in graft outcomes between the AMR patients who were MVI (+) versus MVI (-) on the third biopsy suggests that subsequent response to AMR treatment is less important for prognosis than the initial development of AMR. This reinforces the importance of the prevention of rejection.