Morphometric correlates of renal excretory function

There is often thought to be little or no correlation between renal excretory function and histological changes in the kidney, especially in acute renal failure and in the kidney examined post-mortem. We studied the relationship between renal function and structure in 28 patients at necropsy and in 41 patients who had a renal biopsy. A point-counting method was used on kidney stained by an immunoperoxidase method using an antiserum to proximal tubule brush border; an antiserum to Tamm-Horsfall protein, which is a marker of thick limbs of the loop of Henle; and a monoclonal antibody to epithelial membrane antigen, normally a marker of all parts of the tubule except proximal tubule. There was a correlation between the reciprocal of plasma creatinine concentration, which is a measure of renal function, and the ratio of brush border positive tubules to negative tubules. There was also a less strong correlation between renal function and ratios of Tamm-Horsfall positive tubules to negative tubules and of cast-containing tubules to others. There was no correlation between renal function and the ratio of tubules expressing epithelial membrane antigen to those not expressing it. The method of point-counting tubules stained by the brush border antiserum was a useful, practical way of correlating renal function and structure which could be used even on post-mortem kidney.