Kidney histopathology associated with kidney function at 1 year post severe AKI related to ANCA-associated vasculitis

ANCA-associated vasculitis is a rare autoimmune disease, and is particularly serious when the kidneys are involved. In addition to immunosuppressants, plasma exchanges are used to treat severe forms of vasculitis. The international guidelines recommend kidney biopsies for their diagnostic and prognostic roles. The Berden, ARRS (ANCA Renal Risk Score), and AKRiS (ANCA Kidney Risk Score) classifications show that certain histological lesions, such as interstitial fibrosis, tubular atrophy, and the percentage of normal glomeruli negatively impact kidney prognosis. The aim of this study was to evaluate the renal response of patients with severe forms of ANCA-associated vasculitis undergoing kidney biopsy and plasma exchanges, to identify the histological determinants favorable to kidney recovery.

This was a retrospective multicenter study of 34 patients with ANCA-associated vasculitis with severe kidney involvement who were receiving plasma exchanges. The primary endpoint was death, the need for dialysis, or persistent kidney dysfunction (eGFR < 30 ml/min/1.73 m² for 3 months) at one year.

Among the 34 patients (56% men), 19 (55%) met the primary endpoint. The 15 patients with an eGFR > 30 ml/min/1.73 m² at one year were younger (60 vs. 70 years), mostly male (73% vs. 42%), and had higher CRP levels (107 vs. 32 mg/l). Histologically, this group had more normal glomeruli (25% vs. 11%), less glomerulosclerosis (15% vs. 22%), and more cellular and partial crescents.

Patients treated by therapeutic plasmapheresis with a better kidney prognosis at 1-year had more normal glomeruli, less glomerulosclerosis and was associated with higher CRP. These results could support the systematic use of kidney biopsies for severe forms of ANCA-associated vasculitis, to better adapt treatments.