Clinical assessment of renal vascular involvement and clinical-pathological correlations.
The renal vascular involvement of systemic diseases can be of embolic, thrombotic or inflammatory nature. Occlusion of proximal arterial vessels results in a dissociation between the rapid progression of renal failure, and the urinary abnormalities. Urine examination can be nearly normal and non revealing, except for a loss in maximal concentrating ability. In contrast, inflammatory changes of distal vessels are variably transmitted to the glomeruli, resulting in proteinuria, variable hematuria associated to mixed abnormalities of the urinary sediment. In diffuse vascular involvement acute renal failure can supervene, difficult to distinguish from that of diffuse glomerulonephritides. Most systemic vasculitides, mainly those of SLE, microscopic polyangiitis, Henoch-Schoenlein purpura and that of Wegener granulomatosis cause a clinical picture either of acute, rapidly progressive glomerulonephritis, or of a nephritic syndrome. The vasculitides affecting small arteries, capillaries and venules can result in a clinical-histopathologic picture closely mimicking that of acute tubule-interstitial disease. A thorough evaluation of the clinical picture, of the degree and progression of renal failure, of urine analysis, and clinically guided biopsies of the appropriate tissues can lead to differentiation of the different diseases and precocious diagnosis and effective treatment.