Morphometric studies on acute renal failure in humans during the oligoanuric and polyuric phases

Twelve biopsies from patients in the oligoanuric phase and 17 from patients in the polyuric phase of acute renal failure (ARF) were studied and compared morphometrically with 39 control biopsies. Measurements were taken on silvered semi-thin sections, which were classified according to each of three divisions of the renal cortex. All alterations observed were equally prominent in these three cortical zones. The number of peri- and intertubular capillaries was reduced in both phases of ARF (P less than 0.001), their mean surface area was increased (P less than 0.001), while their total surface area per visual field remained constant. The tubular epithelial tissue was distended in both ARF phases and the tubular lumina were simultaneously widened, as were Bowman's capsular spaces. The causes of these alterations are discussed. The findings are in accord with a concept of the pathogenesis of ARF, which ascribes a central role to damage of individual tubular cells.