Howie et al quantitated histologic changes of chronic damage in a renal biopsy as a simple index. This index correlates with shortened renal survival and need for dialysis. The authors are from the University of Birmingham and Queen Elizabeth Hospital in Birmingham, England.


Analysis: morphometric analysis of a renal biopsy. Area measurements could be in square microns or arbitrary units depending on magnification of the image.



(1) total area of cortex in a renal biopsy

(2) total area of cortex involved by histologic features of chronic renal damage

(2a) glomeruli with global sclerosis (not just segmental sclerosis)

(2b) interstitial fibrosis (solid and deeply stained areas, excluding areas of edema)

(2c) complete occlusion of arteries and veins

(2d) atrophic tubules (tubules smaller than normal with a thickened basement membrane

(2e) dilated tubules (with thinned epithelium, including pseudocysts)


total cortical area affected by chronic injury =

= SUM(areas of all 5 histologic elements)


index of chronic renal injury =

= (total area of chronic renal injury in the cortex) / (total area of the cortex) * 100%



• minimum index: 0%

• maximum index: 100% (in study highest value was 90%)

• The higher the index the greater the risk of end-stage renal disease.


hazard ratio for permanent dialysis =

= 1.5 ^ ((index as a percent from 0 to 100) / 10)


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