Ultrastructure of human acute renal failure

The author studied with light microscopy, scanning electron microscopy, and transmission electron microscopy 19 kidney biopsies from patients with oliguric and nonoliguric acute renal failure, two biopsies from patients with renal failure due to bilateral ureteral obstruction, and 15 biopsies with near normal tubules. In acute renal failure, there were no intrinsic lesions of glomeruli, but lesions of varying severity were found in the proximal and distal tubules. Proximal tubular changes included diminished, bizarre or absent brush border, often with no or multiple cilia (often more severe in the straight segment of the proximal tubule); luminal surface blebs or bizarre projections; decreased, flattened, or absent basal-lateral interdigitations simplified cuboidal appearance; bizarre lateral interdigitations; enlarged "contracted" attachment bodies; increased cytosomes, "osmotic" or autophagic; and decreased apical vacuoles. Distal tubule changes included decreased basal-lateral interdigitations of the convoluted segment, some decrease in microvilli, increased cytosomes and luminal casts, and enlarged "contracted" attachment bodies. These changes imply severe diminution of luminal and antiluminal surface area which may decrease sodium and chloride flux and, thus, might induce renal cortical vasoconstriction by tubuloglomerular feedback mechanisms. Tubular changes resulting from partial ureteral obstruction closely resembled those of acute renal failure.