Background/Purpose: The anti-neutrophil cytoplasmic autoantibody (ANCA)- associated vasculitides (AAVs) include microscopic polyangiitis (MPA), granulomatosis with polyangitis (GPA), and eosinophilic granulomatosis with polyangitis (EGPA). These small-vessel vasculitides are characterized by necrotizing inflammation of the vessel wall, particularly affecting small arteries, arterioles, and capillaries in systemic organs, and the kidney is one of the organs most frequently involved. Although kidney biopsy is necessary for deciding the therapeutic protocol, it is invasive and sometimes difficult to perform in patients who are in poor general condition. We have already reported that T cells and macrophages appear in the urine of patients with glomerulonephritis, accompanied by active cellular infiltration such as cellular crescent formation and diffuse interstitial cell infiltration, but not in the urine of patients with glomerulonephritis without the active inflammatory lesions. In this study, we examined the utility of urinary inflammatory cell analysis for assessment of kidney histopathology in AAVs.

Methods: This was a cross-sectional, retrospective chart study. Thirty-six AAV patients who had been referred to Niigata University Hospital between 2002 and 2018, and had undergone percutaneous kidney biopsy and urinary inflammatory cell analysis, participated. Thirty-two patients had MPA, and 4 had GPA. The kidney biopsy findings were classified according to Berden’s classification (a method for categorizing glomerular lesions into four classes) and Neumann’s classification (a method for evaluating glomerular, tubulo-interstitial, and vascular lesions on the basis of activity indices and chronicity indices). Flow-cytometric analysis of urinary inflammatory cells was performed for each subject. The numbers of urinary T cells or macrophages were determined by multiplying the number of viable cells in the gated mononuclear cell region in each sample by the percentage of urinary CD3-positive or CD14-positive cells in the population, respectively. The correlations between the results of the two methods and the numbers of urinary inflammatory cells were examined using Kruskal-Wallis test and Spearmann’s rank correlation coefficient. Differences at p < 0.05 were considered to be statistically significant.

Results: In Berden’s classification, the numbers of urinary inflammatory cells showed a non-significant tendency to be increased in the crescentic category. Meanwhile, in Neumann’s classification, activity indices showed significant positive correlations with the numbers of urinary CD3-positive cells (r = 0.541, p = < 0.001), CD14-positive cells (r = 0.354, p = 0.034), and total inflammatory cells (r = 0.449, p = 0.006).

Conclusion: The numbers of urinary inflammatory cells reflect kidney histopathology in terms of active lesions, suggesting the usefulness of urinary inflammatory cell analysis for assessment of kidney biopsy findings in patients with AAVs.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/urinary-inflammatory-cell-analysis-reflects-the-renal-histopathology-in-anti-neutrophil-cytoplasmic-antibody-associated-vasculitis/