4.3 Chronic unspecific tubulo-interstitial damage (CID)

Definition: Damage mainly of the tubulo-interstitial space without significant involvement of the vessels and glomeruli

In most cases focal or diffuse interstitial fibrosis is present accompanied by focal or diffuse tubular atrophy. The fibrotic areas are more or less densely infiltrated by small lymphocytes and histiocytes. Eosinophiles and plasma cells are usually not present.

In the well preserved renal tissue, tubulitis or any other specific damage is absent.

In later stages obsolescent glomeruli, FSGS, arteriolar hyalinosis, intimal fibrosis in arteries are found, which must be considered as a consequence of a primary tubulo-interstitial lesion and not as its cause. Obsolescent glomeruli due to primary tubulo-interstitial lesions often show a concentric periglomerular fibrosis.