THE PREVALENCE OF FOCAL TUBULO‐INTERSTITIAL LESIONS IN VARIOUS RENAL DISEASES

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Abstract
The focal tubulo-interstitial lesions (FTIL) described in the present paper appear as short segments of tubules showing epithelial degeneration, necrosis and desquamation. The foci are surrounded by mononuclear cells, among which lymphocytes are most numerous. They infiltrate through the damaged tubular basement membranes and may thus be located between epithelial cells and in the tubular lumen. Older lesions show focal tubular atrophy with thickened basement membranes together with focal interstitial fibrosis and lymphocytic infiltrates. The overall prevalence of this type of lesion in a consecutive renal biopsy series was 36%. It was not detected in 24 biopsies from patients without renal disease. The frequency of FTIL was high in acute renal failure due to hemolysis, shock, etc. or to the action of drugs, as well as in some types of glomerulonephritis (membranous, membrano-proliferative, SLE [systemic lupus erythematous]). Tubular Ig were not demonstrated in 38 biopsies with FTIL. The pathogenesis and possible consequence of the lesions are still unclear but they may in some situations contribute to the nephron atrophy in chronic renal disease.