MON-224 DIAGNOSING RENAL THROMBOTIC MICROANGIOPATHY BASED ON HISTOPATHOLOGY IN RAPIDLY PROGRESSIVE RENAL FAILURE

Abstract

Appart from glomerular and tubulointerstitial lesion of rapidly progressive renal failure (RPRF), renal vascular lesion is a critical prognostic finding in which renal thrombotic microangiopathy (TMA) present with severe clinical manifestation and have a high morality. The aim of this study were to describe (1) the histopatological features of TMA, (2) its classification and (3) the associated lesions in RPRF. We observed 133 kidney biopsies performed in patients presented with RPRF from 2013 to March 2018 by by using light microscopy. Renal TMA was classified as acute TMA, defined by luminal thrombi including fibrin and fragments of red blood cells and associated with ischemic capillaries, mesangiolysis and edematous and mucinous intimal thickening, often infiltrated with foam cells. Chronic TMA was characterized by onion-skin fibrointimal sclerosis. Chronic active TMA showed both acute and chronic changes. There were 38 cases of TMA diagnosed histopathologically including 31/38 (81.6%) lupus nephritis (LN) with 26/31 classIV, 1/31 class V, 1/31 class III-V, 2/31class IV-V; 6/38 (15.8%) IgA nephropathy (IgAN) and 1/38 (2.6%) focal segmental sclerosis (FSGS). All 45% acute TMA were LN. 23% chronic TMA included 13% LN, 8% IgAN and 2% FSGS. 32% Chronic active TMA were 24% LN and 8% IgAN. Only one LN (2.6%) showed thrombus in artery. 34.2% cases with capillary occlusion were LN. The associated arteriolar lesions including thrombi (55.3%), edematous and mucinous intimal thickening (73.7%), fibrointimal sclerosis (34.2%) and immunofluorescence staining of thrombi with fibrin (44.7%) presented both in LN and IgAN. 55% had ischemic glomeruli. The FSGS solely showed arteriolar fibrointimal sclerosis and ischemic loops suggested for chronic TMA. The mesangiolysis, endothelial swelling and subendothelial expansion were not recognised in our observation probably due to the limitation of the quality of the microscopic slides as well as the lack of electromicroscopic equipment. The duplication of the basement membrane features was not applied for defining chronic TMA in capillaries especially in LN because of its frequent presence in many chronic conditions. Pathological features of renal thrombotic microangiopathy can varies considerably and can be seen frequently in many different severe kidney conditions.