Morphometric study showing the importance of distal tubular damage in impaired creatinine clearance

It is established that the glomerular filtration rate (GFR) is affected by tubulointerstitial lesions (TIL) in various glomerulonephritides. The fall in GFR is believed to be the result of damage to tubules, mainly the proximal tubules, and interstitial widening. We performed the morphometric point-counting study in 45 renal biopsies with various glomerular diseases, and 10 controls, to quantify interstitial widening, proximal and distal tubular damage, and to study their relation to serum creatinine clearance, and also to determine the best predictor, and the degree of damage in each component of the tubulointerstitium. There was a statistically significant correlation of serum creatinine clearance to interstitial widening (r = -0.748; p = 0.0001) and decrease in proximal (r = 0.611; p = 0.0001) and distal tubular area percentages, with a maximum value of the correlation coefficient for the distal tubules (r = 0.818; p = 0.0001). On the basis of relative mean difference values, it appeared that in the presence of tubulointerstitial damage, the distal tubule sustained greater damage. Therefore, distal tubular damage may serve as an important prognostic parameter.